// Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include <byteswap.h>
#include <limits.h>

#include <bitset>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <vector>

#include "base/logging.h"

#include "perf_reader.h"
#include "quipper_string.h"
#include "utils.h"

namespace quipper {

struct BufferWithSize {
  char* ptr;
  size_t size;
};

// If the buffer is read-only, it is not sufficient to mark the previous struct
// as const, as this only means that the pointer cannot be changed, and says
// nothing about the contents of the buffer.  So, we need another struct.
struct ConstBufferWithSize {
  const char* ptr;
  size_t size;
};

namespace {

// The type of the number of string data, found in the command line metadata in
// the perf data file.
typedef u32 num_string_data_type;

// Types of the event desc fields that are not found in other structs.
typedef u32 event_desc_num_events;
typedef u32 event_desc_attr_size;
typedef u32 event_desc_num_unique_ids;

// The type of the number of nodes field in NUMA topology.
typedef u32 numa_topology_num_nodes_type;

// The first 64 bits of the perf header, used as a perf data file ID tag.
const uint64 kPerfMagic = 0x32454c4946524550LL;

// A mask that is applied to metadata_mask_ in order to get a mask for
// only the metadata supported by quipper.
// Currently, we support build ids, hostname, osrelease, version, arch, nrcpus,
// cpudesc, cpuid, totalmem, cmdline, eventdesc, cputopology, numatopology, and
// branchstack.
// The mask is computed as (1 << HEADER_BUILD_ID) |
// (1 << HEADER_HOSTNAME) | ... | (1 << HEADER_BRANCH_STACK)
const uint32 kSupportedMetadataMask = 0xfffc;

// By default, the build ID event has PID = -1.
const uint32 kDefaultBuildIDEventPid = static_cast<uint32>(-1);

// Eight bits in a byte.
size_t BytesToBits(size_t num_bytes) {
  return num_bytes * 8;
}

template <class T>
void ByteSwap(T* input) {
  switch (sizeof(T)) {
  case sizeof(uint8):
    LOG(WARNING) << "Attempting to byte swap on a single byte.";
    break;
  case sizeof(uint16):
    *input = bswap_16(*input);
    break;
  case sizeof(uint32):
    *input = bswap_32(*input);
    break;
  case sizeof(uint64):
    *input = bswap_64(*input);
    break;
  default:
    LOG(FATAL) << "Invalid size for byte swap: " << sizeof(T) << " bytes";
    break;
  }
}

// The code currently assumes that the compiler will not add any padding to the
// various structs.  These CHECKs make sure that this is true.
void CheckNoEventHeaderPadding() {
  perf_event_header header;
  CHECK_EQ(sizeof(header),
           sizeof(header.type) + sizeof(header.misc) + sizeof(header.size));
}

void CheckNoPerfEventAttrPadding() {
  perf_event_attr attr;
  CHECK_EQ(sizeof(attr),
           (reinterpret_cast<u64>(&attr.branch_sample_type) -
            reinterpret_cast<u64>(&attr)) +
           sizeof(attr.branch_sample_type));
}

void CheckNoEventTypePadding() {
  perf_trace_event_type event_type;
  CHECK_EQ(sizeof(event_type),
           sizeof(event_type.event_id) + sizeof(event_type.name));
}

void CheckNoBuildIDEventPadding() {
  build_id_event event;
  CHECK_EQ(sizeof(event),
           sizeof(event.header.type) + sizeof(event.header.misc) +
           sizeof(event.header.size) + sizeof(event.pid) +
           sizeof(event.build_id));
}

// Creates/updates a build id event with |build_id| and |filename|.
// Passing "" to |build_id| or |filename| will leave the corresponding field
// unchanged (in which case |event| must be non-null).
// If |event| is null or is not large enough, a new event will be created.
// In this case, if |event| is non-null, it will be freed.
// Otherwise, updates the fields of the existing event.
// |new_misc| indicates kernel vs user space, and is only used to fill in the
// |header.misc| field of new events.
// In either case, returns a pointer to the event containing the updated data,
// or NULL in the case of a failure.
build_id_event* CreateOrUpdateBuildID(const string& build_id,
                                      const string& filename,
                                      uint16 new_misc,
                                      build_id_event* event) {
  // When creating an event from scratch, build id and filename must be present.
  if (!event && (build_id.empty() || filename.empty()))
    return NULL;
  size_t new_len = GetUint64AlignedStringLength(
      filename.empty() ? event->filename : filename);

  // If event is null, or we don't have enough memory, allocate more memory, and
  // switch the new pointer with the existing pointer.
  size_t new_size = sizeof(*event) + new_len;
  if (!event || new_size > event->header.size) {
    build_id_event* new_event = CallocMemoryForBuildID(new_size);

    if (event) {
      // Copy over everything except the filename and free the event.
      // It is guaranteed that we are changing the filename - otherwise, the old
      // size and the new size would be equal.
      *new_event = *event;
      free(event);
    } else {
      // Fill in the fields appropriately.
      new_event->header.type = HEADER_BUILD_ID;
      new_event->header.misc = new_misc;
      new_event->pid = kDefaultBuildIDEventPid;
    }
    event = new_event;
  }

  // Here, event is the pointer to the build_id_event that we are keeping.
  // Update the event's size, build id, and filename.
  if (!build_id.empty() &&
      !StringToHex(build_id, event->build_id, arraysize(event->build_id))) {
    free(event);
    return NULL;
  }

  if (!filename.empty())
    CHECK_GT(snprintf(event->filename, new_len, "%s", filename.c_str()), 0);

  event->header.size = new_size;
  return event;
}

// Reads |size| bytes from |buffer| into |dest| and advances |src_offset|.
bool ReadDataFromBuffer(const ConstBufferWithSize& buffer,
                        size_t size,
                        const string& value_name,
                        size_t* src_offset,
                        void* dest) {
  size_t end_offset = *src_offset + size / sizeof(*buffer.ptr);
  if (buffer.size < end_offset) {
    LOG(ERROR) << "Not enough bytes to read " << value_name;
    return false;
  }
  memcpy(dest, buffer.ptr + *src_offset, size);
  *src_offset = end_offset;
  return true;
}

// Reads |size| bytes from |data| into |buffer| and advances |buffer_offset|.
bool WriteDataToBuffer(const void* data,
                       size_t size,
                       const string& value_name,
                       size_t* buffer_offset,
                       const BufferWithSize& buffer) {
  size_t end_offset = *buffer_offset + size / sizeof(*buffer.ptr);
  if (buffer.size < end_offset) {
    LOG(ERROR) << "No space in buffer to write " << value_name;
    return false;
  }
  memcpy(buffer.ptr + *buffer_offset, data, size);
  *buffer_offset = end_offset;
  return true;
}

// Reads a CStringWithLength from |buffer| into |dest|, and advances the offset.
bool ReadStringFromBuffer(const ConstBufferWithSize& buffer,
                          bool is_cross_endian,
                          size_t* offset,
                          CStringWithLength* dest) {
  if (!ReadDataFromBuffer(buffer, sizeof(dest->len), "string length",
                          offset, &dest->len)) {
    return false;
  }
  if (is_cross_endian)
    ByteSwap(&dest->len);

  if (buffer.size < *offset + dest->len) {
    LOG(ERROR) << "Not enough bytes to read string";
    return false;
  }
  dest->str = string(buffer.ptr + *offset);
  *offset += dest->len / sizeof(*buffer.ptr);
  return true;
}

// Writes a CStringWithLength from |src| to |buffer|, and advances the offset.
bool WriteStringToBuffer(const CStringWithLength& src,
                         const BufferWithSize& buffer,
                         size_t* offset) {
  const size_t kDestUnitSize = sizeof(*buffer.ptr);
  size_t final_offset = *offset + src.len + sizeof(src.len) / kDestUnitSize;
  if (buffer.size < final_offset) {
    LOG(ERROR) << "Not enough space to write string";
    return false;
  }

  if (!WriteDataToBuffer(&src.len, sizeof(src.len),
                         "length of string metadata", offset, buffer)) {
    return false;
  }

  memset(buffer.ptr + *offset, 0, src.len * kDestUnitSize);
  snprintf(buffer.ptr + *offset, src.len, "%s", src.str.c_str());
  *offset += src.len;
  return true;
}

// Read read info from perf data.  Corresponds to sample format type
// PERF_SAMPLE_READ.
const uint64* ReadReadInfo(const uint64* array,
                           bool swap_bytes,
                           uint64 read_format,
                           struct perf_sample* sample) {
  if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
    sample->read.time_enabled = *array++;
  if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
    sample->read.time_running = *array++;
  if (read_format & PERF_FORMAT_ID)
    sample->read.id = *array++;

  if (swap_bytes) {
    ByteSwap(&sample->read.time_enabled);
    ByteSwap(&sample->read.time_running);
    ByteSwap(&sample->read.id);
  }

  return array;
}

// Read call chain info from perf data.  Corresponds to sample format type
// PERF_SAMPLE_CALLCHAIN.
const uint64* ReadCallchain(const uint64* array,
                            bool swap_bytes,
                            struct perf_sample* sample) {
  // Make sure there is no existing allocated memory in |sample->callchain|.
  CHECK_EQ(static_cast<void*>(NULL), sample->callchain);

  // The callgraph data consists of a uint64 value |nr| followed by |nr|
  // addresses.
  uint64 callchain_size = *array++;
  if (swap_bytes)
    ByteSwap(&callchain_size);
  struct ip_callchain* callchain =
      reinterpret_cast<struct ip_callchain*>(new uint64[callchain_size + 1]);
  callchain->nr = callchain_size;
  for (size_t i = 0; i < callchain_size; ++i) {
    callchain->ips[i] = *array++;
    if (swap_bytes)
      ByteSwap(&callchain->ips[i]);
  }
  sample->callchain = callchain;

  return array;
}

// Read raw info from perf data.  Corresponds to sample format type
// PERF_SAMPLE_RAW.
const uint64* ReadRawData(const uint64* array,
                          bool swap_bytes,
                          struct perf_sample* sample) {
  // First read the size.
  const uint32* ptr = reinterpret_cast<const uint32*>(array);
  sample->raw_size = *ptr++;
  if (swap_bytes)
    ByteSwap(&sample->raw_size);

  // Allocate space for and read the raw data bytes.
  sample->raw_data = new uint8[sample->raw_size];
  memcpy(sample->raw_data, ptr, sample->raw_size);

  // Determine the bytes that were read, and align to the next 64 bits.
  int bytes_read = AlignSize(sizeof(sample->raw_size) + sample->raw_size,
                             sizeof(uint64));
  array += bytes_read / sizeof(uint64);

  return array;
}

// Read call chain info from perf data.  Corresponds to sample format type
// PERF_SAMPLE_CALLCHAIN.
const uint64* ReadBranchStack(const uint64* array,
                              bool swap_bytes,
                              struct perf_sample* sample) {
  // Make sure there is no existing allocated memory in
  // |sample->branch_stack|.
  CHECK_EQ(static_cast<void*>(NULL), sample->branch_stack);

  // The branch stack data consists of a uint64 value |nr| followed by |nr|
  // branch_entry structs.
  uint64 branch_stack_size = *array++;
  if (swap_bytes)
    ByteSwap(&branch_stack_size);
  struct branch_stack* branch_stack =
      reinterpret_cast<struct branch_stack*>(
          new uint8[sizeof(uint64) +
                    branch_stack_size * sizeof(struct branch_entry)]);
  branch_stack->nr = branch_stack_size;
  for (size_t i = 0; i < branch_stack_size; ++i) {
    memcpy(&branch_stack->entries[i], array, sizeof(struct branch_entry));
    array += sizeof(struct branch_entry) / sizeof(*array);
    if (swap_bytes) {
      ByteSwap(&branch_stack->entries[i].from);
      ByteSwap(&branch_stack->entries[i].to);
    }
  }
  sample->branch_stack = branch_stack;

  return array;
}

size_t ReadPerfSampleFromData(const uint64* array,
                              const uint64 sample_fields,
                              const uint64 read_format,
                              bool swap_bytes,
                              struct perf_sample* sample) {
  const uint64* initial_array_ptr = array;
  const uint64 k32BitFields = PERF_SAMPLE_TID | PERF_SAMPLE_CPU;
  bool read_read_info = false;
  bool read_raw_data = false;
  bool read_callchain = false;
  bool read_branch_stack = false;

  for (int index = 0; (sample_fields >> index) > 0; ++index) {
    uint64 sample_type = (1 << index);
    union {
      uint32 val32[sizeof(uint64) / sizeof(uint32)];
      uint64 val64;
    };
    if (!(sample_type & sample_fields))
      continue;

    val64 = *array;

    if (swap_bytes) {
      if (k32BitFields & sample_type) {
        ByteSwap(&val32[0]);
        ByteSwap(&val32[1]);
      } else {
        ByteSwap(&val64);
      }
    }

    switch (sample_type) {
    case PERF_SAMPLE_IP:
      sample->ip = val64;
      break;
    case PERF_SAMPLE_TID:
      sample->pid = val32[0];
      sample->tid = val32[1];
      break;
    case PERF_SAMPLE_TIME:
      sample->time = val64;
      break;
    case PERF_SAMPLE_ADDR:
      sample->addr = val64;
      break;
    case PERF_SAMPLE_ID:
      sample->id = val64;
      break;
    case PERF_SAMPLE_STREAM_ID:
      sample->stream_id = val64;
      break;
    case PERF_SAMPLE_CPU:
      sample->cpu = val32[0];
      break;
    case PERF_SAMPLE_PERIOD:
      sample->period = val64;
      break;
    case PERF_SAMPLE_READ:
      read_read_info = true;
      break;
    case PERF_SAMPLE_RAW:
      read_raw_data = true;
      break;
    case PERF_SAMPLE_CALLCHAIN:
      read_callchain = true;
      break;
    case PERF_SAMPLE_BRANCH_STACK:
      read_branch_stack = true;
      break;
    default:
      LOG(FATAL) << "Invalid sample type 0x" << std::hex << sample_type;
      break;
    }

    switch (sample_type) {
    case PERF_SAMPLE_IP:
    case PERF_SAMPLE_TID:
    case PERF_SAMPLE_TIME:
    case PERF_SAMPLE_ADDR:
    case PERF_SAMPLE_ID:
    case PERF_SAMPLE_STREAM_ID:
    case PERF_SAMPLE_CPU:
    case PERF_SAMPLE_PERIOD:
      ++array;
      break;
    case PERF_SAMPLE_READ:
    case PERF_SAMPLE_RAW:
    case PERF_SAMPLE_CALLCHAIN:
    case PERF_SAMPLE_BRANCH_STACK:
      // Read info, raw info, call chain, and branch stack are special cases.
      // They come after the other fields in the sample info data, regardless of
      // the order of |sample_type| bits.  So do not increment the data pointer.
      break;
    default:
      LOG(FATAL) << "Invalid sample type 0x" << std::hex << sample_type;
    }
  }

  // Read each of the complex sample info fields.
  if (read_read_info) {
    // TODO(cwp-team): support grouped read info.
    if (read_format & PERF_FORMAT_GROUP)
      return 0;
    array = ReadReadInfo(array, swap_bytes, read_format, sample);
  }
  if (read_callchain) {
    array = ReadCallchain(array, swap_bytes, sample);
  }
  if (read_raw_data) {
    array = ReadRawData(array, swap_bytes, sample);
  }
  if (read_branch_stack) {
    array = ReadBranchStack(array, swap_bytes, sample);
  }

  return (array - initial_array_ptr) * sizeof(uint64);
}

size_t WritePerfSampleToData(const struct perf_sample& sample,
                             const uint64 sample_fields,
                             const uint64 read_format,
                             uint64* array) {
  uint64* initial_array_ptr = array;
  bool write_read_info = false;
  bool write_raw_data = false;
  bool write_callchain = false;
  bool write_branch_stack = false;

  for (int index = 0; (sample_fields >> index) > 0; ++index) {
    uint64 sample_type = (1 << index);
    union {
      uint32 val32[sizeof(uint64) / sizeof(uint32)];
      uint64 val64;
    };
    if (!(sample_type & sample_fields))
      continue;

    switch (sample_type) {
    case PERF_SAMPLE_IP:
      val64 = sample.ip;
      break;
    case PERF_SAMPLE_TID:
      val32[0] = sample.pid;
      val32[1] = sample.tid;
      break;
    case PERF_SAMPLE_TIME:
      val64 = sample.time;
      break;
    case PERF_SAMPLE_ADDR:
      val64 = sample.addr;
      break;
    case PERF_SAMPLE_ID:
      val64 = sample.id;
      break;
    case PERF_SAMPLE_STREAM_ID:
      val64 = sample.stream_id;
      break;
    case PERF_SAMPLE_CPU:
      val64 = sample.cpu;
      break;
    case PERF_SAMPLE_PERIOD:
      val64 = sample.period;
      break;
    case PERF_SAMPLE_READ:
      write_read_info = true;
      continue;
    case PERF_SAMPLE_RAW:
      write_raw_data = true;
      continue;
    case PERF_SAMPLE_CALLCHAIN:
      write_callchain = true;
      continue;
    case PERF_SAMPLE_BRANCH_STACK:
      write_branch_stack = true;
      continue;
    default:
      LOG(FATAL) << "Invalid sample type " << std::hex << sample_type;
    }
    *array++ = val64;
  }

  if (write_read_info) {
    // TODO(cwp-team): support grouped read info.
    if (read_format & PERF_FORMAT_GROUP)
      return 0;
    if (read_format & PERF_FORMAT_TOTAL_TIME_ENABLED)
      *array++ = sample.read.time_enabled;
    if (read_format & PERF_FORMAT_TOTAL_TIME_RUNNING)
      *array++ = sample.read.time_running;
    if (read_format & PERF_FORMAT_ID)
      *array++ = sample.read.id;
  }

  if (write_callchain) {
    if (!sample.callchain) {
      LOG(ERROR) << "Expecting callchain data, but none was found.";
    } else {
      *array++ = sample.callchain->nr;
      for (size_t i = 0; i < sample.callchain->nr; ++i)
        *array++ = sample.callchain->ips[i];
    }
  }

  if (write_raw_data) {
    uint32* ptr = reinterpret_cast<uint32*>(array);
    *ptr++ = sample.raw_size;
    memcpy(ptr, sample.raw_data, sample.raw_size);

    // Update the data read pointer after aligning to the next 64 bytes.
    int num_bytes = AlignSize(sizeof(sample.raw_size) + sample.raw_size,
                              sizeof(uint64));
    array += num_bytes / sizeof(uint64);
  }

  if (write_branch_stack) {
    if (!sample.branch_stack) {
      LOG(ERROR) << "Expecting branch stack data, but none was found.";
    } else {
      *array++ = sample.branch_stack->nr;
      for (size_t i = 0; i < sample.branch_stack->nr; ++i) {
        *array++ = sample.branch_stack->entries[i].from;
        *array++ = sample.branch_stack->entries[i].to;
        memcpy(array++, &sample.branch_stack->entries[i].flags, sizeof(uint64));
      }
    }
  }
  return (array - initial_array_ptr) * sizeof(uint64);
}

}  // namespace

PerfReader::~PerfReader() {
  // Free allocated memory.
  for (size_t i = 0; i < events_.size(); ++i)
    if (events_[i])
      free(events_[i]);

  for (size_t i = 0; i < build_id_events_.size(); ++i)
    if (build_id_events_[i])
      free(build_id_events_[i]);
}

void PerfReader::PerfizeBuildIDString(string* build_id) {
  build_id->resize(kBuildIDStringLength, '0');
}

void PerfReader::UnperfizeBuildIDString(string* build_id) {
  const size_t kPaddingSize = 8;
  const string kBuildIDPadding = string(kPaddingSize, '0');

  // Remove kBuildIDPadding from the end of build_id until we cannot remove any
  // more, or removing more would cause the build id to be empty.
  while (build_id->size() > kPaddingSize &&
         build_id->substr(build_id->size() - kPaddingSize) == kBuildIDPadding) {
    build_id->resize(build_id->size() - kPaddingSize);
  }
}

bool PerfReader::ReadFile(const string& filename) {
  std::vector<char> data;
  if (!ReadFileToData(filename, &data))
    return false;
  return ReadFromVector(data);
}

bool PerfReader::ReadFromVector(const std::vector<char>& data) {
  return ReadFromPointer(&data[0], data.size());
}

bool PerfReader::ReadFromString(const string& str) {
  return ReadFromPointer(str.c_str(), str.size());
}

bool PerfReader::ReadFromPointer(const char* perf_data, size_t size) {
  const ConstBufferWithSize data = { perf_data, size };

  if (data.size == 0)
    return false;
  if (!ReadHeader(data))
    return false;

  // Check if it is normal perf data.
  if (header_.size == sizeof(header_)) {
    DLOG(INFO) << "Perf data is in normal format.";
    metadata_mask_ = header_.adds_features[0];
    return (ReadAttrs(data) && ReadEventTypes(data) && ReadData(data)
            && ReadMetadata(data));
  }

  // Otherwise it is piped data.
  if (piped_header_.size != sizeof(piped_header_)) {
    LOG(ERROR) << "Expecting piped data format, but header size "
               << piped_header_.size << " does not match expected size "
               << sizeof(piped_header_);
    return false;
  }

  return ReadPipedData(data);
}

bool PerfReader::WriteFile(const string& filename) {
  std::vector<char> data;
  return WriteToVector(&data) && WriteDataToFile(data, filename);
}

bool PerfReader::WriteToVector(std::vector<char>* data) {
  data->resize(GetSize());
  return WriteToPointerWithoutCheckingSize(&data->at(0), data->size());
}

bool PerfReader::WriteToString(string* str) {
  str->resize(GetSize());
  return WriteToPointerWithoutCheckingSize(&str->at(0), str->size());
}

bool PerfReader::WriteToPointer(char* buffer, size_t size) {
  size_t required_size = GetSize();
  if (size < required_size) {
    LOG(ERROR) << "Buffer is too small - buffer size is " << size
               << " and required size is " << required_size;
    return false;
  }
  return WriteToPointerWithoutCheckingSize(buffer, size);
}


bool PerfReader::WriteToPointerWithoutCheckingSize(char* buffer, size_t size) {
  BufferWithSize data = { buffer, size };
  if (!WriteHeader(data) ||
      !WriteAttrs(data) ||
      !WriteEventTypes(data) ||
      !WriteData(data) ||
      !WriteMetadata(data)) {
    return false;
  }
  return true;
}

size_t PerfReader::GetSize() {
  // TODO(rohinmshah): This is not a good CHECK.  See TODO in perf_reader.h.
  CHECK(RegenerateHeader());

  size_t total_size = 0;
  total_size = 0;
  total_size += out_header_.size;
  total_size += out_header_.attrs.size;
  total_size += out_header_.event_types.size;
  total_size += out_header_.data.size;
  // Add the ID info, whose size is not explicitly included in the header.
  for (size_t i = 0; i < attrs_.size(); ++i)
    total_size += attrs_[i].ids.size() * sizeof(attrs_[i].ids[0]);

  // Additional info about metadata.  See WriteMetadata for explanation.
  total_size += (GetNumMetadata() + 1) * 2 * sizeof(u64);

  // Add the sizes of the various metadata.
  total_size += GetBuildIDMetadataSize();
  total_size += GetStringMetadataSize();
  total_size += GetUint32MetadataSize();
  total_size += GetUint64MetadataSize();
  total_size += GetEventDescMetadataSize();
  total_size += GetCPUTopologyMetadataSize();
  total_size += GetNUMATopologyMetadataSize();
  return total_size;
}

bool PerfReader::RegenerateHeader() {
  // This is the order of the input perf file contents in normal mode:
  // 1. Header
  // 2. Attribute IDs (pointed to by attr.ids.offset)
  // 3. Attributes
  // 4. Event types
  // 5. Data
  // 6. Metadata

  // Compute offsets in the above order.
  CheckNoEventHeaderPadding();
  memset(&out_header_, 0, sizeof(out_header_));
  out_header_.magic = kPerfMagic;
  out_header_.size = sizeof(out_header_);
  out_header_.attr_size = sizeof(attrs_[0].attr) + sizeof(perf_file_section);
  out_header_.attrs.size = out_header_.attr_size * attrs_.size();
  for (size_t i = 0; i < events_.size(); i++)
    out_header_.data.size += events_[i]->header.size;
  out_header_.event_types.size = event_types_.size() * sizeof(event_types_[0]);

  u64 current_offset = 0;
  current_offset += out_header_.size;
  for (size_t i = 0; i < attrs_.size(); i++)
    current_offset += sizeof(attrs_[i].ids[0]) * attrs_[i].ids.size();
  out_header_.attrs.offset = current_offset;
  current_offset += out_header_.attrs.size;
  out_header_.event_types.offset = current_offset;
  current_offset += out_header_.event_types.size;

  out_header_.data.offset = current_offset;

  // Construct the header feature bits.
  memset(&out_header_.adds_features, 0, sizeof(out_header_.adds_features));
  // The following code makes the assumption that all feature bits are in the
  // first word of |adds_features|.  If the perf data format changes and the
  // assumption is no longer valid, this CHECK will fail, at which point the
  // below code needs to be updated.  For now, sticking to that assumption keeps
  // the code simple.
  // This assumption is also used when reading metadata, so that code
  // will also have to be updated if this CHECK starts to fail.
  CHECK_LE(static_cast<size_t>(HEADER_LAST_FEATURE),
           BytesToBits(sizeof(out_header_.adds_features[0])));
  if (sample_type_ & PERF_SAMPLE_BRANCH_STACK)
    out_header_.adds_features[0] |= (1 << HEADER_BRANCH_STACK);
  out_header_.adds_features[0] |= metadata_mask_ & kSupportedMetadataMask;

  return true;
}

bool PerfReader::InjectBuildIDs(
    const std::map<string, string>& filenames_to_build_ids) {
  metadata_mask_ |= (1 << HEADER_BUILD_ID);
  std::set<string> updated_filenames;
  // Inject new build ID's for existing build ID events.
  for (size_t i = 0; i < build_id_events_.size(); ++i) {
    build_id_event* event = build_id_events_[i];
    string filename = event->filename;
    if (filenames_to_build_ids.find(filename) == filenames_to_build_ids.end())
      continue;

    string build_id = filenames_to_build_ids.at(filename);
    PerfizeBuildIDString(&build_id);
    // Changing a build id should always result in an update, never creation.
    CHECK_EQ(event, CreateOrUpdateBuildID(build_id, "", 0, event));
    updated_filenames.insert(filename);
  }

  // For files with no existing build ID events, create new build ID events.
  // This requires a lookup of all MMAP's to determine the |misc| field of each
  // build ID event.
  std::map<string, uint16> filename_to_misc;
  for (size_t i = 0; i < events_.size(); ++i) {
    const event_t& event = *events_[i];
    if (event.header.type != PERF_RECORD_MMAP)
      continue;
    filename_to_misc[event.mmap.filename] = event.header.misc;
  }

  std::map<string, string>::const_iterator it;
  for (it = filenames_to_build_ids.begin();
       it != filenames_to_build_ids.end();
       ++it) {
    const string& filename = it->first;
    if (updated_filenames.find(filename) != updated_filenames.end())
      continue;

    // Determine the misc field.
    uint16 new_misc = PERF_RECORD_MISC_KERNEL;
    std::map<string, uint16>::const_iterator misc_iter =
        filename_to_misc.find(filename);
    if (misc_iter != filename_to_misc.end())
      new_misc = misc_iter->second;

    string build_id = it->second;
    PerfizeBuildIDString(&build_id);
    build_id_event* event =
        CreateOrUpdateBuildID(build_id, filename, new_misc, NULL);
    CHECK(event);
    build_id_events_.push_back(event);
  }

  return true;
}

bool PerfReader::Localize(
    const std::map<string, string>& build_ids_to_filenames) {
  std::map<string, string> perfized_build_ids_to_filenames;
  std::map<string, string>::const_iterator it;
  for (it = build_ids_to_filenames.begin();
       it != build_ids_to_filenames.end();
       ++it) {
    string build_id = it->first;
    PerfizeBuildIDString(&build_id);
    perfized_build_ids_to_filenames[build_id] = it->second;
  }

  std::map<string, string> filename_map;
  for (size_t i = 0; i < build_id_events_.size(); ++i) {
    build_id_event* event = build_id_events_[i];
    string build_id = HexToString(event->build_id, kBuildIDArraySize);
    if (perfized_build_ids_to_filenames.find(build_id) ==
        perfized_build_ids_to_filenames.end()) {
      continue;
    }

    string new_name = perfized_build_ids_to_filenames.at(build_id);
    filename_map[string(event->filename)] = new_name;
    build_id_event* new_event = CreateOrUpdateBuildID("", new_name, 0, event);
    CHECK(new_event);
    build_id_events_[i] = new_event;
  }

  LocalizeUsingFilenames(filename_map);
  return true;
}

bool PerfReader::LocalizeUsingFilenames(
    const std::map<string, string>& filename_map) {
  LocalizeMMapFilenames(filename_map);
  for (size_t i = 0; i < build_id_events_.size(); ++i) {
    build_id_event* event = build_id_events_[i];
    string old_name = event->filename;

    if (filename_map.find(event->filename) != filename_map.end()) {
      const string& new_name = filename_map.at(old_name);
      build_id_event* new_event = CreateOrUpdateBuildID("", new_name, 0, event);
      CHECK(new_event);
      build_id_events_[i] = new_event;
    }
  }
  return true;
}

void PerfReader::GetFilenames(std::vector<string>* filenames) const {
  std::set<string> filename_set;
  GetFilenamesAsSet(&filename_set);
  filenames->clear();
  filenames->insert(filenames->begin(), filename_set.begin(),
                    filename_set.end());
}

void PerfReader::GetFilenamesAsSet(std::set<string>* filenames) const {
  filenames->clear();
  for (size_t i = 0; i < events_.size(); ++i) {
    const event_t& event = *events_[i];
    if (event.header.type == PERF_RECORD_MMAP)
      filenames->insert(event.mmap.filename);
  }
}

void PerfReader::GetFilenamesToBuildIDs(
    std::map<string, string>* filenames_to_build_ids) const {
  filenames_to_build_ids->clear();
  for (size_t i = 0; i < build_id_events_.size(); ++i) {
    const build_id_event& event = *build_id_events_[i];
    string build_id = HexToString(event.build_id, kBuildIDArraySize);
    (*filenames_to_build_ids)[event.filename] = build_id;
  }
}

bool PerfReader::IsSupportedEventType(uint32 type) {
  switch (type) {
  case PERF_RECORD_SAMPLE:
  case PERF_RECORD_MMAP:
  case PERF_RECORD_FORK:
  case PERF_RECORD_EXIT:
  case PERF_RECORD_COMM:
  case PERF_RECORD_LOST:
  case PERF_RECORD_THROTTLE:
  case PERF_RECORD_UNTHROTTLE:
    return true;
  case PERF_RECORD_READ:
  case PERF_RECORD_MAX:
    return false;
  default:
    LOG(FATAL) << "Unknown event type " << type;
    return false;
  }
}

bool PerfReader::ReadPerfSampleInfo(const event_t& event,
                                    struct perf_sample* sample) const {
  CHECK(sample);

  if (!IsSupportedEventType(event.header.type)) {
    LOG(ERROR) << "Unsupported event type " << event.header.type;
    return false;
  }

  uint64 sample_format = GetSampleFieldsForEventType(event.header.type,
                                                     sample_type_);
  uint64 offset = GetPerfSampleDataOffset(event);
  size_t size_read = ReadPerfSampleFromData(
      reinterpret_cast<const uint64*>(&event) + offset / sizeof(uint64),
      sample_format,
      read_format_,
      is_cross_endian_,
      sample);

  if (event.header.type == PERF_RECORD_SAMPLE) {
    sample->pid = event.ip.pid;
    sample->tid = event.ip.tid;
    if (is_cross_endian_) {
      ByteSwap(&sample->pid);
      ByteSwap(&sample->tid);
    }
  }

  size_t expected_size = event.header.size - offset;
  if (size_read != expected_size) {
    LOG(ERROR) << "Read " << size_read << " bytes, expected "
               << expected_size << " bytes.";
  }

  return (size_read == expected_size);
}

bool PerfReader::WritePerfSampleInfo(const perf_sample& sample,
                                     event_t* event) const {
  CHECK(event);

  if (!IsSupportedEventType(event->header.type)) {
    LOG(ERROR) << "Unsupported event type " << event->header.type;
    return false;
  }

  uint64 sample_format = GetSampleFieldsForEventType(event->header.type,
                                                     sample_type_);
  uint64 offset = GetPerfSampleDataOffset(*event);

  size_t expected_size = event->header.size - offset;
  memset(reinterpret_cast<uint8*>(event) + offset, 0, expected_size);
  size_t size_written = WritePerfSampleToData(
      sample,
      sample_format,
      read_format_,
      reinterpret_cast<uint64*>(event) + offset / sizeof(uint64));
  if (size_written != expected_size) {
    LOG(ERROR) << "Wrote " << size_written << " bytes, expected "
               << expected_size << " bytes.";
  }

  return (size_written == expected_size);
}

bool PerfReader::ReadHeader(const ConstBufferWithSize& data) {
  CheckNoEventHeaderPadding();
  size_t offset = 0;
  if (!ReadDataFromBuffer(data, sizeof(header_), "header data",
                          &offset, &header_)) {
    return false;
  }
  if (header_.magic != kPerfMagic && header_.magic != bswap_64(kPerfMagic)) {
    LOG(ERROR) << "Read wrong magic. Expected: 0x" << std::hex << kPerfMagic
               << " or 0x" << std::hex << bswap_64(kPerfMagic)
               << " Got: 0x" << std::hex << header_.magic;
    return false;
  }
  is_cross_endian_ = (header_.magic != kPerfMagic);
  if (is_cross_endian_)
    ByteSwap(&header_.size);

  // Header can be a piped header.
  if (header_.size != sizeof(header_))
    return true;

  DLOG(INFO) << "event_types.size: " << header_.event_types.size;
  DLOG(INFO) << "event_types.offset: " << header_.event_types.offset;

  return true;
}

bool PerfReader::ReadAttrs(const ConstBufferWithSize& data) {
  size_t num_attrs = header_.attrs.size / header_.attr_size;
  size_t offset = header_.attrs.offset;
  for (size_t i = 0; i < num_attrs; i++) {
    if (!ReadAttr(data, &offset))
      return false;
  }
  return true;
}

bool PerfReader::ReadAttr(const ConstBufferWithSize& data, size_t* offset) {
  PerfFileAttr attr;
  if (!ReadEventAttr(data, offset, &attr.attr))
    return false;

  perf_file_section ids;
  if (!ReadDataFromBuffer(data, sizeof(ids), "ID section info", offset, &ids))
    return false;
  if (is_cross_endian_) {
    ByteSwap(&ids.offset);
    ByteSwap(&ids.size);
  }

  size_t num_ids = ids.size / sizeof(attr.ids[0]);
  // Convert the offset from u64 to size_t.
  size_t ids_offset = ids.offset;
  if (!ReadUniqueIDs(data, num_ids, &ids_offset, &attr.ids))
    return false;
  attrs_.push_back(attr);
  return true;
}

bool PerfReader::ReadEventAttr(const ConstBufferWithSize& data, size_t* offset,
                               perf_event_attr* attr) {
  CheckNoPerfEventAttrPadding();
  if (!ReadDataFromBuffer(data, sizeof(*attr), "attribute", offset, attr))
    return false;

  if (is_cross_endian_) {
    ByteSwap(&attr->type);
    ByteSwap(&attr->size);
    ByteSwap(&attr->config);
    ByteSwap(&attr->sample_period);
    ByteSwap(&attr->sample_type);
    ByteSwap(&attr->read_format);
    ByteSwap(&attr->wakeup_events);
    ByteSwap(&attr->bp_type);
    ByteSwap(&attr->bp_addr);
    ByteSwap(&attr->bp_len);
    ByteSwap(&attr->branch_sample_type);
  }

  // The actual perf_event_attr data size might be different from the size of
  // the struct definition.  Check against perf_event_attr's |size| field.
  int size_diff = attr->size - sizeof(*attr);
  *offset += size_diff;
  attr->size = sizeof(*attr);

  // Assign sample type if it hasn't been assigned, otherwise make sure all
  // subsequent attributes have the same sample type bits set.
  if (sample_type_ == 0) {
    sample_type_ = attr->sample_type;
  } else {
    CHECK_EQ(sample_type_, attr->sample_type)
        << "Event type sample format does not match sample format of other "
        << "event type.";
  }

  if (read_format_ == 0) {
    read_format_ = attr->read_format;
  } else {
    CHECK_EQ(read_format_, attr->read_format)
        << "Event type read format does not match read format of other event "
        << "types.";
  }

  return true;
}

bool PerfReader::ReadUniqueIDs(const ConstBufferWithSize& data, size_t num_ids,
                               size_t* offset, std::vector<u64>* ids) {
  ids->resize(num_ids);
  for (size_t j = 0; j < num_ids; j++) {
    if (!ReadDataFromBuffer(data, sizeof(ids->at(j)), "ID", offset,
                            &ids->at(j))) {
      return false;
    }
    if (is_cross_endian_)
      ByteSwap(&ids->at(j));
  }
  return true;
}

bool PerfReader::ReadEventTypes(const ConstBufferWithSize& data) {
  size_t num_event_types = header_.event_types.size /
      sizeof(struct perf_trace_event_type);
  CHECK_EQ(sizeof(perf_trace_event_type) * num_event_types,
           header_.event_types.size);
  size_t offset = header_.event_types.offset;
  for (size_t i = 0; i < num_event_types; ++i) {
    if (!ReadEventType(data, &offset))
      return false;
  }
  return true;
}

bool PerfReader::ReadEventType(const ConstBufferWithSize& data,
                               size_t* offset) {
  CheckNoEventTypePadding();
  perf_trace_event_type type;
  memset(&type, 0, sizeof(type));
  if (!ReadDataFromBuffer(data, sizeof(type.event_id), "event id",
                          offset, &type.event_id)) {
    return false;
  }
  const char* event_name = reinterpret_cast<const char*>(data.ptr + *offset);
  CHECK_GT(snprintf(type.name, sizeof(type.name), "%s", event_name), 0);
  *offset += sizeof(type.name);
  event_types_.push_back(type);
  return true;
}

bool PerfReader::ReadData(const ConstBufferWithSize& data) {
  u64 data_remaining_bytes = header_.data.size;
  size_t offset = header_.data.offset;
  while (data_remaining_bytes != 0) {
    if (data.size < offset) {
      LOG(ERROR) << "Not enough data to read a perf event.";
      return false;
    }

    const event_t* event = reinterpret_cast<const event_t*>(data.ptr + offset);
    if (!ReadPerfEventBlock(*event))
      return false;
    data_remaining_bytes -= event->header.size;
    offset += event->header.size;
  }

  DLOG(INFO) << "Number of events stored: "<< events_.size();
  return true;
}

bool PerfReader::ReadMetadata(const ConstBufferWithSize& data) {
  size_t offset = header_.data.offset + header_.data.size;

  for (u32 type = HEADER_FIRST_FEATURE; type != HEADER_LAST_FEATURE; ++type) {
    if ((metadata_mask_ & (1 << type)) == 0)
      continue;

    if (data.size < offset) {
      LOG(ERROR) << "Not enough data to read offset and size of metadata.";
      return false;
    }

    u64 metadata_offset, metadata_size;
    if (!ReadDataFromBuffer(data, sizeof(metadata_offset), "metadata offset",
                            &offset, &metadata_offset) ||
        !ReadDataFromBuffer(data, sizeof(metadata_size), "metadata size",
                            &offset, &metadata_size)) {
      return false;
    }

    if (data.size < metadata_offset + metadata_size) {
      LOG(ERROR) << "Not enough data to read metadata.";
      return false;
    }

    switch (type) {
    case HEADER_BUILD_ID:
      if (!ReadBuildIDMetadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_HOSTNAME:
    case HEADER_OSRELEASE:
    case HEADER_VERSION:
    case HEADER_ARCH:
    case HEADER_CPUDESC:
    case HEADER_CPUID:
    case HEADER_CMDLINE:
      if (!ReadStringMetadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_NRCPUS:
      if (!ReadUint32Metadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_TOTAL_MEM:
      if (!ReadUint64Metadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_EVENT_DESC:
      break;
    case HEADER_CPU_TOPOLOGY:
      if (!ReadCPUTopologyMetadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_NUMA_TOPOLOGY:
      if (!ReadNUMATopologyMetadata(data, type, metadata_offset, metadata_size))
        return false;
      break;
    case HEADER_BRANCH_STACK:
      continue;
    default: LOG(INFO) << "Unsupported metadata type: " << type;
      break;
    }
  }

  // Event type events are optional in some newer versions of perf. They
  // contain the same information that is already in |attrs_|. Make sure the
  // number of event types matches the number of attrs, but only if there are
  // event type events present.
  if (event_types_.size() > 0) {
    if (event_types_.size() != attrs_.size()) {
      LOG(ERROR) << "Mismatch between number of event type events and attr "
                 << "events: " << event_types_.size() << " vs "
                 << attrs_.size();
      return false;
    }
    metadata_mask_ |= (1 << HEADER_EVENT_DESC);
  }
  return true;
}

bool PerfReader::ReadBuildIDMetadata(const ConstBufferWithSize& data, u32 type,
                                     size_t offset, size_t size) {
  CheckNoBuildIDEventPadding();
  while (size > 0) {
    // Make sure there is enough data for everything but the filename.
    if (data.size < offset + sizeof(build_id_event) / sizeof(*data.ptr)) {
      LOG(ERROR) << "Not enough bytes to read build id event";
      return false;
    }

    const build_id_event* temp_ptr =
        reinterpret_cast<const build_id_event*>(data.ptr + offset);
    u16 event_size = temp_ptr->header.size;
    if (is_cross_endian_)
      ByteSwap(&event_size);

    // Make sure there is enough data for the rest of the event.
    if (data.size < offset + event_size / sizeof(*data.ptr)) {
      LOG(ERROR) << "Not enough bytes to read build id event";
      return false;
    }

    // Allocate memory for the event and copy over the bytes.
    build_id_event* event = CallocMemoryForBuildID(event_size);
    if (!ReadDataFromBuffer(data, event_size, "build id event",
                            &offset, event)) {
      return false;
    }
    if (is_cross_endian_) {
      ByteSwap(&event->header.type);
      ByteSwap(&event->header.misc);
      ByteSwap(&event->header.size);
      ByteSwap(&event->pid);
    }
    size -= event_size;

    // Perf tends to use more space than necessary, so fix the size.
    event->header.size =
        sizeof(*event) + GetUint64AlignedStringLength(event->filename);
    build_id_events_.push_back(event);
  }

  return true;
}

bool PerfReader::ReadStringMetadata(const ConstBufferWithSize& data, u32 type,
                                    size_t offset, size_t size) {
  PerfStringMetadata str_data;
  str_data.type = type;

  size_t start_offset = offset;
  // Skip the number of string data if it is present.
  if (NeedsNumberOfStringData(type))
    offset += sizeof(num_string_data_type) / sizeof(*data.ptr);

  while ((offset - start_offset) < size) {
    CStringWithLength single_string;
    if (!ReadStringFromBuffer(data, is_cross_endian_, &offset, &single_string))
      return false;
    str_data.data.push_back(single_string);
  }

  string_metadata_.push_back(str_data);
  return true;
}

bool PerfReader::ReadUint32Metadata(const ConstBufferWithSize& data, u32 type,
                                    size_t offset, size_t size) {
  PerfUint32Metadata uint32_data;
  uint32_data.type = type;

  size_t start_offset = offset;
  while (size > offset - start_offset) {
    uint32 item;
    if (!ReadDataFromBuffer(data, sizeof(item), "uint32 data", &offset, &item))
      return false;
    if (is_cross_endian_)
      ByteSwap(&item);
    uint32_data.data.push_back(item);
  }

  uint32_metadata_.push_back(uint32_data);
  return true;
}

bool PerfReader::ReadUint64Metadata(const ConstBufferWithSize& data, u32 type,
                                    size_t offset, size_t size) {
  PerfUint64Metadata uint64_data;
  uint64_data.type = type;

  size_t start_offset = offset;
  while (size > offset - start_offset) {
    uint64 item;
    if (!ReadDataFromBuffer(data, sizeof(item), "uint64 data", &offset, &item))
      return false;
    if (is_cross_endian_)
      ByteSwap(&item);
    uint64_data.data.push_back(item);
  }

  uint64_metadata_.push_back(uint64_data);
  return true;
}

bool PerfReader::ReadCPUTopologyMetadata(
    const ConstBufferWithSize& data, u32 type, size_t offset, size_t size) {
  num_siblings_type num_core_siblings;
  if (!ReadDataFromBuffer(data, sizeof(num_core_siblings), "num cores",
                          &offset, &num_core_siblings)) {
    return false;
  }
  if (is_cross_endian_)
    ByteSwap(&num_core_siblings);

  cpu_topology_.core_siblings.resize(num_core_siblings);
  for (size_t i = 0; i < num_core_siblings; ++i) {
    if (!ReadStringFromBuffer(data, is_cross_endian_, &offset,
                              &cpu_topology_.core_siblings[i])) {
      return false;
    }
  }

  num_siblings_type num_thread_siblings;
  if (!ReadDataFromBuffer(data, sizeof(num_thread_siblings), "num threads",
                          &offset, &num_thread_siblings)) {
    return false;
  }
  if (is_cross_endian_)
    ByteSwap(&num_thread_siblings);

  cpu_topology_.thread_siblings.resize(num_thread_siblings);
  for (size_t i = 0; i < num_thread_siblings; ++i) {
    if (!ReadStringFromBuffer(data, is_cross_endian_, &offset,
                              &cpu_topology_.thread_siblings[i])) {
      return false;
    }
  }

  return true;
}

bool PerfReader::ReadNUMATopologyMetadata(
    const ConstBufferWithSize& data, u32 type, size_t offset, size_t size) {
  numa_topology_num_nodes_type num_nodes;
  if (!ReadDataFromBuffer(data, sizeof(num_nodes), "num nodes",
                          &offset, &num_nodes)) {
    return false;
  }
  if (is_cross_endian_)
    ByteSwap(&num_nodes);

  for (size_t i = 0; i < num_nodes; ++i) {
    PerfNodeTopologyMetadata node;
    if (!ReadDataFromBuffer(data, sizeof(node.id), "node id",
                            &offset, &node.id) ||
        !ReadDataFromBuffer(data, sizeof(node.total_memory),
                            "node total memory", &offset,
                            &node.total_memory) ||
        !ReadDataFromBuffer(data, sizeof(node.free_memory),
                            "node free memory", &offset, &node.free_memory) ||
        !ReadStringFromBuffer(data, is_cross_endian_, &offset,
                              &node.cpu_list)) {
      return false;
    }
    if (is_cross_endian_) {
      ByteSwap(&node.id);
      ByteSwap(&node.total_memory);
      ByteSwap(&node.free_memory);
    }
    numa_topology_.push_back(node);
  }
  return true;
}

bool PerfReader::ReadPipedData(const ConstBufferWithSize& data) {
  size_t offset = piped_header_.size;
  bool result = true;
  metadata_mask_ = 0;
  CheckNoEventHeaderPadding();

  while (offset < data.size && result) {
    perf_event_header header;
    if (offset + sizeof(header) > data.size) {
      LOG(ERROR) << "Not enough bytes left in data to read header.  Required: "
                 << sizeof(header) << " bytes.  Available: "
                 << data.size - offset << " bytes.";
      return true;
    }

    // Copy the header and swap bytes if necessary.
    header = *reinterpret_cast<const perf_event_header*>(data.ptr + offset);
    if (is_cross_endian_) {
      ByteSwap(&header.type);
      ByteSwap(&header.misc);
      ByteSwap(&header.size);
    }

    if (header.size == 0) {
      // Avoid an infinite loop.
      LOG(ERROR) << "Event size is zero. Type: " << header.type;
      return false;
    }

    if (data.size < offset + header.size) {
      LOG(ERROR) << "Not enough bytes to read piped event.  Required: "
                 << header.size << " bytes.  Available: "
                 << data.size - offset << " bytes.";
      return true;
    }

    size_t new_offset = offset + sizeof(header);
    size_t size_without_header = header.size - sizeof(header);

    if (header.type < PERF_RECORD_MAX) {
      const event_t* event =
          reinterpret_cast<const event_t*>(data.ptr + offset);
      result = ReadPerfEventBlock(*event);
      offset += header.size;
      continue;
    }

    switch (header.type) {
    case PERF_RECORD_HEADER_ATTR:
      result = ReadAttrEventBlock(data, new_offset, size_without_header);
      break;
    case PERF_RECORD_HEADER_EVENT_TYPE:
      result = ReadEventType(data, &new_offset);
      break;
    case PERF_RECORD_HEADER_EVENT_DESC:
      break;
    case PERF_RECORD_HEADER_BUILD_ID:
      metadata_mask_ |= (1 << HEADER_BUILD_ID);
      result = ReadBuildIDMetadata(data, HEADER_BUILD_ID, offset, header.size);
      break;
    case PERF_RECORD_HEADER_HOSTNAME:
      metadata_mask_ |= (1 << HEADER_HOSTNAME);
      result = ReadStringMetadata(data, HEADER_HOSTNAME, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_OSRELEASE:
      metadata_mask_ |= (1 << HEADER_OSRELEASE);
      result = ReadStringMetadata(data, HEADER_OSRELEASE, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_VERSION:
      metadata_mask_ |= (1 << HEADER_VERSION);
      result = ReadStringMetadata(data, HEADER_VERSION, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_ARCH:
      metadata_mask_ |= (1 << HEADER_ARCH);
      result = ReadStringMetadata(data, HEADER_ARCH, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_CPUDESC:
      metadata_mask_ |= (1 << HEADER_CPUDESC);
      result = ReadStringMetadata(data, HEADER_CPUDESC, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_CPUID:
      metadata_mask_ |= (1 << HEADER_CPUID);
      result = ReadStringMetadata(data, HEADER_CPUID, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_CMDLINE:
      metadata_mask_ |= (1 << HEADER_CMDLINE);
      result = ReadStringMetadata(data, HEADER_CMDLINE, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_NRCPUS:
      metadata_mask_ |= (1 << HEADER_NRCPUS);
      result = ReadUint32Metadata(data, HEADER_NRCPUS, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_TOTAL_MEM:
      metadata_mask_ |= (1 << HEADER_TOTAL_MEM);
      result = ReadUint64Metadata(data, HEADER_TOTAL_MEM, new_offset,
                                  size_without_header);
      break;
    case PERF_RECORD_HEADER_CPU_TOPOLOGY:
      metadata_mask_ |= (1 << HEADER_CPU_TOPOLOGY);
      result = ReadCPUTopologyMetadata(data, HEADER_CPU_TOPOLOGY, new_offset,
                                       size_without_header);
      break;
    case PERF_RECORD_HEADER_NUMA_TOPOLOGY:
      metadata_mask_ |= (1 << HEADER_NUMA_TOPOLOGY);
      result = ReadNUMATopologyMetadata(data, HEADER_NUMA_TOPOLOGY, new_offset,
                                        size_without_header);
      break;
    default:
      LOG(WARNING) << "Event type " << header.type
                   << " is not yet supported!";
      break;
    }
    offset += header.size;
  }

  if (!result) {
    return false;
  }
  // Event type events are optional in some newer versions of perf. They
  // contain the same information that is already in |attrs_|. Make sure the
  // number of event types matches the number of attrs, but only if there are
  // event type events present.
  if (event_types_.size() > 0) {
    if (event_types_.size() != attrs_.size()) {
      LOG(ERROR) << "Mismatch between number of event type events and attr "
                 << "events: " << event_types_.size() << " vs "
                 << attrs_.size();
      return false;
    }
    metadata_mask_ |= (1 << HEADER_EVENT_DESC);
  }
  return result;
}

bool PerfReader::WriteHeader(const BufferWithSize& data) const {
  CheckNoEventHeaderPadding();
  size_t size = sizeof(out_header_);
  size_t offset = 0;
  return WriteDataToBuffer(&out_header_, size, "file header", &offset, data);
}

bool PerfReader::WriteAttrs(const BufferWithSize& data) const {
  CheckNoPerfEventAttrPadding();
  size_t offset = out_header_.attrs.offset;
  size_t id_offset = out_header_.size;

  for (size_t i = 0; i < attrs_.size(); i++) {
    const PerfFileAttr& attr = attrs_[i];
    struct perf_file_section ids;
    ids.offset = id_offset;
    ids.size = attr.ids.size() * sizeof(attr.ids[0]);

    for (size_t j = 0; j < attr.ids.size(); j++) {
      const uint64 id = attr.ids[j];
      if (!WriteDataToBuffer(&id, sizeof(id), "ID info", &id_offset, data))
        return false;
    }

    if (!WriteDataToBuffer(&attr.attr, sizeof(attr.attr), "attribute",
                           &offset, data) ||
        !WriteDataToBuffer(&ids, sizeof(ids), "ID section", &offset, data)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::WriteData(const BufferWithSize& data) const {
  size_t offset = out_header_.data.offset;
  for (size_t i = 0; i < events_.size(); ++i) {
    if (!WriteDataToBuffer(events_[i], events_[i]->header.size, "event data",
                           &offset, data)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::WriteMetadata(const BufferWithSize& data) const {
  size_t header_offset = out_header_.data.offset + out_header_.data.size;

  // Before writing the metadata, there is one header for each piece
  // of metadata, and one extra showing the end of the file.
  // Each header contains two 64-bit numbers (offset and size).
  size_t metadata_offset =
      header_offset + (GetNumMetadata() + 1) * 2 * sizeof(u64);

  // Zero out the memory used by the headers
  memset(data.ptr + header_offset, 0,
         (metadata_offset - header_offset) * sizeof(*data.ptr));

  for (u32 type = HEADER_FIRST_FEATURE; type != HEADER_LAST_FEATURE; ++type) {
    if ((out_header_.adds_features[0] & (1 << type)) == 0)
      continue;

    u64 start_offset = metadata_offset;
    // Write actual metadata to address metadata_offset
    switch (type) {
    case HEADER_BUILD_ID:
      if (!WriteBuildIDMetadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_HOSTNAME:
    case HEADER_OSRELEASE:
    case HEADER_VERSION:
    case HEADER_ARCH:
    case HEADER_CPUDESC:
    case HEADER_CPUID:
    case HEADER_CMDLINE:
      if (!WriteStringMetadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_NRCPUS:
      if (!WriteUint32Metadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_TOTAL_MEM:
      if (!WriteUint64Metadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_EVENT_DESC:
      if (!WriteEventDescMetadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_CPU_TOPOLOGY:
      if (!WriteCPUTopologyMetadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_NUMA_TOPOLOGY:
      if (!WriteNUMATopologyMetadata(type, &metadata_offset, data))
        return false;
      break;
    case HEADER_BRANCH_STACK:
      continue;
    default: LOG(ERROR) << "Unsupported metadata type: " << type;
      return false;
    }

    // Write metadata offset and size to address header_offset.
    u64 metadata_size = metadata_offset - start_offset;
    if (!WriteDataToBuffer(&start_offset, sizeof(start_offset),
                           "metadata offset", &header_offset, data) ||
        !WriteDataToBuffer(&metadata_size, sizeof(metadata_size),
                           "metadata size", &header_offset, data)) {
      return false;
    }
  }

  // Write the last entry - a pointer to the end of the file
  if (!WriteDataToBuffer(&metadata_offset, sizeof(metadata_offset),
                         "metadata offset", &header_offset, data)) {
    return false;
  }

  return true;
}

bool PerfReader::WriteBuildIDMetadata(u32 type, size_t* offset,
                                      const BufferWithSize& data) const {
  CheckNoBuildIDEventPadding();
  for (size_t i = 0; i < build_id_events_.size(); ++i) {
    const build_id_event* event = build_id_events_[i];
    if (!WriteDataToBuffer(event, event->header.size, "Build ID metadata",
                           offset, data)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::WriteStringMetadata(u32 type, size_t* offset,
                                     const BufferWithSize& data) const {
  for (size_t i = 0; i < string_metadata_.size(); ++i) {
    const PerfStringMetadata& str_data = string_metadata_[i];
    if (str_data.type == type) {
      num_string_data_type num_strings = str_data.data.size();
      if (NeedsNumberOfStringData(type) &&
          !WriteDataToBuffer(&num_strings, sizeof(num_strings),
                             "number of string metadata", offset, data)) {
        return false;
      }

      for (size_t j = 0; j < num_strings; ++j) {
        const CStringWithLength& single_string = str_data.data[j];
        if (!WriteStringToBuffer(single_string, data, offset))
          return false;
      }

      return true;
    }
  }
  LOG(ERROR) << "String metadata of type " << type << " not present";
  return false;
}

bool PerfReader::WriteUint32Metadata(u32 type, size_t* offset,
                                     const BufferWithSize& data) const {
  for (size_t i = 0; i < uint32_metadata_.size(); ++i) {
    const PerfUint32Metadata& uint32_data = uint32_metadata_[i];
    if (uint32_data.type == type) {
      const std::vector<uint32>& int_vector = uint32_data.data;

      for (size_t j = 0; j < int_vector.size(); ++j) {
        if (!WriteDataToBuffer(&int_vector[j], sizeof(int_vector[j]),
                               "uint32 metadata", offset, data)) {
          return false;
        }
      }

      return true;
    }
  }
  LOG(ERROR) << "Uint32 metadata of type " << type << " not present";
  return false;
}

bool PerfReader::WriteUint64Metadata(u32 type, size_t* offset,
                                     const BufferWithSize& data) const {
  for (size_t i = 0; i < uint64_metadata_.size(); ++i) {
    const PerfUint64Metadata& uint64_data = uint64_metadata_[i];
    if (uint64_data.type == type) {
      const std::vector<uint64>& int_vector = uint64_data.data;

      for (size_t j = 0; j < int_vector.size(); ++j) {
        if (!WriteDataToBuffer(&int_vector[j], sizeof(int_vector[j]),
                               "uint64 metadata", offset, data)) {
          return false;
        }
      }

      return true;
    }
  }
  LOG(ERROR) << "Uint64 metadata of type " << type << " not present";
  return false;
}

bool PerfReader::WriteEventDescMetadata(u32 type, size_t* offset,
                                        const BufferWithSize& data) const {
  if (event_types_.empty()) {
    return true;
  }

  CheckNoPerfEventAttrPadding();

  // There should be an attribute for each event type.
  if (event_types_.size() != attrs_.size()) {
    LOG(ERROR) << "Mismatch between number of event type events and attr "
               << "events: " << event_types_.size() << " vs "
               << attrs_.size();
    return false;
  }

  event_desc_num_events num_events = event_types_.size();
  if (!WriteDataToBuffer(&num_events, sizeof(num_events),
                         "event_desc num_events", offset, data)) {
    return false;
  }
  event_desc_attr_size attr_size = sizeof(perf_event_attr);
  if (!WriteDataToBuffer(&attr_size, sizeof(attr_size),
                         "event_desc attr_size", offset, data)) {
    return false;
  }

  for (size_t i = 0; i < num_events; ++i) {
    const perf_trace_event_type event_type = event_types_[i];
    const PerfFileAttr& attr = attrs_[i];
    if (!WriteDataToBuffer(&attr.attr, sizeof(attr.attr),
                           "event_desc attribute", offset, data)) {
      return false;
    }

    event_desc_num_unique_ids num_ids = attr.ids.size();
    if (!WriteDataToBuffer(&num_ids, sizeof(num_ids),
                           "event_desc num_unique_ids", offset, data)) {
      return false;
    }

    CStringWithLength container;
    container.len = GetUint64AlignedStringLength(event_type.name);
    container.str = string(event_type.name);
    if (!WriteStringToBuffer(container, data, offset))
      return false;

    if (!WriteDataToBuffer(&attr.ids[0], num_ids * sizeof(attr.ids[0]),
                           "event_desc unique_ids", offset, data)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::WriteCPUTopologyMetadata(u32 type, size_t* offset,
                                          const BufferWithSize& data) const {
  const std::vector<CStringWithLength>& cores = cpu_topology_.core_siblings;
  num_siblings_type num_cores = cores.size();
  if (!WriteDataToBuffer(&num_cores, sizeof(num_cores), "num cores",
                         offset, data)) {
    return false;
  }
  for (size_t i = 0; i < num_cores; ++i) {
    if (!WriteStringToBuffer(cores[i], data, offset))
      return false;
  }

  const std::vector<CStringWithLength>& threads = cpu_topology_.thread_siblings;
  num_siblings_type num_threads = threads.size();
  if (!WriteDataToBuffer(&num_threads, sizeof(num_threads), "num threads",
                         offset, data)) {
    return false;
  }
  for (size_t i = 0; i < num_threads; ++i) {
    if (!WriteStringToBuffer(threads[i], data, offset))
      return false;
  }

  return true;
}

bool PerfReader::WriteNUMATopologyMetadata(u32 type, size_t* offset,
                                           const BufferWithSize& data) const {
  numa_topology_num_nodes_type num_nodes = numa_topology_.size();
  if (!WriteDataToBuffer(&num_nodes, sizeof(num_nodes), "num nodes",
                         offset, data)) {
    return false;
  }

  for (size_t i = 0; i < num_nodes; ++i) {
    const PerfNodeTopologyMetadata& node = numa_topology_[i];
    if (!WriteDataToBuffer(&node.id, sizeof(node.id), "node id",
                           offset, data) ||
        !WriteDataToBuffer(&node.total_memory, sizeof(node.total_memory),
                           "node total memory", offset, data) ||
        !WriteDataToBuffer(&node.free_memory, sizeof(node.free_memory),
                           "node free memory", offset, data) ||
        !WriteStringToBuffer(node.cpu_list, data, offset)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::WriteEventTypes(const BufferWithSize& data) const {
  CheckNoEventTypePadding();
  size_t offset = out_header_.event_types.offset;
  for (size_t i = 0; i < event_types_.size(); ++i) {
    const struct perf_trace_event_type& event_type = event_types_[i];
    if (!WriteDataToBuffer(&event_type, sizeof(event_type), "event type info",
                           &offset, data)) {
      return false;
    }
  }
  return true;
}

bool PerfReader::ReadAttrEventBlock(const ConstBufferWithSize& data,
                                    size_t offset, size_t size) {
  PerfFileAttr attr;
  if (!ReadEventAttr(data, &offset, &attr.attr))
    return false;

  size_t num_ids = (size - attr.attr.size) / sizeof(attr.ids[0]);
  if (!ReadUniqueIDs(data, num_ids, &offset, &attr.ids))
    return false;

  // Event types are found many times in the perf data file.
  // Only add this event type if it is not already present.
  for (size_t i = 0; i < attrs_.size(); ++i) {
    if (attrs_[i].ids[0] == attr.ids[0])
      return true;
  }
  attrs_.push_back(attr);
  return true;
}

// When this method is called, |event| is a reference to the bytes in the data
// vector that contains the entire perf.data file.  As a result, we need to be
// careful to only copy event.header.size bytes.
// In particular, something like
// event_t event_copy = event;
// would be bad, because it would read past the end of the event, and possibly
// pass the end of the data vector as well.
bool PerfReader::ReadPerfEventBlock(const event_t& event) {
  u16 size = event.header.size;
  if (is_cross_endian_)
    ByteSwap(&size);

  if (size > sizeof(event_t)) {
    LOG(INFO) << "Data size: " << size << " sizeof(event_t): "
              << sizeof(event_t);
    return false;
  }

  // Copy only the part of the event that is needed.
  event_t* event_copy = CallocMemoryForEvent(size);
  memcpy(event_copy, &event, size);
  if (is_cross_endian_) {
    ByteSwap(&event_copy->header.type);
    ByteSwap(&event_copy->header.misc);
    ByteSwap(&event_copy->header.size);
  }

  uint32 type = event_copy->header.type;
  if (is_cross_endian_) {
    switch (type) {
    case PERF_RECORD_SAMPLE:
      ByteSwap(&event_copy->ip.ip);
      ByteSwap(&event_copy->ip.pid);
      ByteSwap(&event_copy->ip.tid);
      break;
    case PERF_RECORD_MMAP:
      ByteSwap(&event_copy->mmap.pid);
      ByteSwap(&event_copy->mmap.tid);
      ByteSwap(&event_copy->mmap.start);
      ByteSwap(&event_copy->mmap.len);
      ByteSwap(&event_copy->mmap.pgoff);
      break;
    case PERF_RECORD_FORK:
    case PERF_RECORD_EXIT:
      ByteSwap(&event_copy->fork.pid);
      ByteSwap(&event_copy->fork.tid);
      ByteSwap(&event_copy->fork.ppid);
      ByteSwap(&event_copy->fork.ptid);
      break;
    case PERF_RECORD_COMM:
      ByteSwap(&event_copy->comm.pid);
      ByteSwap(&event_copy->comm.tid);
      break;
    case PERF_RECORD_LOST:
      ByteSwap(&event_copy->lost.id);
      ByteSwap(&event_copy->lost.lost);
      break;
    case PERF_RECORD_THROTTLE:
    case PERF_RECORD_UNTHROTTLE:
      ByteSwap(&event_copy->throttle.time);
      ByteSwap(&event_copy->throttle.id);
      ByteSwap(&event_copy->throttle.stream_id);
      break;
    case PERF_RECORD_READ:
      ByteSwap(&event_copy->read.pid);
      ByteSwap(&event_copy->read.tid);
      ByteSwap(&event_copy->read.value);
      ByteSwap(&event_copy->read.time_enabled);
      ByteSwap(&event_copy->read.time_running);
      ByteSwap(&event_copy->read.id);
      break;
    default:
      LOG(FATAL) << "Unknown event type: " << type;
    }
  }

  events_.push_back(event_copy);

  return true;
}

size_t PerfReader::GetNumMetadata() const {
  // This is just the number of 1s in the binary representation of the metadata
  // mask.  However, make sure to only use supported metadata, and don't include
  // branch stack (since it doesn't have an entry in the metadata section).
  uint64 new_mask = metadata_mask_;
  new_mask &= kSupportedMetadataMask & ~(1 << HEADER_BRANCH_STACK);
  std::bitset<sizeof(new_mask) * CHAR_BIT> bits(new_mask);
  return bits.count();
}

size_t PerfReader::GetEventDescMetadataSize() const {
  size_t size = 0;
  if (event_types_.empty()) {
    return size;
  }
  if (metadata_mask_ & (1 << HEADER_EVENT_DESC)) {
    if (event_types_.size() > 0 && event_types_.size() != attrs_.size()) {
      LOG(ERROR) << "Mismatch between number of event type events and attr "
                 << "events: " << event_types_.size() << " vs "
                 << attrs_.size();
      return size;
    }
    size += sizeof(event_desc_num_events) + sizeof(event_desc_attr_size);
    CStringWithLength dummy;
    for (size_t i = 0; i < attrs_.size(); ++i) {
      size += sizeof(perf_event_attr) + sizeof(dummy.len);
      size += sizeof(event_desc_num_unique_ids);
      size += GetUint64AlignedStringLength(event_types_[i].name) * sizeof(char);
      size += attrs_[i].ids.size() * sizeof(attrs_[i].ids[0]);
    }
  }
  return size;
}

size_t PerfReader::GetBuildIDMetadataSize() const {
  size_t size = 0;
  for (size_t i = 0; i < build_id_events_.size(); ++i)
    size += build_id_events_[i]->header.size;
  return size;
}

size_t PerfReader::GetStringMetadataSize() const {
  size_t size = 0;
  for (size_t i = 0; i < string_metadata_.size(); ++i) {
    const PerfStringMetadata& metadata = string_metadata_[i];
    if (NeedsNumberOfStringData(metadata.type))
      size += sizeof(num_string_data_type);

    for (size_t j = 0; j < metadata.data.size(); ++j) {
      const CStringWithLength& str = metadata.data[j];
      size += sizeof(str.len) + (str.len * sizeof(char));
    }
  }
  return size;
}

size_t PerfReader::GetUint32MetadataSize() const {
  size_t size = 0;
  for (size_t i = 0; i < uint32_metadata_.size(); ++i) {
    const PerfUint32Metadata& metadata = uint32_metadata_[i];
    size += metadata.data.size() * sizeof(metadata.data[0]);
  }
  return size;
}

size_t PerfReader::GetUint64MetadataSize() const {
  size_t size = 0;
  for (size_t i = 0; i < uint64_metadata_.size(); ++i) {
    const PerfUint64Metadata& metadata = uint64_metadata_[i];
    size += metadata.data.size() * sizeof(metadata.data[0]);
  }
  return size;
}

size_t PerfReader::GetCPUTopologyMetadataSize() const {
  // Core siblings.
  size_t size = sizeof(num_siblings_type);
  for (size_t i = 0; i < cpu_topology_.core_siblings.size(); ++i) {
    const CStringWithLength& str = cpu_topology_.core_siblings[i];
    size += sizeof(str.len) + (str.len * sizeof(char));
  }

  // Thread siblings.
  size += sizeof(num_siblings_type);
  for (size_t i = 0; i < cpu_topology_.thread_siblings.size(); ++i) {
    const CStringWithLength& str = cpu_topology_.thread_siblings[i];
    size += sizeof(str.len) + (str.len * sizeof(char));
  }

  return size;
}

size_t PerfReader::GetNUMATopologyMetadataSize() const {
  size_t size = sizeof(numa_topology_num_nodes_type);
  for (size_t i = 0; i < numa_topology_.size(); ++i) {
    const PerfNodeTopologyMetadata& node = numa_topology_[i];
    size += sizeof(node.id);
    size += sizeof(node.total_memory) + sizeof(node.free_memory);
    size += sizeof(node.cpu_list.len) + node.cpu_list.len * sizeof(char);
  }
  return size;
}

bool PerfReader::NeedsNumberOfStringData(u32 type) const {
  return type == HEADER_CMDLINE;
}

bool PerfReader::LocalizeMMapFilenames(
    const std::map<string, string>& filename_map) {
  // Search for mmap events for which the filename needs to be updated.
  for (size_t i = 0; i < events_.size(); ++i) {
    event_t* event = events_[i];
    if (event->header.type != PERF_RECORD_MMAP)
      continue;

    string key = string(event->mmap.filename);
    if (filename_map.find(key) == filename_map.end())
      continue;

    string new_filename = filename_map.at(key);
    size_t old_len = GetUint64AlignedStringLength(key);
    size_t new_len = GetUint64AlignedStringLength(new_filename);
    size_t old_offset = GetPerfSampleDataOffset(*event);
    size_t sample_size = event->header.size - old_offset;

    int size_increase = new_len - old_len;
    size_t new_size = event->header.size + size_increase;
    size_t new_offset = old_offset + size_increase;

    if (size_increase > 0) {
      // Allocate memory for a new event.
      event_t* old_event = event;
      event = CallocMemoryForEvent(new_size);

      // Copy over everything except filename and sample info.
      memcpy(event, old_event,
             sizeof(event->mmap) - sizeof(event->mmap.filename));

      // Copy over the sample info to the correct location.
      char* old_addr = reinterpret_cast<char*>(old_event);
      char* new_addr = reinterpret_cast<char*>(event);
      memcpy(new_addr + new_offset, old_addr + old_offset, sample_size);

      free(old_event);
      events_[i] = event;
    } else if (size_increase < 0) {
      // Move the perf sample data to its new location.
      // Since source and dest could overlap, use memmove instead of memcpy.
      char* start_addr = reinterpret_cast<char*>(event);
      memmove(start_addr + new_offset, start_addr + old_offset, sample_size);
    }

    // Copy over the new filename and fix the size of the event.
    CHECK_GT(snprintf(event->mmap.filename, new_filename.size() + 1, "%s",
                      new_filename.c_str()),
             0);
    event->header.size = new_size;
  }

  return true;
}

}  // namespace quipper