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// Copyright 2019 the V8 project 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 "src/inspector/v8-string-conversions.h"
#include <limits>
#include <vector>
#include "src/base/logging.h"
#include "src/base/v8-fallthrough.h"
namespace v8_inspector {
namespace {
using UChar = uint16_t;
using UChar32 = uint32_t;
bool isASCII(UChar c) { return !(c & ~0x7F); }
const UChar replacementCharacter = 0xFFFD;
inline int inlineUTF8SequenceLengthNonASCII(char b0) {
if ((b0 & 0xC0) != 0xC0) return 0;
if ((b0 & 0xE0) == 0xC0) return 2;
if ((b0 & 0xF0) == 0xE0) return 3;
if ((b0 & 0xF8) == 0xF0) return 4;
return 0;
}
inline int inlineUTF8SequenceLength(char b0) {
return isASCII(b0) ? 1 : inlineUTF8SequenceLengthNonASCII(b0);
}
// Once the bits are split out into bytes of UTF-8, this is a mask OR-ed
// into the first byte, depending on how many bytes follow. There are
// as many entries in this table as there are UTF-8 sequence types.
// (I.e., one byte sequence, two byte... etc.). Remember that sequences
// for *legal* UTF-8 will be 4 or fewer bytes total.
static const unsigned char firstByteMark[7] = {0x00, 0x00, 0xC0, 0xE0,
0xF0, 0xF8, 0xFC};
typedef enum {
conversionOK, // conversion successful
sourceExhausted, // partial character in source, but hit end
targetExhausted, // insuff. room in target for conversion
sourceIllegal // source sequence is illegal/malformed
} ConversionResult;
ConversionResult convertUTF16ToUTF8(const UChar** sourceStart,
const UChar* sourceEnd, char** targetStart,
char* targetEnd, bool strict) {
ConversionResult result = conversionOK;
const UChar* source = *sourceStart;
char* target = *targetStart;
while (source < sourceEnd) {
UChar32 ch;
uint32_t bytesToWrite = 0;
const UChar32 byteMask = 0xBF;
const UChar32 byteMark = 0x80;
const UChar* oldSource =
source; // In case we have to back up because of target overflow.
ch = static_cast<uint16_t>(*source++);
// If we have a surrogate pair, convert to UChar32 first.
if (ch >= 0xD800 && ch <= 0xDBFF) {
// If the 16 bits following the high surrogate are in the source buffer...
if (source < sourceEnd) {
UChar32 ch2 = static_cast<uint16_t>(*source);
// If it's a low surrogate, convert to UChar32.
if (ch2 >= 0xDC00 && ch2 <= 0xDFFF) {
ch = ((ch - 0xD800) << 10) + (ch2 - 0xDC00) + 0x0010000;
++source;
} else if (strict) { // it's an unpaired high surrogate
--source; // return to the illegal value itself
result = sourceIllegal;
break;
}
} else { // We don't have the 16 bits following the high surrogate.
--source; // return to the high surrogate
result = sourceExhausted;
break;
}
} else if (strict) {
// UTF-16 surrogate values are illegal in UTF-32
if (ch >= 0xDC00 && ch <= 0xDFFF) {
--source; // return to the illegal value itself
result = sourceIllegal;
break;
}
}
// Figure out how many bytes the result will require
if (ch < static_cast<UChar32>(0x80)) {
bytesToWrite = 1;
} else if (ch < static_cast<UChar32>(0x800)) {
bytesToWrite = 2;
} else if (ch < static_cast<UChar32>(0x10000)) {
bytesToWrite = 3;
} else if (ch < static_cast<UChar32>(0x110000)) {
bytesToWrite = 4;
} else {
bytesToWrite = 3;
ch = replacementCharacter;
}
target += bytesToWrite;
if (target > targetEnd) {
source = oldSource; // Back up source pointer!
target -= bytesToWrite;
result = targetExhausted;
break;
}
switch (bytesToWrite) {
case 4:
*--target = static_cast<char>((ch | byteMark) & byteMask);
ch >>= 6;
V8_FALLTHROUGH;
case 3:
*--target = static_cast<char>((ch | byteMark) & byteMask);
ch >>= 6;
V8_FALLTHROUGH;
case 2:
*--target = static_cast<char>((ch | byteMark) & byteMask);
ch >>= 6;
V8_FALLTHROUGH;
case 1:
*--target = static_cast<char>(ch | firstByteMark[bytesToWrite]);
}
target += bytesToWrite;
}
*sourceStart = source;
*targetStart = target;
return result;
}
/**
* Is this code point a BMP code point (U+0000..U+ffff)?
* @param c 32-bit code point
* @return TRUE or FALSE
* @stable ICU 2.8
*/
#define U_IS_BMP(c) ((uint32_t)(c) <= 0xFFFF)
/**
* Is this code point a supplementary code point (U+010000..U+10FFFF)?
* @param c 32-bit code point
* @return TRUE or FALSE
* @stable ICU 2.8
*/
#define U_IS_SUPPLEMENTARY(c) ((uint32_t)((c)-0x010000) <= 0xFFFFF)
/**
* Is this code point a surrogate (U+d800..U+dfff)?
* @param c 32-bit code point
* @return TRUE or FALSE
* @stable ICU 2.4
*/
#define U_IS_SURROGATE(c) (((c)&0xFFFFF800) == 0xD800)
/**
* Get the lead surrogate (0xD800..0xDBFF) for a
* supplementary code point (0x010000..0x10FFFF).
* @param supplementary 32-bit code point (U+010000..U+10FFFF)
* @return lead surrogate (U+D800..U+DBFF) for supplementary
* @stable ICU 2.4
*/
#define U16_LEAD(supplementary) (UChar)(((supplementary) >> 10) + 0xD7C0)
/**
* Get the trail surrogate (0xDC00..0xDFFF) for a
* supplementary code point (0x010000..0x10FFFF).
* @param supplementary 32-bit code point (U+010000..U+10FFFF)
* @return trail surrogate (U+DC00..U+DFFF) for supplementary
* @stable ICU 2.4
*/
#define U16_TRAIL(supplementary) (UChar)(((supplementary)&0x3FF) | 0xDC00)
// This must be called with the length pre-determined by the first byte.
// If presented with a length > 4, this returns false. The Unicode
// definition of UTF-8 goes up to 4-byte sequences.
static bool isLegalUTF8(const unsigned char* source, int length) {
unsigned char a;
const unsigned char* srcptr = source + length;
switch (length) {
default:
return false;
// Everything else falls through when "true"...
case 4:
if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
V8_FALLTHROUGH;
case 3:
if ((a = (*--srcptr)) < 0x80 || a > 0xBF) return false;
V8_FALLTHROUGH;
case 2:
if ((a = (*--srcptr)) > 0xBF) return false;
// no fall-through in this inner switch
switch (*source) {
case 0xE0:
if (a < 0xA0) return false;
break;
case 0xED:
if (a > 0x9F) return false;
break;
case 0xF0:
if (a < 0x90) return false;
break;
case 0xF4:
if (a > 0x8F) return false;
break;
default:
if (a < 0x80) return false;
}
V8_FALLTHROUGH;
case 1:
if (*source >= 0x80 && *source < 0xC2) return false;
}
if (*source > 0xF4) return false;
return true;
}
// Magic values subtracted from a buffer value during UTF8 conversion.
// This table contains as many values as there might be trailing bytes
// in a UTF-8 sequence.
static const UChar32 offsetsFromUTF8[6] = {0x00000000UL,
0x00003080UL,
0x000E2080UL,
0x03C82080UL,
static_cast<UChar32>(0xFA082080UL),
static_cast<UChar32>(0x82082080UL)};
static inline UChar32 readUTF8Sequence(const char*& sequence, size_t length) {
UChar32 character = 0;
// The cases all fall through.
switch (length) {
case 6:
character += static_cast<unsigned char>(*sequence++);
character <<= 6;
V8_FALLTHROUGH;
case 5:
character += static_cast<unsigned char>(*sequence++);
character <<= 6;
V8_FALLTHROUGH;
case 4:
character += static_cast<unsigned char>(*sequence++);
character <<= 6;
V8_FALLTHROUGH;
case 3:
character += static_cast<unsigned char>(*sequence++);
character <<= 6;
V8_FALLTHROUGH;
case 2:
character += static_cast<unsigned char>(*sequence++);
character <<= 6;
V8_FALLTHROUGH;
case 1:
character += static_cast<unsigned char>(*sequence++);
}
return character - offsetsFromUTF8[length - 1];
}
ConversionResult convertUTF8ToUTF16(const char** sourceStart,
const char* sourceEnd, UChar** targetStart,
UChar* targetEnd, bool* sourceAllASCII,
bool strict) {
ConversionResult result = conversionOK;
const char* source = *sourceStart;
UChar* target = *targetStart;
UChar orAllData = 0;
while (source < sourceEnd) {
int utf8SequenceLength = inlineUTF8SequenceLength(*source);
if (sourceEnd - source < utf8SequenceLength) {
result = sourceExhausted;
break;
}
// Do this check whether lenient or strict
if (!isLegalUTF8(reinterpret_cast<const unsigned char*>(source),
utf8SequenceLength)) {
result = sourceIllegal;
break;
}
UChar32 character = readUTF8Sequence(source, utf8SequenceLength);
if (target >= targetEnd) {
source -= utf8SequenceLength; // Back up source pointer!
result = targetExhausted;
break;
}
if (U_IS_BMP(character)) {
// UTF-16 surrogate values are illegal in UTF-32
if (U_IS_SURROGATE(character)) {
if (strict) {
source -= utf8SequenceLength; // return to the illegal value itself
result = sourceIllegal;
break;
}
*target++ = replacementCharacter;
orAllData |= replacementCharacter;
} else {
*target++ = static_cast<UChar>(character); // normal case
orAllData |= character;
}
} else if (U_IS_SUPPLEMENTARY(character)) {
// target is a character in range 0xFFFF - 0x10FFFF
if (target + 1 >= targetEnd) {
source -= utf8SequenceLength; // Back up source pointer!
result = targetExhausted;
break;
}
*target++ = U16_LEAD(character);
*target++ = U16_TRAIL(character);
orAllData = 0xFFFF;
} else {
if (strict) {
source -= utf8SequenceLength; // return to the start
result = sourceIllegal;
break; // Bail out; shouldn't continue
} else {
*target++ = replacementCharacter;
orAllData |= replacementCharacter;
}
}
}
*sourceStart = source;
*targetStart = target;
if (sourceAllASCII) *sourceAllASCII = !(orAllData & ~0x7F);
return result;
}
// Helper to write a three-byte UTF-8 code point to the buffer, caller must
// check room is available.
static inline void putUTF8Triple(char*& buffer, UChar ch) {
*buffer++ = static_cast<char>(((ch >> 12) & 0x0F) | 0xE0);
*buffer++ = static_cast<char>(((ch >> 6) & 0x3F) | 0x80);
*buffer++ = static_cast<char>((ch & 0x3F) | 0x80);
}
} // namespace
std::string UTF16ToUTF8(const UChar* stringStart, size_t length) {
if (!stringStart || !length) return std::string();
// Allocate a buffer big enough to hold all the characters
// (an individual UTF-16 UChar can only expand to 3 UTF-8 bytes).
// Optimization ideas, if we find this function is hot:
// * We could speculatively create a CStringBuffer to contain 'length'
// characters, and resize if necessary (i.e. if the buffer contains
// non-ascii characters). (Alternatively, scan the buffer first for
// ascii characters, so we know this will be sufficient).
// * We could allocate a CStringBuffer with an appropriate size to
// have a good chance of being able to write the string into the
// buffer without reallocing (say, 1.5 x length).
if (length > std::numeric_limits<unsigned>::max() / 3) return std::string();
std::string output(length * 3, '\0');
const UChar* characters = stringStart;
const UChar* characters_end = characters + length;
char* buffer = &*output.begin();
char* buffer_end = &*output.end();
while (characters < characters_end) {
// Use strict conversion to detect unpaired surrogates.
ConversionResult result = convertUTF16ToUTF8(
&characters, characters_end, &buffer, buffer_end, /* strict= */ true);
DCHECK_NE(result, targetExhausted);
// Conversion fails when there is an unpaired surrogate. Put
// replacement character (U+FFFD) instead of the unpaired
// surrogate.
if (result != conversionOK) {
DCHECK_LE(0xD800, *characters);
DCHECK_LE(*characters, 0xDFFF);
// There should be room left, since one UChar hasn't been
// converted.
DCHECK_LE(buffer + 3, buffer_end);
putUTF8Triple(buffer, replacementCharacter);
++characters;
}
}
output.resize(buffer - output.data());
return output;
}
std::basic_string<UChar> UTF8ToUTF16(const char* stringStart, size_t length) {
if (!stringStart || !length) return std::basic_string<UChar>();
std::vector<uint16_t> buffer(length);
UChar* bufferStart = buffer.data();
UChar* bufferCurrent = bufferStart;
const char* stringCurrent = reinterpret_cast<const char*>(stringStart);
if (convertUTF8ToUTF16(&stringCurrent,
reinterpret_cast<const char*>(stringStart + length),
&bufferCurrent, bufferCurrent + buffer.size(), nullptr,
true) != conversionOK)
return std::basic_string<uint16_t>();
size_t utf16Length = bufferCurrent - bufferStart;
return std::basic_string<UChar>(bufferStart, bufferStart + utf16Length);
}
} // namespace v8_inspector