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// Copyright 2022 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef IPCZ_INCLUDE_IPCZ_IPCZ_H_
#define IPCZ_INCLUDE_IPCZ_IPCZ_H_
// ipcz is a cross-platform C library for interprocess communication (IPC) which
// supports efficient routing and data transfer over a large number of
// dynamically relocatable messaging endpoints.
//
// ipcz operates in terms of a small handful of abstractions encapsulated in
// this header: nodes, portals, parcels, drivers, boxes, and traps.
//
// NOTE: This header is intended to compile under C++11 or newer, and C99 or
// newer. The ABI defined here can be considered stable.
//
// Glossary
// --------
// *Nodes* are used by ipcz to model isolated units of an application. A typical
// application will create one ipcz node within each OS process it controls.
//
// *Portals* are messaging endpoints which belong to a specific node. Portals
// are created in entangled pairs: whatever goes into one portal comes out the
// other (its "peer"). Pairs may be created local to a single node, or they may
// be created to span two nodes. Portals may also be transferred freely through
// other portals.
//
// *Parcels* are the unit of communication between portals. Parcels can contain
// arbitrary application data as well as ipcz handles. Handles within a parcel
// are used to transfer objects (namely other portals, or driver-defined
// objects) from one portal to another, potentially on a different node.
//
// *Traps* provide a flexible mechanism to observe interesting portal state
// changes such as new parcels arriving or a portal's peer being closed.
//
// *Drivers* are provided by applications to implement platform-specific IPC
// details. They may also define new types of objects to be transmitted in
// parcels via boxes.
//
// *Boxes* are opaque objects used to wrap driver-defined objects for seamless
// transmission across portals. Drivers define how to serialize and deserialize
// such objects, and applications use the Box() and Unbox() APIs to go between
// concrete driver objects and transferrable handles.
//
// Overview
// --------
// To use ipcz effectively, an application must create multiple nodes to be
// interconnected. One node must be designated as the "broker" by the
// application (see CreateNode() flags). The broker is used by ipcz to
// coordinate certain types of internal transactions which demand a heightened
// level of trust and capability, so a broker node should always live in a more
// trustworthy process. For example in Chrome, the browser process is
// designated as the broker.
//
// In order for a node to communicate with other nodes in the system, the
// application must explicitly connect it to ONE other node using the
// ConnectNode() API. Once this is done, ipcz can automatically connect the node
// to additional other nodes as needed for efficient portal operation.
//
// In the example below, assume node A is designated as the broker. Nodes A and
// B have been connected directly by ConnectNode() calls in the application.
// Nodes A and C have been similarly connected:
//
// ┌───────┐
// ConnectNode() │ │ ConnectNode()
// ┌──────────>O A O<───────────┐
// │ │ │ │
// │ └───────┘ │
// │ │
// v ConnectNode() v ConnectNode()
// ┌───O───┐ ┌───O───┐
// │ │ │ │
// │ B │ │ C │
// │ │ │ │
// └───────┘ └───────┘
//
// ConnectNode() establishes initial portal pairs to link the two nodes
// together, illustrated above as "O"s. Once ConnectNode() returns, the
// application may immediately begin transmitting parcels through these portals.
//
// Now suppose node B creates a new local pair of portals (using OpenPortals())
// and sends one of those new portals in a parcel through its
// already-established portal to node A. The sent portal is effectively
// transferred to node A, and because its entangled peer still lives on node B
// there are now TWO portal pairs between nodes A and B:
//
// ┌───────┐
// │ │
// ┌──────────>O A O<───────────┐
// │ ┌────────>O │ │
// │ │ └───────┘ │
// │ │ │
// v v v
// ┌───O─O─┐ ┌───O───┐
// │ │ │ │
// │ B │ │ C │
// │ │ │ │
// └───────┘ └───────┘
//
// Finally, suppose now the application takes this new portal on node A and
// sends it further along, through node A's already-established portal to node
// C. Because the transferred portal's peer still lives on node B, there is now
// a portal pair spanning nodes B and C:
//
// ┌───────┐
// │ │
// ┌──────────>O A O<───────────┐
// │ │ │ │
// │ └───────┘ │
// │ │
// v v
// ┌───O───┐ ┌───O───┐
// │ │ │ │
// │ B O────────────────────────O C │
// │ │ │ │
// └───────┘ └───────┘
//
// These two nodes were never explicitly connected by the application, but ipcz
// ensures that the portals will operate as expected. Behind the scenes, ipcz
// achieves this by establishing a direct, secure, and efficient communication
// channel between nodes B and C.
#include <stddef.h>
#include <stdint.h>
#define IPCZ_NO_FLAGS ((uint32_t)0)
// Helper to clarify flag definitions.
#define IPCZ_FLAG_BIT(bit) ((uint32_t)(1u << bit))
// Opaque handle to an ipcz object.
typedef uintptr_t IpczHandle;
// An IpczHandle value which is always invalid. Note that arbitrary non-zero
// values are not necessarily valid either, but zero is never valid.
#define IPCZ_INVALID_HANDLE ((IpczHandle)0)
// Generic result code for all ipcz operations. See IPCZ_RESULT_* values below.
typedef int IpczResult;
// Specific meaning of each value depends on context, but IPCZ_RESULT_OK always
// indicates success. These values are derived from common status code
// definitions across Google software.
#define IPCZ_RESULT_OK ((IpczResult)0)
#define IPCZ_RESULT_CANCELLED ((IpczResult)1)
#define IPCZ_RESULT_UNKNOWN ((IpczResult)2)
#define IPCZ_RESULT_INVALID_ARGUMENT ((IpczResult)3)
#define IPCZ_RESULT_DEADLINE_EXCEEDED ((IpczResult)4)
#define IPCZ_RESULT_NOT_FOUND ((IpczResult)5)
#define IPCZ_RESULT_ALREADY_EXISTS ((IpczResult)6)
#define IPCZ_RESULT_PERMISSION_DENIED ((IpczResult)7)
#define IPCZ_RESULT_RESOURCE_EXHAUSTED ((IpczResult)8)
#define IPCZ_RESULT_FAILED_PRECONDITION ((IpczResult)9)
#define IPCZ_RESULT_ABORTED ((IpczResult)10)
#define IPCZ_RESULT_OUT_OF_RANGE ((IpczResult)11)
#define IPCZ_RESULT_UNIMPLEMENTED ((IpczResult)12)
#define IPCZ_RESULT_INTERNAL ((IpczResult)13)
#define IPCZ_RESULT_UNAVAILABLE ((IpczResult)14)
#define IPCZ_RESULT_DATA_LOSS ((IpczResult)15)
// Helper to specify explicit struct alignment across C and C++ compilers.
#if defined(__cplusplus)
#define IPCZ_ALIGN(alignment) alignas(alignment)
#elif defined(__GNUC__)
#define IPCZ_ALIGN(alignment) __attribute__((aligned(alignment)))
#elif defined(_MSC_VER)
#define IPCZ_ALIGN(alignment) __declspec(align(alignment))
#else
#error "IPCZ_ALIGN() is not defined for your compiler."
#endif
// Helper to generate the smallest constant value which is aligned with
// `alignment` and at least as large as `value`.
#define IPCZ_ALIGNED(value, alignment) \
((((value) + ((alignment)-1)) / (alignment)) * (alignment))
// Helper used to explicitly specify calling convention or other
// compiler-specific annotations for each API function.
#if defined(IPCZ_API_OVERRIDE)
#define IPCZ_API IPCZ_API_OVERRIDE
#elif defined(_WIN32)
#define IPCZ_API __cdecl
#else
#define IPCZ_API
#endif
// An opaque handle value created by an IpczDriver implementation. ipcz uses
// such handles to provide relevant context when calling back into the driver.
typedef uintptr_t IpczDriverHandle;
#define IPCZ_INVALID_DRIVER_HANDLE ((IpczDriverHandle)0)
// Flags given to the ipcz activity handler by a driver transport to notify ipcz
// about incoming data or state changes.
typedef uint32_t IpczTransportActivityFlags;
// If set, the driver encountered an unrecoverable error using the transport and
// ipcz should discard it. Note that the driver is free to issue such
// notifications many times as long as it remans active, but ipcz will generally
// request deactivation ASAP once an error is signaled.
#define IPCZ_TRANSPORT_ACTIVITY_ERROR IPCZ_FLAG_BIT(0)
// When ipcz wants to deactivate a transport, it invokes the driver's
// DeactivateTransport() function. Once the driver has finished any clean up and
// can ensure that the transport's activity handler will no longer be invoked,
// it must then invoke the activity handler one final time with this flag set.
// This finalizes deactivation and allows ipcz to free any associated resources.
#define IPCZ_TRANSPORT_ACTIVITY_DEACTIVATED IPCZ_FLAG_BIT(1)
#if defined(__cplusplus)
extern "C" {
#endif
// Notifies ipcz of activity on a transport. `transport` must be a handle to a
// transport which is currently activated. The `transport` handle is acquired
// exclusively by the driver transport via an ipcz call to the driver's
// ActivateTransport(), which also provides the handle to the driver.
//
// The driver must use this function to feed incoming data and driver handles
// from the transport to ipcz, or to inform ipcz of any error conditions
// resulting in unexpected and irrecoverable dysfunction of the transport.
//
// If the driver encounters an unrecoverable error while performing I/O on the
// transport, it should invoke this with the IPCZ_TRANSPORT_ACTIVITY_ERROR flag
// to instigate deactivation of the transport by ipcz via a subsequent
// DeactivateTransport() call.
//
// `options` is currently unused and must be null.
//
// NOTE: It is the driver's responsibility to ensure that calls to this function
// for the same value of `transport` are mututally exclusive. Overlapping calls
// are unsafe and will result in undefined behavior.
typedef IpczResult(IPCZ_API* IpczTransportActivityHandler)(
IpczHandle transport, // in
const void* data, // in
size_t num_bytes, // in
const IpczDriverHandle* driver_handles, // in
size_t num_driver_handles, // in
IpczTransportActivityFlags flags, // in
const void* options); // in
// Structure to be filled in by a driver's GetSharedMemoryInfo().
struct IPCZ_ALIGN(8) IpczSharedMemoryInfo {
// The exact size of this structure in bytes. Set by ipcz before passing the
// structure to the driver.
size_t size;
// The size of the shared memory region in bytes.
size_t region_num_bytes;
};
// IpczDriver is a function table to be populated by the application and
// provided to ipcz when creating a new node. The driver implements concrete
// I/O operations to facilitate communication between nodes, giving embedding
// systems full control over choice of OS-specific transport mechanisms and I/O
// scheduling decisions.
//
// The driver API is meant to be used by both the application embedding ipcz,
// particularly for creating transports to make initial contact between nodes,
// as well as by ipcz itself to delegate creation and management of new
// transports which ipcz brokers between nodes.
struct IPCZ_ALIGN(8) IpczDriver {
// The exact size of this structure in bytes. Must be set accurately by the
// application before passing this structure to any ipcz API functions.
size_t size;
// Called by ipcz to request that the driver release the object identified by
// `handle`.
IpczResult(IPCZ_API* Close)(IpczDriverHandle handle, // in
uint32_t flags, // in
const void* options); // in
// Serializes a driver object identified by `handle` into a collection of
// bytes and readily transmissible driver objects, for eventual transmission
// over `transport`. At a minimum this must support serialization of transport
// and memory objects allocated by ipcz through the driver. Any other driver
// objects intended for applications to box and transmit through portals must
// also be serializable here.
//
// If the specified object is invalid or unserializable, the driver must
// ignore all other arguments (including `transport`) and return
// IPCZ_RESULT_INVALID_ARGUMENT.
//
// If the object can be serialized but success may depend on the value of
// `transport`, and `transport` is IPCZ_INVALID_DRIVER_HANDLE, the driver must
// return IPCZ_RESULT_ABORTED. ipcz may invoke Serialize() in this way to
// query whether a specific object can be serialized at all, even when it
// doesn't have a specific transport in mind.
//
// If the object can be serialized or transmitted as-is and `transport` is
// valid, but the serialized outputs would not be transmissible over
// `transport` specifically, the driver must ignore all other arguments and
// return IPCZ_RESULT_PERMISSION_DENIED. This implies that neither end of
// `transport` is sufficiently privileged or otherwise able to transfer the
// object directly, and in this case ipcz may instead attempt to relay the
// object through a more capable broker node.
//
// For all other outcomes, the object identified by `handle` is considered to
// be serializable and ultimately transmissible.
//
// `num_bytes` and `num_handles` on input point to the capacities of the
// respective output buffers provided by ipcz. If either capacity pointer is
// null, a capacity of zero is implied; and if either input capacity is zero,
// the corresponding input buffer may be null.
//
// Except in the failure modes described above, the driver must update any
// non-null capacity input to reflect the exact capacity required to serialize
// the object. For example if `num_bytes` is non-null and the object
// serializes to 8 bytes of data, `*num_bytes` must be set to 8 upon return.
//
// If the required data or handle capacity is larger than the respective input
// capacity, the driver must return IPCZ_RESULT_RESUORCE_EXHAUSTED without
// modifying the contents of either `data` or `handles` buffers.
//
// Finally, if the input capacities were both sufficient, the driver must fill
// `data` and `handles` with a serialized representation of the object and
// return IPCZ_RESULT_OK. In this case ipcz relinquishes `handle` and will no
// longer refer to it unless the driver outputs it back in `handles`, implying
// that it was already transmissible as-is.
IpczResult(IPCZ_API* Serialize)(IpczDriverHandle handle, // in
IpczDriverHandle transport, // in
uint32_t flags, // in
const void* options, // in
void* data, // out
size_t* num_bytes, // in/out
IpczDriverHandle* handles, // out
size_t* num_handles); // in/out
// Deserializes a driver object from a collection of bytes and transmissible
// driver objects which which was originally produced by Serialize() and
// received on the calling node via `transport`.
//
// Any return value other than IPCZ_RESULT_OK indicates an error and implies
// that `handle` is unmodified. Otherwise `handle` must contain a valid driver
// handle to the deserialized object.
IpczResult(IPCZ_API* Deserialize)(
const void* data, // in
size_t num_bytes, // in
const IpczDriverHandle* driver_handles, // in
size_t num_driver_handles, // in
IpczDriverHandle transport, // in
uint32_t flags, // in
const void* options, // in
IpczDriverHandle* handle); // out
// Creates a new pair of entangled bidirectional transports, returning them in
// `new_transport0` and `new_transport1`.
//
// The input `transport0` and `transport1` are provided for context which may
// be important to the driver: the output transport in `new_transport0` will
// be sent over `transport0`, while the output transport in `new_transport1`
// will be sent over `transport1`. That is, the new transport is being created
// to establish a direct link between the remote node on `transport0` and the
// remote node on `transport1`.
//
// Any return value other than IPCZ_RESULT_OK indicates an error and implies
// that `new_transport0` and `new_transport1` are unmodified.
IpczResult(IPCZ_API* CreateTransports)(
IpczDriverHandle transport0, // in
IpczDriverHandle transport1, // in
uint32_t flags, // in
const void* options, // in
IpczDriverHandle* new_transport0, // out
IpczDriverHandle* new_transport1); // out
// Called by ipcz to activate a transport. `driver_transport` is the
// driver-side handle assigned to the transport by the driver, either as given
// to ipcz via ConnectNode(), or as returned by the driver from an ipcz call
// out to CreateTransports().
//
// `transport` is a handle the driver can use when calling `activity_handler`
// to update ipcz regarding any incoming data or state changes from the
// transport.
//
// Before this returns, the driver should establish any I/O monitoring or
// scheduling state necessary to support operation of the endpoint, and once
// it returns ipcz may immediately begin making Transmit() calls on
// `driver_transport`.
//
// Any return value other than IPCZ_RESULT_OK indicates an error, and the
// endpoint will be dropped by ipcz. Otherwise the endpoint may be used
// immediately to accept or submit data, and it should continue to operate
// until ipcz calls Close() on `driver_transport`.
//
// Note that `activity_handler` invocations MUST be mutually exclusive,
// because transmissions from ipcz are expected to arrive and be processed
// strictly in-order.
//
// The driver may elicit forced destruction of itself by calling
// `activity_handler` with the flag IPCZ_TRANSPORT_ACTIVITY_DEACTIVATED.
IpczResult(IPCZ_API* ActivateTransport)(
IpczDriverHandle driver_transport, // in
IpczHandle transport, // in
IpczTransportActivityHandler activity_handler, // in
uint32_t flags, // in
const void* options); // in
// Called by ipcz to deactivate a transport. The driver does not need to
// complete deactivation synchronously, but it must begin to deactivate the
// transport and must invoke the transport's activity handler one final time
// with IPCZ_TRANSPORT_ACTIVITY_DEACTIVATED once finished. Beyond that point,
// the activity handler must no longer be invoked for that transport.
//
// Note that even after deactivatoin, ipcz may continue to call into the
// transport until it's closed with an explicit call to the driver's Close()
// by ipcz.
IpczResult(IPCZ_API* DeactivateTransport)(
IpczDriverHandle driver_transport, // in
uint32_t flags, // in
const void* options); // in
// Called by ipcz to delegate transmission of data and driver handles over the
// identified transport endpoint. If the driver cannot fulfill the request,
// it must return a result other than IPCZ_RESULT_OK, and this will cause the
// transport's connection to be severed.
//
// Note that any driver handles in `driver_handles` were obtained by ipcz from
// the driver itself, by some prior call to the driver's own Serialize()
// function. These handles are therefore expected to be directly transmissible
// by the driver alongside any data in `data`.
//
// The net result of this transmission should be an activity handler
// invocation on the corresponding remote transport by the driver on its node.
// It is the driver's responsibility to get any data and handles to the other
// transport, and to ensure that all transmissions from transport end up
// invoking the activity handler on the peer transport in the same order they
// were transmitted.
//
// If ipcz only wants to wake the peer node rather than transmit data or
// handles, `num_bytes` and `num_driver_handles` may both be zero.
IpczResult(IPCZ_API* Transmit)(IpczDriverHandle driver_transport, // in
const void* data, // in
size_t num_bytes, // in
const IpczDriverHandle* driver_handles, // in
size_t num_driver_handles, // in
uint32_t flags, // in
const void* options); // in
// Allocates a shared memory region and returns a driver handle in
// `driver_memory` which can be used to reference it in other calls to the
// driver.
IpczResult(IPCZ_API* AllocateSharedMemory)(
size_t num_bytes, // in
uint32_t flags, // in
const void* options, // in
IpczDriverHandle* driver_memory); // out
// Returns information about the shared memory region identified by
// `driver_memory`.
IpczResult(IPCZ_API* GetSharedMemoryInfo)(
IpczDriverHandle driver_memory, // in
uint32_t flags, // in
const void* options, // in
struct IpczSharedMemoryInfo* info); // out
// Duplicates a shared memory region handle into a new distinct handle
// referencing the same underlying region.
IpczResult(IPCZ_API* DuplicateSharedMemory)(
IpczDriverHandle driver_memory, // in
uint32_t flags, // in
const void* options, // in
IpczDriverHandle* new_driver_memory); // out
// Maps a shared memory region identified by `driver_memory` and returns its
// mapped address in `address` on success and a driver handle in
// `driver_mapping` which can be passed to the driver's Close() to unmap the
// region later.
//
// Note that the lifetime of `driver_mapping` should be independent from that
// of `driver_memory`. That is, if `driver_memory` is closed immediately after
// this call succeeds, the returned mapping must still remain valid until the
// mapping itself is closed.
IpczResult(IPCZ_API* MapSharedMemory)(
IpczDriverHandle driver_memory, // in
uint32_t flags, // in
const void* options, // in
void** address, // out
IpczDriverHandle* driver_mapping); // out
// Generates `num_bytes` bytes of random data to fill `buffer`.
IpczResult(IPCZ_API* GenerateRandomBytes)(size_t num_bytes, // in
uint32_t flags, // in
const void* options, // in
void* buffer); // out
};
#if defined(__cplusplus)
} // extern "C"
#endif
// See CreateNode() and the IPCZ_CREATE_NODE_* flag descriptions below.
typedef uint32_t IpczCreateNodeFlags;
// Indicates that the created node will serve as the broker in its cluster.
//
// Brokers are expected to live in relatively trusted processes -- not
// necessarily elevated in privilege but also generally not restricted by
// sandbox constraints and not prone to processing risky, untrusted data -- as
// they're responsible for helping other nodes establish direct lines of
// communication as well as in some cases relaying data and driver handles
// between lesser-privileged nodes.
//
// Broker nodes do not expose any additional ipcz APIs or require much other
// special care on the part of the application**, but every cluster of connected
// nodes must have a node designated as the broker. Typically this is the first
// node created by an application's main process or a system-wide service
// coordinator, and all other nodes are created in processes spawned by that one
// or in processes which otherwise trust it.
//
// ** See notes on Close() regarding destruction of broker nodes.
#define IPCZ_CREATE_NODE_AS_BROKER IPCZ_FLAG_BIT(0)
// See ConnectNode() and the IPCZ_CONNECT_NODE_* flag descriptions below.
typedef uint32_t IpczConnectNodeFlags;
// Indicates that the remote node for this connection is expected to be a broker
// node, and it will be treated as such. Do not use this flag when connecting to
// any untrusted process.
#define IPCZ_CONNECT_NODE_TO_BROKER IPCZ_FLAG_BIT(0)
// Indicates that the remote node for this connection is expected not to be a
// broker, but to already have a link to a broker; and that the calling node
// wishes to inherit the remote node's broker as well. This flag must only be
// used when connecting to a node the caller trusts. The calling node must not
// already have an established broker from a previous ConnectNode() call. The
// remote node must specify IPCZ_CONNECT_NODE_SHARE_BROKER as well.
#define IPCZ_CONNECT_NODE_INHERIT_BROKER IPCZ_FLAG_BIT(1)
// Indicates that the calling node already has a broker, and that this broker
// will be inherited by the remote node. The remote node must also specify
// IPCZ_CONNECT_NODE_INHERIT_BROKER in its corresponding ConnectNode() call.
#define IPCZ_CONNECT_NODE_SHARE_BROKER IPCZ_FLAG_BIT(2)
// ipcz may periodically allocate shared memory regions to facilitate
// communication between two nodes. In many runtime environments, even within
// a security sandbox, the driver can do do this safely and directly by
// interfacing with the OS. In some environments however, direct allocation is
// not possible. In such cases a node must delegate this responsibility to some
// other trusted node in the system, typically the broker node.
//
// Specifying this flag ensures that all shared memory allocation elicited by
// the connecting node will be delegated to the connectee.
#define IPCZ_CONNECT_NODE_TO_ALLOCATION_DELEGATE IPCZ_FLAG_BIT(3)
// Optional limits provided by IpczPutOptions for Put() or IpczBeginPutOptions
// for BeginPut().
struct IPCZ_ALIGN(8) IpczPutLimits {
// The exact size of this structure in bytes. Must be set accurately before
// passing the structure to any API functions.
size_t size;
// Specifies the maximum number of unread parcels to allow in a portal's
// queue. If a Put() or BeginPut() call specifying this limit would cause the
// receiver's number of number of queued unread parcels to exceed this value,
// the call will fail with IPCZ_RESULT_RESOURCE_EXHAUSTED.
size_t max_queued_parcels;
// Specifies the maximum number of data bytes to allow in a portal's queue.
// If a Put() or BeginPut() call specifying this limit would cause the number
// of data bytes across all queued unread parcels to exceed this value, the
// call will fail with IPCZ_RESULT_RESOURCE_EXHAUSTED.
size_t max_queued_bytes;
};
// Options given to Put() to modify its default behavior.
struct IPCZ_ALIGN(8) IpczPutOptions {
// The exact size of this structure in bytes. Must be set accurately before
// passing the structure to Put().
size_t size;
// Optional limits to apply when determining if the Put() should be completed.
const struct IpczPutLimits* limits;
};
// See BeginPut() and the IPCZ_BEGIN_PUT_* flags described below.
typedef uint32_t IpczBeginPutFlags;
// Indicates that the caller is willing to produce less data than originally
// requested by their `*num_bytes` argument to BeginPut(). If the implementation
// would prefer a smaller chunk of data or if the requested size would exceed
// limits specified in the call's corresponding IpczPutLimits, passing this flag
// may allow the call to succeed while returning a smaller acceptable value in
// `*num_bytes`, rather than simply failing the call with
// IPCZ_RESULT_RESOURCE_EXHAUSTED.
#define IPCZ_BEGIN_PUT_ALLOW_PARTIAL IPCZ_FLAG_BIT(0)
// Options given to BeginPut() to modify its default behavior.
struct IPCZ_ALIGN(8) IpczBeginPutOptions {
// The exact size of this structure in bytes. Must be set accurately before
// passing the structure to BeginPut().
size_t size;
// Optional limits to apply when determining if the BeginPut() should be
// completed.
const struct IpczPutLimits* limits;
};
// See EndPut() and the IPCZ_END_PUT_* flags described below.
typedef uint32_t IpczEndPutFlags;
// If this flag is given to EndPut(), any in-progress two-phase put operation is
// aborted without committing a parcel to the portal.
#define IPCZ_END_PUT_ABORT IPCZ_FLAG_BIT(0)
// See Get() and the IPCZ_GET_* flag descriptions below.
typedef uint32_t IpczGetFlags;
// When given to Get(), this flag indicates that the caller is willing to accept
// a partial retrieval of the next available parcel. This means that in
// situations where Get() would normally return IPCZ_RESULT_RESOURCE_EXHAUSTED,
// it will instead return IPCZ_RESULT_OK with as much data and handles as the
// caller indicated they could accept.
#define IPCZ_GET_PARTIAL IPCZ_FLAG_BIT(0)
// See EndGet() and the IPCZ_END_GET_* flag descriptions below.
typedef uint32_t IpczEndGetFlags;
// If this flag is given to EndGet(), any in-progress two-phase get operation is
// aborted without consuming any data from the portal.
#define IPCZ_END_GET_ABORT IPCZ_FLAG_BIT(0)
// See Unbox() and the IPCZ_UNBOX_* flags described below.
typedef uint32_t IpczUnboxFlags;
// If set, the box is not consumed and the driver handle returned is not removed
// from the box.
#define IPCZ_UNBOX_PEEK IPCZ_FLAG_BIT(0)
// Flags given by the `flags` field in IpczPortalStatus.
typedef uint32_t IpczPortalStatusFlags;
// Indicates that the opposite portal is closed. Subsequent put operations on
// this portal will always fail with IPCZ_RESULT_NOT_FOUND. If there are not
// currently any unretrieved parcels in the portal either, subsequent get
// operations will also fail with the same error.
#define IPCZ_PORTAL_STATUS_PEER_CLOSED IPCZ_FLAG_BIT(0)
// Indicates that the opposite portal is closed AND no more parcels can be
// expected to arrive from it. If this bit is set on a portal's status, the
// portal is essentially useless. Such portals no longer support Put() or
// Get() operations, and those operations will subsequently always return
// IPCZ_RESULT_NOT_FOUND.
#define IPCZ_PORTAL_STATUS_DEAD IPCZ_FLAG_BIT(1)
// Information returned by QueryPortalStatus() or provided to
// IpczTrapEventHandlers when a trap's conditions are met on a portal.
struct IPCZ_ALIGN(8) IpczPortalStatus {
// The exact size of this structure in bytes. Must be set accurately before
// passing the structure to any functions.
size_t size;
// Flags. See the IPCZ_PORTAL_STATUS_* flags described above for the possible
// flags combined in this value.
IpczPortalStatusFlags flags;
// The number of unretrieved parcels queued on this portal.
size_t num_local_parcels;
// The number of unretrieved bytes (across all unretrieved parcels) queued on
// this portal.
size_t num_local_bytes;
// The number of unretrieved parcels queued on the opposite portal.
size_t num_remote_parcels;
// The number of unretrieved bytes (across all unretrieved parcels) queued on
// the opposite portal.
size_t num_remote_bytes;
};
// Flags given to IpczTrapConditions to indicate which types of conditions a
// trap should observe.
//
// Note that each type of condition may be considered edge-triggered or
// level-triggered. An edge-triggered condition is one which is only
// observable momentarily in response to a state change, while a level-triggered
// condition is continuously observable as long as some constraint about a
// portal's state is met.
//
// Level-triggered conditions can cause a Trap() attempt to fail if they're
// already satisfied when attempting to install a trap to monitor them.
typedef uint32_t IpczTrapConditionFlags;
// Triggers a trap event when the trap's portal is itself closed. This condition
// is always observed even if not explicitly set in the IpczTrapConditions given
// to the Trap() call. If a portal is closed while a trap is installed on it,
// an event will fire for the trap with this condition flag set. This condition
// is effectively edge-triggered, because as soon as it becomes true, any
// observing trap as well as its observed subject cease to exist.
#define IPCZ_TRAP_REMOVED IPCZ_FLAG_BIT(0)
// Triggers a trap event whenever the opposite portal is closed. Typically
// applications are interested in the more specific IPCZ_TRAP_DEAD.
// Level-triggered.
#define IPCZ_TRAP_PEER_CLOSED IPCZ_FLAG_BIT(1)
// Triggers a trap event whenever there are no more parcels available to
// retrieve from this portal AND the opposite portal is closed. This means the
// portal will never again have parcels to retrieve and is effectively useless.
// Level-triggered.
#define IPCZ_TRAP_DEAD IPCZ_FLAG_BIT(2)
// Triggers a trap event whenever the number of parcels queued for retrieval by
// this portal exceeds the threshold given by `min_local_parcels` in
// IpczTrapConditions. Level-triggered.
#define IPCZ_TRAP_ABOVE_MIN_LOCAL_PARCELS IPCZ_FLAG_BIT(3)
// Triggers a trap event whenever the number of bytes queued for retrieval by
// this portal exceeds the threshold given by `min_local_bytes` in
// IpczTrapConditions. Level-triggered.
#define IPCZ_TRAP_ABOVE_MIN_LOCAL_BYTES IPCZ_FLAG_BIT(4)
// Triggers a trap event whenever the number of parcels queued for retrieval on
// the opposite portal drops below the threshold given by `max_remote_parcels`
// IpczTrapConditions. Level-triggered.
#define IPCZ_TRAP_BELOW_MAX_REMOTE_PARCELS IPCZ_FLAG_BIT(5)
// Triggers a trap event whenever the number of bytes queued for retrieval on
// the opposite portal drops below the threshold given by `max_remote_bytes` in
// IpczTrapConditions. Level-triggered.
#define IPCZ_TRAP_BELOW_MAX_REMOTE_BYTES IPCZ_FLAG_BIT(6)
// Triggers a trap event whenever the number of locally available parcels
// increases by any amount. Edge-triggered.
#define IPCZ_TRAP_NEW_LOCAL_PARCEL IPCZ_FLAG_BIT(7)
// Triggers a trap event whenever the number of queued remote parcels decreases
// by any amount. Edge-triggered.
#define IPCZ_TRAP_CONSUMED_REMOTE_PARCEL IPCZ_FLAG_BIT(8)
// A structure describing portal conditions necessary to trigger a trap and
// invoke its event handler.
struct IPCZ_ALIGN(8) IpczTrapConditions {
// The exact size of this structure in bytes. Must be set accurately before
// passing the structure to Trap().
size_t size;
// See the IPCZ_TRAP_* flags described above.
IpczTrapConditionFlags flags;
// See IPCZ_TRAP_ABOVE_MIN_LOCAL_PARCELS. If that flag is not set in `flags`,
// this field is ignord.
size_t min_local_parcels;
// See IPCZ_TRAP_ABOVE_MIN_LOCAL_BYTES. If that flag is not set in `flags`,
// this field is ignored.
size_t min_local_bytes;
// See IPCZ_TRAP_BELOW_MAX_REMOTE_PARCELS. If that flag is not set in `flags`,
// this field is ignored.
size_t max_remote_parcels;
// See IPCZ_TRAP_BELOW_MAX_REMOTE_BYTES. If that flag is not set in `flags`,
// this field is ignored.
size_t max_remote_bytes;
};
// Structure passed to each IpczTrapEventHandler invocation with details about
// the event.
struct IPCZ_ALIGN(8) IpczTrapEvent {
// The size of this structure in bytes. Populated by ipcz to indicate which
// version is being provided to the handler.
size_t size;
// The context value that was given to Trap() when installing the trap that
// fired this event.
uintptr_t context;
// Flags indicating which condition(s) triggered this event.
IpczTrapConditionFlags condition_flags;
// The current status of the portal which triggered this event. This address
// is only valid through the extent of the event handler invocation.
const struct IpczPortalStatus* status;
};
// An application-defined function to be invoked by a trap when its observed
// conditions are satisfied on the monitored portal.
typedef void(IPCZ_API* IpczTrapEventHandler)(const struct IpczTrapEvent* event);
#if defined(__cplusplus)
extern "C" {
#endif
// Table of API functions defined by ipcz. Instances of this structure may be
// populated by passing them to an implementation of IpczGetAPIFn.
//
// Note that all functions follow a consistent parameter ordering:
//
// 1. Object handle (node or portal) if applicable
// 2. Function-specific strict input values
// 3. Flags - possibly untyped and unused
// 4. Options struct - possibly untyped and unused
// 5. Function-specific in/out values
// 6. Function-specific strict output values
//
// The rationale behind this convention is generally to have order flow from
// input to output. Flags are inputs, and options provide an extension point for
// future versions of these APIs; as such they skirt the boundary between strict
// input values and in/out values.
//
// The order and signature (ABI) of functions defined here must never change,
// but new functions may be added to the end.
struct IPCZ_ALIGN(8) IpczAPI {
// The exact size of this structure in bytes. Must be set accurately by the
// application before passing the structure to an implementation of
// IpczGetAPIFn.
size_t size;
// Releases the object identified by `handle`. If it's a portal, the portal is
// closed. If it's a node, the node is destroyed. If it's a wrapped driver
// object, the object is released via the driver API's Close().
//
// This function is NOT thread-safe. It is the application's responsibility to
// ensure that no other threads are performing other operations on `handle`
// concurrently with this call or any time thereafter.
//
// Note that while closure is itself a (non-blocking) synchronous operation,
// closure of various objects may have asynchronous side effects. For example,
// closing a portal might asynchronously trigger a trap event on the portal's
// remote peer.
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// NOTE: If `handle` is a broker node in its cluster of connected nodes,
// certain operations across the cluster -- such as driver object transmission
// through portals or portal transference in general -- may begin to fail
// spontaneously once destruction is complete.
//
// Returns:
//
// IPCZ_RESULT_OK if `handle` referred to a valid object and was
// successfully closed by this operation.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `handle` is invalid.
IpczResult(IPCZ_API* Close)(IpczHandle handle, // in
uint32_t flags, // in
const void* options); // in
// Initializes a new ipcz node. Applications typically need only one node in
// each communicating process, but it's OK to create more. Practical use cases
// for multiple nodes per process may include various testing scenarios, and
// any situation where simulating a multiprocess environment is useful.
//
// All other ipcz calls are scoped to a specific node, or to a more specific
// object which is itself scoped to a specific node.
//
// `driver` is the driver to use when coordinating internode communication.
// Nodes which will be interconnected must use the same or compatible driver
// implementations.
//
// `driver_node` is a driver-side handle to assign to the node throughout its
// lifetime. This handle provides the driver with additional context when ipcz
// makes driver API calls pertaining to a specific node. May be
// IPCZ_INVALID_DRIVER_HANDLE if not used by the driver.
//
// If `flags` contains IPCZ_CREATE_NODE_AS_BROKER then the node will act as
// the broker in its cluster of connected nodes. See details on that flag
// description above.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if a new node was created. In this case, `*node` is
// populated with a valid node handle upon return.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `node` is null, or `driver` is null or
// invalid.
//
// IPCZ_RESULT_UNIMPLEMENTED if some condition of the runtime environment
// or architecture-specific details of the ipcz build would prevent it
// from operating correctly. For example, the is returned if ipcz was
// built against a std::atomic implementation which does not provide
// lock-free 32-bit and 64-bit atomics.
IpczResult(IPCZ_API* CreateNode)(const struct IpczDriver* driver, // in
IpczDriverHandle driver_node, // in
IpczCreateNodeFlags flags, // in
const void* options, // in
IpczHandle* node); // out
// Connects `node` to another node in the system using an application-provided
// driver transport handle in `driver_transport` for communication. If this
// call will succeed, ipcz will call back into the driver to activate this
// transport via ActivateTransport() before returning.
//
// The application is responsible for delivering the other endpoint of the
// transport to whatever other node will use it with its own corresponding
// ConnectNode() call.
//
// The calling node opens a number of initial portals (given by
// `num_initial_portals`) linked to corresponding initial portals on the
// remote node as soon as a two-way connection is fully established.
//
// Establishment of this connection is typically asynchronous, but this
// depends on the driver implementation. In any case, the initial portals are
// created and returned synchronously and can be used immediately by the
// application. If the remote node issues a corresponding ConnectNode() call
// with a smaller `num_initial_portals`, the excess portals created by this
// node will behave as if their peer has been closed. On the other hand if the
// remote node gives a larger `num_initial_portals`, then its own excess
// portals will behave as if their peer has been closed.
//
//
// If IPCZ_CONNECT_NODE_TO_BROKER is given in `flags`, the remote node must
// be a broker node, and the calling node will treat it as such. If the
// calling node is also a broker, the brokers' respective networks will be
// effectively merged as long as both brokers remain alive: nodes in one
// network will be able to discover and communicate directly with nodes in the
// other network. Note that when two networks are merged, each broker remains
// as the only broker within its own network; but brokers share enough
// information to allow for discovery and interconnection of nodes between
// networks.
//
// Conversely if IPCZ_CONNECT_NODE_TO_BROKER is *not* given and neither the
// local nor remote nodes is a broker, one of the two nodes MUST NOT have a
// broker yet and must specify IPCZ_CONNECT_NODE_INHERIT_BROKER in its
// ConnectNode() call. The other node MUST have a broker already and it must
// specify IPCZ_CONNECT_NODE_SHARE_BROKER in its own corresponding
// ConnectNode() call.
//
// If IPCZ_CONNECT_NODE_TO_ALLOCATION_DELEGATE is given in `flags`, the
// calling node delegates all ipcz internal shared memory allocation
// operations to the remote node. This flag should only be used when the
// calling node is operating in a restricted environment where direct shared
// memory allocation is not possible.
//
// Returns:
//
// IPCZ_RESULT_OK if all arguments were valid and connection was initiated.
// `num_initial_portals` portal handles are populated in
// `initial_portals`. These may be used immediately by the application.
//
// Note that because the underlying connection may be established
// asynchronously (depending on the driver implementation), this
// operation may still fail after returning this value. If this
// happens, all of the returned initial portals will behave as if their
// peer has been closed.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `node` is invalid, `num_initial_portals`
// is zero, `initial_portals` is null, or `flags` specifies one or more
// flags which are invalid for `node` or invalid when combined.
//
// IPCZ_RESULT_OUT_OF_RANGE if `num_initial_portals` is larger than the
// ipcz implementation allows. There is no hard limit specified, but
// any ipcz implementation must support at least 8 initial portals.
IpczResult(IPCZ_API* ConnectNode)(IpczHandle node, // in
IpczDriverHandle driver_transport, // in
size_t num_initial_portals, // in
IpczConnectNodeFlags flags, // in
const void* options, // in
IpczHandle* initial_portals); // out
// Opens two new portals which exist as each other's opposite.
//
// Data and handles can be put in a portal with put operations (see Put(),
// BeginPut(), EndPut()). Anything placed into a portal can be retrieved in
// the same order by get operations (Get(), BeginGet(), EndGet()) on the
// opposite portal.
//
// To open portals which span two different nodes at creation time, see
// ConnectNode().
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if portal creation was successful. `*portal0` and
// `*portal1` are each populated with opaque portal handles which
// identify the new pair of portals. The new portals are each other's
// opposite and are entangled until one of them is closed.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `node` is invalid, or if either
// `portal0` or `portal1` is null.
IpczResult(IPCZ_API* OpenPortals)(IpczHandle node, // in
uint32_t flags, // in
const void* options, // in
IpczHandle* portal0, // out
IpczHandle* portal1); // out
// Merges two portals into each other, effectively destroying both while
// linking their respective peer portals with each other. A portal cannot
// merge with its own peer, and a portal cannot be merged into another if one
// or more parcels have already been put into or taken out of either of them.
// There are however no restrictions on what can be done to the portal's peer
// prior to merging the portal with another.
//
// If we have two portal pairs:
//
// A ---- B and C ---- D
//
// some parcels are placed into A, and some parcels are placed into D, and
// then we merge B with C, the net result will be a single portal pair:
//
// A ---- D
//
// All past and future parcels placed into A will arrive at D, and vice versa.
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the two portals were merged successfully. Neither
// handle is valid past this point. Parcels now travel between the
// merged portals' respective peers, including any parcels that were
// in flight or queued at the time of this merge.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `first` or `second` is invalid, if
// `first` and `second` are each others' peer, or `first` and `second`
// refer to the same portal.
//
// IPCZ_RESULT_FAILED_PRECONDITION if either `first` or `second` has
// already had one or more parcels put into or gotten out of them.
IpczResult(IPCZ_API* MergePortals)(IpczHandle first, // in
IpczHandle second, // in
uint32_t flags, // in
const void* options); // out
// Queries specific details regarding the status of a portal, such as the
// number of unread parcels or data bytes available on the portal or its
// opposite, or whether the opposite portal has already been closed.
//
// Note that because the portal's status is inherently dynamic and may be
// modified at any time by any thread in any process with a handle to either
// the portal or its opposite, the information returned in `status` may be
// stale by the time a successful QueryPortalStatus() call returns.
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the requested query was completed successfully.
// `status` is populated with details.
//
// IPCZ_RESULT_INVALID_ARGUMENT `portal` is invalid. `status` is null or
// invalid.
IpczResult(IPCZ_API* QueryPortalStatus)(
IpczHandle portal, // in
uint32_t flags, // in
const void* options, // in
struct IpczPortalStatus* status); // out
// Puts any combination of data and handles into the portal identified by
// `portal`. Everything put into a portal can be retrieved in the same order
// by a corresponding get operation on the opposite portal. Depending on the
// driver and the state of the relevant portals, the data and handles may
// be delivered and retreivable immediately by the remote portal, or they may
// be delivered asynchronously.
//
// `flags` is unused and must be IPCZ_NO_FLAGS.
//
// `options` may be null.
//
// If this call fails (returning anything other than IPCZ_RESULT_OK), any
// provided handles remain property of the caller. If it succeeds, their
// ownership is assumed by ipcz.
//
// Data to be submitted is read directly from the address given by the `data`
// argument, and `num_bytes` specifies how many bytes of data to copy from
// there.
//
// Callers may wish to request a view directly into portal memory for direct
// writing. In such cases, a two-phase put operation can be used instead, by
// calling BeginPut() and EndPut() as defined below.
//
// Returns:
//
// IPCZ_RESULT_OK if the provided data and handles were successfull placed
// into the portal as a new parcel.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, `data` is null but
// `num_bytes` is non-zero, `handles` is null but `num_handles` is
// non-zero, `options` is non-null but invalid, one of the handles in
// `handles` is equal to `portal` or its (local) opposite if
// applicable, or if any handle in `handles` is invalid or not
// serializable.
//
// IPCZ_RESULT_RESOURCE_EXHAUSTED if `options->limits` is non-null and at
// least one of the specified limits would be violated by the
// successful completion of this call.
//
// IPCZ_RESULT_NOT_FOUND if it is known that the opposite portal has
// already been closed and anything put into this portal would be lost.
IpczResult(IPCZ_API* Put)(IpczHandle portal, // in
const void* data, // in
size_t num_bytes, // in
const IpczHandle* handles, // in
size_t num_handles, // in
uint32_t flags, // in
const struct IpczPutOptions* options); // in
// Begins a two-phase put operation on `portal`. While a two-phase put
// operation is in progress on a portal, any other BeginPut() call on the same
// portal will fail with IPCZ_RESULT_ALREADY_EXISTS.
//
// Unlike a plain Put() call, two-phase put operations allow the application
// to write directly into portal memory, potentially reducing memory access
// costs by eliminating redundant copying and caching.
//
// The input value of `*num_bytes` tells ipcz how much data the caller would
// like to place into the portal.
//
// Limits provided to BeginPut() elicit similar behavior to Put(), with the
// exception that `flags` may specify IPCZ_BEGIN_PUT_ALLOW_PARTIAL to allow
// BeginPut() to succeed even the caller's suggested value of
// `*num_bytes` would cause the portal to exceed the maximum queued byte limit
// given by `options->limits`. In that case BeginPut() may update `*num_bytes`
// to reflect the remaining capacity of the portal, allowing the caller to
// commit at least some portion of their data with EndPut().
//
// Handles for two-phase puts are only provided when finalizing the operation
// with EndPut().
//
// Returns:
//
// IPCZ_RESULT_OK if the two-phase put operation has been successfully
// initiated. This operation must be completed with EndPut() before any
// further Put() or BeginPut() calls are allowed on `portal`. `*data`
// is set to the address of a portal buffer into which the application
// may copy its data, and `*num_bytes` is updated to reflect the
// capacity of that buffer, which may be greater than (or less than, if
// and only if IPCZ_BEGIN_PUT_ALLOW_PARTIAL was set in `flags`) the
// capacity requested by the input value of `*num_bytes`.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, `*num_bytes` is
// non-zero but `data` is null, or options is non-null and invalid.
//
// IPCZ_RESULT_RESOURCE_EXHAUSTED if completing the put with the number of
// bytes specified by `*num_bytes` would cause the portal to exceed the
// queued parcel limit or (if IPCZ_BEGIN_PUT_ALLOW_PARTIAL is not
// specified in `flags`) data byte limit specified by
// `options->limits`.
//
// IPCZ_RESULT_ALREADY_EXISTS if there is already a two-phase put operation
// in progress on `portal`.
//
// IPCZ_RESULT_NOT_FOUND if it is known that the opposite portal has
// already been closed and anything put into this portal would be lost.
IpczResult(IPCZ_API* BeginPut)(
IpczHandle portal, // in
IpczBeginPutFlags flags, // in
const struct IpczBeginPutOptions* options, // in
size_t* num_bytes, // out
void** data); // out
// Ends the two-phase put operation started by the most recent successful call
// to BeginPut() on `portal`.
//
// `num_bytes_produced` specifies the number of bytes actually written into
// the buffer that was returned from the original BeginPut() call.
//
// Usage of `handles` and `num_handles` is identical to Put().
//
// If this call fails (returning anything other than IPCZ_RESULT_OK), any
// provided handles remain property of the caller. If it succeeds, their
// ownership is assumed by ipcz.
//
// If IPCZ_END_PUT_ABORT is given in `flags` and there is a two-phase put
// operation in progress on `portal`, all other arguments are ignored and the
// pending two-phase put operation is cancelled without committing a new
// parcel to the portal.
//
// If EndPut() fails for any reason other than
// IPCZ_RESULT_FAILED_PRECONDITION, the two-phase put operation remains in
// progress, and EndPut() must be called again to abort the operation or
// attempt completion with different arguments.
//
// `options` is unused and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the two-phase operation was successfully completed or
// aborted. If not aborted all data and handles were committed to a new
// parcel enqueued for retrieval by the opposite portal.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, `num_handles` is
// non-zero but `handles` is null, `num_bytes_produced` is larger than
// the capacity of the buffer originally returned by BeginPut(), or any
// handle in `handles` is invalid or not serializable.
//
// IPCZ_RESULT_FAILED_PRECONDITION if there was no two-phase put operation
// in progress on `portal`.
//
// IPCZ_RESULT_NOT_FOUND if it is known that the opposite portal has
// already been closed and anything put into this portal would be lost.
IpczResult(IPCZ_API* EndPut)(IpczHandle portal, // in
size_t num_bytes_produced, // in
const IpczHandle* handles, // in
size_t num_handles, // in
IpczEndPutFlags flags, // in
const void* options); // in
// Retrieves some combination of data and handles from a portal, as placed by
// a prior put operation on the opposite portal.
//
// On input, the values pointed to by `num_bytes` and `num_handles` must
// specify the capacity of each corresponding buffer argument. A null pointer
// implies zero capacity. It is an error to specify non-zero capacity if the
// corresponding buffer (`data` or `handles`) is null.
//
// Normally the data consumed by this call is copied directly to the address
// given by the `data` argument, and `*num_bytes` specifies how many bytes of
// storage are available there. If an application wishes to read directly
// from portal memory instead, a two-phase get operation can be used by
// calling BeginGet() and EndGet() as defined below.
//
// Note that if the caller does not provide enough storage capacity for a
// complete parcel and does not specify IPCZ_GET_PARTIAL in `flags`, this
// returns IPCZ_RESULT_RESOURCE_EXHAUSTED and outputs the actual capacity
// required for the message without copying any of its contents. See details
// of that return value below.
//
// If IPCZ_GET_PARTIAL is specified, the call succeeds as long as a parcel is
// available, and the caller retrieves as much data and handles as their
// expressed capacity will allow. In this case, the in/out capacity arguments
// (`num_bytes` and `num_handles`) are still updated as specified in the
// IPCZ_RESULT_OK details below.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if there was a parcel available in the portal's queue and
// its data and handles were able to be copied into the caller's
// provided buffers. In this case values pointed to by `num_bytes` and
// `num_handles` (for each one that is non-null) are updated to reflect
// what was actually consumed. Note that the caller assumes ownership
// of all returned handles.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, `data` is null but
// `*num_bytes` is non-zero, or `handles` is null but `*num_handles` is
// non-zero.
//
// IPCZ_RESULT_RESOURCE_EXHAUSTED if the next available parcel would exceed
// the caller's specified capacity for either data bytes or handles,
// and IPCZ_GET_PARTIAL was not specified in `flags`. In this case, any
// non-null size pointer is updated to convey the minimum capacity that
// would have been required for an otherwise identical Get() call to
// have succeeded. Callers observing this result may wish to allocate
// storage accordingly and retry with updated parameters.
//
// IPCZ_RESULT_UNAVAILABLE if the portal's parcel queue is currently empty.
// In this case callers should wait before attempting to get anything
// from the same portal again.
//
// IPCZ_RESULT_NOT_FOUND if there are no more parcels in the portal's queue
// AND the opposite portal is known to be closed. If this result is
// returned, no parcels can ever be read from this portal again.
//
// IPCZ_RESULT_ALREADY_EXISTS if there is a two-phase get operation in
// progress on `portal`.
IpczResult(IPCZ_API* Get)(IpczHandle portal, // in
IpczGetFlags flags, // in
const void* options, // in
void* data, // out
size_t* num_bytes, // in/out
IpczHandle* handles, // out
size_t* num_handles); // in/out
// Begins a two-phase get operation on `portal` to retrieve data and handles.
// While a two-phase get operation is in progress on a portal, all other get
// operations on the same portal will fail with IPCZ_RESULT_ALREADY_EXISTS.
//
// Unlike a plain Get() call, two-phase get operations allow the application
// to read directly from portal memory, potentially reducing memory access
// costs by eliminating redundant copying and caching.
//
// If `data` or `num_bytes` is null and the available parcel has at least one
// byte of data, or if there are handles present but `num_handles` is null,
// this returns IPCZ_RESULT_RESOURCE_EXHAUSTED.
//
// Otherwise a successful BeginGet() updates values pointed to by `data`,
// `num_bytes`, and `num_handles` to convey the parcel's data storage and
// capacity as well as the capacity required to read out any handles.
//
// NOTE: When performing two-phase get operations, callers should be mindful
// of time-of-check/time-of-use (TOCTOU) vulnerabilities. Exposed parcel
// memory may be shared with (and writable in) the process which placed the
// parcel into the portal, and that process may not be trustworthy. In such
// cases, applications should be careful to copy the data out before
// validating and using it.
//
// `flags` is ignored and must be IPCZ_NO_FLAGS.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the two-phase get was successfully initiated. In this
// case both `*data` and `*num_bytes` are updated (if `data` and
// `num_bytes` were non-null) to describe the portal memory from which
// the application is free to read parcel data. If `num_handles` is
// is non-null, the value pointed to is updated to reflect the number
// of handles available to retrieve.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid.
//
// IPCZ_RESULT_RESOURCE_EXHAUSTED if the next available parcel has at least
// one data byte but `data` or `num_bytes` is null; or if the parcel
// has any handles but `num_handles` null.
//
// IPCZ_RESULT_UNAVAILABLE if the portal's parcel queue is currently empty.
// In this case callers should wait before attempting to get anything
// from the same portal again.
//
// IPCZ_RESULT_NOT_FOUND if there are no more parcels in the portal's queue
// AND the opposite portal is known to be closed. In this case, no get
// operation can ever succeed again on this portal.
//
// IPCZ_RESULT_ALREADY_EXISTS if there is already a two-phase get operation
// in progress on `portal`.
IpczResult(IPCZ_API* BeginGet)(IpczHandle portal, // in
uint32_t flags, // in
const void* options, // in
const void** data, // out
size_t* num_bytes, // out
size_t* num_handles); // out
// Ends the two-phase get operation started by the most recent successful call
// to BeginGet() on `portal`.
//
// `num_bytes_consumed` specifies the number of bytes actually read from the
// buffer that was returned from the original BeginGet() call. `num_handles`
// specifies the capacity of `handles` and must be no larger than the
// capacity indicated by the corresponding output from BeginGet().
//
// If IPCZ_END_GET_ABORT is given in `flags` and there is a two-phase get
// operation in progress on `portal`, all other arguments are ignored and the
// pending operation is cancelled without consuming any data from the portal.
//
// `options` is unused and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the two-phase operation was successfully completed or
// aborted. Note that if the frontmost parcel wasn't fully consumed by
// the caller, it will remain in queue with the rest of its data intact
// for a subsequent get operation to retrieve. Exactly `num_handles`
// handles will be copied into `handles`.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, or if `num_handles`
// is non-zero but `handles` is null.
//
// IPCZ_RESULT_OUT_OF_RANGE if either `num_bytes_consumed` or `num_handles`
// is larger than the capacity returned by BeginGet().
//
// IPCZ_RESULT_FAILED_PRECONDITION if there was no two-phase get operation
// in progress on `portal`.
IpczResult(IPCZ_API* EndGet)(IpczHandle portal, // in
size_t num_bytes_consumed, // in
size_t num_handles, // in
IpczEndGetFlags flags, // in
const void* options, // in
IpczHandle* handles); // out
// Attempts to install a trap to catch interesting changes to a portal's
// state. The condition(s) to observe are specified in `conditions`.
// Regardless of what conditions the caller specifies, all successfully
// installed traps also implicitly observe IPCZ_TRAP_REMOVED.
//
// If successful, ipcz guarantees that `handler` will be invoked -- with the
// the `context` field of the invocation's IpczTrapEvent reflecting the value
// of `context` given here -- once any of the specified conditions have been
// met.
//
// Immediately before invoking its handler, the trap is removed from the
// portal and must be reinstalled in order to observe further state changes.
//
// When a portal is closed, any traps still installed on it are notified by
// invoking their handler with IPCZ_TRAP_REMOVED in the event's
// `condition_flags`. This effectively guarantees that all installed traps
// eventually see a handler invocation.
//
// Note that `handler` may be invoked from any thread that can modify the
// state of the observed portal. This is limited to threads which make direct
// ipcz calls on the portal, and any threads on which the portal's node may
// receive notifications from a driver transport.
//
// If any of the specified conditions are already met, the trap is not
// installed and this call returns IPCZ_RESULT_FAILED_PRECONDITION. See below
// for details.
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the trap was installed successfully. In this case
// `flags` and `status` arguments are ignored.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `portal` is invalid, `conditions` is
// null or invalid, `handler` is null, or `status` is non-null but its
// `size` field specifies an invalid value.
//
// IPCZ_RESULT_FAILED_PRECONDITION if the conditions specified are already
// met on the portal. If `satisfied_condition_flags` is non-null, then
// its pointee value will be updated to reflect the flags in
// `conditions` which were already satisfied by the portal's state. If
// `status` is non-null, a copy of the portal's last known status will
// also be stored there.
IpczResult(IPCZ_API* Trap)(
IpczHandle portal, // in
const struct IpczTrapConditions* conditions, // in
IpczTrapEventHandler handler, // in
uintptr_t context, // in
uint32_t flags, // in
const void* options, // in
IpczTrapConditionFlags* satisfied_condition_flags, // out
struct IpczPortalStatus* status); // out
// Boxes an object managed by a node's driver and returns a new IpczHandle to
// reference the box. If the driver is able to serialize the boxed object, the
// box can be placed into a portal for transmission to the other side.
//
// Boxes can be sent through portals along with other IpczHandles, effectively
// allowing drivers to introduce new types of transferrable objects via boxes.
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the driver handle was boxed and a new IpczHandle is
// returned in `handle`.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `driver_handle` was invalid.
IpczResult(IPCZ_API* Box)(IpczHandle node, // in
IpczDriverHandle driver_handle, // in
uint32_t flags, // in
const void* options, // in
IpczHandle* handle); // out
// Unboxes a driver object from an IpczHandle previously produced by Box().
//
// `flags` is ignored and must be 0.
//
// `options` is ignored and must be null.
//
// Returns:
//
// IPCZ_RESULT_OK if the driver object was successfully unboxed. A driver
// handle to the object is placed in `*driver_handle`.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `handle` is invalid or does not
// reference a box.
IpczResult(IPCZ_API* Unbox)(IpczHandle handle, // in
IpczUnboxFlags flags, // in
const void* options, // in
IpczDriverHandle* driver_handle); // out
};
// A function which populates `api` with a table of ipcz API functions. The
// `size` field must be set by the caller to the size of the structure before
// issuing this call.
//
// In practice ipcz defines IpczGetAPI() as an implementation of this function
// type. How applications acquire a reference to that function depends on how
// the application builds and links against ipcz.
//
// Upon return, `api->size` indicates the size of the function table actually
// populated and therefore which version of the ipcz implementation is in use.
// Note that this size will never exceed the input value of `api->size`: if the
// caller is built against an older version than what is available, the
// available implementation will only populate the functions appropriate for
// that older version. Conversely if the caller is built against a newer version
// than what is available, `api->size` on output may be smaller than its value
// was on input.
//
// Returns:
//
// IPCZ_RESULT_OK if `api` was successfully populated. In this case
// `api->size` effectively indicates the API version provided, and the
// appropriate function pointers within `api` are filled in.
//
// IPCZ_RESULT_INVALID_ARGUMENT if `api` is null or the caller's provided
// `api->size` is less than the size of the function table required to
// host API version 0.
typedef IpczResult(IPCZ_API* IpczGetAPIFn)(struct IpczAPI* api);
#if defined(__cplusplus)
} // extern "C"
#endif
#endif // IPCZ_INCLUDE_IPCZ_IPCZ_H_