| // Copyright 2014 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. |
| |
| // This file contains types/constants and functions specific to message pipes. |
| // |
| // Note: This header should be compilable as C. |
| |
| #ifndef MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_ |
| #define MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_ |
| |
| #include "mojo/public/c/system/macros.h" |
| #include "mojo/public/c/system/system_export.h" |
| #include "mojo/public/c/system/types.h" |
| |
| // |MojoCreateMessagePipeOptions|: Used to specify creation parameters for a |
| // message pipe to |MojoCreateMessagePipe()|. |
| // |uint32_t struct_size|: Set to the size of the |
| // |MojoCreateMessagePipeOptions| struct. (Used to allow for future |
| // extensions.) |
| // |MojoCreateMessagePipeOptionsFlags flags|: Reserved for future use. |
| // |MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE|: No flags; default mode. |
| |
| typedef uint32_t MojoCreateMessagePipeOptionsFlags; |
| |
| #ifdef __cplusplus |
| const MojoCreateMessagePipeOptionsFlags |
| MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE = 0; |
| #else |
| #define MOJO_CREATE_MESSAGE_PIPE_OPTIONS_FLAG_NONE \ |
| ((MojoCreateMessagePipeOptionsFlags)0) |
| #endif |
| |
| MOJO_STATIC_ASSERT(MOJO_ALIGNOF(int64_t) == 8, "int64_t has weird alignment"); |
| struct MOJO_ALIGNAS(8) MojoCreateMessagePipeOptions { |
| uint32_t struct_size; |
| MojoCreateMessagePipeOptionsFlags flags; |
| }; |
| MOJO_STATIC_ASSERT(sizeof(MojoCreateMessagePipeOptions) == 8, |
| "MojoCreateMessagePipeOptions has wrong size"); |
| |
| // |MojoWriteMessageFlags|: Used to specify different modes to |
| // |MojoWriteMessage()|. |
| // |MOJO_WRITE_MESSAGE_FLAG_NONE| - No flags; default mode. |
| |
| typedef uint32_t MojoWriteMessageFlags; |
| |
| #ifdef __cplusplus |
| const MojoWriteMessageFlags MOJO_WRITE_MESSAGE_FLAG_NONE = 0; |
| #else |
| #define MOJO_WRITE_MESSAGE_FLAG_NONE ((MojoWriteMessageFlags)0) |
| #endif |
| |
| // |MojoReadMessageFlags|: Used to specify different modes to |
| // |MojoReadMessage()|. |
| // |MOJO_READ_MESSAGE_FLAG_NONE| - No flags; default mode. |
| // |MOJO_READ_MESSAGE_FLAG_MAY_DISCARD| - If the message is unable to be read |
| // for whatever reason (e.g., the caller-supplied buffer is too small), |
| // discard the message (i.e., simply dequeue it). |
| |
| typedef uint32_t MojoReadMessageFlags; |
| |
| #ifdef __cplusplus |
| const MojoReadMessageFlags MOJO_READ_MESSAGE_FLAG_NONE = 0; |
| const MojoReadMessageFlags MOJO_READ_MESSAGE_FLAG_MAY_DISCARD = 1 << 0; |
| #else |
| #define MOJO_READ_MESSAGE_FLAG_NONE ((MojoReadMessageFlags)0) |
| #define MOJO_READ_MESSAGE_FLAG_MAY_DISCARD ((MojoReadMessageFlags)1 << 0) |
| #endif |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| // Note: See the comment in functions.h about the meaning of the "optional" |
| // label for pointer parameters. |
| |
| // Creates a message pipe, which is a bidirectional communication channel for |
| // framed data (i.e., messages). Messages can contain plain data and/or Mojo |
| // handles. |
| // |
| // |options| may be set to null for a message pipe with the default options. |
| // |
| // On success, |*message_pipe_handle0| and |*message_pipe_handle1| are set to |
| // handles for the two endpoints (ports) for the message pipe. |
| // |
| // Returns: |
| // |MOJO_RESULT_OK| on success. |
| // |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., |
| // |*options| is invalid). |
| // |MOJO_RESULT_RESOURCE_EXHAUSTED| if a process/system/quota/etc. limit has |
| // been reached. |
| MOJO_SYSTEM_EXPORT MojoResult MojoCreateMessagePipe( |
| const struct MojoCreateMessagePipeOptions* options, // Optional. |
| MojoHandle* message_pipe_handle0, // Out. |
| MojoHandle* message_pipe_handle1); // Out. |
| |
| // Writes a message to the message pipe endpoint given by |message_pipe_handle|, |
| // with message data specified by |bytes| of size |num_bytes| and attached |
| // handles specified by |handles| of count |num_handles|, and options specified |
| // by |flags|. If there is no message data, |bytes| may be null, in which case |
| // |num_bytes| must be zero. If there are no attached handles, |handles| may be |
| // null, in which case |num_handles| must be zero. |
| // |
| // If handles are attached, on success the handles will no longer be valid (the |
| // receiver will receive equivalent, but logically different, handles). Handles |
| // to be sent should not be in simultaneous use (e.g., on another thread). |
| // |
| // Returns: |
| // |MOJO_RESULT_OK| on success (i.e., the message was enqueued). |
| // |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., if |
| // |message_pipe_handle| is not a valid handle, or some of the |
| // requirements above are not satisfied). |
| // |MOJO_RESULT_RESOURCE_EXHAUSTED| if some system limit has been reached, or |
| // the number of handles to send is too large (TODO(vtl): reconsider the |
| // latter case). |
| // |MOJO_RESULT_FAILED_PRECONDITION| if the other endpoint has been closed. |
| // Note that closing an endpoint is not necessarily synchronous (e.g., |
| // across processes), so this function may succeed even if the other |
| // endpoint has been closed (in which case the message would be dropped). |
| // |MOJO_RESULT_UNIMPLEMENTED| if an unsupported flag was set in |*options|. |
| // |MOJO_RESULT_BUSY| if some handle to be sent is currently in use. |
| // |
| // TODO(vtl): Add a notion of capacity for message pipes, and return |
| // |MOJO_RESULT_SHOULD_WAIT| if the message pipe is full. |
| MOJO_SYSTEM_EXPORT MojoResult |
| MojoWriteMessage(MojoHandle message_pipe_handle, |
| const void* bytes, // Optional. |
| uint32_t num_bytes, |
| const MojoHandle* handles, // Optional. |
| uint32_t num_handles, |
| MojoWriteMessageFlags flags); |
| |
| // Reads the next message from a message pipe, or indicates the size of the |
| // message if it cannot fit in the provided buffers. The message will be read |
| // in its entirety or not at all; if it is not, it will remain enqueued unless |
| // the |MOJO_READ_MESSAGE_FLAG_MAY_DISCARD| flag was passed. At most one |
| // message will be consumed from the queue, and the return value will indicate |
| // whether a message was successfully read. |
| // |
| // |num_bytes| and |num_handles| are optional in/out parameters that on input |
| // must be set to the sizes of the |bytes| and |handles| arrays, and on output |
| // will be set to the actual number of bytes or handles contained in the |
| // message (even if the message was not retrieved due to being too large). |
| // Either |num_bytes| or |num_handles| may be null if the message is not |
| // expected to contain the corresponding type of data, but such a call would |
| // fail with |MOJO_RESULT_RESOURCE_EXHAUSTED| if the message in fact did |
| // contain that type of data. |
| // |
| // |bytes| and |handles| will receive the contents of the message, if it is |
| // retrieved. Either or both may be null, in which case the corresponding size |
| // parameter(s) must also be set to zero or passed as null. |
| // |
| // Returns: |
| // |MOJO_RESULT_OK| on success (i.e., a message was actually read). |
| // |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid. |
| // |MOJO_RESULT_FAILED_PRECONDITION| if the other endpoint has been closed. |
| // |MOJO_RESULT_RESOURCE_EXHAUSTED| if the message was too large to fit in the |
| // provided buffer(s). The message will have been left in the queue or |
| // discarded, depending on flags. |
| // |MOJO_RESULT_SHOULD_WAIT| if no message was available to be read. |
| // |
| // TODO(vtl): Reconsider the |MOJO_RESULT_RESOURCE_EXHAUSTED| error code; should |
| // distinguish this from the hitting-system-limits case. |
| MOJO_SYSTEM_EXPORT MojoResult |
| MojoReadMessage(MojoHandle message_pipe_handle, |
| void* bytes, // Optional out. |
| uint32_t* num_bytes, // Optional in/out. |
| MojoHandle* handles, // Optional out. |
| uint32_t* num_handles, // Optional in/out. |
| MojoReadMessageFlags flags); |
| |
| #ifdef __cplusplus |
| } // extern "C" |
| #endif |
| |
| #endif // MOJO_PUBLIC_C_SYSTEM_MESSAGE_PIPE_H_ |