data_pipe.h revision cedac228d2dd51db4b79ea1e72c7f249408ee061
1// Copyright 2014 The Chromium Authors. All rights reserved. 2// Use of this source code is governed by a BSD-style license that can be 3// found in the LICENSE file. 4 5// This file contains types/constants and functions specific to data pipes. 6// 7// Note: This header should be compilable as C. 8 9#ifndef MOJO_PUBLIC_C_SYSTEM_DATA_PIPE_H_ 10#define MOJO_PUBLIC_C_SYSTEM_DATA_PIPE_H_ 11 12#include "mojo/public/c/system/macros.h" 13#include "mojo/public/c/system/system_export.h" 14#include "mojo/public/c/system/types.h" 15 16// |MojoCreateDataPipeOptions|: Used to specify creation parameters for a data 17// pipe to |MojoCreateDataPipe()|. 18// |uint32_t struct_size|: Set to the size of the |MojoCreateDataPipeOptions| 19// struct. (Used to allow for future extensions.) 20// |MojoCreateDataPipeOptionsFlags flags|: Used to specify different modes of 21// operation. 22// |MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE|: No flags; default mode. 23// |MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD|: May discard data for 24// whatever reason; best-effort delivery. In particular, if the capacity 25// is reached, old data may be discard to make room for new data. 26// |uint32_t element_num_bytes|: The size of an element, in bytes. All 27// transactions and buffers will consist of an integral number of 28// elements. Must be nonzero. 29// |uint32_t capacity_num_bytes|: The capacity of the data pipe, in number of 30// bytes; must be a multiple of |element_num_bytes|. The data pipe will 31// always be able to queue AT LEAST this much data. Set to zero to opt for 32// a system-dependent automatically-calculated capacity (which will always 33// be at least one element). 34 35typedef uint32_t MojoCreateDataPipeOptionsFlags; 36 37#ifdef __cplusplus 38const MojoCreateDataPipeOptionsFlags 39 MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE = 0; 40const MojoCreateDataPipeOptionsFlags 41 MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD = 1 << 0; 42#else 43#define MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_NONE \ 44 ((MojoCreateDataPipeOptionsFlags) 0) 45#define MOJO_CREATE_DATA_PIPE_OPTIONS_FLAG_MAY_DISCARD \ 46 ((MojoCreateDataPipeOptionsFlags) 1 << 0) 47#endif 48 49MOJO_COMPILE_ASSERT(MOJO_ALIGNOF(int64_t) == 8, int64_t_has_weird_alignment); 50struct MOJO_ALIGNAS(8) MojoCreateDataPipeOptions { 51 uint32_t struct_size; 52 MojoCreateDataPipeOptionsFlags flags; 53 uint32_t element_num_bytes; 54 uint32_t capacity_num_bytes; 55}; 56MOJO_COMPILE_ASSERT(sizeof(MojoCreateDataPipeOptions) == 16, 57 MojoCreateDataPipeOptions_has_wrong_size); 58 59// |MojoWriteDataFlags|: Used to specify different modes to |MojoWriteData()| 60// and |MojoBeginWriteData()|. 61// |MOJO_WRITE_DATA_FLAG_NONE| - No flags; default mode. 62// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| - Write either all the elements 63// requested or none of them. 64 65typedef uint32_t MojoWriteDataFlags; 66 67#ifdef __cplusplus 68const MojoWriteDataFlags MOJO_WRITE_DATA_FLAG_NONE = 0; 69const MojoWriteDataFlags MOJO_WRITE_DATA_FLAG_ALL_OR_NONE = 1 << 0; 70#else 71#define MOJO_WRITE_DATA_FLAG_NONE ((MojoWriteDataFlags) 0) 72#define MOJO_WRITE_DATA_FLAG_ALL_OR_NONE ((MojoWriteDataFlags) 1 << 0) 73#endif 74 75// |MojoReadDataFlags|: Used to specify different modes to |MojoReadData()| and 76// |MojoBeginReadData()|. 77// |MOJO_READ_DATA_FLAG_NONE| - No flags; default mode. 78// |MOJO_READ_DATA_FLAG_ALL_OR_NONE| - Read (or discard) either the requested 79// number of elements or none. 80// |MOJO_READ_DATA_FLAG_DISCARD| - Discard (up to) the requested number of 81// elements. 82// |MOJO_READ_DATA_FLAG_QUERY| - Query the number of elements available to 83// read. For use with |MojoReadData()| only. Mutually exclusive with 84// |MOJO_READ_DATA_FLAG_DISCARD| and |MOJO_READ_DATA_FLAG_ALL_OR_NONE| is 85// ignored if this flag is set. 86 87typedef uint32_t MojoReadDataFlags; 88 89#ifdef __cplusplus 90const MojoReadDataFlags MOJO_READ_DATA_FLAG_NONE = 0; 91const MojoReadDataFlags MOJO_READ_DATA_FLAG_ALL_OR_NONE = 1 << 0; 92const MojoReadDataFlags MOJO_READ_DATA_FLAG_DISCARD = 1 << 1; 93const MojoReadDataFlags MOJO_READ_DATA_FLAG_QUERY = 1 << 2; 94#else 95#define MOJO_READ_DATA_FLAG_NONE ((MojoReadDataFlags) 0) 96#define MOJO_READ_DATA_FLAG_ALL_OR_NONE ((MojoReadDataFlags) 1 << 0) 97#define MOJO_READ_DATA_FLAG_DISCARD ((MojoReadDataFlags) 1 << 1) 98#define MOJO_READ_DATA_FLAG_QUERY ((MojoReadDataFlags) 1 << 2) 99#endif 100 101#ifdef __cplusplus 102extern "C" { 103#endif 104 105// Note: See the comment in functions.h about the meaning of the "optional" 106// label for pointer parameters. 107 108// Creates a data pipe, which is a unidirectional communication channel for 109// unframed data, with the given options. Data is unframed, but must come as 110// (multiples of) discrete elements, of the size given in |options|. See 111// |MojoCreateDataPipeOptions| for a description of the different options 112// available for data pipes. 113// 114// |options| may be set to null for a data pipe with the default options (which 115// will have an element size of one byte and have some system-dependent 116// capacity). 117// 118// On success, |*data_pipe_producer_handle| will be set to the handle for the 119// producer and |*data_pipe_consumer_handle| will be set to the handle for the 120// consumer. (On failure, they are not modified.) 121// 122// Returns: 123// |MOJO_RESULT_OK| on success. 124// |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., if 125// |*options| is invalid or one of the pointer handles looks invalid). 126// |MOJO_RESULT_RESOURCE_EXHAUSTED| if a process/system/quota/etc. limit has 127// been reached (e.g., if the requested capacity was too large, or if the 128// maximum number of handles was exceeded). 129MOJO_SYSTEM_EXPORT MojoResult MojoCreateDataPipe( 130 const struct MojoCreateDataPipeOptions* options, // Optional. 131 MojoHandle* data_pipe_producer_handle, // Out. 132 MojoHandle* data_pipe_consumer_handle); // Out. 133 134// Writes the given data to the data pipe producer given by 135// |data_pipe_producer_handle|. |elements| points to data of size |*num_bytes|; 136// |*num_bytes| should be a multiple of the data pipe's element size. If 137// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| is set in |flags|, either all the data 138// will be written or none is. 139// 140// On success, |*num_bytes| is set to the amount of data that was actually 141// written. 142// 143// Note: If the data pipe has the "may discard" option flag (specified on 144// creation), this will discard as much data as required to write the given 145// data, starting with the earliest written data that has not been consumed. 146// However, even with "may discard", if |*num_bytes| is greater than the data 147// pipe's capacity (and |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| is not set), this 148// will write the maximum amount possible (namely, the data pipe's capacity) and 149// set |*num_bytes| to that amount. It will *not* discard data from |elements|. 150// 151// Returns: 152// |MOJO_RESULT_OK| on success. 153// |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., if 154// |data_pipe_producer_dispatcher| is not a handle to a data pipe 155// producer, |elements| does not look like a valid pointer, or 156// |*num_bytes| is not a multiple of the data pipe's element size). 157// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe consumer handle has been 158// closed. 159// |MOJO_RESULT_OUT_OF_RANGE| if |flags| has 160// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set and the required amount of data 161// (specified by |*num_bytes|) could not be written. 162// |MOJO_RESULT_BUSY| if there is a two-phase write ongoing with 163// |data_pipe_producer_handle| (i.e., |MojoBeginWriteData()| has been 164// called, but not yet the matching |MojoEndWriteData()|). 165// |MOJO_RESULT_SHOULD_WAIT| if no data can currently be written (and the 166// consumer is still open) and |flags| does *not* have 167// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set. 168// 169// TODO(vtl): Should there be a way of querying how much data can be written? 170MOJO_SYSTEM_EXPORT MojoResult MojoWriteData( 171 MojoHandle data_pipe_producer_handle, 172 const void* elements, 173 uint32_t* num_bytes, // In/out. 174 MojoWriteDataFlags flags); 175 176// Begins a two-phase write to the data pipe producer given by 177// |data_pipe_producer_handle|. On success, |*buffer| will be a pointer to which 178// the caller can write |*buffer_num_bytes| bytes of data. If flags has 179// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set, then the output value 180// |*buffer_num_bytes| will be at least as large as its input value, which must 181// also be a multiple of the element size (if |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| 182// is not set, the input value of |*buffer_num_bytes| is ignored). 183// 184// During a two-phase write, |data_pipe_producer_handle| is *not* writable. 185// E.g., if another thread tries to write to it, it will get |MOJO_RESULT_BUSY|; 186// that thread can then wait for |data_pipe_producer_handle| to become writable 187// again. 188// 189// Once the caller has finished writing data to |*buffer|, it should call 190// |MojoEndWriteData()| to specify the amount written and to complete the 191// two-phase write. 192// 193// Note: If the data pipe has the "may discard" option flag (specified on 194// creation) and |flags| has |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set, this may 195// discard some data. 196// 197// Returns: 198// |MOJO_RESULT_OK| on success. 199// |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., if 200// |data_pipe_producer_handle| is not a handle to a data pipe producer, 201// |buffer| or |buffer_num_bytes| does not look like a valid pointer, or 202// flags has |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set and 203// |*buffer_num_bytes| is not a multiple of the element size). 204// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe consumer handle has been 205// closed. 206// |MOJO_RESULT_OUT_OF_RANGE| if |flags| has 207// |MOJO_WRITE_DATA_FLAG_ALL_OR_NONE| set and the required amount of data 208// (specified by |*buffer_num_bytes|) cannot be written contiguously at 209// this time. (Note that there may be space available for the required 210// amount of data, but the "next" write position may not be large enough.) 211// |MOJO_RESULT_BUSY| if there is already a two-phase write ongoing with 212// |data_pipe_producer_handle| (i.e., |MojoBeginWriteData()| has been 213// called, but not yet the matching |MojoEndWriteData()|). 214// |MOJO_RESULT_SHOULD_WAIT| if no data can currently be written (and the 215// consumer is still open). 216MOJO_SYSTEM_EXPORT MojoResult MojoBeginWriteData( 217 MojoHandle data_pipe_producer_handle, 218 void** buffer, // Out. 219 uint32_t* buffer_num_bytes, // In/out. 220 MojoWriteDataFlags flags); 221 222// Ends a two-phase write to the data pipe producer given by 223// |data_pipe_producer_handle| that was begun by a call to 224// |MojoBeginWriteData()| on the same handle. |num_bytes_written| should 225// indicate the amount of data actually written; it must be less than or equal 226// to the value of |*buffer_num_bytes| output by |MojoBeginWriteData()| and must 227// be a multiple of the element size. The buffer given by |*buffer| from 228// |MojoBeginWriteData()| must have been filled with exactly |num_bytes_written| 229// bytes of data. 230// 231// On failure, the two-phase write (if any) is ended (so the handle may become 232// writable again, if there's space available) but no data written to |*buffer| 233// is "put into" the data pipe. 234// 235// Returns: 236// |MOJO_RESULT_OK| on success. 237// |MOJO_RESULT_INVALID_ARGUMENT| if |data_pipe_producer_handle| is not a 238// handle to a data pipe producer or |num_bytes_written| is invalid 239// (greater than the maximum value provided by |MojoBeginWriteData()| or 240// not a multiple of the element size). 241// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe producer is not in a 242// two-phase write (e.g., |MojoBeginWriteData()| was not called or 243// |MojoEndWriteData()| has already been called). 244MOJO_SYSTEM_EXPORT MojoResult MojoEndWriteData( 245 MojoHandle data_pipe_producer_handle, 246 uint32_t num_bytes_written); 247 248// Reads data from the data pipe consumer given by |data_pipe_consumer_handle|. 249// May also be used to discard data or query the amount of data available. 250// 251// If |flags| has neither |MOJO_READ_DATA_FLAG_DISCARD| nor 252// |MOJO_READ_DATA_FLAG_QUERY| set, this tries to read up to |*num_bytes| (which 253// must be a multiple of the data pipe's element size) bytes of data to 254// |elements| and set |*num_bytes| to the amount actually read. If flags has 255// |MOJO_READ_DATA_FLAG_ALL_OR_NONE| set, it will either read exactly 256// |*num_bytes| bytes of data or none. 257// 258// If flags has |MOJO_READ_DATA_FLAG_DISCARD| set, it discards up to 259// |*num_bytes| (which again be a multiple of the element size) bytes of data, 260// setting |*num_bytes| to the amount actually discarded. If flags has 261// |MOJO_READ_DATA_FLAG_ALL_OR_NONE|, it will either discard exactly 262// |*num_bytes| bytes of data or none. In this case, |MOJO_READ_DATA_FLAG_QUERY| 263// must not be set, and |elements| is ignored (and should typically be set to 264// null). 265// 266// If flags has |MOJO_READ_DATA_FLAG_QUERY| set, it queries the amount of data 267// available, setting |*num_bytes| to the number of bytes available. In this 268// case, |MOJO_READ_DATA_FLAG_DISCARD| must not be set, and 269// |MOJO_READ_DATA_FLAG_ALL_OR_NONE| is ignored, as are |elements| and the input 270// value of |*num_bytes|. 271// 272// Returns: 273// |MOJO_RESULT_OK| on success (see above for a description of the different 274// operations). 275// |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., 276// |data_pipe_consumer_handle| is invalid, the combination of flags in 277// |flags| is invalid, etc.). 278// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe producer handle has been 279// closed and data (or the required amount of data) was not available to 280// be read or discarded. 281// |MOJO_RESULT_OUT_OF_RANGE| if |flags| has |MOJO_READ_DATA_FLAG_ALL_OR_NONE| 282// set and the required amount of data is not available to be read or 283// discarded (and the producer is still open). 284// |MOJO_RESULT_BUSY| if there is a two-phase read ongoing with 285// |data_pipe_consumer_handle| (i.e., |MojoBeginReadData()| has been 286// called, but not yet the matching |MojoEndReadData()|). 287// |MOJO_RESULT_SHOULD_WAIT| if there is no data to be read or discarded (and 288// the producer is still open) and |flags| does *not* have 289// |MOJO_READ_DATA_FLAG_ALL_OR_NONE| set. 290MOJO_SYSTEM_EXPORT MojoResult MojoReadData( 291 MojoHandle data_pipe_consumer_handle, 292 void* elements, // Out. 293 uint32_t* num_bytes, // In/out. 294 MojoReadDataFlags flags); 295 296// Begins a two-phase read from the data pipe consumer given by 297// |data_pipe_consumer_handle|. On success, |*buffer| will be a pointer from 298// which the caller can read |*buffer_num_bytes| bytes of data. If flags has 299// |MOJO_READ_DATA_FLAG_ALL_OR_NONE| set, then the output value 300// |*buffer_num_bytes| will be at least as large as its input value, which must 301// also be a multiple of the element size (if |MOJO_READ_DATA_FLAG_ALL_OR_NONE| 302// is not set, the input value of |*buffer_num_bytes| is ignored). |flags| must 303// not have |MOJO_READ_DATA_FLAG_DISCARD| or |MOJO_READ_DATA_FLAG_QUERY| set. 304// 305// During a two-phase read, |data_pipe_consumer_handle| is *not* readable. 306// E.g., if another thread tries to read from it, it will get 307// |MOJO_RESULT_BUSY|; that thread can then wait for |data_pipe_consumer_handle| 308// to become readable again. 309// 310// Once the caller has finished reading data from |*buffer|, it should call 311// |MojoEndReadData()| to specify the amount read and to complete the two-phase 312// read. 313// 314// Returns: 315// |MOJO_RESULT_OK| on success. 316// |MOJO_RESULT_INVALID_ARGUMENT| if some argument was invalid (e.g., if 317// |data_pipe_consumer_handle| is not a handle to a data pipe consumer, 318// |buffer| or |buffer_num_bytes| does not look like a valid pointer, 319// |flags| has |MOJO_READ_DATA_FLAG_ALL_OR_NONE| set and 320// |*buffer_num_bytes| is not a multiple of the element size, or |flags| 321// has invalid flags set). 322// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe producer handle has been 323// closed. 324// |MOJO_RESULT_OUT_OF_RANGE| if |flags| has |MOJO_READ_DATA_FLAG_ALL_OR_NONE| 325// set and the required amount of data (specified by |*buffer_num_bytes|) 326// cannot be read from a contiguous buffer at this time. (Note that there 327// may be the required amount of data, but it may not be contiguous.) 328// |MOJO_RESULT_BUSY| if there is already a two-phase read ongoing with 329// |data_pipe_consumer_handle| (i.e., |MojoBeginReadData()| has been 330// called, but not yet the matching |MojoEndReadData()|). 331// |MOJO_RESULT_SHOULD_WAIT| if no data can currently be read (and the 332// producer is still open). 333MOJO_SYSTEM_EXPORT MojoResult MojoBeginReadData( 334 MojoHandle data_pipe_consumer_handle, 335 const void** buffer, // Out. 336 uint32_t* buffer_num_bytes, // In/out. 337 MojoReadDataFlags flags); 338 339// Ends a two-phase read from the data pipe consumer given by 340// |data_pipe_consumer_handle| that was begun by a call to |MojoBeginReadData()| 341// on the same handle. |num_bytes_read| should indicate the amount of data 342// actually read; it must be less than or equal to the value of 343// |*buffer_num_bytes| output by |MojoBeginReadData()| and must be a multiple of 344// the element size. 345// 346// On failure, the two-phase read (if any) is ended (so the handle may become 347// readable again) but no data is "removed" from the data pipe. 348// 349// Returns: 350// |MOJO_RESULT_OK| on success. 351// |MOJO_RESULT_INVALID_ARGUMENT| if |data_pipe_consumer_handle| is not a 352// handle to a data pipe consumer or |num_bytes_written| is invalid 353// (greater than the maximum value provided by |MojoBeginReadData()| or 354// not a multiple of the element size). 355// |MOJO_RESULT_FAILED_PRECONDITION| if the data pipe consumer is not in a 356// two-phase read (e.g., |MojoBeginReadData()| was not called or 357// |MojoEndReadData()| has already been called). 358MOJO_SYSTEM_EXPORT MojoResult MojoEndReadData( 359 MojoHandle data_pipe_consumer_handle, 360 uint32_t num_bytes_read); 361 362#ifdef __cplusplus 363} // extern "C" 364#endif 365 366#endif // MOJO_PUBLIC_C_SYSTEM_DATA_PIPE_H_ 367