| /* |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /** |
| * @addtogroup Memory |
| * @{ |
| */ |
| |
| /** |
| * @file sharedmem.h |
| */ |
| |
| #ifndef ANDROID_SHARED_MEMORY_H |
| #define ANDROID_SHARED_MEMORY_H |
| |
| #include <stddef.h> |
| #include <sys/cdefs.h> |
| |
| /****************************************************************** |
| * |
| * IMPORTANT NOTICE: |
| * |
| * This file is part of Android's set of stable system headers |
| * exposed by the Android NDK (Native Development Kit). |
| * |
| * Third-party source AND binary code relies on the definitions |
| * here to be FROZEN ON ALL UPCOMING PLATFORM RELEASES. |
| * |
| * - DO NOT MODIFY ENUMS (EXCEPT IF YOU ADD NEW 32-BIT VALUES) |
| * - DO NOT MODIFY CONSTANTS OR FUNCTIONAL MACROS |
| * - DO NOT CHANGE THE SIGNATURE OF FUNCTIONS IN ANY WAY |
| * - DO NOT CHANGE THE LAYOUT OR SIZE OF STRUCTURES |
| */ |
| |
| /** |
| * Structures and functions for a shared memory buffer that can be shared across process. |
| */ |
| |
| #ifdef __cplusplus |
| extern "C" { |
| #endif |
| |
| #if __ANDROID_API__ >= 26 |
| |
| /** |
| * Create a shared memory region. |
| * |
| * Create shared memory region and returns an file descriptor. The resulting file descriptor can be |
| * mmap'ed to process memory space with PROT_READ | PROT_WRITE | PROT_EXEC. Access to shared memory |
| * region can be restricted with {@link ASharedMemory_setProt}. |
| * |
| * Use close() to release the shared memory region. |
| * |
| * \param name an optional name. |
| * \param size size of the shared memory region |
| * \return file descriptor that denotes the shared memory; error code on failure. |
| */ |
| int ASharedMemory_create(const char *name, size_t size) __INTRODUCED_IN(26); |
| |
| /** |
| * Get the size of the shared memory region. |
| * |
| * \param fd file descriptor of the shared memory region |
| * \return size in bytes; 0 if fd is not a valid shared memory file descriptor. |
| */ |
| size_t ASharedMemory_getSize(int fd) __INTRODUCED_IN(26); |
| |
| /** |
| * Restrict access of shared memory region. |
| * |
| * This function restricts access of a shared memory region. Access can only be removed. The effect |
| * applies globally to all file descriptors in all processes across the system that refer to this |
| * shared memory region. Existing memory mapped regions are not affected. |
| * |
| * It is a common use case to create a shared memory region, map it read/write locally to intialize |
| * content, and then send the shared memory to another process with read only access. Code example |
| * as below (error handling omited). |
| * |
| * |
| * int fd = ASharedMemory_create("memory", 128); |
| * |
| * // By default it has PROT_READ | PROT_WRITE | PROT_EXEC. |
| * char *buffer = (char *) mmap(NULL, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0); |
| * |
| * strcpy(buffer, "This is an example."); // trivially initialize content |
| * |
| * // limit access to read only |
| * ASharedMemory_setProt(fd, PROT_READ); |
| * |
| * // share fd with another process here and the other process can only map with PROT_READ. |
| * |
| * \param fd file descriptor of the shared memory region. |
| * \param prot any bitwise-or'ed combination of PROT_READ, PROT_WRITE, PROT_EXEC denoting |
| * updated access. Note access can only be removed, but not added back. |
| * \return 0 for success, error code on failure. |
| */ |
| int ASharedMemory_setProt(int fd, int prot) __INTRODUCED_IN(26); |
| |
| #endif // __ANDROID_API__ >= 26 |
| |
| #ifdef __cplusplus |
| }; |
| #endif |
| |
| #endif // ANDROID_SHARED_MEMORY_H |
| |
| /** @} */ |