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// 如果是Android平台，且尚未定义_ANDROID_ASHMEM_H，则定义它
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#ifdef __ANDROID__
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#ifndef _ANDROID_ASHMEM_H
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#define _ANDROID_ASHMEM_H
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// 包含所需的头文件
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#include <fcntl.h>
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#include <linux/ashmem.h> // 包含ashmem相关的ioctl操作
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#include <linux/shm.h>
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#include <sys/ioctl.h>
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#include <sys/mman.h> // 包含内存映射函数
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// 如果Android API级别大于或等于26（Android 8.0），则使用Bionic的shm*函数
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#if __ANDROID_API__ >= 26
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#define shmat bionic_shmat
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#define shmctl bionic_shmctl
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#define shmdt bionic_shmdt
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#define shmget bionic_shmget
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#endif
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#include <sys/shm.h> // 包含标准的共享内存函数
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#undef shmat
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#undef shmctl
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#undef shmdt
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#undef shmget // 取消对Bionic函数的重定义
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#include <stdio.h>
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// 定义ashmem设备的路径
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#define ASHMEM_DEVICE "/dev/ashmem"
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// 定义shmctl函数的封装，用于删除共享内存
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static inline int shmctl(int __shmid, int __cmd, struct shmid_ds* __buf) {
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int ret = 0;
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if (__cmd == IPC_RMID) {
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int length = ioctl(__shmid, ASHMEM_GET_SIZE, NULL);
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struct ashmem_pin pin = { 0, length };
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ret = ioctl(__shmid, ASHMEM_UNPIN, &pin);
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close(__shmid);
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}
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return ret;
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}
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// 定义shmget函数的封装，用于创建共享内存
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static inline int shmget(key_t __key, size_t __size, int __shmflg) {
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(void)__shmflg;
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int fd, ret;
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char ourkey[11];
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fd = open(ASHMEM_DEVICE, O_RDWR);
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if (fd < 0)
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return fd;
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sprintf(ourkey, "%d", __key);
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ret = ioctl(fd, ASHMEM_SET_NAME, ourkey);
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if (ret < 0)
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goto error;
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ret = ioctl(fd, ASHMEM_SET_SIZE, __size);
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if (ret < 0)
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goto error;
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return fd;
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error:
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close(fd);
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return ret;
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}
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// 定义shmat函数的封装，用于将共享内存附加到进程地址空间
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static inline void* shmat(int __shmid, const void* __shmaddr, int __shmflg) {
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(void)__shmflg;
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int size;
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void* ptr;
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size = ioctl(__shmid, ASHMEM_GET_SIZE, NULL);
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if (size < 0) {
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return NULL;
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}
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ptr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, __shmid, 0);
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if (ptr == MAP_FAILED) {
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return NULL;
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}
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return ptr;
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}
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#endif /* !_ANDROID_ASHMEM_H */
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#endif /* !__ANDROID__ */ |
