/*********************************************************************************
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* Copyright: (C) 2025 LingYun IoT System Studio
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* All rights reserved.
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*
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* Filename: mmap_file.c
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* Description: This file Memory Map(file) example program
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*
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* Version: 1.0.0(11/10/2025)
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* Author: Guo Wenxue <guowenxue@gmail.com>
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* ChangeLog: 1, Release initial version on "11/10/2025 12:44:56 PM"
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*
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********************************************************************************/
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#include <stdio.h>
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#include <stdlib.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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int main(void)
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{
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int fd, rv=0;
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struct stat st;
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char *mapped;
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char *file = "test.txt";
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fd = open(file, O_RDWR);
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if (fd < 0)
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{
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printf("open \"%s\" failure: %s\n", file, strerror(errno));
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return 1;
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}
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/* 获取文件大小 */
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if (fstat(fd, &st) == -1)
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{
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printf("fstat failure %s\n", strerror(errno));
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rv = 2;
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goto cleanup;
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}
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/* 将文件映射到内存 */
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mapped = mmap(NULL, st.st_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (mapped == MAP_FAILED)
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{
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printf("mmap failure %s\n", strerror(errno));
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rv = 4;
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goto cleanup;
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}
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/* 修改文件内容 */
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printf("Original content: %s\n", mapped);
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strcpy(mapped, "Hello mmap!\n");
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printf("Modify content: %s\n", mapped);
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/* 解除映射并关闭文件 */
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munmap(mapped, st.st_size);
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cleanup:
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close(fd);
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return 0;
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}
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