116 lines
1.6 KiB
C++
116 lines
1.6 KiB
C++
#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/mman.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#define FILE_NAME "test-file"
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#define FILE_SIZE (1024*1024)
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int prepare_file()
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{
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int fd = open(FILE_NAME, O_RDWR | O_TRUNC | O_CREAT, 0666);
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if (fd == -1)
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{
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perror("open");
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return 1;
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}
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void* null_buffer = malloc(FILE_SIZE);
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memset(null_buffer, 0x00, FILE_SIZE);
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if (write(fd, null_buffer, FILE_SIZE) == -1)
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{
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perror("write");
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return 1;
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}
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free(null_buffer);
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close(fd);
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printf("file created\n");
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return 0;
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}
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int job1()
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{
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int fd = open(FILE_NAME, O_RDONLY);
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if (fd == -1)
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{
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perror("open");
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return 1;
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}
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void* addr = mmap(nullptr, FILE_SIZE, PROT_READ, MAP_SHARED, fd, 0);
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if (addr == MAP_FAILED)
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{
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perror("mmap");
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return 1;
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}
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sleep(4);
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size_t sum = 0;
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for (int i = 0; i < FILE_SIZE; i++)
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sum += ((uint8_t*)addr)[i];
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munmap(addr, FILE_SIZE);
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close(fd);
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printf("sum: %zu\n", sum);
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return 0;
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}
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int job2()
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{
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sleep(2);
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int fd = open(FILE_NAME, O_RDWR);
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if (fd == -1)
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{
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perror("open");
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return 1;
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}
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void* addr = mmap(nullptr, FILE_SIZE, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
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if (addr == MAP_FAILED)
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{
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perror("mmap");
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return 1;
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}
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memset(addr, 'a', FILE_SIZE);
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munmap(addr, FILE_SIZE);
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close(fd);
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printf("expecting: %zu\n", (size_t)'a' * FILE_SIZE);
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return 0;
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}
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int main()
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{
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if (int ret = prepare_file())
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return ret;
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pid_t pid = fork();
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if (pid == 0)
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return job1();
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if (pid == -1)
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{
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perror("fork");
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return 1;
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}
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int ret = job2();
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waitpid(pid, nullptr, 0);
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return ret;
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}
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