41 lines
1.1 KiB
C++
41 lines
1.1 KiB
C++
#include <stdio.h>
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#include <fcntl.h>
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#include <unistd.h>
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#include <errno.h>
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#include <string.h>
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bool writeall(int fd, const void* buffer, size_t len)
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{
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const char* buf = (const char*) buffer;
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while ( len )
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{
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ssize_t byteswritten = write(fd, buf, len);
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if ( byteswritten < 0 ) { return false; }
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buf += byteswritten;
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len -= byteswritten;
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}
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return true;
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}
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int main(int argc, char* argv[])
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{
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if ( argc != 3 ) { printf("usage: %s <from> <to>\n", argv[0]); return 0; }
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int fromfd = open(argv[1], O_RDONLY);
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if ( fromfd < 0 ) { printf("%s: %s: %s\n", argv[0], argv[1], strerror(errno)); return 1; }
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int tofd = open(argv[2], O_WRONLY | O_TRUNC | O_CREAT, 0777);
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if ( tofd < 0 ) { printf("%s: %s: %s\n", argv[0], argv[2], strerror(errno)); return 1; }
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while ( true )
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{
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const size_t BUFFER_SIZE = 4096;
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char buffer[BUFFER_SIZE];
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ssize_t bytesread = read(fromfd, buffer, BUFFER_SIZE);
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if ( bytesread < 0 ) { printf("%s: %s: %s\n", argv[0], argv[1], strerror(errno)); return 1; }
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if ( bytesread == 0 ) { return 0; }
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if ( !writeall(tofd, buffer, bytesread) ) { printf("%s: %s: %s\n", argv[0], argv[2], strerror(errno)); return 1; }
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}
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}
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