71 lines
2.5 KiB
C
71 lines
2.5 KiB
C
/*************************************************************************\
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* Copyright (C) Michael Kerrisk, 2015. *
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* *
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* This program is free software. You may use, modify, and redistribute it *
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* under the terms of the GNU Lesser General Public License as published *
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* by the Free Software Foundation, either version 3 or (at your option) *
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* any later version. This program is distributed without any warranty. *
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* See the files COPYING.lgpl-v3 and COPYING.gpl-v3 for details. *
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\*************************************************************************/
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/* read_line.c
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Implementation of readLine().
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*/
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#include <unistd.h>
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#include <errno.h>
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#include "readline.h" /* Declaration of readLine() */
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/* Read characters from 'fd' until a newline is encountered. If a newline
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character is not encountered in the first (n - 1) bytes, then the excess
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characters are discarded. The returned string placed in 'buf' is
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null-terminated and includes the newline character if it was read in the
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first (n - 1) bytes. The function return value is the number of bytes
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placed in buffer (which includes the newline character if encountered,
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but excludes the terminating null byte). */
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ssize_t
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readline(int fd, void *buffer, size_t n)
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{
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ssize_t numRead; /* # of bytes fetched by last read() */
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size_t totRead; /* Total bytes read so far */
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char *buf;
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char ch;
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if (n <= 0 || buffer == NULL) {
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errno = EINVAL;
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return -1;
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}
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buf = buffer; /* No pointer arithmetic on "void *" */
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totRead = 0;
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for (;;) {
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numRead = read(fd, &ch, 1);
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if (numRead == -1) {
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if (errno == EINTR) /* Interrupted --> restart read() */
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continue;
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else
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return -1; /* Some other error */
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} else if (numRead == 0) { /* EOF */
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if (totRead == 0) /* No bytes read; return 0 */
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return 0;
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else /* Some bytes read; add '\0' */
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break;
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} else { /* 'numRead' must be 1 if we get here */
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if (totRead < n - 1) { /* Discard > (n - 1) bytes */
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totRead++;
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*buf++ = ch;
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}
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if (ch == '\n')
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break;
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}
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}
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*buf = '\0';
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return totRead;
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}
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