138 lines
2.7 KiB
C
138 lines
2.7 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Utility routines.
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*
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* Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
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*
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* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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*/
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#include "libbb.h"
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ssize_t safe_read(int fd, void *buf, size_t count)
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{
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ssize_t n;
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do {
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n = read(fd, buf, count);
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} while (n < 0 && errno == EINTR);
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return n;
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}
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/*
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* Read all of the supplied buffer from a file.
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* This does multiple reads as necessary.
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* Returns the amount read, or -1 on an error.
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* A short read is returned on an end of file.
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*/
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ssize_t full_read(int fd, void *buf, size_t len)
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{
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ssize_t cc;
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ssize_t total;
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total = 0;
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while (len) {
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cc = safe_read(fd, buf, len);
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if (cc < 0)
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return cc; /* read() returns -1 on failure. */
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if (cc == 0)
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break;
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buf = ((char *)buf) + cc;
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total += cc;
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len -= cc;
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}
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return total;
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}
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// Die with an error message if we can't read the entire buffer.
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void xread(int fd, void *buf, size_t count)
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{
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if (count) {
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ssize_t size = full_read(fd, buf, count);
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if (size != count)
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bb_error_msg_and_die("short read");
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}
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}
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// Die with an error message if we can't read one character.
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unsigned char xread_char(int fd)
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{
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char tmp;
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xread(fd, &tmp, 1);
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return tmp;
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}
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// Read one line a-la fgets. Works only on seekable streams
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char *reads(int fd, char *buffer, size_t size)
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{
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char *p;
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if (size < 2)
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return NULL;
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size = full_read(fd, buffer, size-1);
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if ((ssize_t)size <= 0)
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return NULL;
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buffer[size] = '\0';
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p = strchr(buffer, '\n');
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if (p) {
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off_t offset;
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*p++ = '\0';
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// avoid incorrect (unsigned) widening
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offset = (off_t)(p-buffer) - (off_t)size;
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// set fd position the right after the \n
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if (offset && lseek(fd, offset, SEEK_CUR) == (off_t)-1)
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return NULL;
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}
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return buffer;
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}
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ssize_t read_close(int fd, void *buf, size_t size)
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{
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int e;
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size = full_read(fd, buf, size);
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e = errno;
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close(fd);
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errno = e;
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return size;
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}
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ssize_t open_read_close(const char *filename, void *buf, size_t size)
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{
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int fd = open(filename, O_RDONLY);
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if (fd < 0)
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return fd;
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return read_close(fd, buf, size);
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}
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void *xmalloc_open_read_close(const char *filename, size_t *sizep)
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{
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char *buf;
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size_t size = sizep ? *sizep : INT_MAX;
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int fd = xopen(filename, O_RDONLY);
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/* /proc/N/stat files report len 0 here */
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/* In order to make such files readable, we add small const */
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off_t len = xlseek(fd, 0, SEEK_END) + 256;
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xlseek(fd, 0, SEEK_SET);
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if (len > size)
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bb_error_msg_and_die("file '%s' is too big", filename);
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size = len;
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buf = xmalloc(size + 1);
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size = read_close(fd, buf, size);
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if ((ssize_t)size < 0)
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bb_perror_msg_and_die("'%s'", filename);
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xrealloc(buf, size + 1);
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buf[size] = '\0';
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if (sizep) *sizep = size;
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return buf;
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}
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