LXR busybox/libbb/read.c

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Utility routines.
   4 *
   5 * Copyright (C) 1999-2004 by Erik Andersen <andersen@codepoet.org>
   6 *
   7 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
   8 */
   9#include "libbb.h"
  10
  11ssize_t FAST_FUNC safe_read(int fd, void *buf, size_t count)
  12{
  13        ssize_t n;
  14
  15        for (;;) {
  16                n = read(fd, buf, count);
  17                if (n >= 0 || errno != EINTR)
  18                        break;
  19                /* Some callers set errno=0, are upset when they see EINTR.
  20                 * Returning EINTR is wrong since we retry read(),
  21                 * the "error" was transient.
  22                 */
  23                errno = 0;
  24                /* repeat the read() */
  25        }
  26
  27        return n;
  28}
  29
  30/*
  31 * Read all of the supplied buffer from a file.
  32 * This does multiple reads as necessary.
  33 * Returns the amount read, or -1 on an error.
  34 * A short read is returned on an end of file.
  35 */
  36ssize_t FAST_FUNC full_read(int fd, void *buf, size_t len)
  37{
  38        ssize_t cc;
  39        ssize_t total;
  40
  41        total = 0;
  42
  43        while (len) {
  44                cc = safe_read(fd, buf, len);
  45
  46                if (cc < 0) {
  47                        if (total) {
  48                                /* we already have some! */
  49                                /* user can do another read to know the error code */
  50                                return total;
  51                        }
  52                        return cc; /* read() returns -1 on failure. */
  53                }
  54                if (cc == 0)
  55                        break;
  56                buf = ((char *)buf) + cc;
  57                total += cc;
  58                len -= cc;
  59        }
  60
  61        return total;
  62}
  63
  64ssize_t FAST_FUNC read_close(int fd, void *buf, size_t size)
  65{
  66        /*int e;*/
  67        size = full_read(fd, buf, size);
  68        /*e = errno;*/
  69        close(fd);
  70        /*errno = e;*/
  71        return size;
  72}
  73
  74ssize_t FAST_FUNC open_read_close(const char *filename, void *buf, size_t size)
  75{
  76        int fd = open(filename, O_RDONLY);
  77        if (fd < 0)
  78                return fd;
  79        return read_close(fd, buf, size);
  80}
  81