LXR busybox/libbb/get

   1/* vi: set sw=4 ts=4: */
   2/*
   3 * Utility routines.
   4 *
   5 * Copyright (C) 2010 Denys Vlasenko
   6 *
   7 * Licensed under GPLv2, see file LICENSE in this source tree.
   8 */
   9#include "libbb.h"
  10
  11uoff_t FAST_FUNC get_volume_size_in_bytes(int fd,
  12                const char *override,
  13                unsigned override_units,
  14                int extend)
  15{
  16        uoff_t result;
  17
  18        if (override) {
  19                result = XATOOFF(override);
  20                if (result >= (uoff_t)(MAXINT(off_t)) / override_units)
  21                        bb_error_msg_and_die("image size is too big");
  22                result *= override_units;
  23                /* seek past end fails on block devices but works on files */
  24                if (lseek(fd, result - 1, SEEK_SET) != (off_t)-1) {
  25                        if (extend)
  26                                xwrite(fd, "", 1); /* file grows if needed */
  27                }
  28                //else {
  29                //      bb_error_msg("warning, block device is smaller");
  30                //}
  31        } else {
  32                /* more portable than BLKGETSIZE[64] */
  33                result = xlseek(fd, 0, SEEK_END);
  34        }
  35
  36        xlseek(fd, 0, SEEK_SET);
  37
  38        /* Prevent things like this:
  39         * $ dd if=/dev/zero of=foo count=1 bs=1024
  40         * $ mkswap foo
  41         * Setting up swapspace version 1, size = 18446744073709548544 bytes
  42         *
  43         * Picked 16k arbitrarily: */
  44        if (result < 16*1024)
  45                bb_error_msg_and_die("image is too small");
  46
  47        return result;
  48}
  49