contrib/file/src/buffer.c

   1 /*
   2  * Copyright (c) Christos Zoulas 2017.
   3  * All Rights Reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice immediately at the beginning of the file, without modification,
  10  *    this list of conditions, and the following disclaimer.
  11  * 2. Redistributions in binary form must reproduce the above copyright
  12  *    notice, this list of conditions and the following disclaimer in the
  13  *    documentation and/or other materials provided with the distribution.
  14  *
  15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  16  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  17  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  18  * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR
  19  * ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  21  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  25  * SUCH DAMAGE.
  26  */
  27 #include "file.h"
  28
  29 #ifndef lint
  30 FILE_RCSID("@(#)$File: buffer.c,v 1.7 2019/06/10 21:35:26 christos Exp $")
  31 #endif  /* lint */
  32
  33 #include "magic.h"
  34 #include <unistd.h>
  35 #include <string.h>
  36 #include <stdlib.h>
  37 #include <sys/stat.h>
  38
  39 void
  40 buffer_init(struct buffer *b, int fd, const struct stat *st, const void *data,
  41     size_t len)
  42 {
  43         b->fd = fd;
  44         if (st)
  45                 memcpy(&b->st, st, sizeof(b->st));
  46         else if (b->fd == -1 || fstat(b->fd, &b->st) == -1)
  47                 memset(&b->st, 0, sizeof(b->st));
  48         b->fbuf = data;
  49         b->flen = len;
  50         b->eoff = 0;
  51         b->ebuf = NULL;
  52         b->elen = 0;
  53 }
  54
  55 void
  56 buffer_fini(struct buffer *b)
  57 {
  58         free(b->ebuf);
  59 }
  60
  61 int
  62 buffer_fill(const struct buffer *bb)
  63 {
  64         struct buffer *b = CCAST(struct buffer *, bb);
  65
  66         if (b->elen != 0)
  67                 return b->elen == CAST(size_t, ~0) ? -1 : 0;
  68
  69         if (!S_ISREG(b->st.st_mode))
  70                 goto out;
  71
  72         b->elen =  CAST(size_t, b->st.st_size) < b->flen ?
  73             CAST(size_t, b->st.st_size) : b->flen;
  74         if ((b->ebuf = malloc(b->elen)) == NULL)
  75                 goto out;
  76
  77         b->eoff = b->st.st_size - b->elen;
  78         if (pread(b->fd, b->ebuf, b->elen, b->eoff) == -1) {
  79                 free(b->ebuf);
  80                 b->ebuf = NULL;
  81                 goto out;
  82         }
  83
  84         return 0;
  85 out:
  86         b->elen = CAST(size_t, ~0);
  87         return -1;
  88 }