io/pread.c

   1 /*
   2  * Copyright (c) 2003 Silicon Graphics, Inc.  All Rights Reserved.
   3  *
   4  * This program is free software; you can redistribute it and/or modify it
   5  * under the terms of version 2 of the GNU General Public License as
   6  * published by the Free Software Foundation.
   7  *
   8  * This program is distributed in the hope that it would be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
  11  *
  12  * Further, this software is distributed without any warranty that it is
  13  * free of the rightful claim of any third person regarding infringement
  14  * or the like.  Any license provided herein, whether implied or
  15  * otherwise, applies only to this software file.  Patent licenses, if
  16  * any, provided herein do not apply to combinations of this program with
  17  * other software, or any other product whatsoever.
  18  *
  19  * You should have received a copy of the GNU General Public License along
  20  * with this program; if not, write the Free Software Foundation, Inc., 59
  21  * Temple Place - Suite 330, Boston MA 02111-1307, USA.
  22  *
  23  * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
  24  * Mountain View, CA  94043, or:
  25  *
  26  * http://www.sgi.com
  27  *
  28  * For further information regarding this notice, see:
  29  *
  30  * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
  31  */
  32
  33 #include <libxfs.h>
  34 #include <ctype.h>
  35 #include "command.h"
  36 #include "input.h"
  37 #include "init.h"
  38
  39 static cmdinfo_t pread_cmd;
  40
  41 static void
  42 pread_help(void)
  43 {
  44         printf(_(
  45 "\n"
  46 " reads a range of bytes in a specified block size from the given offset\n"
  47 "\n"
  48 " Example:\n"
  49 " 'read -v 512 20' - dumps 20 bytes read from 512 bytes into the file\n"
  50 "\n"
  51 " Reads a segment of the currently open file, optionally dumping it to the\n"
  52 " standard output stream (with -v option) for subsequent inspection.\n"
  53 " The reads are performed in sequential blocks starting at offset, with the\n"
  54 " blocksize tunable using the -b option (default blocksize is 4096 bytes).\n"
  55 "\n"));
  56 }
  57
  58 void    *buffer;
  59 ssize_t buffersize;
  60
  61 int
  62 alloc_buffer(
  63         ssize_t         bsize,
  64         unsigned int    seed)
  65 {
  66         if (bsize > buffersize) {
  67                 buffer = realloc(buffer, buffersize = bsize);
  68                 if (!buffer) {
  69                         perror("realloc");
  70                         buffersize = 0;
  71                         return 0;
  72                 }
  73         }
  74         memset(buffer, seed, buffersize);
  75         return 1;
  76 }
  77
  78 static void
  79 dump_buffer(
  80         off64_t         offset,
  81         ssize_t         len)
  82 {
  83         int             i, j;
  84         char            *p;
  85
  86         for (i = 0, p = (char *)buffer; i < len; i += 16) {
  87                 char    *s = p;
  88
  89                 printf("%08llx:  ", (off64_t)i + offset);
  90                 for (j = 0; j < 16 && i + j < len; j++, p++)
  91                         printf("%02x ", *p);
  92                 printf(" ");
  93                 for (j = 0; j < 16 && i + j < len; j++, s++) {
  94                         if (isalnum(*s))
  95                                 printf("%c", *s);
  96                         else
  97                                 printf(".");
  98                 }
  99                 printf("\n");
 100         }
 101 }
 102
 103 int
 104 read_buffer(
 105         int             fd,
 106         off64_t         offset,
 107         ssize_t         count,
 108         ssize_t         *total,
 109         int             verbose,
 110         int             onlyone)
 111 {
 112         ssize_t         bytes;
 113
 114         *total = 0;
 115         while (count > 0) {
 116                 bytes = pread64(fd, buffer, min(count,buffersize), offset);
 117                 if (bytes == 0)
 118                         break;
 119                 if (bytes < 0) {
 120                         perror("pread64");
 121                         return 0;
 122                 }
 123                 if (verbose)
 124                         dump_buffer(offset, bytes);
 125                 *total += bytes;
 126                 if (onlyone || bytes < count)
 127                         break;
 128                 offset += bytes;
 129                 count -= bytes;
 130         }
 131         return 1;
 132 }
 133
 134 static int
 135 pread_f(
 136         int             argc,
 137         char            **argv)
 138 {
 139         off64_t         offset;
 140         ssize_t         count, total;
 141         unsigned int    bsize = 4096;
 142         char            *sp;
 143         int             vflag = 0;
 144         int             c;
 145
 146         while ((c = getopt(argc, argv, "b:v")) != EOF) {
 147                 switch (c) {
 148                 case 'b':
 149                         bsize = strtoul(optarg, &sp, 0);
 150                         if (!sp || sp == optarg) {
 151                                 printf(_("non-numeric bsize -- %s\n"), optarg);
 152                                 return 0;
 153                         }
 154                         break;
 155                 case 'v':
 156                         vflag = 1;
 157                         break;
 158                 default:
 159                         printf("%s %s\n", pread_cmd.name, pread_cmd.oneline);
 160                         return 0;
 161                 }
 162         }
 163         if (optind != argc - 2) {
 164                 printf("%s %s\n", pread_cmd.name, pread_cmd.oneline);
 165                 return 0;
 166         }
 167         offset = strtoul(argv[optind], &sp, 0);
 168         if (!sp || sp == argv[optind]) {
 169                 printf(_("non-numeric offset argument -- %s\n"), argv[optind]);
 170                 return 0;
 171         }
 172         optind++;
 173         count = strtoul(argv[optind], &sp, 0);
 174         if (!sp || sp == argv[optind]) {
 175                 printf(_("non-numeric length argument -- %s\n"), argv[optind]);
 176                 return 0;
 177         }
 178
 179         if (!alloc_buffer(bsize, 0xabababab))
 180                 return 0;
 181
 182         if (!read_buffer(fdesc, offset, count, &total, vflag, 0))
 183                 return 0;
 184
 185         printf(_("read %u/%u bytes at offset %llu\n"), total, count, offset);
 186         return 0;
 187 }
 188
 189 void
 190 pread_init(void)
 191 {
 192         pread_cmd.name = _("pread");
 193         pread_cmd.altname = _("r");
 194         pread_cmd.cfunc = pread_f;
 195         pread_cmd.argmin = 2;
 196         pread_cmd.argmax = -1;
 197         pread_cmd.args = _("[-b bs] [-v] off len");
 198         pread_cmd.oneline = _("reads a number of bytes at a specified offset");
 199         pread_cmd.help = pread_help;
 200
 201         add_command(&pread_cmd);
 202 }