support/support_quote_blob.c

   1 /* Quote a blob so that it can be used in C literals.
   2    Copyright (C) 2018-2019 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <support/support.h>
  20 #include <support/xmemstream.h>
  21
  22 char *
  23 support_quote_blob (const void *blob, size_t length)
  24 {
  25   struct xmemstream out;
  26   xopen_memstream (&out);
  27
  28   const unsigned char *p = blob;
  29   for (size_t i = 0; i < length; ++i)
  30     {
  31       unsigned char ch = p[i];
  32
  33       /* Use C backslash escapes for those control characters for
  34          which they are defined.  */
  35       switch (ch)
  36         {
  37           case '\a':
  38             putc_unlocked ('\\', out.out);
  39             putc_unlocked ('a', out.out);
  40             break;
  41           case '\b':
  42             putc_unlocked ('\\', out.out);
  43             putc_unlocked ('b', out.out);
  44             break;
  45           case '\f':
  46             putc_unlocked ('\\', out.out);
  47             putc_unlocked ('f', out.out);
  48             break;
  49           case '\n':
  50             putc_unlocked ('\\', out.out);
  51             putc_unlocked ('n', out.out);
  52             break;
  53           case '\r':
  54             putc_unlocked ('\\', out.out);
  55             putc_unlocked ('r', out.out);
  56             break;
  57           case '\t':
  58             putc_unlocked ('\\', out.out);
  59             putc_unlocked ('t', out.out);
  60             break;
  61           case '\v':
  62             putc_unlocked ('\\', out.out);
  63             putc_unlocked ('v', out.out);
  64             break;
  65           case '\\':
  66           case '\'':
  67           case '\"':
  68             putc_unlocked ('\\', out.out);
  69             putc_unlocked (ch, out.out);
  70             break;
  71         default:
  72           if (ch < ' ' || ch > '~')
  73             /* Use octal sequences because they are fixed width,
  74                unlike hexadecimal sequences.  */
  75             fprintf (out.out, "\\%03o", ch);
  76           else
  77             putc_unlocked (ch, out.out);
  78         }
  79     }
  80
  81   xfclose_memstream (&out);
  82   return out.buffer;
  83 }