usr/src/lib/libast/common/string/fmtbuf.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                   Phong Vo <kpv@research.att.com>                    *
  20 *                                                                      *
  21 ***********************************************************************/
  22 #pragma prototyped
  23
  24 #include <ast.h>
  25
  26 /*
  27  * return small format buffer chunk of size n
  28  * spin lock for thread access
  29  * format buffers are short lived
  30  * only one concurrent buffer with size > sizeof(buf)
  31  */
  32
  33 static char             buf[16 * 1024];
  34 static char*            nxt = buf;
  35 static int              lck = -1;
  36
  37 static char*            big;
  38 static size_t           bigsiz;
  39
  40 char*
  41 fmtbuf(size_t n)
  42 {
  43         register char*  cur;
  44
  45         while (++lck)
  46                 lck--;
  47         if (n > (&buf[elementsof(buf)] - nxt))
  48         {
  49                 if (n > elementsof(buf))
  50                 {
  51                         if (n > bigsiz)
  52                         {
  53                                 bigsiz = roundof(n, 8 * 1024);
  54                                 if (!(big = newof(big, char, bigsiz, 0)))
  55                                 {
  56                                         lck--;
  57                                         return 0;
  58                                 }
  59                         }
  60                         lck--;
  61                         return big;
  62                 }
  63                 nxt = buf;
  64         }
  65         cur = nxt;
  66         nxt += n;
  67         lck--;
  68         return cur;
  69 }