lib/sbuf.h

   1 /*
   2  * Simple string buffer
   3  *
   4  * Copyright (C) 2017 Christian Franke
   5  *
   6  * This file is part of FRR.
   7  *
   8  * FRR is free software; you can redistribute it and/or modify it
   9  * under the terms of the GNU General Public License as published by the
  10  * Free Software Foundation; either version 2, or (at your option) any
  11  * later version.
  12  *
  13  * FRR is distributed in the hope that it will be useful, but
  14  * WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with FRR; see the file COPYING.  If not, write to the Free
  20  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
  21  * 02111-1307, USA.
  22  */
  23 #ifndef SBUF_H
  24 #define SBUF_H
  25
  26 /*
  27  * sbuf provides a simple string buffer. One application where this comes
  28  * in handy is the parsing of binary data: If there is an error in the parsing
  29  * process due to invalid input data, printing an error message explaining what
  30  * went wrong is definitely useful. However, just printing the actual error,
  31  * without any information about the previous parsing steps, is usually not very
  32  * helpful.
  33  * Using sbuf, the parser can log the whole parsing process into a buffer using
  34  * a printf like API. When an error ocurrs, all the information about previous
  35  * parsing steps is there in the log, without any need for backtracking, and can
  36  * be used to give a detailed and useful error description.
  37  * When parsing completes successfully without any error, the log can just be
  38  * discarded unless debugging is turned on, to not spam the log.
  39  *
  40  * For the described usecase, the code would look something like this:
  41  *
  42  * int sbuf_example(..., char **parser_log)
  43  * {
  44  *         struct sbuf logbuf;
  45  *
  46  *         sbuf_init(&logbuf, NULL, 0);
  47  *         sbuf_push(&logbuf, 0, "Starting parser\n");
  48  *
  49  *         int rv = do_parse(&logbuf, ...);
  50  *
  51  *         *parser_log = sbuf_buf(&logbuf);
  52  *
  53  *         return 1;
  54  * }
  55  *
  56  * In this case, sbuf_example uses a string buffer with undefined size, which
  57  * will
  58  * be allocated on the heap by sbuf. The caller of sbuf_example is expected to
  59  * free
  60  * the string returned in parser_log.
  61  */
  62
  63 struct sbuf {
  64         bool fixed;
  65         char *buf;
  66         size_t size;
  67         size_t pos;
  68         int indent;
  69 };
  70
  71 void sbuf_init(struct sbuf *dest, char *buf, size_t size);
  72 void sbuf_reset(struct sbuf *buf);
  73 const char *sbuf_buf(struct sbuf *buf);
  74 void sbuf_free(struct sbuf *buf);
  75 #include "lib/log.h"
  76 void sbuf_push(struct sbuf *buf, int indent, const char *format, ...)
  77         PRINTF_ATTRIBUTE(3, 4);
  78
  79 #endif