external/ibm-public/postfix/dist/src/util/line_wrap.c

   1 /*      $NetBSD$        */
   2
   3 /*++
   4 /* NAME
   5 /*      line_wrap 3
   6 /* SUMMARY
   7 /*      wrap long lines upon output
   8 /* SYNOPSIS
   9 /*      #include <line_wrap.h>
  10 /*
  11 /*      void    line_wrap(string, len, indent, output_fn, context)
  12 /*      const char *buf;
  13 /*      int     len;
  14 /*      int     indent;
  15 /*      void    (*output_fn)(const char *str, int len, int indent, char *context);
  16 /*      char    *context;
  17 /* DESCRIPTION
  18 /*      The \fBline_wrap\fR routine outputs the specified string via
  19 /*      the specified output function, and attempts to keep output lines
  20 /*      shorter than the specified length. The routine does not attempt to
  21 /*      break long words that do not fit on a single line. Upon output,
  22 /*      trailing whitespace is stripped.
  23 /*
  24 /* Arguments
  25 /* .IP string
  26 /*      The input, which cannot contain any newline characters.
  27 /* .IP len
  28 /*      The desired maximal output line length.
  29 /* .IP indent
  30 /*      The desired amount of indentation of the second etc. output lines
  31 /*      with respect to the first output line. A negative indent causes
  32 /*      only the first line to be indented; a positive indent causes all
  33 /*      but the first line to be indented. A zero count causes no indentation.
  34 /* .IP output_fn
  35 /*      The output function that is called with as arguments a string
  36 /*      pointer, a string length, a non-negative indentation count, and
  37 /*      application context. A typical implementation looks like this:
  38 /* .sp
  39 /* .nf
  40 /* .na
  41 void print(const char *str, int len, int indent, char *context)
  42 {
  43     VSTREAM *fp = (VSTREAM *) context;
  44
  45     vstream_fprintf(fp, "%*s%.*s", indent, "", len, str);
  46 }
  47 /* .fi
  48 /* .ad
  49 /* .IP context
  50 /*      Application context that is passed on to the output function.
  51 /*      For example, a VSTREAM pointer, or a structure that contains
  52 /*      a VSTREAM pointer.
  53 /* BUGS
  54 /*      No tab expansion and no backspace processing.
  55 /* LICENSE
  56 /* .ad
  57 /* .fi
  58 /*      The Secure Mailer license must be distributed with this software.
  59 /* AUTHOR(S)
  60 /*      Wietse Venema
  61 /*      IBM T.J. Watson Research
  62 /*      P.O. Box 704
  63 /*      Yorktown Heights, NY 10598, USA
  64 /*--*/
  65
  66 /* System library. */
  67
  68 #include <sys_defs.h>
  69 #include <string.h>
  70 #include <ctype.h>
  71
  72 /* Utility library. */
  73
  74 #include <line_wrap.h>
  75
  76 /* line_wrap - wrap long lines upon output */
  77
  78 void    line_wrap(const char *str, int len, int indent, LINE_WRAP_FN output_fn,
  79                           char *context)
  80 {
  81     const char *start_line;
  82     const char *word;
  83     const char *next_word;
  84     const char *next_space;
  85     int     line_len;
  86     int     curr_len;
  87     int     curr_indent;
  88
  89     if (indent < 0) {
  90         curr_indent = -indent;
  91         curr_len = len + indent;
  92     } else {
  93         curr_indent = 0;
  94         curr_len = len;
  95     }
  96
  97     /*
  98      * At strategic positions, output what we have seen, after stripping off
  99      * trailing blanks.
 100      */
 101     for (start_line = word = str; word != 0; word = next_word) {
 102         next_space = word + strcspn(word, " \t");
 103         if (word > start_line) {
 104             if (next_space - start_line > curr_len) {
 105                 line_len = word - start_line;
 106                 while (line_len > 0 && ISSPACE(start_line[line_len - 1]))
 107                     line_len--;
 108                 output_fn(start_line, line_len, curr_indent, context);
 109                 while (*word && ISSPACE(*word))
 110                     word++;
 111                 if (start_line == str) {
 112                     curr_indent += indent;
 113                     curr_len -= indent;
 114                 }
 115                 start_line = word;
 116             }
 117         }
 118         next_word = *next_space ? next_space + 1 : 0;
 119     }
 120     line_len = strlen(start_line);
 121     while (line_len > 0 && ISSPACE(start_line[line_len - 1]))
 122         line_len--;
 123     output_fn(start_line, line_len, curr_indent, context);
 124 }