4.3BSD - /usr/src/new/bib/src/alpha.seek.c

   1: #ifndef lint
   2: static char sccsid[] = "@(#)alpha.seek.c	2.2	9/23/83";
   3: #endif not lint
   4: #
   5: 
   6: # include "stdio.h"
   7: # include "ctype.h"
   8: # include "streams.h"
   9: # define  nexttry           ((high+low)/2)
  10: 
  11: /*  alpha_seek(stream, word, s_size, fold)
  12:         seeks the first line in stream that is at least word.
  13:     assumes that stream is a sorted file of lines.  (last char must be \n)
  14:     if fold, assumes that word is lowercase and folds stream to lowercase.
  15:     s_size = size of stream
  16:     returns 1 if word = line, 0 o.w.
  17: */
  18: int alpha_seek(stream, word, s_size, fold)
  19: FILE *stream;
  20: char *word;
  21: long int s_size;
  22: int  fold;
  23: {   long int high, low, mid;    /*  point to beginning of a line in stream  */
  24:     int      ans;               /*  line(low) < word <= line(high)          */
  25:     char     line[maxstr];
  26: 
  27: 
  28:     /*  initialize low (return if first line >= word)       */
  29:         low= 0L;
  30:         pos(low); getline(stream, line);
  31:         if (fold) foldline(line);
  32:         ans= strcmp(line,word);
  33: 
  34:         if ( ans >= 0)
  35:         {   pos(low);   return(ans==0); }
  36: 
  37:     /*  initialize high to "line" after last line           */
  38:         high= s_size;
  39: 
  40:     mid= nextline(stream, nexttry );
  41:     while (mid < high )
  42:     {   getline(stream,line);
  43:         if (fold) foldline(line);
  44:         if (strcmp(line,word) < 0)    low=  mid;
  45:         else                          high= mid;
  46:         mid= nextline(stream, nexttry );
  47:     }
  48: 
  49:     /* linear search from low to high   */
  50:         low= nextline(stream,low);
  51:         for(;;)
  52:         {   if (low>=high)      break;
  53: 
  54:             getline(stream,line);
  55:             if (fold) foldline(line);
  56:             ans=strcmp(line,word);
  57: 
  58:             if (ans>=0)         break;
  59:             low= ftell(stream);
  60:         }
  61: 
  62:     pos(low);
  63:     if (low==high)  return(0);
  64:     else            return(ans==0);
  65: }
  66: 
  67: 
  68: /*  foldline(p):    change all uppercase to lowercase in string p
  69: */
  70: foldline(p)
  71: char *p;
  72: {   for (; *p!=NULL;  p++)
  73:     {   if (isupper(*p))    *p = tolower(*p);
  74:     }
  75: }

Defined functions

Defined variables

Defined macros