BSD 4_3_Tahoe release

[unix-history] / usr / src / new / bib / src / alpha.seek.c

#ifndef lint
static char sccsid[] = "@(#)alpha.seek.c        2.2     9/23/83";
#endif not lint
#

# include "stdio.h"
# include "ctype.h"
# include "streams.h"
# define  nexttry           ((high+low)/2)

/*  alpha_seek(stream, word, s_size, fold)
       seeks the first line in stream that is at least word.
   assumes that stream is a sorted file of lines.  (last char must be \n)
   if fold, assumes that word is lowercase and folds stream to lowercase.
   s_size = size of stream
   returns 1 if word = line, 0 o.w.
*/
int alpha_seek(stream, word, s_size, fold)
FILE *stream;
char *word;
long int s_size;
int  fold;
{   long int high, low, mid;    /*  point to beginning of a line in stream  */
   int      ans;               /*  line(low) < word <= line(high)          */
   char     line[maxstr];


   /*  initialize low (return if first line >= word)       */
       low= 0L;
       pos(low); getline(stream, line);
       if (fold) foldline(line);
       ans= strcmp(line,word);

       if ( ans >= 0)
       {   pos(low);   return(ans==0); }

   /*  initialize high to "line" after last line           */
       high= s_size;

   mid= nextline(stream, nexttry );
   while (mid < high )
   {   getline(stream,line);
       if (fold) foldline(line);
       if (strcmp(line,word) < 0)    low=  mid;
       else                          high= mid;
       mid= nextline(stream, nexttry );
   }

   /* linear search from low to high   */
       low= nextline(stream,low);
       for(;;)
       {   if (low>=high)      break;

           getline(stream,line);
           if (fold) foldline(line);
           ans=strcmp(line,word);

           if (ans>=0)         break;
           low= ftell(stream);
       }

   pos(low);
   if (low==high)  return(0);
   else            return(ans==0);
}


/*  foldline(p):    change all uppercase to lowercase in string p
*/
foldline(p)
char *p;
{   for (; *p!=NULL;  p++)
   {   if (isupper(*p))    *p = tolower(*p);
   }
}