char commlist[MAXCOMM]= /* list of strings of common words */
"";
int firsttime = 1;
/* makekey(p,max_klen,common): compresses *p into a key
folds upper to lower case. ignores non-alphanumeric
drops keys of length <= 1.
drops words in common (name of file of words, one per line)
(first call determines common for all later calls)
*/
makekey(p,max_klen,common)
char *p;
int max_klen; /* max key length */
char *common;
{ register char *from, *to, *stop;
if (firsttime) {firsttime= 0; load_comm(common); }
from= p; to= p; stop= max_klen+p;
while (*from != NULL && to < stop)
{ if (islower(*from)) *to++ = *from++;
else if (isdigit(*from)) *to++ = *from++;
else if (isupper(*from)) { *to++ = tolower(*from); from++; }
else from++;
}
*to= NULL;
if (to<=p+1 ||
lookup(commlist, p) ) *p= NULL;
}
/* list is a string of null terminated strings, final string is null.
p is a null terminated string.
return 1 if p is a string in list, 0 ow.
*/
int lookup(list,p)
char *list, *p;
{ int len;
len= strlen(list);
while (len!=0 && strcmp(list,p)!=0)
{ list += (len+1);
len= strlen(list);
}
return(len!=0);
}
/* read file common into commlist
*/
load_comm(common)
char *common;
{ FILE *commfile; /* stream of common words */
char *p, *stop;
commfile= fopen(common,"r");
if (commfile==NULL) fprintf(stderr, "cannot open '%s'\n", common);
else
{ /* read commfile into commlist */
p= commlist; stop= commlist+MAXCOMM-1;
while (p<stop && ((*p= getc(commfile))!=EOF))
{ if (*p=='\n') *p= NULL;
p++;
}
if (*p==EOF) *p= NULL;
else
{ fprintf(stderr, "invert: too many common words\n");
commlist[0]= NULL;
}
fclose(commfile);
}
}
