Initial import of the CDE 2.1.30 sources from the Open Group.

cde/lib/DtSearch/bmstrstr.c

@@ -0,0 +1,229 @@
+/*
+ *   COMPONENT_NAME: austext
+ *
+ *   FUNCTIONS: bmhcore
+ *		bmhtable_build
+ *		bmstrstr
+ *		main
+ *
+ *   ORIGINS: 27
+ *
+ *
+ *   (C) COPYRIGHT International Business Machines Corp. 1992,1995
+ *   All Rights Reserved
+ *   Licensed Materials - Property of IBM
+ *   US Government Users Restricted Rights - Use, duplication or
+ *   disclosure restricted by GSA ADP Schedule Contract with IBM Corp.
+ */
+/************************* BMSTRSTR.C ****************************
+ * $TOG: bmstrstr.c /main/6 1998/04/17 11:25:23 mgreess $
+ * Original module named fastsearch.c
+ * and included colocation string search functions.
+ * Modification of Boyer-Moore-Horspool algorithm,
+ * Sec 10.5.2 of Information Retrieval, Frakes and Baeza-Yates, editors.
+ * Provides a generalized boyer-moore
+ * strstr() function.  The table used in the BMH algorithm is
+ * generated in a separate function to improve efficiency when 
+ * looking for the same substring pattern in multiple text strings.
+ * The 'length' arguments can be passed if known, or passed as
+ * strlen(xxx) if not known.  HOWEVER the string arrays MUST be at
+ * least 1 char larger then strlen() says ('cause we insert a \0).
+ * This whole thing has been coded for SPEED!
+ *
+ * $Log$
+ * Revision 2.2  1995/10/26  15:37:42  miker
+ * Added prolog.
+ *
+ * Revision 2.1  1995/09/22  19:10:39  miker
+ * Freeze DtSearch 0.1, AusText 2.1.8
+ *
+ * Revision 1.2  1995/08/31  22:12:05  miker
+ * Minor changes for DtSearch.
+ */
+#include "SearchP.h"
+#include <stdio.h>
+#include <string.h>
+#include <sys/param.h>
+
+#ifndef _AIX
+#define __strcmp	strcmp
+#endif
+
+/*********#define TEST_BMSTRSTR**************/
+
+/****************************************/
+/*					*/
+/*	      bmhtable_build		*/
+/*					*/
+/****************************************/
+/* Builds the table for search substring 'pattern'
+ * used by the BMH core search algorithm.
+ * 'patlen' is the string length of 'pattern'.
+ * The caller defines and passes 'bmhtable',
+ * an array of long integers (size_t) of size MAX_BMHTAB.
+ * This function initializes bmhtable for later search call.
+ */
+void            bmhtable_build (
+                    unsigned char *pattern,
+                    size_t patlen,
+                    size_t * bmhtable)
+{
+    int             k;
+
+    for (k = 0; k < MAX_BMHTAB; k++)
+	bmhtable[k] = patlen;
+    patlen--;
+    for (k = 0; k < patlen; k++)
+	bmhtable[pattern[k]] = (patlen - k);
+    return;
+}  /* bmhtable_build() */
+
+
+/****************************************/
+/*					*/
+/*		 bmhcore		*/
+/*					*/
+/****************************************/
+/* Performs 'core' BMH search after bmhtable is built.
+ * Returns ptr to first occurrence of pattern in text or NULL.
+ * WARNING! IF EITHER txtlen OR patlen <= 0, THIS FUNCTION WILL CRASH!!!
+ * Pattern and patlen MUST BE identical with those used to build
+ * bmhtable.
+ */
+
+char           *bmhcore (
+                    unsigned char	*text,
+                    size_t		txtlen,
+                    unsigned char	*pattern,
+                    size_t		patlen,
+                    size_t		*bmhtable)
+{
+    register unsigned char
+		lastchar = pattern[patlen - 1];
+    register unsigned char
+		textchar;
+    register unsigned char
+		*cp;
+    register unsigned char	
+		*last;
+    int		savechar;
+    int		savechar2;
+    unsigned char
+		*result = NULL;
+
+    /* Terminate pattern with a char we KNOW is not in text.
+     * Note that this requires string to have room for \0 at end.
+     */
+    savechar = pattern[patlen];
+    pattern[patlen] = '\0';
+
+    last = text + txtlen;
+    for (cp = text + patlen - 1; cp < last; cp += bmhtable[textchar]) {
+	/*
+	 * Check if last character matches. If it doesn't, no need
+	 * to check any further. 
+	 */
+	if ((textchar = *cp) != lastchar)
+	    continue;
+	savechar2 = cp[1];
+	cp[1] = '\0';
+	if (!__strcmp ((char *) (cp + 1 - patlen), (char *) pattern))
+	    result = cp + 1 - patlen;
+	cp[1] = savechar2;
+	if (result)
+	    break;
+    }
+    pattern[patlen] = savechar;	/* restore last char */
+    return (char *) result;
+}  /* bmhcore() */
+
+
+/****************************************/
+/*					*/
+/*		 bmstrstr		*/
+/*					*/
+/****************************************/
+/* Search in text [1..txtlen] for pattern [1..patlen].
+ * Returns ptr to first occurrence of pattern, or NULL.
+ */
+char           *bmstrstr (
+                    unsigned char *text,
+                    size_t txtlen,
+                    unsigned char *pattern,
+                    size_t patlen)
+{
+    size_t          bmhtable[MAX_BMHTAB];
+
+    bmhtable_build (pattern, patlen, bmhtable);
+    return bmhcore (text, txtlen, pattern, patlen, bmhtable);
+}  /* bmstrstr() */
+
+
+#ifdef TEST_BMSTRSTR	/* for test only */
+#include <sys/stat.h>
+/****************************************/
+/*					*/
+/*		   main			*/
+/*					*/
+/****************************************/
+/* tests bmstrstr() against standard strstr() on a specified file */
+main ()
+{
+    FILE           *f;
+    struct stat     statbuf;
+    size_t          fsize = 0L;
+    char            fname[BUFSIZ+1];
+    char            pattern[MAXPATHLEN+1];
+    char           *readbuf = NULL;
+    char           *ptr;
+
+MAIN_LOOP:
+    printf ("\nEnter a filename (Ctrl-C quits) > ");
+
+    *fname = '\0';
+    fgets (fname, sizeof(fname), stdin);
+    if (strlen(fname) && fname[strlen(fname)-1] == '\n')
+      fname[strlen(fname)-1] = '\0';
+
+    if ((f = fopen (fname, "r")) == NULL) {
+	printf ("Can't open '%s': %s\n", fname, strerror (errno));
+	goto MAIN_LOOP;
+    }
+
+    fstat (fileno (f), &statbuf);
+    if (fsize > statbuf.st_size) {
+	free (readbuf);
+	readbuf = NULL;
+    }
+    fsize = statbuf.st_size;
+    if (readbuf == NULL)
+	readbuf = malloc (fsize + 64L);
+
+    fread (readbuf, fsize, 1L, f);
+    fclose (f);
+
+    printf ("Enter a search pattern > ");
+
+    *pattern = '\0';
+    fgets (pattern, sizeof(pattern), stdin);
+    if (strlen(pattern) && pattern[strlen(pattern)-1] == '\n')
+      pattern[strlen(pattern)-1] = '\0';
+
+    ptr = bmstrstr (readbuf, fsize, pattern, strlen (pattern));
+    if (ptr == NULL)
+	puts ("bmstrstr: Pattern not found.");
+    else
+	printf ("bmstrstr: Pattern found at offset %ld.\n", ptr - readbuf);
+
+    ptr = strstr (readbuf, pattern);
+    if (ptr == NULL)
+	puts ("strstr:   Pattern not found.");
+    else
+	printf ("strstr:   Pattern found at offset %ld.\n", ptr - readbuf);
+
+    goto MAIN_LOOP;
+}  /* main() test program */
+
+#endif
+
+/************************* BMSTRSTR.C ****************************/