add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/elvis/regsub.c

@@ -0,0 +1,86 @@
+/*
+ * regsub
+ *
+ *	Copyright (c) 1986 by University of Toronto.
+ *	Written by Henry Spencer.  Not derived from licensed software.
+ *
+ *	Permission is granted to anyone to use this software for any
+ *	purpose on any computer system, and to redistribute it freely,
+ *	subject to the following restrictions:
+ *
+ *	1. The author is not responsible for the consequences of use of
+ *		this software, no matter how awful, even if they arise
+ *		from defects in it.
+ *
+ *	2. The origin of this software must not be misrepresented, either
+ *		by explicit claim or by omission.
+ *
+ *	3. Altered versions must be plainly marked as such, and must not
+ *		be misrepresented as being the original software.
+ */
+#include "regexp.h"
+#define NULL	(char *)0
+/*
+ * The first byte of the regexp internal "program" is actually this magic
+ * number; the start node begins in the second byte.
+ */
+#define	MAGIC	0234
+
+
+#define CHARBITS 0377
+#ifndef CHARBITS
+#define	UCHARAT(p)	((int)*(unsigned char *)(p))
+#else
+#define	UCHARAT(p)	((int)*(p)&CHARBITS)
+#endif
+
+/*
+ - regsub - perform substitutions after a regexp match
+ */
+void regsub(prog, source, dest)
+regexp *prog;
+char *source;
+char *dest;
+{
+	register char *src;
+	register char *dst;
+	register char c;
+	register int no;
+	register int len;
+	extern char *strncpy();
+
+	if (!prog || !source || !dest) {
+		regerror("NULL parm to regsub");
+		return;
+	}
+	if (UCHARAT(prog->program) != MAGIC) {
+		regerror("damaged regexp fed to regsub");
+		return;
+	}
+
+	src = source;
+	dst = dest;
+	while ((c = *src++) != '\0') {
+		if (c == '&')
+			no = 0;
+		else if (c == '\\' && '0' <= *src && *src <= '9')
+			no = *src++ - '0';
+		else
+			no = -1;
+
+		if (no < 0) {	/* Ordinary character. */
+			if (c == '\\' && *src != '\0')
+				c = *src++;
+			*dst++ = c;
+		} else if (prog->startp[no] != NULL && prog->endp[no] != NULL) {
+			len = (int)(prog->endp[no] - prog->startp[no]);
+			strncpy(dst, prog->startp[no], len);
+			dst += len;
+			if (len !=0 && *(dst-1) == '\0') { /* strncpy hit NUL. */
+				regerror("damaged match string");
+				return;
+			}
+		}
+	}
+	*dst++ = '\0';
+}