1 files changed, 109 insertions, 0 deletions
diff --git a/lib/libpathconv/abs2rel.c b/lib/libpathconv/abs2rel.c
new file mode 100644
index 000000000000..a71009112fb2
--- /dev/null
+++ b/lib/libpathconv/abs2rel.c
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 1997 Shigio Yamaguchi. All rights reserved.
+ * Copyright (c) 1999 Tama Communications Corporation. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include <errno.h>
+#include <stdlib.h>
+#include <string.h>
+#include "pathconv.h" /* prototypes */
+/*
+ * abs2rel: convert an absolute path name into relative.
+ *
+ *	i)	path	absolute path
+ *	i)	base	base directory (must be absolute path)
+ *	o)	result	result buffer
+ *	i)	size	size of result buffer
+ *	r)		!= NULL: relative path
+ *			== NULL: error
+ */
+char *
+abs2rel(const char *path, const char *base, char *result, const size_t size)
+{
+	const char *pp, *bp, *branch;
+	/*
+	 * endp points the last position which is safe in the result buffer.
+	 */
+	const char *endp = result + size - 1;
+	char *rp;
+
+	if (*path != '/') {
+		if (strlen(path) >= size)
+			goto erange;
+		strcpy(result, path);
+		goto finish;
+	} else if (*base != '/' || !size) {
+		errno = EINVAL;
+		return (NULL);
+	} else if (size == 1)
+		goto erange;
+	/*
+	 * seek to branched point.
+	 */
+	branch = path;
+	for (pp = path, bp = base; *pp && *bp && *pp == *bp; pp++, bp++)
+		if (*pp == '/')
+			branch = pp;
+	if ((*pp == 0 || (*pp == '/' && *(pp + 1) == 0)) &&
+	    (*bp == 0 || (*bp == '/' && *(bp + 1) == 0))) {
+		rp = result;
+		*rp++ = '.';
+		if (*pp == '/' || *(pp - 1) == '/')
+			*rp++ = '/';
+		if (rp > endp)
+			goto erange;
+		*rp = 0;
+		goto finish;
+	}
+	if ((*pp == 0 && *bp == '/') || (*pp == '/' && *bp == 0))
+		branch = pp;
+	/*
+	 * up to root.
+	 */
+	rp = result;
+	for (bp = base + (branch - path); *bp; bp++)
+		if (*bp == '/' && *(bp + 1) != 0) {
+			if (rp + 3 > endp)
+				goto erange;
+			*rp++ = '.';
+			*rp++ = '.';
+			*rp++ = '/';
+		}
+	if (rp > endp)
+		goto erange;
+	*rp = 0;
+	/*
+	 * down to leaf.
+	 */
+	if (*branch) {
+		if (rp + strlen(branch + 1) > endp)
+			goto erange;
+		strcpy(rp, branch + 1);
+	} else
+		*--rp = 0;
+finish:
+	return result;
+erange:
+	errno = ERANGE;
+	return (NULL);
+}