From 007df69fc5987f30ef9494ccbbb87aa058d6b732 Mon Sep 17 00:00:00 2001
From: FRIGN <dev@frign.de>
Date: Wed, 30 Sep 2015 01:19:01 +0200
Subject: [PATCH] Add parseoffset()

This is a utility function to allow easy parsing of file or other
offsets, automatically taking in regard suffixes, proper bases and
so on, for instance used in split(1) -b or od -j, -N(1).
Of course, POSIX is very arbitrary when it comes to defining the
parsing rules for different tools.
The main focus here lies on being as flexible and consistent as
possible. One central utility-function handling the parsing makes
this stuff a lot more trivial.
---
 Makefile              |  1 +
 libutil/parseoffset.c | 59 +++++++++++++++++++++++++++++++++++++++++++
 util.h                |  1 +
 3 files changed, 61 insertions(+)
 create mode 100644 libutil/parseoffset.c

diff --git a/Makefile b/Makefile
index 9f60a13..9d1293a 100644
--- a/Makefile
+++ b/Makefile
@@ -56,6 +56,7 @@ LIBUTILSRC =\
 	libutil/md5.c\
 	libutil/mkdirp.c\
 	libutil/mode.c\
+	libutil/parseoffset.c\
 	libutil/putword.c\
 	libutil/reallocarray.c\
 	libutil/recurse.c\
diff --git a/libutil/parseoffset.c b/libutil/parseoffset.c
new file mode 100644
index 0000000..451d913
--- /dev/null
+++ b/libutil/parseoffset.c
@@ -0,0 +1,59 @@
+/* See LICENSE file for copyright and license details. */
+#include <ctype.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "../util.h"
+
+off_t
+parseoffset(const char *str)
+{
+	off_t res;
+	size_t scale;
+	int base = 10;
+	char *end;
+
+	/* bases */
+	if (!strncasecmp(str, "0x", strlen("0x"))) {
+		base = 16;
+	} else if (*str == '0') {
+		str++;
+		base = 8;
+	}
+
+	res = strtol(str, &end, base);
+	if (res < 0) {
+		weprintf("invalid file offset: %s\n", str);
+		return -1;
+	}
+
+	/* suffix */
+	if (*end) {
+		switch (toupper((int)*end)) {
+		case 'B':
+			scale = 512L;
+			break;
+		case 'K':
+			scale = 1024L;
+			break;
+		case 'M':
+			scale = 1024L * 1024L;
+			break;
+		case 'G':
+			scale = 1024L * 1024L * 1024L;
+			break;
+		default:
+			weprintf("invalid file offset suffix: %s\n", str);
+			return -1;
+		}
+	}
+
+	/* prevent overflow */
+	if (res > (SIZE_MAX / scale)) {
+		weprintf("file offset out of range: %s\n", str);
+		return -1;
+	}
+
+	return res;
+}
diff --git a/util.h b/util.h
index b0bf0f4..4c973d1 100644
--- a/util.h
+++ b/util.h
@@ -68,6 +68,7 @@ void fnck(const char *, const char *, int (*)(const char *, const char *, int),
 mode_t getumask(void);
 char *humansize(off_t);
 mode_t parsemode(const char *, mode_t, mode_t);
+off_t parseoffset(const char *);
 void putword(FILE *, const char *);
 #undef strtonum
 long long strtonum(const char *, long long, long long, const char **);