config/git: import suckless sbase

i currently use the output of sha512sum in several
places of xbmk, which is a bit unreliable in case
output changes.

other cases where i use util outputs in variables
are probably reliable, because i'm using mostly
posix utilities in those.

to mitigate this, i now import suckless sbase, which
has a reasonable sha512sum implementation.

*every* binary it builds is being placed in build.list,
because i'll probably start using more of them.

for example, i may start modifying the "date"
implementation, adding the GNU-specific options that
i need as mentioned on init.sh

i'm importing it in util/ because the sha512sum
util is needed for verifying project sources, so
if sbase itself is a "project source", that means
we can into a chicken and egg bootstrapping problem.

this is sbase at revision:
055cc1ae1b3a13c3d8f25af0a4a3316590efcd48

Signed-off-by: Leah Rowe <leah@libreboot.org>

util/sbase/libutil/parseoffset.c

@@ -0,0 +1,61 @@
+/* See LICENSE file for copyright and license details. */
+#include <ctype.h>
+#include <errno.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "../util.h"
+
+off_t
+parseoffset(const char *str)
+{
+	off_t res, scale = 1;
+	char *end;
+
+	/* strictly check what strtol() usually would let pass */
+	if (!str || !*str || isspace(*str) || *str == '+' || *str == '-') {
+		weprintf("parseoffset %s: invalid value\n", str);
+		return -1;
+	}
+
+	errno = 0;
+	res = strtol(str, &end, 0);
+	if (errno) {
+		weprintf("parseoffset %s: invalid value\n", str);
+		return -1;
+	}
+	if (res < 0) {
+		weprintf("parseoffset %s: negative value\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("parseoffset %s: invalid suffix '%s'\n", str, end);
+			return -1;
+		}
+	}
+
+	/* prevent overflow */
+	if (res > (SSIZE_MAX / scale)) {
+		weprintf("parseoffset %s: out of range\n", str);
+		return -1;
+	}
+
+	return res * scale;
+}