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/strnsubst.c

@@ -0,0 +1,61 @@
+/*
+ * Copyright (c) 2002 J. Mallett.  All rights reserved.
+ * You may do whatever you want with this file as long as
+ * the above copyright and this notice remain intact, along
+ * with the following statement:
+ * 	For the man who taught me vi, and who got too old, too young.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include "../util.h"
+
+/*
+ * Replaces str with a string consisting of str with match replaced with
+ * replstr as many times as can be done before the constructed string is
+ * maxsize bytes large.  It does not free the string pointed to by str, it
+ * is up to the calling program to be sure that the original contents of
+ * str as well as the new contents are handled in an appropriate manner.
+ * If replstr is NULL, then that internally is changed to a nil-string, so
+ * that we can still pretend to do somewhat meaningful substitution.
+ * No value is returned.
+ */
+void
+strnsubst(char **str, const char *match, const char *replstr, size_t maxsize)
+{
+	char *s1, *s2, *this;
+	size_t matchlen, s2len;
+	int n;
+
+	if ((s1 = *str) == NULL)
+		return;
+	s2 = emalloc(maxsize);
+
+	if (replstr == NULL)
+		replstr = "";
+
+	if (match == NULL || *match == '\0' || strlen(s1) >= maxsize) {
+		strlcpy(s2, s1, maxsize);
+		goto done;
+	}
+
+	*s2 = '\0';
+	s2len = 0;
+	matchlen = strlen(match);
+	for (;;) {
+		if ((this = strstr(s1, match)) == NULL)
+			break;
+		n = snprintf(s2 + s2len, maxsize - s2len, "%.*s%s",
+		    (int)(this - s1), s1, replstr);
+		if (n == -1 || n + s2len + strlen(this + matchlen) >= maxsize)
+			break;			/* out of room */
+		s2len += n;
+		s1 = this + matchlen;
+	}
+	strlcpy(s2 + s2len, s1, maxsize - s2len);
+done:
+	*str = s2;
+	return;
+}