util/nvmutil: better hexdump

this is a more generic one that i implemented
for "lottery.c" (which is really just a tester
of my rset function in lib/rand.c)

i could probably actually write a full hexdump
program in libreboot-utils to be honest.

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

util/libreboot-utils/lib/num.c

@@ -16,8 +16,10 @@
     defined(__NetBSD__) || defined(__APPLE__))
 #include <fcntl.h> /* if not arc4random: /dev/urandom */
 #endif
+#include <ctype.h>
 #include <limits.h>
 #include <stddef.h>
+#include <stdio.h>
 #include <string.h>
 #include <unistd.h>
 
@@ -47,6 +49,48 @@ hextonum(char ch_s)
 	return 16;
 }
 
+/* basically hexdump -C */
+void
+spew_hex(const void *data, size_t len)
+{
+	const unsigned char *buf = (const unsigned char *)data;
+	unsigned char c;
+	size_t i;
+	size_t j;
+
+	if (buf == NULL ||
+	    len == 0)
+		return;
+
+	for (i = 0; i < len; i += 16) {
+
+		printf("%08zx  ", i);
+
+		for (j = 0; j < 16; j++) {
+
+			if (i + j < len)
+				printf("%02x ", buf[i + j]);
+			else
+				printf("   ");
+
+			if (j == 7)
+				printf(" ");
+		}
+
+		printf(" |");
+
+		for (j = 0; j < 16 && i + j < len; j++) {
+
+			c = buf[i + j];
+			printf("%c", isprint(c) ? c : '.');
+		}
+
+		printf("|\n");
+	}
+
+	printf("%08zx\n", len);
+}
+
 void
 check_bin(size_t a, const char *a_name)
 {