t/helper/hexdump: add helper to print hexdump of stdin

Co-authored-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -729,6 +729,7 @@ TEST_BUILTINS_OBJS += test-getcwd.o
 TEST_BUILTINS_OBJS += test-hash-speed.o
 TEST_BUILTINS_OBJS += test-hash.o
 TEST_BUILTINS_OBJS += test-hashmap.o
+TEST_BUILTINS_OBJS += test-hexdump.o
 TEST_BUILTINS_OBJS += test-index-version.o
 TEST_BUILTINS_OBJS += test-json-writer.o
 TEST_BUILTINS_OBJS += test-lazy-init-name-hash.o

t/helper/test-hexdump.c

@@ -0,0 +1,30 @@
+#include "test-tool.h"
+#include "git-compat-util.h"
+
+/*
+ * Read stdin and print a hexdump to stdout.
+ */
+int cmd__hexdump(int argc, const char **argv)
+{
+	char buf[1024];
+	ssize_t i, len;
+	int have_data = 0;
+
+	for (;;) {
+		len = xread(0, buf, sizeof(buf));
+		if (len < 0)
+			die_errno("failure reading stdin");
+		if (!len)
+			break;
+
+		have_data = 1;
+
+		for (i = 0; i < len; i++)
+			printf("%02x ", (unsigned char)buf[i]);
+	}
+
+	if (have_data)
+		putchar('\n');
+
+	return 0;
+}

t/helper/test-tool.c

@@ -38,6 +38,7 @@ static struct test_cmd cmds[] = {
 	{ "getcwd", cmd__getcwd },
 	{ "hashmap", cmd__hashmap },
 	{ "hash-speed", cmd__hash_speed },
+	{ "hexdump", cmd__hexdump },
 	{ "index-version", cmd__index_version },
 	{ "json-writer", cmd__json_writer },
 	{ "lazy-init-name-hash", cmd__lazy_init_name_hash },

t/helper/test-tool.h

@@ -29,6 +29,7 @@ int cmd__genzeros(int argc, const char **argv);
 int cmd__getcwd(int argc, const char **argv);
 int cmd__hashmap(int argc, const char **argv);
 int cmd__hash_speed(int argc, const char **argv);
+int cmd__hexdump(int argc, const char **argv);
 int cmd__index_version(int argc, const char **argv);
 int cmd__json_writer(int argc, const char **argv);
 int cmd__lazy_init_name_hash(int argc, const char **argv);