Add a single, central base64 decoder

Similar to the hex blob decoder, we need this once for tar and
once for the filemap xattr parser.

Simply add a single, central implementation to libutil, with a
simple unit test, and then use it in both libtar and gensquashfs.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

2 files changed, 78 insertions, 1 deletions

diff --git a/tests/libutil/Makemodule.am b/tests/libutil/Makemodule.am
index 5a69de4..724af50 100644
--- a/tests/libutil/Makemodule.am
+++ b/tests/libutil/Makemodule.am
@@ -33,10 +33,13 @@ test_sdate_epoch_LDADD = libutil.a libcompat.a
 test_hex_decode_SOURCES = tests/libutil/hex_decode.c
 test_hex_decode_LDADD = libutil.a libcompat.a
 
+test_base64_decode_SOURCES = tests/libutil/base64_decode.c
+test_base64_decode_LDADD = libutil.a libcompat.a
+
 LIBUTIL_TESTS = \
 	test_str_table test_rbtree test_xxhash test_threadpool test_ismemzero \
 	test_canonicalize_name test_filename_sane test_filename_sane_w32 \
-	test_sdate_epoch test_hex_decode
+	test_sdate_epoch test_hex_decode test_base64_decode
 
 check_PROGRAMS += $(LIBUTIL_TESTS)
 TESTS += $(LIBUTIL_TESTS)
diff --git a/tests/libutil/base64_decode.c b/tests/libutil/base64_decode.c
new file mode 100644
index 0000000..8f22a86
--- /dev/null
+++ b/tests/libutil/base64_decode.c
@@ -0,0 +1,74 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * base64_decode.c
+ *
+ * Copyright (C) 2022 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "util/util.h"
+#include "util/test.h"
+
+static const struct {
+	int result;
+	const char *in;
+	const char *out;
+} test_vec[] = {
+	{ 0, "", "" },
+	{ 0, "Zg", "f" },
+	{ 0, "Zg==", "f" },
+	{ 0, "Zm8=", "fo" },
+	{ 0, "Zm9v", "foo" },
+	{ 0, "Zm9vYg==", "foob" },
+	{ 0, "Zm9vYmE=", "fooba" },
+	{ 0, "Zm9vYmFy", "foobar" },
+	{ 0, "TGV0J3MgYWxsIGxvdmUgTGFpbiEK", "Let's all love Lain!\n" },
+	{ -1, "Zg==X",     "XX" },
+};
+
+int main(int argc, char **argv)
+{
+	sqfs_u8 buffer[256];
+	size_t i, j;
+	(void)argc; (void)argv;
+
+	for (i = 0; i < sizeof(test_vec) / sizeof(test_vec[0]); ++i) {
+		const size_t in_len = strlen(test_vec[i].in);
+		const size_t out_len = strlen(test_vec[i].out);
+		size_t real_out;
+		int ret;
+
+		/* initialize the buffer */
+		for (j = 0; j < sizeof(buffer); ++j) {
+			buffer[j] = (j % 2) ? 0xAA : 0x55;
+		}
+
+		/* convert */
+		real_out = sizeof(buffer);
+		ret = base64_decode(test_vec[i].in, in_len, buffer, &real_out);
+
+		/* make sure pattern is un-touched after expected offset */
+		j = (in_len / 4) * 3;
+		if (in_len % 4)
+			j += 3;
+
+		for (; j < sizeof(buffer); ++j) {
+			TEST_ASSERT(buffer[j] == ((j % 2) ? 0xAA : 0x55));
+		}
+
+		/* check result */
+		if (test_vec[i].result == 0) {
+			TEST_ASSERT(ret == 0);
+			TEST_EQUAL_UI(real_out, out_len);
+			ret = memcmp(buffer, test_vec[i].out, out_len);
+			TEST_ASSERT(ret == 0);
+		} else {
+			TEST_ASSERT(ret != 0);
+			TEST_EQUAL_UI(real_out, 0);
+		}
+
+		fprintf(stderr, "CASE %lu OK\n", (unsigned long)i);
+	}
+
+	return EXIT_SUCCESS;
+}
+