Add utility function to compute crc32 check sums

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

5 files changed, 74 insertions, 3 deletions

diff --git a/include/util.h b/include/util.h
index 0c36160..2d5d521 100644
--- a/include/util.h
+++ b/include/util.h
@@ -76,4 +76,6 @@ int popd(void);
 */
 int padd_file(int outfd, uint64_t size, size_t blocksize);
 
+uint32_t update_crc32(uint32_t crc, const void *data, size_t size);
+
 #endif /* UTIL_H */
diff --git a/lib/Makemodule.am b/lib/Makemodule.am
index 218adcd..5f0cdae 100644
--- a/lib/Makemodule.am
+++ b/lib/Makemodule.am
@@ -44,7 +44,7 @@ libutil_a_SOURCES += lib/util/read_data.c include/util.h
 libutil_a_SOURCES += lib/util/print_version.c lib/util/mkdir_p.c
 libutil_a_SOURCES += lib/util/str_table.c include/str_table.h
 libutil_a_SOURCES += lib/util/dirstack.c lib/util/padd_file.c
-libutil_a_SOURCES += lib/util/read_data_at.c
+libutil_a_SOURCES += lib/util/read_data_at.c lib/util/crc32.c
 
 if WITH_GZIP
 libcompress_a_SOURCES += lib/comp/gzip.c
diff --git a/lib/util/crc32.c b/lib/util/crc32.c
new file mode 100644
index 0000000..ffe0044
--- /dev/null
+++ b/lib/util/crc32.c
@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "config.h"
+#include "util.h"
+
+/*
+  Karl Malbrain's compact CRC-32. See "A compact CCITT crc16 and crc32 C
+  implementation that balances processor cache usage against speed"
+ */
+static const uint32_t s_crc32[16] = {
+	0x00000000, 0x1DB71064, 0x3B6E20C8, 0x26D930AC,
+	0x76DC4190, 0x6B6B51F4, 0x4DB26158, 0x5005713C,
+	0xEDB88320, 0xF00F9344, 0xD6D6A3E8, 0xCB61B38C,
+	0x9B64C2B0, 0x86D3D2D4, 0xA00AE278, 0xBDBDF21C
+};
+
+uint32_t update_crc32(uint32_t crc, const void *data, size_t size)
+{
+	const uint8_t *ptr = data;
+	uint8_t b;
+
+	crc = ~crc;
+
+	while (size--) {
+		b = *ptr++;
+
+		crc = (crc >> 4) ^ s_crc32[(crc & 0x0F) ^ (b & 0x0F)];
+		crc = (crc >> 4) ^ s_crc32[(crc & 0x0F) ^ (b >> 4)];
+	}
+
+	return ~crc;
+}
diff --git a/tests/Makemodule.am b/tests/Makemodule.am
index 60312dc..e681a33 100644
--- a/tests/Makemodule.am
+++ b/tests/Makemodule.am
@@ -73,12 +73,15 @@ test_str_table_SOURCES = tests/str_table.c
 test_str_table_LDADD = libutil.a
 test_str_table_CPPFLAGS = $(AM_CPPFLAGS) -DTESTPATH=$(top_srcdir)/tests
 
+test_crc32_SOURCES = tests/crc32.c
+test_crc32_LDADD = libutil.a
+
 check_PROGRAMS += test_canonicalize_name test_mknode_simple test_mknode_slink
 check_PROGRAMS += test_mknode_reg test_mknode_dir test_gen_inode_table
 check_PROGRAMS += test_add_by_path test_get_path test_fstree_sort
 check_PROGRAMS += test_fstree_from_file test_fstree_init test_fstree_xattr
 check_PROGRAMS += test_tar_ustar test_tar_pax test_tar_gnu test_tar_sparse_gnu
-check_PROGRAMS += test_tar_sparse_gnu1 test_tar_sparse_gnu2
+check_PROGRAMS += test_tar_sparse_gnu1 test_tar_sparse_gnu2 test_crc32
 check_PROGRAMS += test_tar_xattr_bsd test_tar_xattr_schily test_str_table
 
 TESTS += test_canonicalize_name test_mknode_simple test_mknode_slink
@@ -87,6 +90,6 @@ TESTS += test_add_by_path test_get_path test_fstree_sort test_fstree_from_file
 TESTS += test_fstree_init test_fstree_xattr test_tar_ustar test_tar_pax
 TESTS += test_tar_gnu test_tar_sparse_gnu test_tar_sparse_gnu1
 TESTS += test_tar_sparse_gnu2 test_tar_xattr_bsd test_tar_xattr_schily
-TESTS += test_str_table
+TESTS += test_str_table test_crc32
 
 EXTRA_DIST += $(top_srcdir)/tests/tar $(top_srcdir)/tests/words.txt
diff --git a/tests/crc32.c b/tests/crc32.c
new file mode 100644
index 0000000..290f5cf
--- /dev/null
+++ b/tests/crc32.c
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+#include "config.h"
+#include "util.h"
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+static const struct {
+	const char *str;
+	uint32_t result;
+} test_vectors[] = {
+	{ "", 0 },
+	{ "Hello, World!", 0xEC4AC3D0 },
+	{ "The quick brown fox jumps over the lazy dog", 0x414FA339 },
+};
+
+int main(void)
+{
+	uint32_t crc;
+	size_t i;
+
+	for (i = 0; i < sizeof(test_vectors) / sizeof(test_vectors[0]); ++i) {
+		crc = update_crc32(0, test_vectors[i].str,
+				   strlen(test_vectors[i].str));
+
+		if (crc != test_vectors[i].result) {
+			fprintf(stderr, "Case %zu failed: %08X != %08X\n", i,
+				crc, test_vectors[i].result);
+			return EXIT_FAILURE;
+		}
+	}
+
+	return EXIT_SUCCESS;
+}