Merge pull request #63 from IzumiRaine/zlib-trailing-junk

Add function libdeflate_zlib_decompress_ex

Makefile

@@ -216,7 +216,8 @@ TEST_PROG_SRC        := programs/benchmark.c \
 			programs/checksum.c \
 			programs/test_checksums.c \
 			programs/test_incomplete_codes.c \
-			programs/test_slow_decompression.c
+			programs/test_slow_decompression.c \
+			programs/test_zlib.c
 
 NONTEST_PROGRAMS := $(NONTEST_PROG_SRC:programs/%.c=%$(PROG_SUFFIX))
 DEFAULT_TARGETS  += $(NONTEST_PROGRAMS)

lib/zlib_decompress.c

@@ -33,14 +33,16 @@
 #include "libdeflate.h"
 
 LIBDEFLATEEXPORT enum libdeflate_result LIBDEFLATEAPI
-libdeflate_zlib_decompress(struct libdeflate_decompressor *d,
+libdeflate_zlib_decompress_ex(struct libdeflate_decompressor *d,
 			      const void *in, size_t in_nbytes,
 			      void *out, size_t out_nbytes_avail,
+			      size_t *actual_in_nbytes_ret,
 			      size_t *actual_out_nbytes_ret)
 {
 	const u8 *in_next = in;
 	const u8 * const in_end = in_next + in_nbytes;
 	u16 hdr;
+	size_t actual_in_nbytes;
 	size_t actual_out_nbytes;
 	enum libdeflate_result result;
 
@@ -68,10 +70,10 @@ libdeflate_zlib_decompress(struct libdeflate_decompressor *d,
 		return LIBDEFLATE_BAD_DATA;
 
 	/* Compressed data  */
-	result = libdeflate_deflate_decompress(d, in_next,
+	result = libdeflate_deflate_decompress_ex(d, in_next,
 					in_end - ZLIB_FOOTER_SIZE - in_next,
 					out, out_nbytes_avail,
-					actual_out_nbytes_ret);
+					&actual_in_nbytes, actual_out_nbytes_ret);
 	if (result != LIBDEFLATE_SUCCESS)
 		return result;
 
@@ -80,12 +82,27 @@ libdeflate_zlib_decompress(struct libdeflate_decompressor *d,
 	else
 		actual_out_nbytes = out_nbytes_avail;
 
-	in_next = in_end - ZLIB_FOOTER_SIZE;
+	in_next += actual_in_nbytes;
 
 	/* ADLER32  */
 	if (libdeflate_adler32(1, out, actual_out_nbytes) !=
 	    get_unaligned_be32(in_next))
 		return LIBDEFLATE_BAD_DATA;
+	in_next += 4;
+
+	if (actual_in_nbytes_ret)
+		*actual_in_nbytes_ret = in_next - (u8 *)in;
 
 	return LIBDEFLATE_SUCCESS;
 }
+
+LIBDEFLATEEXPORT enum libdeflate_result LIBDEFLATEAPI
+libdeflate_zlib_decompress(struct libdeflate_decompressor *d,
+			   const void *in, size_t in_nbytes,
+			   void *out, size_t out_nbytes_avail,
+			   size_t *actual_out_nbytes_ret)
+{
+	return libdeflate_zlib_decompress_ex(d, in, in_nbytes,
+					     out, out_nbytes_avail,
+					     NULL, actual_out_nbytes_ret);
+}

libdeflate.h

@@ -255,6 +255,10 @@ libdeflate_deflate_decompress_ex(struct libdeflate_decompressor *decompressor,
 /*
  * Like libdeflate_deflate_decompress(), but assumes the zlib wrapper format
  * instead of raw DEFLATE.
+ *
+ * Decompression will stop at the end of the zlib stream, even if it is shorter
+ * than 'in_nbytes'.  If you need to know exactly where the zlib stream ended,
+ * use libdeflate_zlib_decompress_ex().
  */
 LIBDEFLATEEXPORT enum libdeflate_result LIBDEFLATEAPI
 libdeflate_zlib_decompress(struct libdeflate_decompressor *decompressor,
@@ -262,6 +266,20 @@ libdeflate_zlib_decompress(struct libdeflate_decompressor *decompressor,
 			   void *out, size_t out_nbytes_avail,
 			   size_t *actual_out_nbytes_ret);
 
+/*
+ * Like libdeflate_zlib_decompress(), but adds the 'actual_in_nbytes_ret'
+ * argument.  If 'actual_in_nbytes_ret' is not NULL and the decompression
+ * succeeds (indicating that the first zlib-compressed stream in the input
+ * buffer was decompressed), then the actual number of input bytes consumed is
+ * written to *actual_in_nbytes_ret.
+ */
+LIBDEFLATEEXPORT enum libdeflate_result LIBDEFLATEAPI
+libdeflate_zlib_decompress_ex(struct libdeflate_decompressor *decompressor,
+			      const void *in, size_t in_nbytes,
+			      void *out, size_t out_nbytes_avail,
+			      size_t *actual_in_nbytes_ret,
+			      size_t *actual_out_nbytes_ret);
+
 /*
  * Like libdeflate_deflate_decompress(), but assumes the gzip wrapper format
  * instead of raw DEFLATE.

programs/test_zlib.c

@@ -0,0 +1,106 @@
+/*
+ * test_zlib.c
+ *
+ * Verify that libdeflate_zlib_decompress and libdeflate_zlib_decompress_ex can
+ * correctly decompress the results of libdeflate_zlib_compress.  Also checks
+ * whether decompression correctly handles additional trailing bytes in the
+ * compressed buffer.
+ */
+
+#include <stdlib.h>
+
+#include "test_util.h"
+
+static void
+test_decompress(u8 const* compressed, size_t compressed_nbytes,
+		u8 const* expected, size_t expected_nbytes)
+{
+	struct libdeflate_decompressor* d = libdeflate_alloc_decompressor();
+	ASSERT(d != NULL);
+
+	size_t decompressed_nbytes = expected_nbytes;
+	u8 *decompressed = xmalloc(decompressed_nbytes);
+
+	size_t actual_decompressed_nbytes = 0;
+	enum libdeflate_result res =
+		libdeflate_zlib_decompress(d, compressed, compressed_nbytes,
+					   decompressed, decompressed_nbytes,
+					   &actual_decompressed_nbytes);
+	ASSERT(res == LIBDEFLATE_SUCCESS);
+	ASSERT(actual_decompressed_nbytes == expected_nbytes);
+	ASSERT(memcmp(expected, decompressed, expected_nbytes) == 0);
+
+	free(decompressed);
+	libdeflate_free_decompressor(d);
+}
+
+static void
+test_decompress_ex(u8 const* compressed, size_t compressed_nbytes,
+		   size_t expected_actual_compressed_nbytes,
+		   u8 const* expected, size_t expected_nbytes)
+{
+	struct libdeflate_decompressor* d = libdeflate_alloc_decompressor();
+	ASSERT(d != NULL);
+
+	size_t decompressed_nbytes = expected_nbytes;
+	u8 *decompressed = xmalloc(decompressed_nbytes);
+
+	size_t actual_compressed_nbytes = 0;
+	size_t actual_decompressed_nbytes = 0;
+	enum libdeflate_result res =
+		libdeflate_zlib_decompress_ex(d, compressed, compressed_nbytes,
+					      decompressed, decompressed_nbytes,
+					      &actual_compressed_nbytes,
+					      &actual_decompressed_nbytes);
+	ASSERT(res == LIBDEFLATE_SUCCESS);
+	ASSERT(actual_compressed_nbytes == expected_actual_compressed_nbytes);
+	ASSERT(actual_decompressed_nbytes == expected_nbytes);
+	ASSERT(memcmp(expected, decompressed, expected_nbytes) == 0);
+
+	free(decompressed);
+	libdeflate_free_decompressor(d);
+}
+
+int
+tmain(int argc, tchar *argv[])
+{
+	program_invocation_name = get_filename(argv[0]);
+
+	size_t original_nbytes = 32768;
+	u8 *original = xmalloc(original_nbytes);
+
+	/* Prepare some dummy data to compress */
+	for (size_t i = 0; i < original_nbytes; ++i) {
+		original[i] = (i % 123) + (i % 1023);
+	}
+
+	size_t compressed_nbytes_total = 32768;
+	u8 *compressed = xmalloc(compressed_nbytes_total);
+	memset(compressed, 0x00, compressed_nbytes_total);
+
+	/*
+	 * Don't use the full buffer for compressed data, because we want to
+	 * test whether decompression can deal with additional trailing bytes.
+	 */
+	size_t compressed_nbytes_avail = 30000;
+	ASSERT(compressed_nbytes_avail < compressed_nbytes_total);
+
+	struct libdeflate_compressor* c = libdeflate_alloc_compressor(6);
+	ASSERT(c != NULL);
+	size_t compressed_nbytes =
+		libdeflate_zlib_compress(c, original, original_nbytes,
+					 compressed, compressed_nbytes_avail);
+	ASSERT(compressed_nbytes > 0);
+	libdeflate_free_compressor(c);
+
+	test_decompress(compressed, compressed_nbytes, original, original_nbytes);
+	test_decompress(compressed, compressed_nbytes_total, original, original_nbytes);
+	test_decompress_ex(compressed, compressed_nbytes_total, compressed_nbytes,
+			   original, original_nbytes);
+
+	printf("libdeflate_zlib_* tests passed!\n");
+
+	free(compressed);
+	free(original);
+	return 0;
+}