Adding uncompressed size function

Missing functionality to be able to reuse portable helpers.

Change-Id: If38e5f2b44cff9fb5f1744a59961ee6902f847f2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1876760Reviewed-by: Sam Maier <smaier@chromium.org>
Reviewed-by: Mike Klein <mtklein@chromium.org>
Reviewed-by: Adenilson Cavalcanti <cavalcantii@chromium.org>
Commit-Queue: Adenilson Cavalcanti <cavalcantii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#709081}

third_party/zlib/google/compression_utils.cc

@@ -109,14 +109,8 @@ bool GzipUncompress(base::StringPiece input, std::string* output) {
 }
 
 uint32_t GetUncompressedSize(base::StringPiece compressed_data) {
-  // The uncompressed size is stored in the last 4 bytes of |input| in LE.
-  uint32_t size;
-  if (compressed_data.length() < sizeof(size))
-    return 0;
-  memcpy(&size,
-         &compressed_data.data()[compressed_data.length() - sizeof(size)],
-         sizeof(size));
-  return base::ByteSwapToLE32(size);
+  return zlib_internal::GetUncompressedSize(
+      bit_cast<Bytef*>(compressed_data.data()), compressed_data.length());
 }
 
 }  // namespace compression

third_party/zlib/google/compression_utils_portable.cc

@@ -8,7 +8,6 @@
 #include "third_party/zlib/google/compression_utils_portable.h"
 
 #include <stddef.h>
-#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -33,6 +32,21 @@ uLongf GZipExpectedCompressedSize(uLongf input_size) {
   return kGzipZlibHeaderDifferenceBytes + compressBound(input_size);
 }
 
+// The expected decompressed size is stored in the last
+// 4 bytes of |input| in LE.
+uint32_t GetUncompressedSize(Bytef* compressed_data, size_t length) {
+  uint32_t size;
+  if (length < sizeof(size))
+    return 0;
+
+  memcpy(&size, &compressed_data[length - sizeof(size)], sizeof(size));
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+  return size;
+#else
+  return __builtin_bswap32(size);
+#endif
+}
+
 // This code is taken almost verbatim from third_party/zlib/compress.c. The only
 // difference is deflateInit2() is called which sets the window bits to be > 16.
 // That causes a gzip header to be emitted rather than a zlib header.

third_party/zlib/google/compression_utils_portable.h

@@ -7,6 +7,8 @@
 #ifndef THIRD_PARTY_ZLIB_GOOGLE_COMPRESSION_UTILS_PORTABLE_H_
 #define THIRD_PARTY_ZLIB_GOOGLE_COMPRESSION_UTILS_PORTABLE_H_
 
+#include <stdint.h>
+
 #if defined(USE_SYSTEM_ZLIB)
 #include <zlib.h>
 #else
@@ -17,6 +19,8 @@ namespace zlib_internal {
 
 uLongf GZipExpectedCompressedSize(uLongf input_size);
 
+uint32_t GetUncompressedSize(Bytef* compressed_data, size_t length);
+
 int GzipCompressHelper(Bytef* dest,
                        uLongf* dest_length,
                        const Bytef* source,
@@ -28,6 +32,7 @@ int GzipUncompressHelper(Bytef* dest,
                          uLongf* dest_length,
                          const Bytef* source,
                          uLong source_length);
+
 }  // namespace zlib_internal
 
 #endif  // THIRD_PARTY_ZLIB_GOOGLE_COMPRESSION_UTILS_PORTABLE_H_