Make MetricsService save compressed logs to local state.

components/metrics/compression_utils.cc

Index: components/metrics/compression_utils.cc
===================================================================
--- components/metrics/compression_utils.cc	(working copy)
+++ components/metrics/compression_utils.cc	(working copy)
@@ -2,11 +2,13 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "components/metrics/net/compression_utils.h"
+#include "components/metrics/compression_utils.h"
 
 #include <vector>
 
 #include "base/basictypes.h"
+#include "base/logging.h"
+#include "base/sys_byteorder.h"
 #include "third_party/zlib/zlib.h"
 
 namespace {
@@ -15,7 +17,7 @@
 const size_t kGzipZlibHeaderDifferenceBytes = 16;
 
 // Pass an integer greater than the following get a gzip header instead of a
-// zlib header when calling deflateInit2_.
+// zlib header when calling deflateInit2() and inflateInit2().
 const int kWindowBitsToGetGzipHeader = 16;
 
 // This describes the amount of memory zlib uses to compress data. It can go
@@ -24,53 +26,101 @@
 const int kZlibMemoryLevel = 8;
 
 // 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.
+// 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.
 int GzipCompressHelper(Bytef* dest,
                        uLongf* dest_length,
                        const Bytef* source,
                        uLong source_length) {
-    z_stream stream;
+  z_stream stream;
 
-    stream.next_in = bit_cast<Bytef*>(source);
-    stream.avail_in = static_cast<uInt>(source_length);
-    stream.next_out = dest;
-    stream.avail_out = static_cast<uInt>(*dest_length);
-    if (static_cast<uLong>(stream.avail_out) != *dest_length)
-      return Z_BUF_ERROR;
+  stream.next_in = bit_cast<Bytef*>(source);
+  stream.avail_in = static_cast<uInt>(source_length);
+  stream.next_out = dest;
+  stream.avail_out = static_cast<uInt>(*dest_length);
+  if (static_cast<uLong>(stream.avail_out) != *dest_length)
+    return Z_BUF_ERROR;
 
-    stream.zalloc = static_cast<alloc_func>(0);
-    stream.zfree = static_cast<free_func>(0);
-    stream.opaque = static_cast<voidpf>(0);
+  stream.zalloc = static_cast<alloc_func>(0);
+  stream.zfree = static_cast<free_func>(0);
+  stream.opaque = static_cast<voidpf>(0);
 
-    gz_header gzip_header;
-    memset(&gzip_header, 0, sizeof(gzip_header));
-    int err = deflateInit2_(&stream,
-                            Z_DEFAULT_COMPRESSION,
-                            Z_DEFLATED,
-                            MAX_WBITS + kWindowBitsToGetGzipHeader,
-                            kZlibMemoryLevel,
-                            Z_DEFAULT_STRATEGY,
-                            ZLIB_VERSION,
-                            sizeof(z_stream));
-    if (err != Z_OK)
-      return err;
+  gz_header gzip_header;
+  memset(&gzip_header, 0, sizeof(gzip_header));
+  int err = deflateInit2(&stream,
+                         Z_DEFAULT_COMPRESSION,
+                         Z_DEFLATED,
+                         MAX_WBITS + kWindowBitsToGetGzipHeader,
+                         kZlibMemoryLevel,
+                         Z_DEFAULT_STRATEGY);
+  if (err != Z_OK)
+    return err;
 
-    err = deflateSetHeader(&stream, &gzip_header);
-    if (err != Z_OK)
-      return err;
+  err = deflateSetHeader(&stream, &gzip_header);
+  if (err != Z_OK)
+    return err;
 
-    err = deflate(&stream, Z_FINISH);
-    if (err != Z_STREAM_END) {
-      deflateEnd(&stream);
-      return err == Z_OK ? Z_BUF_ERROR : err;
-    }
-    *dest_length = stream.total_out;
+  err = deflate(&stream, Z_FINISH);
+  if (err != Z_STREAM_END) {
+    deflateEnd(&stream);
+    return err == Z_OK ? Z_BUF_ERROR : err;
+  }
+  *dest_length = stream.total_out;
 
-    err = deflateEnd(&stream);
+  err = deflateEnd(&stream);
+  return err;
+}
+
+// This code is taken almost verbatim from third_party/zlib/uncompr.c. The only
+// difference is inflateInit2() is called which sets the window bits to be > 16.
+// That causes a gzip header to be parsed rather than a zlib header.
+int GzipUncompressHelper(Bytef* dest,
+                         uLongf* dest_length,
+                         const Bytef* source,
+                         uLong source_length) {
+  z_stream stream;
+
+  stream.next_in = bit_cast<Bytef*>(source);
+  stream.avail_in = static_cast<uInt>(source_length);
+  if (static_cast<uLong>(stream.avail_in) != source_length)
+    return Z_BUF_ERROR;
+
+  stream.next_out = dest;
+  stream.avail_out = static_cast<uInt>(*dest_length);
+  if (static_cast<uLong>(stream.avail_out) != *dest_length)
+    return Z_BUF_ERROR;
+
+  stream.zalloc = static_cast<alloc_func>(0);
+  stream.zfree = static_cast<free_func>(0);
+
+  int err = inflateInit2(&stream, MAX_WBITS + kWindowBitsToGetGzipHeader);
+  if (err != Z_OK)
     return err;
+
+  err = inflate(&stream, Z_FINISH);
+  if (err != Z_STREAM_END) {
+    inflateEnd(&stream);
+    if (err == Z_NEED_DICT || (err == Z_BUF_ERROR && stream.avail_in == 0))
+      return Z_DATA_ERROR;
+    return err;
+  }
+  *dest_length = stream.total_out;
+
+  err = inflateEnd(&stream);
+  return err;
 }
 
+// Returns the uncompressed size from GZIP-compressed |compressed_data|.
+uint32 GetUncompressedSize(const std::string& compressed_data) {
+  // The uncompressed size is stored in the last 4 bytes of |input| in LE.
+  uint32 size;
+  if (compressed_data.length() < sizeof(size))
+    return 0;
+  memcpy(&size, &compressed_data[compressed_data.length() - sizeof(size)],
+         sizeof(size));
+  return base::ByteSwapToLE32(size);
+}
+
 }  // namespace
 
 namespace metrics {
@@ -90,7 +140,17 @@
 
   compressed_data.resize(compressed_size);
   output->assign(compressed_data.begin(), compressed_data.end());
+  DCHECK_EQ(input.size(), GetUncompressedSize(*output));
   return true;
 }
 
+bool GzipUncompress(const std::string& input, std::string* output) {
+  output->resize(GetUncompressedSize(input));
+  uLongf uncompressed_size = static_cast<uLongf>(output->length());
+  return GzipUncompressHelper(bit_cast<Bytef*>(output->data()),
+                              &uncompressed_size,
+                              bit_cast<const Bytef*>(input.data()),
+                              static_cast<uLongf>(input.length())) == Z_OK;
+}
+
 }  // namespace metrics