Add 'skiapict' magic bytes to SkPicture format.

src/core/SkPicture.cpp

 
 /*
  * Copyright 2007 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkPictureFlat.h"
@@ skipping 248 matching lines @@
     this->endRecording();
     if (fPlayback) {
         fPlayback->draw(*surface, callback);
     }
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "SkStream.h"
 
+static const char kMagic[] = { 's', 'k', 'i', 'a', 'p', 'i', 'c', 't' };
+
 bool SkPicture::StreamIsSKP(SkStream* stream, SkPictInfo* pInfo) {
     if (NULL == stream) {
         return false;
     }
 
+    // Check magic bytes.
+    uint8_t magic[SK_ARRAY_COUNT(kMagic)];

[reed1, 2013/10/16 15:34:41]

could be sizeof or SK_ARRAY_COUNT. I find the former slightly clearer, but no
big pref.

+    stream->read(magic, SK_ARRAY_COUNT(kMagic));
+    if (0 != memcmp(magic, kMagic, SK_ARRAY_COUNT(kMagic))) {
+        return false;
+    }
+
     SkPictInfo info;
     if (!stream->read(&info, sizeof(SkPictInfo))) {
         return false;
     }
     if (PICTURE_VERSION != info.fVersion
 #ifndef DELETE_THIS_CODE_WHEN_SKPS_ARE_REBUILT_AT_V13_AND_ALL_OTHER_INSTANCES_TOO
         // V13 is backwards compatible with V12
         && PRIOR_PRIOR_PICTURE_VERSION != info.fVersion  // TODO: remove when .skps regenerated
 #endif
 #ifndef DELETE_THIS_CODE_WHEN_SKPS_ARE_REBUILT_AT_V14_AND_ALL_OTHER_INSTANCES_TOO
@@ skipping 50 matching lines @@
     info.fWidth = fWidth;
     info.fHeight = fHeight;
     info.fFlags = SkPictInfo::kCrossProcess_Flag;
 #ifdef SK_SCALAR_IS_FLOAT
     info.fFlags |= SkPictInfo::kScalarIsFloat_Flag;
 #endif
     if (8 == sizeof(void*)) {
         info.fFlags |= SkPictInfo::kPtrIs64Bit_Flag;
     }
 
+    // Write 8 magic bytes to ID this file format.
+    SkASSERT(SK_ARRAY_COUNT(kMagic) == 8);
+    stream->write(kMagic, SK_ARRAY_COUNT(kMagic));
+
     stream->write(&info, sizeof(info));
     if (playback) {
         stream->writeBool(true);
         playback->serialize(stream, encoder);
         // delete playback if it is a local version (i.e. cons'd up just now)
         if (playback != fPlayback) {
             SkDELETE(playback);
         }
     } else {
         stream->writeBool(false);
     }
 }
 
 #ifdef SK_BUILD_FOR_ANDROID
 void SkPicture::abortPlayback() {
     if (NULL == fPlayback) {
         return;
     }
     fPlayback->abort();
 }
 #endif