GIF: Use SkTArray instead of std::vector

Speculative fix for a memory regression seen in Chromium. Chromium
previously used a WTF::Vector, which has a growth factor of 1.5, as does
SkTArray. Depending on the implementation of std::vector, this may slow
the allocation of memory.

Bug: 758946
Change-Id: I323390027467e32a6c66667c927fae0aba292446
Reviewed-on: https://skia-review.googlesource.com/40777
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

third_party/gif/SkGifImageReader.cpp

@@ -344,7 +344,7 @@ sk_sp<SkColorTable> SkGIFColorMap::buildTable(SkStreamBuffer* streamBuffer, SkCo
 }
 
 sk_sp<SkColorTable> SkGifImageReader::getColorTable(SkColorType colorType, int index) {
-    if (index < 0 || static_cast<size_t>(index) >= m_frames.size()) {
+    if (index < 0 || index >= m_frames.count()) {
         return nullptr;
     }
 
@@ -382,8 +382,7 @@ bool SkGIFFrameContext::decode(SkStreamBuffer* streamBuffer, SkGifCodec* client,
     }
 
     // Some bad GIFs have extra blocks beyond the last row, which we don't want to decode.
-    while (static_cast<size_t>(m_currentLzwBlock) < m_lzwBlocks.size()
-           && m_lzwContext->hasRemainingRows()) {
+    while (m_currentLzwBlock < m_lzwBlocks.count() && m_lzwContext->hasRemainingRows()) {
         const auto& block = m_lzwBlocks[m_currentLzwBlock];
         const size_t len = block.blockSize;
 
@@ -430,7 +429,7 @@ SkCodec::Result SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
 
     // SkGIFSizeQuery and SkGIFFrameCountQuery are negative, so this is only meaningful when >= 0.
     const int lastFrameToParse = (int) query;
-    if (lastFrameToParse >= 0 && (int) m_frames.size() > lastFrameToParse
+    if (lastFrameToParse >= 0 && m_frames.count() > lastFrameToParse
                 && m_frames[lastFrameToParse]->isComplete()) {
         // We have already parsed this frame.
         return SkCodec::kSuccess;
@@ -823,7 +822,7 @@ SkCodec::Result SkGifImageReader::parse(SkGifImageReader::SkGIFParseQuery query)
                 // decode all rows but we treat it as frame complete.
                 m_frames.back()->setComplete();
                 GETN(1, SkGIFImageStart);
-                if (lastFrameToParse >= 0 && (int) m_frames.size() > lastFrameToParse) {
+                if (lastFrameToParse >= 0 && m_frames.count() > lastFrameToParse) {
                     m_streamBuffer.flush();
                     return SkCodec::kSuccess;
                 }
@@ -874,9 +873,8 @@ bool SkGifImageReader::hasTransparency(int transparentPixel, bool isLocalColorma
 void SkGifImageReader::addFrameIfNecessary()
 {
     if (m_frames.empty() || m_frames.back()->isComplete()) {
-        const size_t i = m_frames.size();
-        std::unique_ptr<SkGIFFrameContext> frame(new SkGIFFrameContext(this, static_cast<int>(i)));
-        m_frames.push_back(std::move(frame));
+        const int i = m_frames.count();
+        m_frames.emplace_back(new SkGIFFrameContext(this, i));
     }
 }
 

third_party/gif/SkGifImageReader.h

@@ -52,7 +52,6 @@ class SkGifCodec;
 #include "SkStreamBuffer.h"
 #include "../private/SkTArray.h"
 #include <memory>
-#include <vector>
 
 typedef SkTArray<unsigned char, true> SkGIFRow;
 
@@ -218,7 +217,7 @@ public:
 
     void addLzwBlock(size_t position, size_t size)
     {
-        m_lzwBlocks.push_back(SkGIFLZWBlock(position, size));
+        m_lzwBlocks.emplace_back(position, size);
     }
 
     bool decode(SkStreamBuffer*, SkGifCodec* client, bool* frameDecoded);
@@ -265,7 +264,7 @@ private:
 
     std::unique_ptr<SkGIFLZWContext> m_lzwContext;
     // LZW blocks for this frame.
-    std::vector<SkGIFLZWBlock> m_lzwBlocks;
+    SkTArray<SkGIFLZWBlock> m_lzwBlocks;
 
     SkGIFColorMap m_localColorMap;
 
@@ -321,7 +320,7 @@ public:
 
     int imagesCount() const
     {
-        const size_t frames = m_frames.size();
+        const int frames = m_frames.count();
         if (!frames) {
             return 0;
         }
@@ -331,7 +330,7 @@ public:
         // possibly SkGIFImageHeader) but before reading the color table. This
         // ensures that we do not count a frame before we know its required
         // frame.
-        return static_cast<int>(m_frames.back()->reachedStartOfData() ? frames : frames - 1);
+        return m_frames.back()->reachedStartOfData() ? frames : frames - 1;
     }
     int loopCount() const {
         if (cLoopCountNotSeen == m_loopCount) {
@@ -347,12 +346,12 @@ public:
 
     const SkGIFFrameContext* frameContext(int index) const
     {
-        return index >= 0 && index < static_cast<int>(m_frames.size())
+        return index >= 0 && index < m_frames.count()
                 ? m_frames[index].get() : nullptr;
     }
 
     void clearDecodeState() {
-        for (size_t index = 0; index < m_frames.size(); index++) {
+        for (int index = 0; index < m_frames.count(); index++) {
             m_frames[index]->clearDecodeState();
         }
     }
@@ -381,7 +380,7 @@ private:
     void addFrameIfNecessary();
     bool currentFrameIsFirstFrame() const
     {
-        return m_frames.empty() || (m_frames.size() == 1u && !m_frames[0]->isComplete());
+        return m_frames.empty() || (m_frames.count() == 1 && !m_frames[0]->isComplete());
     }
 
     // Unowned pointer
@@ -398,7 +397,7 @@ private:
     static constexpr int cLoopCountNotSeen = -2;
     int m_loopCount; // Netscape specific extension block to control the number of animation loops a GIF renders.
 
-    std::vector<std::unique_ptr<SkGIFFrameContext>> m_frames;
+    SkTArray<std::unique_ptr<SkGIFFrameContext>> m_frames;
 
     SkStreamBuffer m_streamBuffer;
     bool m_parseCompleted;