Change the way ImageDecodeBench supplies data

Source/web/ImageDecodeBench.cpp

Index: Source/web/ImageDecodeBench.cpp
diff --git a/Source/web/ImageDecodeBench.cpp b/Source/web/ImageDecodeBench.cpp
index 2f6f2b47c90d68347c208ef1f0e10f18f6444e69..f2b585002f75ae7830998075e6ac962bc808f6e7 100644
--- a/Source/web/ImageDecodeBench.cpp
+++ b/Source/web/ImageDecodeBench.cpp
@@ -15,11 +15,6 @@ during image decoding on supported platforms (default off). Usage:
 FIXME: Consider adding md5 checksum support to WTF. Use it to compute the
 decoded image frame md5 and output that value.
 
-FIXME: Consider adding an input data packetization option. Break the input
-into network-sized packets, pump the packets into the image decoder until
-the input data is complete (allDataReceived). This to include any internal
-SharedBuffer costs, such as buffer coalescing, in the reported results.
-
 FIXME: Consider integrating this tool in Chrome telemetry for realz, using
 the image corpii used to assess Blink image decode performance. Refer to
 http://crbug.com/398235#c103 and http://crbug.com/258324#c5
@@ -270,19 +265,45 @@ PassRefPtr<SharedBuffer> readFile(const char* fileName)
     return SharedBuffer::create(buffer.get(), fileSize);
 }
 
-bool decodeImageData(SharedBuffer* data, bool colorCorrection)
+bool decodeImageData(SharedBuffer* data, bool colorCorrection, size_t chunkSize)
 {
     OwnPtr<ImageDecoder> decoder = ImageDecoder::create(*data,
         ImageDecoder::AlphaPremultiplied, colorCorrection ?
             ImageDecoder::GammaAndColorProfileApplied : ImageDecoder::GammaAndColorProfileIgnored);
 
-    bool allDataReceived = true;
-    decoder->setData(data, allDataReceived);
+    if (!chunkSize) {
+        bool allDataReceived = true;
+        decoder->setData(data, allDataReceived);
+
+        int frameCount = decoder->frameCount();
+        for (int i = 0; i < frameCount; ++i) {
+            if (!decoder->frameBufferAtIndex(i))
+                return false;
+        }
+
+        return !decoder->failed();
+    }
+
+    RefPtr<SharedBuffer> incrementalData = SharedBuffer::create();

[Noel Gordon, 2015/09/02 23:29:35]

incrementalData -> packetData ?

[scroggo, 2015/09/03 22:10:26]

Done.

+    unsigned position = 0;
+    while (true) {
+        const char* segment;

[Noel Gordon, 2015/09/02 23:29:35]

segment -> packet

[scroggo, 2015/09/03 22:10:26]

Done.

+        unsigned length = data->getSomeData(segment, position);
+
+        length = std::min(static_cast<size_t>(length), chunkSize);
+        incrementalData->append(segment, length);
+        position += length;
+        bool allDataReceived = position == data->size();

[Noel Gordon, 2015/09/02 23:29:35]

Space before this line.

[scroggo, 2015/09/03 22:10:26]

Done.

+        decoder->setData(incrementalData.get(), allDataReceived);
+
+        int frameCount = decoder->frameCount();
+        for (int i = 0; i < frameCount; ++i) {
+            if (!decoder->frameBufferAtIndex(i))
+                break;
+        }
 
-    int frameCount = decoder->frameCount();
-    for (int i = 0; i < frameCount; ++i) {
-        if (!decoder->frameBufferAtIndex(i))
-            return false;
+        if (allDataReceived || decoder->failed())
+            break;
     }
 
     return !decoder->failed();
@@ -301,12 +322,12 @@ int main(int argc, char* argv[])
         applyColorCorrection = (--argc, ++argv, true);
 
     if (argc < 2) {
-        fprintf(stderr, "Usage: %s [--color-correct] file [iterations]\n", name);
+        fprintf(stderr, "Usage: %s [--color-correct] file [iterations] [chunkSize]\n", name);
         exit(1);
     }
 #else
     if (argc < 2) {
-        fprintf(stderr, "Usage: %s file [iterations]\n", name);
+        fprintf(stderr, "Usage: %s file [iterations] [chunkSize]\n", name);
         exit(1);
     }
 #endif
@@ -324,6 +345,18 @@ int main(int argc, char* argv[])
         }
     }
 
+    size_t chunkSize = 0;
+    if (argc >= 4) {
+        char* end = 0;
+        chunkSize = strtol(argv[3], &end, 10);
+        if (*end != '\0') {
+            fprintf(stderr, "Third argument should be chunk size. Default is "
+                "0, meaning to decode the entire image in one chunk. You "
+                "supplied %s\n", argv[3]);
+            exit(1);
+        }
+    }
+
     // Create a web platform without V8.
 
     class WebPlatform : public blink::Platform {
@@ -360,13 +393,19 @@ int main(int argc, char* argv[])
         exit(2);
     }
 
+    // Merge the buffers. This imitates the MemCache case, where the data is

[Noel Gordon, 2015/09/02 23:29:35]

These details about Memcache and packet chunkSize are already in the ChangeLog. 
Adding them here threw me on first reading.  The mystery is data->data() and
what it does, so I'd focus on that ... something like 

// Consolidate the SharedBuffer data() segments into one, contiguous block of
memory.

to set the scene for all that follows?

[scroggo, 2015/09/03 22:10:26]

Done.

+    // consolidated before calling the decoder. This also means that if
+    // chunkSize is not zero, each call to SharedBuffer::append will be of size
+    // chunkSize (except the last, which may be smaller).
+    data->data();
+
     // Image decode bench for iterations.
 
     double totalTime = 0.0;
 
     for (size_t i = 0; i < iterations; ++i) {
         double startTime = getCurrentTime();
-        bool decoded = decodeImageData(data.get(), applyColorCorrection);
+        bool decoded = decodeImageData(data.get(), applyColorCorrection, chunkSize);
         double elapsedTime = getCurrentTime() - startTime;
         totalTime += elapsedTime;
         if (!decoded) {