Make SkCodec support peek() and read()

tests/CodexTest.cpp

Index: tests/CodexTest.cpp
diff --git a/tests/CodexTest.cpp b/tests/CodexTest.cpp
index 697ba749f70861d9678a19894622dff8ec1ed8bf..99a363f53e671eaf8c4be3713226ec60fc249023 100644
--- a/tests/CodexTest.cpp
+++ b/tests/CodexTest.cpp
@@ -877,3 +877,32 @@ DEF_TEST(Codec_wbmp, r) {
     }
     test_info(r, codec, codec->getInfo(), SkCodec::kSuccess, nullptr);
 }
+
+// wbmp images have a header that can be arbitrarily large, depending on the
+// size of the image. We cap the size at 65535, meaning we only need to look at
+// 8 bytes to determine whether we can read the image. This is important
+// because SkCodec only passes 14 bytes to SkWbmpCodec to determine whether the
+// image is a wbmp.
+DEF_TEST(Codec_wbmp_max_size, r) {
+    const unsigned char maxSizeWbmp[] = { 0x00, 0x00,           // Header
+                                          0x83, 0xFF, 0x7F,     // W: 65535
+                                          0x83, 0xFF, 0x7F };   // H: 65535
+    SkAutoTDelete<SkStream> stream(new SkMemoryStream(maxSizeWbmp, sizeof(maxSizeWbmp), false));
+    SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.detach()));
+
+    REPORTER_ASSERT(r, codec);
+    if (!codec) return;
+
+    REPORTER_ASSERT(r, codec->getInfo().width() == 65535);
+    REPORTER_ASSERT(r, codec->getInfo().height() == 65535);
+
+    // Now test an image which is too big. Any image with a larger header (i.e.
+    // has bigger width/height) is also too big.
+    const unsigned char tooBigWbmp[] = { 0x00, 0x00,           // Header
+                                         0x84, 0x80, 0x00,     // W: 65536
+                                         0x84, 0x80, 0x00 };   // H: 65536
+    stream.reset(new SkMemoryStream(tooBigWbmp, sizeof(tooBigWbmp), false));
+    codec.reset(SkCodec::NewFromStream(stream.detach()));
+
+    REPORTER_ASSERT(r, !codec);
+}