Bmp Image Decoding

include/codec/SkCodec.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCodec_DEFINED
 #define SkCodec_DEFINED
 
+#include "SkEndian.h"
 #include "SkImageGenerator.h"
 #include "SkImageInfo.h"
 #include "SkSize.h"
 #include "SkTemplates.h"
 #include "SkTypes.h"
 
 class SkData;
 class SkStream;
 
 /**
@@ skipping 20 matching lines @@
 
     /**
      *  Return a size that approximately supports the desired scale factor.
      *  The codec may not be able to scale efficiently to the exact scale
      *  factor requested, so return a size that approximates that scale.
      *
      *  FIXME: Move to SkImageGenerator?
      */
     SkISize getScaledDimensions(float desiredScale) const;
 
+    /*
+     *
+     * Checks if alpha types are premul and unpremul
+     *
+     */
+    static bool premul_and_unpremul(SkAlphaType dst, SkAlphaType src) {

[scroggo, 2015/03/12 15:19:57]

I think it'd be better if we moved all these static helper functions to a new
file, in src/codec, perhaps named SkCodecPriv.h. They're not really a part of
the API so much as part of the implementation.

[msarett, 2015/03/12 18:37:46]

Agreed.  I didn't really think they belonged here, but wasn't sure where to put
them.  That makes sense.

+        return kPremul_SkAlphaType == dst && kUnpremul_SkAlphaType == src;
+    }
+
 protected:
     SkCodec(const SkImageInfo&, SkStream*);
 
     /**
      *  The SkAlphaType is a conservative answer. i.e. it is possible that it
      *  initially returns a non-opaque answer, but completing the decode
      *  reveals that the image is actually opaque.
      */
     bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
         *info = fInfo;
@@ skipping 15 matching lines @@
      *       - if the stream needed to be rewound, and the rewind
      *         succeeded.
      *       - if the stream did not need to be rewound.
      *      false
      *       - if the stream needed to be rewound, and rewind failed.
      *  Subclasses MUST call this function before reading the stream (e.g. in
      *  onGetPixels). If it returns false, onGetPixels should return
      *  kCouldNotRewind.
      */
     bool SK_WARN_UNUSED_RESULT rewindIfNeeded();
+ 
+    // Additional helper methods for subclasses
+
+     /*
+      *
+      * Get method for the input stream
+      *
+      */
+     SkStream* stream() {
+         return fStream.get();
+     }
+
+    /*
+     *
+     * Get a byte from a buffer
+     * This method is unsafe, the caller is responsible for performing a check
+     *
+     */
+    static uint8_t get_byte(uint8_t* buffer, uint32_t i) {
+        return buffer[i];
+    }
+
+    /*
+     *
+     * Get a short from a buffer
+     * This method is unsafe, the caller is responsible for performing a check
+     *
+     */
+    static uint16_t get_short(uint8_t* buffer, uint32_t i) {
+        uint16_t result;
+        memcpy(&result, &(buffer[i]), 2);
+#ifdef SK_CPU_BENDIAN
+        return SkEndianSwap16(result);
+#else
+        return result;
+#endif
+    }
+
+    /*
+     *
+     * Get an int from a buffer
+     * This method is unsafe, the caller is responsible for performing a check
+     *
+     */
+    static uint32_t get_int(uint8_t* buffer, uint32_t i) {
+        uint32_t result;
+        memcpy(&result, &(buffer[i]), 4);
+#ifdef SK_CPU_BENDIAN
+        return SkEndianSwap32(result);
+#else
+        return result;
+#endif
+    }
 
 private:
     const SkImageInfo fInfo;
     SkAutoTDelete<SkStream> fStream;
     bool fNeedsRewind;
 };
 #endif // SkCodec_DEFINED