Add a WebCrypto API for getting digests by chunk.

public/platform/WebCrypto.h

Index: public/platform/WebCrypto.h
diff --git a/public/platform/WebCrypto.h b/public/platform/WebCrypto.h
index 7b56f4ef7bfd391eb1f6af186fb6449b04f3d94d..abea0f4bbd83726cc15f0e448ade186ffac565c0 100644
--- a/public/platform/WebCrypto.h
+++ b/public/platform/WebCrypto.h
@@ -34,6 +34,7 @@
 #include "WebCommon.h"
 #include "WebCryptoAlgorithm.h"
 #include "WebCryptoKey.h"
+#include "WebPrivateOwnPtr.h"
 #include "WebPrivatePtr.h"
 
 // FIXME: Remove this once chromium side is updated.
@@ -97,6 +98,26 @@ private:
     WebPrivatePtr<WebCore::CryptoResult> m_impl;
 };
 
+class WebCryptoDigestor {
+public:
+    virtual ~WebCryptoDigestor() { }
+
+    // consume() will return |true| on the successful addition of data to the
+    // partially generated digest. It will return |false when that fails. After

[eroman, 2014/03/25 17:37:02]

missing "|false" --> "|false|"

[jww, 2014/03/25 20:18:19]

Done.

+    // a return of |false|, consume() should not be called again (nor should
+    // finish() be called).
+    virtual bool consume(const unsigned char* data, unsigned dataSize) { return false; }
+    // finish() will return |true| if the digest has been successfully computed

[eroman, 2014/03/25 17:37:02]

nit: add a newline

[jww, 2014/03/25 20:18:19]

Done.

+    // and put into the result buffer, otherwise it will return |false|. In
+    // either case, neither finish() nor consume() should be called again after
+    // a call to finish(). resultData is valid until the WebCrytpoDigestor
+    // object is destroyed.
+    virtual bool finish(unsigned char*& resultData, unsigned& resultDataSize) { return false; }
+
+protected:
+    WebCryptoDigestor() { }
+};
+
 class WebCrypto {
 public:
     // WebCrypto is the interface for starting one-shot cryptographic
@@ -182,12 +203,12 @@ public:
     // It is possible that unwrappedKeyAlgorithm.isNull()
     virtual void unwrapKey(WebCryptoKeyFormat, const unsigned char* wrappedKey, unsigned wrappedKeySize, const WebCryptoKey&, const WebCryptoAlgorithm& unwrapAlgorithm, const WebCryptoAlgorithm& unwrappedKeyAlgorithm, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(); }
 
-    // This is the one exception to the "Completing the request" guarantees
-    // outlined above. digestSynchronous must provide the result into result
-    // synchronously. It must return |true| on successful calculation of the
-    // digest and |false| otherwise. This is useful for Blink internal crypto
+    // This is the exception to the "Completing the request" guarantees
+    // outlined above. digestorSynchronous must provide the result via the WebCryptoDigestor object synchronously.

[eroman, 2014/03/25 17:37:02]

Please also mention that 0 can be returned on failure. And that the allocated
object must be freed by the caller.

[jww, 2014/03/25 20:18:19]

Done.

+    // This is useful for Blink internal crypto
     // and is not part of the WebCrypto standard.
     virtual bool digestSynchronous(const WebCryptoAlgorithmId algorithmId, const unsigned char* data, unsigned dataSize, WebArrayBuffer& result) { return false; }
+    virtual WebCryptoDigestor* digestorSynchronous(WebCryptoAlgorithmId algorithmId) { return 0; }

[eroman, 2014/03/25 17:37:02]

I propose calling this "createDigestor()". And leave off the synchronous part.

[jww, 2014/03/25 20:18:19]

Done.

 
 protected:
     virtual ~WebCrypto() { }