Transfer WebCrypto databuffers across the Blink API using blink::WebVector.

third_party/WebKit/public/platform/WebCrypto.h

Index: third_party/WebKit/public/platform/WebCrypto.h
diff --git a/third_party/WebKit/public/platform/WebCrypto.h b/third_party/WebKit/public/platform/WebCrypto.h
index cfd49c5ad5a3c8072bc92b61d489d784d954ac48..ba3d98fa80b84d97ef133c85792cba2943508fe8 100644
--- a/third_party/WebKit/public/platform/WebCrypto.h
+++ b/third_party/WebKit/public/platform/WebCrypto.h
@@ -172,10 +172,8 @@ public:
     // Inputs
     // -----------------------
     //
-    //   * Data buffers are passed as (basePointer, byteLength) pairs.
-    //     These buffers are only valid during the call itself. Asynchronous
-    //     implementations wishing to access it after the function returns
-    //     should make a copy.
+    //   * Data buffers are transfered as WebVectors. Implementations are free
+    //     to re-use or transfer their storage.
     //
     //   * All WebCryptoKeys are guaranteeed to be !isNull().
     //
@@ -200,16 +198,16 @@ public:
     //  * The key usages permit the operation being requested.
     //  * The key's algorithm matches that of the requested operation.
     //
-    virtual void encrypt(const WebCryptoAlgorithm&, const WebCryptoKey&, const unsigned char* data, unsigned dataSize, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    virtual void decrypt(const WebCryptoAlgorithm&, const WebCryptoKey&, const unsigned char* data, unsigned dataSize, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    virtual void sign(const WebCryptoAlgorithm&, const WebCryptoKey&, const unsigned char* data, unsigned dataSize, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    virtual void verifySignature(const WebCryptoAlgorithm&, const WebCryptoKey&, const unsigned char* signature, unsigned signatureSize, const unsigned char* data, unsigned dataSize, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    virtual void digest(const WebCryptoAlgorithm&, const unsigned char* data, unsigned dataSize, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void encrypt(const WebCryptoAlgorithm&, const WebCryptoKey&, WebVector<unsigned char> data, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }

[jochen (gone - plz use gerrit), 2016/07/19 12:27:40]

why not WebVector<unsigned char>&

[eroman, 2016/07/19 16:17:41]

My preference for pass-by-value is:
  * Makes it clear that it is an input parameter (and not an out or in/out
parameter)
  * Self-describes the "pass ownership" semantics
  * [weaker argument] Harder to mis-use, as the implementation cannot
accidentally save a reference to variable owned by caller.

For the other direction, the main advantage I can think of for pass-by-reference
approach, is it makes it harder to accidentally create a copy of vectors when
Blink calls into this interface. This is a consequence of WebVector having
implicit single-parameter constructors that make *copies* of things :(

For instance, in an earlier patchset I was passing in std::move(x) as expected,
and it looked correct. However, "x" was of type "Vector" rather than WeVector.
What this meant is that in reality it was calling into the WebVector(const
Vector& x) constructor, and hence making a copy instead of transferring.

I think the best fix for the problem above is to mark the constructors as
explicit as per the Chromium style guide. In the meantime though, making the
databuffer parameters be of type WebVector& would also catch such bugs since you
cannot take references of temporaries so that would have been a compile failure
I believe.

WDYT?

+    virtual void decrypt(const WebCryptoAlgorithm&, const WebCryptoKey&, WebVector<unsigned char> data, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void sign(const WebCryptoAlgorithm&, const WebCryptoKey&, WebVector<unsigned char> data, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void verifySignature(const WebCryptoAlgorithm&, const WebCryptoKey&, WebVector<unsigned char> signature, WebVector<unsigned char> data, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void digest(const WebCryptoAlgorithm&, WebVector<unsigned char> data, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
     virtual void generateKey(const WebCryptoAlgorithm&, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    virtual void importKey(WebCryptoKeyFormat, const unsigned char* keyData, unsigned keyDataSize, const WebCryptoAlgorithm&, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void importKey(WebCryptoKeyFormat, WebVector<unsigned char> keyData, const WebCryptoAlgorithm&, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
     virtual void exportKey(WebCryptoKeyFormat, const WebCryptoKey&, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
     virtual void wrapKey(WebCryptoKeyFormat, const WebCryptoKey& key, const WebCryptoKey& wrappingKey, const WebCryptoAlgorithm&, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
-    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(WebCryptoErrorTypeNotSupported, ""); }
+    virtual void unwrapKey(WebCryptoKeyFormat, WebVector<unsigned char> wrappedKey, const WebCryptoKey&, const WebCryptoAlgorithm& unwrapAlgorithm, const WebCryptoAlgorithm& unwrappedKeyAlgorithm, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
     virtual void deriveBits(const WebCryptoAlgorithm&, const WebCryptoKey&, unsigned length, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }
     virtual void deriveKey(const WebCryptoAlgorithm& algorithm, const WebCryptoKey& baseKey, const WebCryptoAlgorithm& importAlgorithm, const WebCryptoAlgorithm& keyLengthAlgorithm, bool extractable, WebCryptoKeyUsageMask, WebCryptoResult result) { result.completeWithError(WebCryptoErrorTypeNotSupported, ""); }