[Webkit-unassigned] [Bug 105186] New: V8 SerializedScriptValue assignment is expensive

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=105186

           Summary: V8 SerializedScriptValue assignment is expensive
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore JavaScript
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: alecflett at chromium.org
        Depends on: 104354


After bug 104354 is fixed, the easiest interface to SSV is via Vector<uint8_t>

The problem is that when you assign a Vector<uint8_t> to the SSV, it immediately does a byte-swapping copy (using htons/ntohs) and when you read the buffer from the SSV it does a similar byte-swapping copy.

Two things need to be fixed:
1) The copy should be avoided by also having an adopt-ing constructor
2) The htons/ntohs for parsing/serializing should be happening in the parser/serializer

The reason this is important is that there are use cases (like IDB) where SSV is used as an intermediate stage that MIGHT never get parsed/deserialized.

The IDB case is: A key and value are read from the database, and passed up to a JS caller. The JS caller never looks at the "value" so we shouldn't be paying the price of mucking with those bits.

While there, the whole V8 SSV parser/serializer uses String as its interface, which is really broken simply from a code perspective because a String is a buffer of 16-bit characters, but the parser/serializer internally just deals with a stream of bytes.

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