• Jeremy Roman's avatar
    Reland: Implement and use VectorSegment to avoid repeated allocation of ZoneVector properties. · d0142857
    Jeremy Roman authored
    The parser holds a single vector whose backing storage is reused in calls
    to ParseJsonObject, so that once we reach the peak number of unstored
    properties no more allocations are required.
    
    This improves performance of parsing inputs like those in Speedometer VanillaJS
    by about 2% in my local measurement, and would presumably do better on more
    pathological inputs.
    
    This should also have the side effect of reducing peak memory usage at this time
    slightly, since we do fewer zone allocations which cannot be freed until the
    parse finishes.
    
    Reland switches to use std::vector::data instead of operator[] to avoid an index
    check in debug MSVC. In such cases the out-of-bounds pointer cannot be
    dereferenced, so it is legal.
    
    Bug: chromium:771227
    Change-Id: I21837196372c904bfc799cd14353a73d11dcff32
    Reviewed-on: https://chromium-review.googlesource.com/804062Reviewed-by: 's avatarMarja Hölttä <marja@chromium.org>
    Commit-Queue: Jeremy Roman <jbroman@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#49997}
    d0142857
json-parser.h 6.05 KB