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Commit 72a43b68 authored by Marco Nelissen's avatar Marco Nelissen
Browse files

Speed up id3v2 unsynchronization 

Instead of doing many overlapping memmoves, do a single copy pass
that skips over the inserted unsynchronization bytes. For some
files this reduces parsing time from minutes to milliseconds.

b/9463262

Change-Id: I735b7051e77a093d86fb7a3e46209875946225ed
parent 04411d3e

media/libstagefright/id3/ID3.cpp

+10 −5
Original line number Diff line number Diff line
@@ -357,17 +357,22 @@ bool ID3::removeUnsynchronizationV2_4(bool iTunesHack) { 
        }



        if (flags & 2) {

            // Unsynchronization added.

            // This file has "unsynchronization", so we have to replace occurrences

            // of 0xff 0x00 with just 0xff in order to get the real data.



            size_t readOffset = offset + 11;

            size_t writeOffset = offset + 11;

            for (size_t i = 0; i + 1 < dataSize; ++i) {

                if (mData[offset + 10 + i] == 0xff

                        && mData[offset + 11 + i] == 0x00) {

                    memmove(&mData[offset + 11 + i], &mData[offset + 12 + i],

                            mSize - offset - 12 - i);

                if (mData[readOffset - 1] == 0xff

                        && mData[readOffset] == 0x00) {

                    ++readOffset;

                    --mSize;

                    --dataSize;

                }

                mData[writeOffset++] = mData[readOffset++];

            }

            // move the remaining data following this frame

            memmove(&mData[writeOffset], &mData[readOffset], oldSize - readOffset);



            flags &= ~2;

        }