Merge "Faster sniffing for MIDIExtractor"

bool SniffMidi(CDataSource *source, float *confidence)

{

    MidiEngine p(source, NULL, NULL);

    if (p.initCheck() == OK) {

        *confidence = 0.8;

        ALOGV("SniffMidi: yes");

    // look for standard prefix / magic number info in the files.

    // "MThd" for midi

    // "XMF_"

    // this will be very fast.

    //

    char hdr_magic[4];

    if (source->readAt(source->handle, 0, hdr_magic, sizeof(hdr_magic)) == sizeof(hdr_magic)) {

        if (memcmp(hdr_magic,"MThd", sizeof(hdr_magic)) == 0) {

            *confidence = 0.85;

            ALOGV("SniffMidi: yes, MThd");

            return true;

        }

        if (memcmp(hdr_magic,"XMF_", sizeof(hdr_magic)) == 0) {

            *confidence = 0.85;

            ALOGV("SniffMidi: yes, XMF_");

            return true;

        }

    }

    // alternatives:

    // instantiate MidiEngine, (expensively) parsing the entire file to decide.

    ALOGV("SniffMidi: no");

    return false;