/*

File: NaiveDecoder.c, part of ExampleIPBCodec

Abstract: Core routines of a decoder for a simplistic video encoding format.

Version: 1.0

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#include "NaiveDecoder.h"

// Decode an 8x8 I-block from the bitstream, writing it at destBaseAddr/destRowBytes.

// dataPtr points to the second byte of the encoded block.

// destBaseAddr points where to write the decoded block; destRowBytes is the offset from one row to the next.

// Return in bytesConsumedOut the number of bytes consumed in the bitstream.

static OSStatus 

decodeStandaloneBlock( 

        const UInt8 *dataPtr, 

        int *bytesConsumedOut,

        UInt8 *destBaseAddr,

        size_t destRowBytes )

{

    int firstBit = dataPtr[0];

    int numberOfBits = dataPtr[1];

    int bitIndex, x, y;

    UInt8 *destLine;

    UInt8 bit;

    dataPtr += 2;

    // Sanity check.

    if( ( firstBit > 7 ) || ( numberOfBits > 8 ) )

        return codecBadDataErr;

    // Clear the block.

    destLine = destBaseAddr;

    for( y = 0; y < 8; y++ ) {

        for( x = 0; x < 8; x++ ) {

            destLine[x] = 0;

        }

        destLine += destRowBytes;

    }

    // OR in the other bits.

    bit = 1 << firstBit;

    for( bitIndex = 0; bitIndex < numberOfBits; bitIndex++ ) {

        destLine = destBaseAddr;

        for( y = 0; y < 8; y++ ) {

            UInt8 cluster = *dataPtr++;

            // Spread the 8 bits of cluster across the indexed bit of the 8 output bytes.

            for( x = 0; x < 8; x++ ) {

                if( cluster & ( 1 << ( 7 - x ) ) )

                    destLine[x] |= bit;

            }

            destLine += destRowBytes;

        }

        bit = bit >> 1; 

    }

    *bytesConsumedOut = 2 + 8 * numberOfBits;

    return noErr;

}

// Decode an 8x8 predicted block from the bitstream, writing it at destBaseAddr/destRowBytes.

// dataPtr points to the second byte of the encoded block.

// predBaseAddr points to the prediction block; predRowBytes is the offset from one row to the next.

// destBaseAddr points where to write the decoded block; destRowBytes is the offset from one row to the next.

// Return in bytesConsumedOut the number of bytes consumed in the bitstream.

static OSStatus 

decodePredictedBlock( 

        const UInt8 *dataPtr, 

        int *bytesConsumedOut,

        const UInt8 *predBaseAddr,

        size_t predRowBytes, 

        UInt8 *destBaseAddr,

        size_t destRowBytes )

{

    int firstBit = dataPtr[0];

    int numberOfBits = dataPtr[1];

    int bitIndex, x, y;

    const UInt8 *predLine;

    UInt8 *destLine;

    UInt8 bit;

    dataPtr += 2;

    // Sanity check.

    if( ( firstBit > 7 ) || ( numberOfBits > 8 ) )

        return codecBadDataErr;

    // Copy the prediction block.

    predLine = predBaseAddr;

    destLine = destBaseAddr;

    for( y = 0; y < 8; y++ ) {

        for( x = 0; x < 8; x++ ) {

            destLine[x] = predLine[x];

        }

        predLine += predRowBytes;

        destLine += destRowBytes;

    }

    // XOR in the bits.

    bit = 1 << firstBit;

    for( bitIndex = 0; bitIndex < numberOfBits; bitIndex++ ) {

        destLine = destBaseAddr;

        for( y = 0; y < 8; y++ ) {

            UInt8 cluster = *dataPtr++;

            // Spread the 8 bits of cluster across the indexed bit of the 8 output bytes.

            for( x = 0; x < 8; x++ ) {

                if( cluster & ( 1 << ( 7 - x ) ) )

                    destLine[x] ^= bit;

            }

            destLine += destRowBytes;

        }

        bit = bit >> 1; 

    }

    *bytesConsumedOut = 2 + 8 * numberOfBits;

    return noErr;

}

// Decode a plane of 8x8 blocks from the bitstream.

// destBaseAddr points where to write the decoded block; destRowBytes is the offset from one row to the next.

static OSStatus 

decodePlane(

        size_t width,

        size_t height,

        const UInt8 **dataPtrInOut, 

        ICMDataProcRecord *dataProc,

        size_t *bytesConsumedOut,

        UInt8 *predBaseAddrArray[kMaxStoredFrames],

        size_t predRowBytesArray[kMaxStoredFrames],

        UInt8 *destPlaneBaseAddr,

        size_t destRowBytes )

{

    OSStatus err = noErr;

    const UInt8 *dataPtr = *dataPtrInOut;

    size_t widthInBlocks, heightInBlocks, xblock, yblock;

    int bytesConsumed;

    size_t totalBytesConsumed = 0;

    UInt8 *blockLineBaseAddr = destPlaneBaseAddr;

    widthInBlocks = ( width + 7 ) / 8;

    heightInBlocks = ( height + 7 ) / 8;

    for( yblock = 0; yblock < heightInBlocks; yblock++ ) {

        UInt8 *blockBaseAddr = blockLineBaseAddr;

        if( dataProc ) {

            // Call the data-loading proc to ensure that we have enough data loaded to 

            // output one row of blocks.  (With our data format, the most data we might 

            // need for n blocks is n*(3+8*8).)  It is safe to ask for up to 32K of data

            // at a time.

            // NOTE: During normal movie playback, the data will be fully loaded and

            // dataProc will be NULL.  However, video frames may be transferred to other

            // containers such as PICT files and QuickTime Image files, and when drawing

            // them the data will be provided using data-loading procs.

            long bytesNeeded = widthInBlocks * (3+8*8);

            dataProc->dataProc( (Ptr *)&dataPtr, bytesNeeded, dataProc->dataRefCon );

        }

        for( xblock = 0; xblock < widthInBlocks; xblock++ ) {

            UInt8 predIndex = dataPtr[0];

            dataPtr += 1;

            totalBytesConsumed += 1;

            if( predIndex > kMaxStoredFrames ) {

                // "Predictor index out of range"

                err = codecBadDataErr;

                goto bail;

            }

            if( 0 == predIndex ) {

                err = decodeStandaloneBlock( 

                        dataPtr, &bytesConsumed, blockBaseAddr, destRowBytes );

                if( err )

                    goto bail;

            }

            else {

                const UInt8 *predBaseAddr = predBaseAddrArray[predIndex-1];

                size_t predRowBytes = predRowBytesArray[predIndex-1];

                predBaseAddr += yblock * 8 * predRowBytes + xblock * 8;

                err = decodePredictedBlock( 

                        dataPtr, &bytesConsumed, predBaseAddr, predRowBytes, blockBaseAddr, destRowBytes );

                if( err )

                    goto bail;

            }

            dataPtr += bytesConsumed;

            totalBytesConsumed += bytesConsumed;

            blockBaseAddr += 8;

        }

        blockLineBaseAddr += 8 * destRowBytes;

    }

    *dataPtrInOut = dataPtr;

    *bytesConsumedOut = totalBytesConsumed;

bail:

    return err;

}

// Read the 16-byte header at the start of the frame without advancing dataPtr.

extern OSStatus

NaiveDecoder_DecodeFrameHeader( 

        const UInt8 *dataPtr, 

        Boolean *keyFrameOut,

        Boolean *differenceFrameOut,

        Boolean *droppableFrameOut,

        int *storageIndexOut )

{

    OSStatus err = noErr;

    UInt32 boxSize;

    UInt8 keyFrame, differenceFrame, storageIndex;

    // Check that the header is the right length.

    boxSize = *(UInt32 *)(dataPtr + 0);

    boxSize = EndianU32_BtoN( boxSize );

    if( 11 != boxSize ) {

        // "Header size check failed"

        err = codecDataVersErr;

        goto bail;

    }

    // Check the header has the right check code.

    if( EndianU32_NtoB(kNaiveHeaderCheckCode) != *(OSType *)(dataPtr + 4) ) {

        // "Header check code incorrect"

        err = codecDataVersErr;

        goto bail;

    }

    keyFrame = dataPtr[8];

    if( keyFrame > 1 ) {

        // "Bad keyFrame value"

        err = codecBadDataErr;

        goto bail;

    }

    *keyFrameOut = keyFrame;

    differenceFrame = dataPtr[9];

    if( differenceFrame > 1 ) {

        // "Bad differenceFrame value"

        err = codecBadDataErr;

        goto bail;

    }

    *differenceFrameOut = differenceFrame;

    storageIndex = dataPtr[10];

    if( storageIndex > kMaxStoredFrames ) {

        // "Bad storageIndex value"

        err = codecBadDataErr;

        goto bail;

    }

    *droppableFrameOut = (storageIndex == 0);

    *storageIndexOut = storageIndex - 1;

bail:

    return err;

}

static void

selectPlaneFromEachBuffer( 

        struct InternalPixelBuffer predictionBuffers[kMaxStoredFrames],

        int planeIndex,

        UInt8 *predBaseAddrArray[kMaxStoredFrames],

        size_t predRowBytesArray[kMaxStoredFrames] )

{

    int frameIndex;

    for( frameIndex = 0; frameIndex < kMaxStoredFrames; frameIndex++ ) {

        predBaseAddrArray[frameIndex] = predictionBuffers[frameIndex].planeArray[planeIndex].planeBaseAddr;

        predRowBytesArray[frameIndex] = predictionBuffers[frameIndex].planeArray[planeIndex].planeRowBytes;

    }

}

// Read the frame payload and decode a frame of the given dimensions into destBuffer.

// dataPtrInOut points to a variable that points to the incoming datastream; 

// it will be updated with the advanced datastream pointer after a successful decode.

// dataProc points to a data-loading callback record if the codec is being

// called with one; otherwise it is NULL.  

// dataSize is the total size of compressed data if available, 0 if not.

// (Note that some legacy APIs allow applications to request image decompression 

// without providing the data size; decompressors should handle this case robustly.)

// predictionBuffers is an array of planar YUV 4:2:0 buffers containing 

// previously-decoded frames that this frame may depend upon.

extern OSStatus

NaiveDecoder_DecodeFramePayload( 

        size_t width,

        size_t height,

        const UInt8 **dataPtrInOut, 

        ICMDataProcRecord *dataProc,

        size_t dataSize,

        struct InternalPixelBuffer predictionBuffers[kMaxStoredFrames],

        struct InternalPixelBuffer *destBuffer )

{

    OSStatus err = noErr;

    const UInt8 *dataPtr = *dataPtrInOut;

    size_t bytesConsumed = 0, bytesConsumedByPlane;

    UInt32 boxSize;

    OSType boxKind;

    UInt8 *predBaseAddrArray[kMaxStoredFrames];

    size_t predRowBytesArray[kMaxStoredFrames];

    int planeIndex, subsampling;

    Boolean didPlane[3] = { false, false, false };

    // Our codec data is structured as a sequence of boxes/atoms, each starting with a 4 byte size and 4 byte kind.  

    // We ignore unrecognised boxes provided that they have legal sizes, so the data format can be extended later

    // by introducing new box types.

    while( ( dataSize == 0 ) || ( bytesConsumed + 4 <= dataSize ) ) {

        boxSize = *(UInt32 *)(dataPtr + 0);

        boxSize = EndianU32_BtoN( boxSize );

        if( 0 == boxSize ) {

            // End of frame data indicator.

            break;

        }

        if( ( boxSize < 8 ) || ( ( dataSize != 0 ) && ( bytesConsumed + boxSize > dataSize ) ) ) {

            // "Illegal box size"

            err = codecBadDataErr;

            goto bail;

        }

        boxKind = *(OSType *)(dataPtr + 4);

        boxKind = EndianU32_BtoN( boxKind );

        dataPtr += 8;

        bytesConsumed += 8;

        boxSize -= 8;

        switch( boxKind ) {

            case kNaiveYPlaneCode:

            case kNaiveCbPlaneCode:

            case kNaiveCrPlaneCode:

                switch( boxKind ) {

                    case kNaiveYPlaneCode:

                        planeIndex = 0;

                        subsampling = 1;

                        break;

                    case kNaiveCbPlaneCode:

                        planeIndex = 1;

                        subsampling = 2;

                        break;

                    case kNaiveCrPlaneCode:

                        planeIndex = 2;

                        subsampling = 2;

                        break;

                }

                if( didPlane[planeIndex] ) {

                    // "Plane repeated"

                    err = codecBadDataErr;

                    goto bail;

                }

                selectPlaneFromEachBuffer( predictionBuffers, planeIndex, predBaseAddrArray, predRowBytesArray );

                err = decodePlane( width/subsampling, height/subsampling, 

                        &dataPtr, dataProc, &bytesConsumedByPlane, 

                        predBaseAddrArray, predRowBytesArray,

                        destBuffer->planeArray[planeIndex].planeBaseAddr,

                        destBuffer->planeArray[planeIndex].planeRowBytes );

                if( err )

                    goto bail;

                if( bytesConsumedByPlane != boxSize ) {

                    // "Plane data consumed did not fit box size"

                    err = codecBadDataErr;

                    goto bail;

                }

                // decodePlane advances dataPtr

                bytesConsumed += bytesConsumedByPlane;

                didPlane[planeIndex] = true;

                break;

            default:

                dataPtr += boxSize;

                bytesConsumed += boxSize;

                break;

        }

    }

    if( didPlane[0] && didPlane[1] && didPlane[2] ) {

        err = noErr;

    }

    else {

        // "Plane data missing"

        err = codecBadDataErr;

        goto bail;

    }

    *dataPtrInOut = dataPtr;

bail:

    return err;

}