/*

    Copyright (C) 2015 Apple Inc. All Rights Reserved.

    See LICENSE.txt for this sample’s licensing information

    Abstract:

    Provides code that performs stream compression.

*/

#include "StreamCompression.h"

#include <stdlib.h>

// These buffer sizes are arbitrary. Choose sizes to suit your own purposes.

#define inBufSize 256

#define outBufSize 1024

float doStreamCompression(FILE* fi, FILE* fo, compression_algorithm algorithm, compression_stream_operation operation)

{

    uint8_t *dstBuf = malloc(outBufSize);

    uint8_t *srcBuf = malloc(inBufSize);

    compression_status status;

    size_t size_read;

    size_t size_written;

    float totalInputSize = 0;

    float totalOutputSize = 0;

    compression_stream_flags flags;

    compression_stream stream;

    compression_stream_init(&stream, operation, algorithm);

    stream.dst_ptr = dstBuf;

    stream.dst_size = outBufSize;

    stream.src_ptr = srcBuf;

    stream.src_size = 0;

    flags = 0;

    do {

        if (stream.src_size == 0) {

            // Input buffer empty.

            if (flags != COMPRESSION_STREAM_FINALIZE || operation == COMPRESSION_STREAM_ENCODE) {

                // Refill srcBuf.

                size_read = fread(srcBuf, 1, inBufSize, fi);

                totalInputSize += size_read;

                stream.src_ptr = srcBuf;

                stream.src_size = size_read;

                if (size_read < inBufSize) {

                    // Reached end of data.

                    flags = COMPRESSION_STREAM_FINALIZE;

                }

            }

        }

        if (stream.dst_size == 0) {

            // Output buffer full.

            // Write out dstbuf.

            size_written = fwrite(dstBuf, 1, outBufSize, fo);

            totalOutputSize += size_written;

            // Re-use dstBuf.

            stream.dst_ptr = dstBuf;

            stream.dst_size = outBufSize;

        }

        // Compress.

        status = compression_stream_process(&stream, flags);

        switch (status) {

            case COMPRESSION_STATUS_OK:

                // We are going to call compression_stream_process at least once more, so we prepare for that.

                if (stream.dst_size == 0) {

                    // Output buffer full.

                    // Write out dstbuf.

                    size_written = fwrite(dstBuf, 1, outBufSize, fo);

                    totalOutputSize += size_written;

                    // Re-use dstBuf.

                    stream.dst_ptr = dstBuf;

                    stream.dst_size = outBufSize;

                }

                break;

            case COMPRESSION_STATUS_END:

                // We are done, just write out the output buffer if there's anything in it.

                if (stream.dst_ptr > dstBuf) {

                    // Write out dstbuf.

                    size_written = fwrite(dstBuf, 1, stream.dst_ptr - dstBuf, fo);

                    totalOutputSize += size_written;

                }

                break;

            case COMPRESSION_STATUS_ERROR:

                return 0;

            default:

                break;

        }

    } while (status == COMPRESSION_STATUS_OK);

    compression_stream_destroy(&stream);

    return totalInputSize / totalOutputSize;

}