///////////////////////////////////////////////////////////////////////////////
//
/// \file       stream_buffer_decoder.c
/// \brief      Single-call .xz Stream decoder
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "stream_decoder.h"


extern LZMA_API(lzma_ret)
lzma_stream_buffer_decode(uint64_t *memlimit, uint32_t flags,
        const lzma_allocator *allocator,
        const uint8_t *in, size_t *in_pos, size_t in_size,
        uint8_t *out, size_t *out_pos, size_t out_size)
{
    // Sanity checks
    if (in_pos == NULL || (in == NULL && *in_pos != in_size)
            || *in_pos > in_size || out_pos == NULL
            || (out == NULL && *out_pos != out_size)
            || *out_pos > out_size)
        return LZMA_PROG_ERROR;

    // Catch flags that are not allowed in buffer-to-buffer decoding.
    if (flags & LZMA_TELL_ANY_CHECK)
        return LZMA_PROG_ERROR;

    // Initialize the Stream decoder.
    // TODO: We need something to tell the decoder that it can use the
    // output buffer as workspace, and thus save significant amount of RAM.
    lzma_next_coder stream_decoder = LZMA_NEXT_CODER_INIT;
    lzma_ret ret = lzma_stream_decoder_init(
            &stream_decoder, allocator, *memlimit, flags);

    if (ret == LZMA_OK) {
        // Save the positions so that we can restore them in case
        // an error occurs.
        const size_t in_start = *in_pos;
        const size_t out_start = *out_pos;

        // Do the actual decoding.
        ret = stream_decoder.code(stream_decoder.coder, allocator,
                in, in_pos, in_size, out, out_pos, out_size,
                LZMA_FINISH);

        if (ret == LZMA_STREAM_END) {
            ret = LZMA_OK;
        } else {
            // Something went wrong, restore the positions.
            *in_pos = in_start;
            *out_pos = out_start;

            if (ret == LZMA_OK) {
                // Either the input was truncated or the
                // output buffer was too small.
                assert(*in_pos == in_size
                        || *out_pos == out_size);

                // If all the input was consumed, then the
                // input is truncated, even if the output
                // buffer is also full. This is because
                // processing the last byte of the Stream
                // never produces output.
                if (*in_pos == in_size)
                    ret = LZMA_DATA_ERROR;
                else
                    ret = LZMA_BUF_ERROR;

            } else if (ret == LZMA_MEMLIMIT_ERROR) {
                // Let the caller know how much memory would
                // have been needed.
                uint64_t memusage;
                (void)stream_decoder.memconfig(
                        stream_decoder.coder,
                        memlimit, &memusage, 0);
            }
        }
    }

    // Free the decoder memory. This needs to be done even if
    // initialization fails, because the internal API doesn't
    // require the initialization function to free its memory on error.
    lzma_next_end(&stream_decoder, allocator);

    return ret;
}
