The R Project SVN R

///////////////////////////////////////////////////////////////////////////////
//
/// \file       simple_coder.c
/// \brief      Wrapper for simple filters
///
/// Simple filters don't change the size of the data i.e. number of bytes
/// in equals the number of bytes out.
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
///////////////////////////////////////////////////////////////////////////////

#include "simple_private.h"


/// Copied or encodes/decodes more data to out[].
static lzma_ret
copy_or_code(lzma_coder *coder, lzma_allocator *allocator,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size, uint8_t *restrict out,
        size_t *restrict out_pos, size_t out_size, lzma_action action)
{
    assert(!coder->end_was_reached);

    if (coder->next.code == NULL) {
        lzma_bufcpy(in, in_pos, in_size, out, out_pos, out_size);

        // Check if end of stream was reached.
        if (coder->is_encoder && action == LZMA_FINISH
                && *in_pos == in_size)
            coder->end_was_reached = true;

    } else {
        // Call the next coder in the chain to provide us some data.
        const lzma_ret ret = coder->next.code(
                coder->next.coder, allocator,
                in, in_pos, in_size,
                out, out_pos, out_size, action);

        if (ret == LZMA_STREAM_END) {
            assert(!coder->is_encoder
                    || action == LZMA_FINISH);
            coder->end_was_reached = true;

        } else if (ret != LZMA_OK) {
            return ret;
        }
    }

    return LZMA_OK;
}


static size_t
call_filter(lzma_coder *coder, uint8_t *buffer, size_t size)
{
    const size_t filtered = coder->filter(coder->simple,
            coder->now_pos, coder->is_encoder,
            buffer, size);
    coder->now_pos += filtered;
    return filtered;
}


static lzma_ret
simple_code(lzma_coder *coder, lzma_allocator *allocator,
        const uint8_t *restrict in, size_t *restrict in_pos,
        size_t in_size, uint8_t *restrict out,
        size_t *restrict out_pos, size_t out_size, lzma_action action)
{
    // TODO: Add partial support for LZMA_SYNC_FLUSH. We can support it
    // in cases when the filter is able to filter everything. With most
    // simple filters it can be done at offset that is a multiple of 2,
    // 4, or 16. With x86 filter, it needs good luck, and thus cannot
    // be made to work predictably.
    if (action == LZMA_SYNC_FLUSH)
        return LZMA_OPTIONS_ERROR;

    // Flush already filtered data from coder->buffer[] to out[].
    if (coder->pos < coder->filtered) {
        lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
                out, out_pos, out_size);

        // If we couldn't flush all the filtered data, return to
        // application immediately.
        if (coder->pos < coder->filtered)
            return LZMA_OK;

        if (coder->end_was_reached) {
            assert(coder->filtered == coder->size);
            return LZMA_STREAM_END;
        }
    }

    // If we get here, there is no filtered data left in the buffer.
    coder->filtered = 0;

    assert(!coder->end_was_reached);

    // If there is more output space left than there is unfiltered data
    // in coder->buffer[], flush coder->buffer[] to out[], and copy/code
    // more data to out[] hopefully filling it completely. Then filter
    // the data in out[]. This step is where most of the data gets
    // filtered if the buffer sizes used by the application are reasonable.
    const size_t out_avail = out_size - *out_pos;
    const size_t buf_avail = coder->size - coder->pos;
    if (out_avail > buf_avail || buf_avail == 0) {
        // Store the old position so that we know from which byte
        // to start filtering.
        const size_t out_start = *out_pos;

        // Flush data from coder->buffer[] to out[], but don't reset
        // coder->pos and coder->size yet. This way the coder can be
        // restarted if the next filter in the chain returns e.g.
        // LZMA_MEM_ERROR.
        memcpy(out + *out_pos, coder->buffer + coder->pos, buf_avail);
        *out_pos += buf_avail;

        // Copy/Encode/Decode more data to out[].
        {
            const lzma_ret ret = copy_or_code(coder, allocator,
                    in, in_pos, in_size,
                    out, out_pos, out_size, action);
            assert(ret != LZMA_STREAM_END);
            if (ret != LZMA_OK)
                return ret;
        }

        // Filter out[].
        const size_t size = *out_pos - out_start;
        const size_t filtered = call_filter(
                coder, out + out_start, size);

        const size_t unfiltered = size - filtered;
        assert(unfiltered <= coder->allocated / 2);

        // Now we can update coder->pos and coder->size, because
        // the next coder in the chain (if any) was successful.
        coder->pos = 0;
        coder->size = unfiltered;

        if (coder->end_was_reached) {
            // The last byte has been copied to out[] already.
            // They are left as is.
            coder->size = 0;

        } else if (unfiltered > 0) {
            // There is unfiltered data left in out[]. Copy it to
            // coder->buffer[] and rewind *out_pos appropriately.
            *out_pos -= unfiltered;
            memcpy(coder->buffer, out + *out_pos, unfiltered);
        }
    } else if (coder->pos > 0) {
        memmove(coder->buffer, coder->buffer + coder->pos, buf_avail);
        coder->size -= coder->pos;
        coder->pos = 0;
    }

    assert(coder->pos == 0);

    // If coder->buffer[] isn't empty, try to fill it by copying/decoding
    // more data. Then filter coder->buffer[] and copy the successfully
    // filtered data to out[]. It is probable, that some filtered and
    // unfiltered data will be left to coder->buffer[].
    if (coder->size > 0) {
        {
            const lzma_ret ret = copy_or_code(coder, allocator,
                    in, in_pos, in_size,
                    coder->buffer, &coder->size,
                    coder->allocated, action);
            assert(ret != LZMA_STREAM_END);
            if (ret != LZMA_OK)
                return ret;
        }

        coder->filtered = call_filter(
                coder, coder->buffer, coder->size);

        // Everything is considered to be filtered if coder->buffer[]
        // contains the last bytes of the data.
        if (coder->end_was_reached)
            coder->filtered = coder->size;

        // Flush as much as possible.
        lzma_bufcpy(coder->buffer, &coder->pos, coder->filtered,
                out, out_pos, out_size);
    }

    // Check if we got everything done.
    if (coder->end_was_reached && coder->pos == coder->size)
        return LZMA_STREAM_END;

    return LZMA_OK;
}


static void
simple_coder_end(lzma_coder *coder, lzma_allocator *allocator)
{
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder->simple, allocator);
    lzma_free(coder, allocator);
    return;
}


static lzma_ret
simple_coder_update(lzma_coder *coder, lzma_allocator *allocator,
        const lzma_filter *filters_null lzma_attribute((__unused__)),
        const lzma_filter *reversed_filters)
{
    // No update support, just call the next filter in the chain.
    return lzma_next_filter_update(
            &coder->next, allocator, reversed_filters + 1);
}


extern lzma_ret
lzma_simple_coder_init(lzma_next_coder *next, lzma_allocator *allocator,
        const lzma_filter_info *filters,
        size_t (*filter)(lzma_simple *simple, uint32_t now_pos,
            bool is_encoder, uint8_t *buffer, size_t size),
        size_t simple_size, size_t unfiltered_max,
        uint32_t alignment, bool is_encoder)
{
    // Allocate memory for the lzma_coder structure if needed.
    if (next->coder == NULL) {
        // Here we allocate space also for the temporary buffer. We
        // need twice the size of unfiltered_max, because then it
        // is always possible to filter at least unfiltered_max bytes
        // more data in coder->buffer[] if it can be filled completely.
        next->coder = lzma_alloc(sizeof(lzma_coder)
                + 2 * unfiltered_max, allocator);
        if (next->coder == NULL)
            return LZMA_MEM_ERROR;

        next->code = &simple_code;
        next->end = &simple_coder_end;
        next->update = &simple_coder_update;

        next->coder->next = LZMA_NEXT_CODER_INIT;
        next->coder->filter = filter;
        next->coder->allocated = 2 * unfiltered_max;

        // Allocate memory for filter-specific data structure.
        if (simple_size > 0) {
            next->coder->simple = lzma_alloc(
                    simple_size, allocator);
            if (next->coder->simple == NULL)
                return LZMA_MEM_ERROR;
        } else {
            next->coder->simple = NULL;
        }
    }

    if (filters[0].options != NULL) {
        const lzma_options_bcj *simple = filters[0].options;
        next->coder->now_pos = simple->start_offset;
        if (next->coder->now_pos & (alignment - 1))
            return LZMA_OPTIONS_ERROR;
    } else {
        next->coder->now_pos = 0;
    }

    // Reset variables.
    next->coder->is_encoder = is_encoder;
    next->coder->end_was_reached = false;
    next->coder->pos = 0;
    next->coder->filtered = 0;
    next->coder->size = 0;

    return lzma_next_filter_init(
            &next->coder->next, allocator, filters + 1);
}