alone_decoder.c

Go to the documentation of this file.

//
//
//  Author:     Lasse Collin
//
//  This file has been put into the public domain.
//  You can do whatever you want with this file.
//
 
#include "alone_decoder.h"
#include "lzma_decoder.h"
#include "lz_decoder.h"
 
 
typedef struct {
    lzma_next_coder next;
 
    enum {
        SEQ_PROPERTIES,
        SEQ_DICTIONARY_SIZE,
        SEQ_UNCOMPRESSED_SIZE,
        SEQ_CODER_INIT,
        SEQ_CODE,
    } sequence;
 
    bool picky;
 
    size_t pos;
 
    lzma_vli uncompressed_size;
 
    uint64_t memlimit;
 
    uint64_t memusage;
 
    lzma_options_lzma options;
} lzma_alone_coder;
 
 
static lzma_ret
alone_decode(void *coder_ptr, const 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)
{
    lzma_alone_coder *coder = coder_ptr;
 
    while (*out_pos < out_size
            && (coder->sequence == SEQ_CODE || *in_pos < in_size))
    switch (coder->sequence) {
    case SEQ_PROPERTIES:
        if (lzma_lzma_lclppb_decode(&coder->options, in[*in_pos]))
            return LZMA_FORMAT_ERROR;
 
        coder->sequence = SEQ_DICTIONARY_SIZE;
        ++*in_pos;
        break;
 
    case SEQ_DICTIONARY_SIZE:
        coder->options.dict_size
                |= (size_t)(in[*in_pos]) << (coder->pos * 8);
 
        if (++coder->pos == 4) {
            if (coder->picky && coder->options.dict_size
                    != UINT32_MAX) {
                // A hack to ditch tons of false positives:
                // We allow only dictionary sizes that are
                // 2^n or 2^n + 2^(n-1). LZMA_Alone created
                // only files with 2^n, but accepts any
                // dictionary size.
                uint32_t d = coder->options.dict_size - 1;
                d |= d >> 2;
                d |= d >> 3;
                d |= d >> 4;
                d |= d >> 8;
                d |= d >> 16;
                ++d;
 
                if (d != coder->options.dict_size)
                    return LZMA_FORMAT_ERROR;
            }
 
            coder->pos = 0;
            coder->sequence = SEQ_UNCOMPRESSED_SIZE;
        }
 
        ++*in_pos;
        break;
 
    case SEQ_UNCOMPRESSED_SIZE:
        coder->uncompressed_size
                |= (lzma_vli)(in[*in_pos]) << (coder->pos * 8);
        ++*in_pos;
        if (++coder->pos < 8)
            break;
 
        // Another hack to ditch false positives: Assume that
        // if the uncompressed size is known, it must be less
        // than 256 GiB.
        if (coder->picky
                && coder->uncompressed_size != LZMA_VLI_UNKNOWN
                && coder->uncompressed_size
                    >= (LZMA_VLI_C(1) << 38))
            return LZMA_FORMAT_ERROR;
 
        // Calculate the memory usage so that it is ready
        // for SEQ_CODER_INIT.
        coder->memusage = lzma_lzma_decoder_memusage(&coder->options)
                + LZMA_MEMUSAGE_BASE;
 
        coder->pos = 0;
        coder->sequence = SEQ_CODER_INIT;
 
    // Fall through
 
    case SEQ_CODER_INIT: {
        if (coder->memusage > coder->memlimit)
            return LZMA_MEMLIMIT_ERROR;
 
        lzma_filter_info filters[2] = {
            {
                .init = &lzma_lzma_decoder_init,
                .options = &coder->options,
            }, {
                .init = NULL,
            }
        };
 
        const lzma_ret ret = lzma_next_filter_init(&coder->next,
                allocator, filters);
        if (ret != LZMA_OK)
            return ret;
 
        // Use a hack to set the uncompressed size.
        lzma_lz_decoder_uncompressed(coder->next.coder,
                coder->uncompressed_size);
 
        coder->sequence = SEQ_CODE;
        break;
    }
 
    case SEQ_CODE: {
        return coder->next.code(coder->next.coder,
                allocator, in, in_pos, in_size,
                out, out_pos, out_size, action);
    }
 
    default:
        return LZMA_PROG_ERROR;
    }
 
    return LZMA_OK;
}
 
 
static void
alone_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
    lzma_alone_coder *coder = coder_ptr;
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder, allocator);
    return;
}
 
 
static lzma_ret
alone_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
        uint64_t *old_memlimit, uint64_t new_memlimit)
{
    lzma_alone_coder *coder = coder_ptr;
 
    *memusage = coder->memusage;
    *old_memlimit = coder->memlimit;
 
    if (new_memlimit != 0) {
        if (new_memlimit < coder->memusage)
            return LZMA_MEMLIMIT_ERROR;
 
        coder->memlimit = new_memlimit;
    }
 
    return LZMA_OK;
}
 
 
extern lzma_ret
lzma_alone_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
        uint64_t memlimit, bool picky)
{
    lzma_next_coder_init(&lzma_alone_decoder_init, next, allocator);
 
    lzma_alone_coder *coder = next->coder;
 
    if (coder == NULL) {
        coder = lzma_alloc(sizeof(lzma_alone_coder), allocator);
        if (coder == NULL)
            return LZMA_MEM_ERROR;
 
        next->coder = coder;
        next->code = &alone_decode;
        next->end = &alone_decoder_end;
        next->memconfig = &alone_decoder_memconfig;
        coder->next = LZMA_NEXT_CODER_INIT;
    }
 
    coder->sequence = SEQ_PROPERTIES;
    coder->picky = picky;
    coder->pos = 0;
    coder->options.dict_size = 0;
    coder->options.preset_dict = NULL;
    coder->options.preset_dict_size = 0;
    coder->uncompressed_size = 0;
    coder->memlimit = my_max(1, memlimit);
    coder->memusage = LZMA_MEMUSAGE_BASE;
 
    return LZMA_OK;
}
 
 
extern LZMA_API(lzma_ret)
lzma_alone_decoder(lzma_stream *strm, uint64_t memlimit)
{
    lzma_next_strm_init(lzma_alone_decoder_init, strm, memlimit, false);
 
    strm->internal->supported_actions[LZMA_RUN] = true;
    strm->internal->supported_actions[LZMA_FINISH] = true;
 
    return LZMA_OK;
}