auto_decoder.c

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//
//
//  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"
#include "alone_decoder.h"
 
 
typedef struct {
    lzma_next_coder next;
 
    uint64_t memlimit;
    uint32_t flags;
 
    enum {
        SEQ_INIT,
        SEQ_CODE,
        SEQ_FINISH,
    } sequence;
} lzma_auto_coder;
 
 
static lzma_ret
auto_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_auto_coder *coder = coder_ptr;
 
    switch (coder->sequence) {
    case SEQ_INIT:
        if (*in_pos >= in_size)
            return LZMA_OK;
 
        // Update the sequence now, because we want to continue from
        // SEQ_CODE even if we return some LZMA_*_CHECK.
        coder->sequence = SEQ_CODE;
 
        // Detect the file format. For now this is simple, since if
        // it doesn't start with 0xFD (the first magic byte of the
        // new format), it has to be LZMA_Alone, or something that
        // we don't support at all.
        if (in[*in_pos] == 0xFD) {
            return_if_error(lzma_stream_decoder_init(
                    &coder->next, allocator,
                    coder->memlimit, coder->flags));
        } else {
            return_if_error(lzma_alone_decoder_init(&coder->next,
                    allocator, coder->memlimit, true));
 
            // If the application wants to know about missing
            // integrity check or about the check in general, we
            // need to handle it here, because LZMA_Alone decoder
            // doesn't accept any flags.
            if (coder->flags & LZMA_TELL_NO_CHECK)
                return LZMA_NO_CHECK;
 
            if (coder->flags & LZMA_TELL_ANY_CHECK)
                return LZMA_GET_CHECK;
        }
 
    // Fall through
 
    case SEQ_CODE: {
        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
                || (coder->flags & LZMA_CONCATENATED) == 0)
            return ret;
 
        coder->sequence = SEQ_FINISH;
    }
 
    // Fall through
 
    case SEQ_FINISH:
        // When LZMA_DECODE_CONCATENATED was used and we were decoding
        // LZMA_Alone file, we need to check check that there is no
        // trailing garbage and wait for LZMA_FINISH.
        if (*in_pos < in_size)
            return LZMA_DATA_ERROR;
 
        return action == LZMA_FINISH ? LZMA_STREAM_END : LZMA_OK;
 
    default:
        assert(0);
        return LZMA_PROG_ERROR;
    }
}
 
 
static void
auto_decoder_end(void *coder_ptr, const lzma_allocator *allocator)
{
    lzma_auto_coder *coder = coder_ptr;
    lzma_next_end(&coder->next, allocator);
    lzma_free(coder, allocator);
    return;
}
 
 
static lzma_check
auto_decoder_get_check(const void *coder_ptr)
{
    const lzma_auto_coder *coder = coder_ptr;
 
    // It is LZMA_Alone if get_check is NULL.
    return coder->next.get_check == NULL ? LZMA_CHECK_NONE
            : coder->next.get_check(coder->next.coder);
}
 
 
static lzma_ret
auto_decoder_memconfig(void *coder_ptr, uint64_t *memusage,
        uint64_t *old_memlimit, uint64_t new_memlimit)
{
    lzma_auto_coder *coder = coder_ptr;
 
    lzma_ret ret;
 
    if (coder->next.memconfig != NULL) {
        ret = coder->next.memconfig(coder->next.coder,
                memusage, old_memlimit, new_memlimit);
        assert(*old_memlimit == coder->memlimit);
    } else {
        // No coder is configured yet. Use the base value as
        // the current memory usage.
        *memusage = LZMA_MEMUSAGE_BASE;
        *old_memlimit = coder->memlimit;
 
        ret = LZMA_OK;
        if (new_memlimit != 0 && new_memlimit < *memusage)
            ret = LZMA_MEMLIMIT_ERROR;
    }
 
    if (ret == LZMA_OK && new_memlimit != 0)
        coder->memlimit = new_memlimit;
 
    return ret;
}
 
 
static lzma_ret
auto_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
        uint64_t memlimit, uint32_t flags)
{
    lzma_next_coder_init(&auto_decoder_init, next, allocator);
 
    if (flags & ~LZMA_SUPPORTED_FLAGS)
        return LZMA_OPTIONS_ERROR;
 
    lzma_auto_coder *coder = next->coder;
    if (coder == NULL) {
        coder = lzma_alloc(sizeof(lzma_auto_coder), allocator);
        if (coder == NULL)
            return LZMA_MEM_ERROR;
 
        next->coder = coder;
        next->code = &auto_decode;
        next->end = &auto_decoder_end;
        next->get_check = &auto_decoder_get_check;
        next->memconfig = &auto_decoder_memconfig;
        coder->next = LZMA_NEXT_CODER_INIT;
    }
 
    coder->memlimit = my_max(1, memlimit);
    coder->flags = flags;
    coder->sequence = SEQ_INIT;
 
    return LZMA_OK;
}
 
 
extern LZMA_API(lzma_ret)
lzma_auto_decoder(lzma_stream *strm, uint64_t memlimit, uint32_t flags)
{
    lzma_next_strm_init(auto_decoder_init, strm, memlimit, flags);
 
    strm->internal->supported_actions[LZMA_RUN] = true;
    strm->internal->supported_actions[LZMA_FINISH] = true;
 
    return LZMA_OK;
}