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Diffstat (limited to 'src/liblzma/common/microlzma_decoder.c')
| -rw-r--r-- | src/liblzma/common/microlzma_decoder.c | 221 |
1 files changed, 221 insertions, 0 deletions
diff --git a/src/liblzma/common/microlzma_decoder.c b/src/liblzma/common/microlzma_decoder.c new file mode 100644 index 0000000..e473373 --- /dev/null +++ b/src/liblzma/common/microlzma_decoder.c @@ -0,0 +1,221 @@ +/////////////////////////////////////////////////////////////////////////////// +// +/// \file microlzma_decoder.c +/// \brief Decode MicroLZMA format +// +// Author: Lasse Collin +// +// This file has been put into the public domain. +// You can do whatever you want with this file. +// +/////////////////////////////////////////////////////////////////////////////// + +#include "lzma_decoder.h" +#include "lz_decoder.h" + + +typedef struct { + /// LZMA1 decoder + lzma_next_coder lzma; + + /// Compressed size of the stream as given by the application. + /// This must be exactly correct. + /// + /// This will be decremented when input is read. + uint64_t comp_size; + + /// Uncompressed size of the stream as given by the application. + /// This may be less than the actual uncompressed size if + /// uncomp_size_is_exact is false. + /// + /// This will be decremented when output is produced. + lzma_vli uncomp_size; + + /// LZMA dictionary size as given by the application + uint32_t dict_size; + + /// If true, the exact uncompressed size is known. If false, + /// uncomp_size may be smaller than the real uncompressed size; + /// uncomp_size may never be bigger than the real uncompressed size. + bool uncomp_size_is_exact; + + /// True once the first byte of the MicroLZMA stream + /// has been processed. + bool props_decoded; +} lzma_microlzma_coder; + + +static lzma_ret +microlzma_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_microlzma_coder *coder = coder_ptr; + + // Remember the in start position so that we can update comp_size. + const size_t in_start = *in_pos; + + // Remember the out start position so that we can update uncomp_size. + const size_t out_start = *out_pos; + + // Limit the amount of input so that the decoder won't read more than + // comp_size. This is required when uncomp_size isn't exact because + // in that case the LZMA decoder will try to decode more input even + // when it has no output space (it can be looking for EOPM). + if (in_size - *in_pos > coder->comp_size) + in_size = *in_pos + (size_t)(coder->comp_size); + + // When the exact uncompressed size isn't known, we must limit + // the available output space to prevent the LZMA decoder from + // trying to decode too much. + if (!coder->uncomp_size_is_exact + && out_size - *out_pos > coder->uncomp_size) + out_size = *out_pos + (size_t)(coder->uncomp_size); + + if (!coder->props_decoded) { + // There must be at least one byte of input to decode + // the properties byte. + if (*in_pos >= in_size) + return LZMA_OK; + + lzma_options_lzma options = { + .dict_size = coder->dict_size, + .preset_dict = NULL, + .preset_dict_size = 0, + .ext_flags = 0, // EOPM not allowed when size is known + .ext_size_low = UINT32_MAX, // Unknown size by default + .ext_size_high = UINT32_MAX, + }; + + if (coder->uncomp_size_is_exact) + lzma_set_ext_size(options, coder->uncomp_size); + + // The properties are stored as bitwise-negation + // of the typical encoding. + if (lzma_lzma_lclppb_decode(&options, ~in[*in_pos])) + return LZMA_OPTIONS_ERROR; + + ++*in_pos; + + // Initialize the decoder. + lzma_filter_info filters[2] = { + { + .id = LZMA_FILTER_LZMA1EXT, + .init = &lzma_lzma_decoder_init, + .options = &options, + }, { + .init = NULL, + } + }; + + return_if_error(lzma_next_filter_init(&coder->lzma, + allocator, filters)); + + // Pass one dummy 0x00 byte to the LZMA decoder since that + // is what it expects the first byte to be. + const uint8_t dummy_in = 0; + size_t dummy_in_pos = 0; + if (coder->lzma.code(coder->lzma.coder, allocator, + &dummy_in, &dummy_in_pos, 1, + out, out_pos, out_size, LZMA_RUN) != LZMA_OK) + return LZMA_PROG_ERROR; + + assert(dummy_in_pos == 1); + coder->props_decoded = true; + } + + // The rest is normal LZMA decoding. + lzma_ret ret = coder->lzma.code(coder->lzma.coder, allocator, + in, in_pos, in_size, + out, out_pos, out_size, action); + + // Update the remaining compressed size. + assert(coder->comp_size >= *in_pos - in_start); + coder->comp_size -= *in_pos - in_start; + + if (coder->uncomp_size_is_exact) { + // After successful decompression of the complete stream + // the compressed size must match. + if (ret == LZMA_STREAM_END && coder->comp_size != 0) + ret = LZMA_DATA_ERROR; + } else { + // Update the amount of output remaining. + assert(coder->uncomp_size >= *out_pos - out_start); + coder->uncomp_size -= *out_pos - out_start; + + // - We must not get LZMA_STREAM_END because the stream + // shouldn't have EOPM. + // - We must use uncomp_size to determine when to + // return LZMA_STREAM_END. + if (ret == LZMA_STREAM_END) + ret = LZMA_DATA_ERROR; + else if (coder->uncomp_size == 0) + ret = LZMA_STREAM_END; + } + + return ret; +} + + +static void +microlzma_decoder_end(void *coder_ptr, const lzma_allocator *allocator) +{ + lzma_microlzma_coder *coder = coder_ptr; + lzma_next_end(&coder->lzma, allocator); + lzma_free(coder, allocator); + return; +} + + +static lzma_ret +microlzma_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator, + uint64_t comp_size, + uint64_t uncomp_size, bool uncomp_size_is_exact, + uint32_t dict_size) +{ + lzma_next_coder_init(µlzma_decoder_init, next, allocator); + + lzma_microlzma_coder *coder = next->coder; + + if (coder == NULL) { + coder = lzma_alloc(sizeof(lzma_microlzma_coder), allocator); + if (coder == NULL) + return LZMA_MEM_ERROR; + + next->coder = coder; + next->code = µlzma_decode; + next->end = µlzma_decoder_end; + + coder->lzma = LZMA_NEXT_CODER_INIT; + } + + // The public API is uint64_t but the internal LZ decoder API uses + // lzma_vli. + if (uncomp_size > LZMA_VLI_MAX) + return LZMA_OPTIONS_ERROR; + + coder->comp_size = comp_size; + coder->uncomp_size = uncomp_size; + coder->uncomp_size_is_exact = uncomp_size_is_exact; + coder->dict_size = dict_size; + + coder->props_decoded = false; + + return LZMA_OK; +} + + +extern LZMA_API(lzma_ret) +lzma_microlzma_decoder(lzma_stream *strm, uint64_t comp_size, + uint64_t uncomp_size, lzma_bool uncomp_size_is_exact, + uint32_t dict_size) +{ + lzma_next_strm_init(microlzma_decoder_init, strm, comp_size, + uncomp_size, uncomp_size_is_exact, dict_size); + + strm->internal->supported_actions[LZMA_RUN] = true; + strm->internal->supported_actions[LZMA_FINISH] = true; + + return LZMA_OK; +} |