diff options
| -rw-r--r-- | src/liblzma/api/lzma/container.h | 6 | ||||
| -rw-r--r-- | src/liblzma/common/stream_decoder_mt.c | 42 |
2 files changed, 48 insertions, 0 deletions
diff --git a/src/liblzma/api/lzma/container.h b/src/liblzma/api/lzma/container.h index 564c6aaf..c0e1f5b4 100644 --- a/src/liblzma/api/lzma/container.h +++ b/src/liblzma/api/lzma/container.h @@ -623,6 +623,12 @@ extern LZMA_API(lzma_ret) lzma_microlzma_encoder( * decompressed multiple times with this flag, a different amount of output * may be produced by different runs, and even the error code might vary. * + * When using LZMA_FAIL_FAST, it is recommended to use LZMA_FINISH to tell + * the decoder when no more input will be coming because it can help fast + * detection and reporting of truncated files. Note that in this situation + * truncated files might be diagnosed with LZMA_DATA_ERROR instead of + * LZMA_OK or LZMA_BUF_ERROR! + * * Without this flag the threaded decoder will provide as much output as * possible at first and then report the pending error. This default behavior * matches the single-threaded decoder and provides repeatable behavior diff --git a/src/liblzma/common/stream_decoder_mt.c b/src/liblzma/common/stream_decoder_mt.c index 3786b2aa..840051b0 100644 --- a/src/liblzma/common/stream_decoder_mt.c +++ b/src/liblzma/common/stream_decoder_mt.c @@ -1143,6 +1143,35 @@ stream_decode_mt(void *coder_ptr, const lzma_allocator *allocator, // of "called with an empty input buffer". assert(*in_pos == in_size); + // If LZMA_FINISH was used we know that we won't get + // more input, so the file must be truncated if we + // get here. If worker threads don't detect any + // errors, eventually there will be no more output + // while we keep returning LZMA_OK which gets + // converted to LZMA_BUF_ERROR in lzma_code(). + // + // If fail-fast is enabled then we will return + // immediately using LZMA_DATA_ERROR instead of + // LZMA_OK or LZMA_BUF_ERROR. Rationale for the + // error code: + // + // - Worker threads may have a large amount of + // not-yet-decoded input data and we don't + // know for sure if all data is valid. Bad + // data there would result in LZMA_DATA_ERROR + // when fail-fast isn't used. + // + // - Immediate LZMA_BUF_ERROR would be a bit weird + // considering the older liblzma code. lzma_code() + // even has an assertion to prevent coders from + // returning LZMA_BUF_ERROR directly. + // + // The downside of this is that with fail-fast apps + // cannot always distinguish between corrupt and + // truncated files. + if (action == LZMA_FINISH && coder->fail_fast) + return LZMA_DATA_ERROR; + return_if_error(read_output_and_wait(coder, allocator, out, out_pos, out_size, NULL, waiting_allowed, @@ -1478,6 +1507,19 @@ stream_decode_mt(void *coder_ptr, const lzma_allocator *allocator, // Fall through case SEQ_BLOCK_THR_RUN: { + if (action == LZMA_FINISH && coder->fail_fast) { + // We know that we won't get more input and that + // the caller wants fail-fast behavior. If we see + // that we don't have enough input to finish this + // Block, return LZMA_DATA_ERROR immediately. + // See SEQ_BLOCK_HEADER for the error code rationale. + const size_t in_avail = in_size - *in_pos; + const size_t in_needed = coder->thr->in_size + - coder->thr->in_filled; + if (in_avail < in_needed) + return LZMA_DATA_ERROR; + } + // Copy input to the worker thread. size_t cur_in_filled = coder->thr->in_filled; lzma_bufcpy(in, in_pos, in_size, coder->thr->in, |