--- /dev/null
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file index_decoder.c
+/// \brief Decodes the Index field
+//
+// Author: Lasse Collin
+//
+// This file has been put into the public domain.
+// You can do whatever you want with this file.
+//
+///////////////////////////////////////////////////////////////////////////////
+
+#include "index.h"
+#include "check.h"
+
+
+struct lzma_coder_s {
+ enum {
+ SEQ_INDICATOR,
+ SEQ_COUNT,
+ SEQ_MEMUSAGE,
+ SEQ_UNPADDED,
+ SEQ_UNCOMPRESSED,
+ SEQ_PADDING_INIT,
+ SEQ_PADDING,
+ SEQ_CRC32,
+ } sequence;
+
+ /// Memory usage limit
+ uint64_t memlimit;
+
+ /// Target Index
+ lzma_index *index;
+
+ /// Pointer give by the application, which is set after
+ /// successful decoding.
+ lzma_index **index_ptr;
+
+ /// Number of Records left to decode.
+ lzma_vli count;
+
+ /// The most recent Unpadded Size field
+ lzma_vli unpadded_size;
+
+ /// The most recent Uncompressed Size field
+ lzma_vli uncompressed_size;
+
+ /// Position in integers
+ size_t pos;
+
+ /// CRC32 of the List of Records field
+ uint32_t crc32;
+};
+
+
+static lzma_ret
+index_decode(lzma_coder *coder, const lzma_allocator *allocator,
+ const uint8_t *restrict in, size_t *restrict in_pos,
+ size_t in_size,
+ uint8_t *restrict out lzma_attribute((__unused__)),
+ size_t *restrict out_pos lzma_attribute((__unused__)),
+ size_t out_size lzma_attribute((__unused__)),
+ lzma_action action lzma_attribute((__unused__)))
+{
+ // Similar optimization as in index_encoder.c
+ const size_t in_start = *in_pos;
+ lzma_ret ret = LZMA_OK;
+
+ while (*in_pos < in_size)
+ switch (coder->sequence) {
+ case SEQ_INDICATOR:
+ // Return LZMA_DATA_ERROR instead of e.g. LZMA_PROG_ERROR or
+ // LZMA_FORMAT_ERROR, because a typical usage case for Index
+ // decoder is when parsing the Stream backwards. If seeking
+ // backward from the Stream Footer gives us something that
+ // doesn't begin with Index Indicator, the file is considered
+ // corrupt, not "programming error" or "unrecognized file
+ // format". One could argue that the application should
+ // verify the Index Indicator before trying to decode the
+ // Index, but well, I suppose it is simpler this way.
+ if (in[(*in_pos)++] != 0x00)
+ return LZMA_DATA_ERROR;
+
+ coder->sequence = SEQ_COUNT;
+ break;
+
+ case SEQ_COUNT:
+ ret = lzma_vli_decode(&coder->count, &coder->pos,
+ in, in_pos, in_size);
+ if (ret != LZMA_STREAM_END)
+ goto out;
+
+ coder->pos = 0;
+ coder->sequence = SEQ_MEMUSAGE;
+
+ // Fall through
+
+ case SEQ_MEMUSAGE:
+ if (lzma_index_memusage(1, coder->count) > coder->memlimit) {
+ ret = LZMA_MEMLIMIT_ERROR;
+ goto out;
+ }
+
+ // Tell the Index handling code how many Records this
+ // Index has to allow it to allocate memory more efficiently.
+ lzma_index_prealloc(coder->index, coder->count);
+
+ ret = LZMA_OK;
+ coder->sequence = coder->count == 0
+ ? SEQ_PADDING_INIT : SEQ_UNPADDED;
+ break;
+
+ case SEQ_UNPADDED:
+ case SEQ_UNCOMPRESSED: {
+ lzma_vli *size = coder->sequence == SEQ_UNPADDED
+ ? &coder->unpadded_size
+ : &coder->uncompressed_size;
+
+ ret = lzma_vli_decode(size, &coder->pos,
+ in, in_pos, in_size);
+ if (ret != LZMA_STREAM_END)
+ goto out;
+
+ ret = LZMA_OK;
+ coder->pos = 0;
+
+ if (coder->sequence == SEQ_UNPADDED) {
+ // Validate that encoded Unpadded Size isn't too small
+ // or too big.
+ if (coder->unpadded_size < UNPADDED_SIZE_MIN
+ || coder->unpadded_size
+ > UNPADDED_SIZE_MAX)
+ return LZMA_DATA_ERROR;
+
+ coder->sequence = SEQ_UNCOMPRESSED;
+ } else {
+ // Add the decoded Record to the Index.
+ return_if_error(lzma_index_append(
+ coder->index, allocator,
+ coder->unpadded_size,
+ coder->uncompressed_size));
+
+ // Check if this was the last Record.
+ coder->sequence = --coder->count == 0
+ ? SEQ_PADDING_INIT
+ : SEQ_UNPADDED;
+ }
+
+ break;
+ }
+
+ case SEQ_PADDING_INIT:
+ coder->pos = lzma_index_padding_size(coder->index);
+ coder->sequence = SEQ_PADDING;
+
+ // Fall through
+
+ case SEQ_PADDING:
+ if (coder->pos > 0) {
+ --coder->pos;
+ if (in[(*in_pos)++] != 0x00)
+ return LZMA_DATA_ERROR;
+
+ break;
+ }
+
+ // Finish the CRC32 calculation.
+ coder->crc32 = lzma_crc32(in + in_start,
+ *in_pos - in_start, coder->crc32);
+
+ coder->sequence = SEQ_CRC32;
+
+ // Fall through
+
+ case SEQ_CRC32:
+ do {
+ if (*in_pos == in_size)
+ return LZMA_OK;
+
+ if (((coder->crc32 >> (coder->pos * 8)) & 0xFF)
+ != in[(*in_pos)++])
+ return LZMA_DATA_ERROR;
+
+ } while (++coder->pos < 4);
+
+ // Decoding was successful, now we can let the application
+ // see the decoded Index.
+ *coder->index_ptr = coder->index;
+
+ // Make index NULL so we don't free it unintentionally.
+ coder->index = NULL;
+
+ return LZMA_STREAM_END;
+
+ default:
+ assert(0);
+ return LZMA_PROG_ERROR;
+ }
+
+out:
+ // Update the CRC32,
+ coder->crc32 = lzma_crc32(in + in_start,
+ *in_pos - in_start, coder->crc32);
+
+ return ret;
+}
+
+
+static void
+index_decoder_end(lzma_coder *coder, const lzma_allocator *allocator)
+{
+ lzma_index_end(coder->index, allocator);
+ lzma_free(coder, allocator);
+ return;
+}
+
+
+static lzma_ret
+index_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
+ uint64_t *old_memlimit, uint64_t new_memlimit)
+{
+ *memusage = lzma_index_memusage(1, coder->count);
+ *old_memlimit = coder->memlimit;
+
+ if (new_memlimit != 0) {
+ if (new_memlimit < *memusage)
+ return LZMA_MEMLIMIT_ERROR;
+
+ coder->memlimit = new_memlimit;
+ }
+
+ return LZMA_OK;
+}
+
+
+static lzma_ret
+index_decoder_reset(lzma_coder *coder, const lzma_allocator *allocator,
+ lzma_index **i, uint64_t memlimit)
+{
+ // Remember the pointer given by the application. We will set it
+ // to point to the decoded Index only if decoding is successful.
+ // Before that, keep it NULL so that applications can always safely
+ // pass it to lzma_index_end() no matter did decoding succeed or not.
+ coder->index_ptr = i;
+ *i = NULL;
+
+ // We always allocate a new lzma_index.
+ coder->index = lzma_index_init(allocator);
+ if (coder->index == NULL)
+ return LZMA_MEM_ERROR;
+
+ // Initialize the rest.
+ coder->sequence = SEQ_INDICATOR;
+ coder->memlimit = memlimit;
+ coder->count = 0; // Needs to be initialized due to _memconfig().
+ coder->pos = 0;
+ coder->crc32 = 0;
+
+ return LZMA_OK;
+}
+
+
+static lzma_ret
+index_decoder_init(lzma_next_coder *next, const lzma_allocator *allocator,
+ lzma_index **i, uint64_t memlimit)
+{
+ lzma_next_coder_init(&index_decoder_init, next, allocator);
+
+ if (i == NULL || memlimit == 0)
+ return LZMA_PROG_ERROR;
+
+ if (next->coder == NULL) {
+ next->coder = lzma_alloc(sizeof(lzma_coder), allocator);
+ if (next->coder == NULL)
+ return LZMA_MEM_ERROR;
+
+ next->code = &index_decode;
+ next->end = &index_decoder_end;
+ next->memconfig = &index_decoder_memconfig;
+ next->coder->index = NULL;
+ } else {
+ lzma_index_end(next->coder->index, allocator);
+ }
+
+ return index_decoder_reset(next->coder, allocator, i, memlimit);
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_index_decoder(lzma_stream *strm, lzma_index **i, uint64_t memlimit)
+{
+ lzma_next_strm_init(index_decoder_init, strm, i, memlimit);
+
+ strm->internal->supported_actions[LZMA_RUN] = true;
+ strm->internal->supported_actions[LZMA_FINISH] = true;
+
+ return LZMA_OK;
+}
+
+
+extern LZMA_API(lzma_ret)
+lzma_index_buffer_decode(lzma_index **i, uint64_t *memlimit,
+ const lzma_allocator *allocator,
+ const uint8_t *in, size_t *in_pos, size_t in_size)
+{
+ // Sanity checks
+ if (i == NULL || memlimit == NULL
+ || in == NULL || in_pos == NULL || *in_pos > in_size)
+ return LZMA_PROG_ERROR;
+
+ // Initialize the decoder.
+ lzma_coder coder;
+ return_if_error(index_decoder_reset(&coder, allocator, i, *memlimit));
+
+ // Store the input start position so that we can restore it in case
+ // of an error.
+ const size_t in_start = *in_pos;
+
+ // Do the actual decoding.
+ lzma_ret ret = index_decode(&coder, allocator, in, in_pos, in_size,
+ NULL, NULL, 0, LZMA_RUN);
+
+ if (ret == LZMA_STREAM_END) {
+ ret = LZMA_OK;
+ } else {
+ // Something went wrong, free the Index structure and restore
+ // the input position.
+ lzma_index_end(coder.index, allocator);
+ *in_pos = in_start;
+
+ if (ret == LZMA_OK) {
+ // The input is truncated or otherwise corrupt.
+ // Use LZMA_DATA_ERROR instead of LZMA_BUF_ERROR
+ // like lzma_vli_decode() does in single-call mode.
+ ret = LZMA_DATA_ERROR;
+
+ } else if (ret == LZMA_MEMLIMIT_ERROR) {
+ // Tell the caller how much memory would have
+ // been needed.
+ *memlimit = lzma_index_memusage(1, coder.count);
+ }
+ }
+
+ return ret;
+}
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