--- /dev/null
+///////////////////////////////////////////////////////////////////////////////
+//
+/// \file alone_decoder.c
+/// \brief Decoder for LZMA_Alone files
+//
+// 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"
+
+
+struct lzma_coder_s {
+ lzma_next_coder next;
+
+ enum {
+ SEQ_PROPERTIES,
+ SEQ_DICTIONARY_SIZE,
+ SEQ_UNCOMPRESSED_SIZE,
+ SEQ_CODER_INIT,
+ SEQ_CODE,
+ } sequence;
+
+ /// If true, reject files that are unlikely to be .lzma files.
+ /// If false, more non-.lzma files get accepted and will give
+ /// LZMA_DATA_ERROR either immediately or after a few output bytes.
+ bool picky;
+
+ /// Position in the header fields
+ size_t pos;
+
+ /// Uncompressed size decoded from the header
+ lzma_vli uncompressed_size;
+
+ /// Memory usage limit
+ uint64_t memlimit;
+
+ /// Amount of memory actually needed (only an estimate)
+ uint64_t memusage;
+
+ /// Options decoded from the header needed to initialize
+ /// the LZMA decoder
+ lzma_options_lzma options;
+};
+
+
+static lzma_ret
+alone_decode(lzma_coder *coder,
+ const lzma_allocator *allocator lzma_attribute((__unused__)),
+ 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)
+{
+ 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(lzma_coder *coder, const lzma_allocator *allocator)
+{
+ lzma_next_end(&coder->next, allocator);
+ lzma_free(coder, allocator);
+ return;
+}
+
+
+static lzma_ret
+alone_decoder_memconfig(lzma_coder *coder, uint64_t *memusage,
+ uint64_t *old_memlimit, uint64_t new_memlimit)
+{
+ *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);
+
+ if (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 = &alone_decode;
+ next->end = &alone_decoder_end;
+ next->memconfig = &alone_decoder_memconfig;
+ next->coder->next = LZMA_NEXT_CODER_INIT;
+ }
+
+ next->coder->sequence = SEQ_PROPERTIES;
+ next->coder->picky = picky;
+ next->coder->pos = 0;
+ next->coder->options.dict_size = 0;
+ next->coder->options.preset_dict = NULL;
+ next->coder->options.preset_dict_size = 0;
+ next->coder->uncompressed_size = 0;
+ next->coder->memlimit = memlimit;
+ next->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;
+}
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