LXR linux/fs/ntfs3/lib/xpress

   1// SPDX-License-Identifier: GPL-2.0-or-later
   2/*
   3 * xpress_decompress.c - A decompressor for the XPRESS compression format
   4 * (Huffman variant), which can be used in "System Compressed" files.  This is
   5 * based on the code from wimlib.
   6 *
   7 * Copyright (C) 2015 Eric Biggers
   8 */
   9
  10#include "decompress_common.h"
  11#include "lib.h"
  12
  13#define XPRESS_NUM_SYMBOLS      512
  14#define XPRESS_MAX_CODEWORD_LEN 15
  15#define XPRESS_MIN_MATCH_LEN    3
  16
  17/* This value is chosen for fast decompression.  */
  18#define XPRESS_TABLEBITS 12
  19
  20/* Reusable heap-allocated memory for XPRESS decompression  */
  21struct xpress_decompressor {
  22
  23        /* The Huffman decoding table  */
  24        u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS];
  25
  26        /* An array that maps symbols to codeword lengths  */
  27        u8 lens[XPRESS_NUM_SYMBOLS];
  28
  29        /* Temporary space for make_huffman_decode_table()  */
  30        u16 working_space[2 * (1 + XPRESS_MAX_CODEWORD_LEN) +
  31                          XPRESS_NUM_SYMBOLS];
  32};
  33
  34/*
  35 * xpress_allocate_decompressor - Allocate an XPRESS decompressor
  36 *
  37 * Return the pointer to the decompressor on success, or return NULL and set
  38 * errno on failure.
  39 */
  40struct xpress_decompressor *xpress_allocate_decompressor(void)
  41{
  42        return kmalloc(sizeof(struct xpress_decompressor), GFP_NOFS);
  43}
  44
  45/*
  46 * xpress_decompress - Decompress a buffer of XPRESS-compressed data
  47 *
  48 * @decompressor:       A decompressor that was allocated with
  49 *                      xpress_allocate_decompressor()
  50 * @compressed_data:    The buffer of data to decompress
  51 * @compressed_size:    Number of bytes of compressed data
  52 * @uncompressed_data:  The buffer in which to store the decompressed data
  53 * @uncompressed_size:  The number of bytes the data decompresses into
  54 *
  55 * Return 0 on success, or return -1 and set errno on failure.
  56 */
  57int xpress_decompress(struct xpress_decompressor *decompressor,
  58                      const void *compressed_data, size_t compressed_size,
  59                      void *uncompressed_data, size_t uncompressed_size)
  60{
  61        struct xpress_decompressor *d = decompressor;
  62        const u8 * const in_begin = compressed_data;
  63        u8 * const out_begin = uncompressed_data;
  64        u8 *out_next = out_begin;
  65        u8 * const out_end = out_begin + uncompressed_size;
  66        struct input_bitstream is;
  67        u32 i;
  68
  69        /* Read the Huffman codeword lengths.  */
  70        if (compressed_size < XPRESS_NUM_SYMBOLS / 2)
  71                goto invalid;
  72        for (i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) {
  73                d->lens[i*2 + 0] = in_begin[i] & 0xF;
  74                d->lens[i*2 + 1] = in_begin[i] >> 4;
  75        }
  76
  77        /* Build a decoding table for the Huffman code.  */
  78        if (make_huffman_decode_table(d->decode_table, XPRESS_NUM_SYMBOLS,
  79                                      XPRESS_TABLEBITS, d->lens,
  80                                      XPRESS_MAX_CODEWORD_LEN,
  81                                      d->working_space))
  82                goto invalid;
  83
  84        /* Decode the matches and literals.  */
  85
  86        init_input_bitstream(&is, in_begin + XPRESS_NUM_SYMBOLS / 2,
  87                             compressed_size - XPRESS_NUM_SYMBOLS / 2);
  88
  89        while (out_next != out_end) {
  90                u32 sym;
  91                u32 log2_offset;
  92                u32 length;
  93                u32 offset;
  94
  95                sym = read_huffsym(&is, d->decode_table,
  96                                   XPRESS_TABLEBITS, XPRESS_MAX_CODEWORD_LEN);
  97                if (sym < 256) {
  98                        /* Literal  */
  99                        *out_next++ = sym;
 100                } else {
 101                        /* Match  */
 102                        length = sym & 0xf;
 103                        log2_offset = (sym >> 4) & 0xf;
 104
 105                        bitstream_ensure_bits(&is, 16);
 106
 107                        offset = ((u32)1 << log2_offset) |
 108                                 bitstream_pop_bits(&is, log2_offset);
 109
 110                        if (length == 0xf) {
 111                                length += bitstream_read_byte(&is);
 112                                if (length == 0xf + 0xff)
 113                                        length = bitstream_read_u16(&is);
 114                        }
 115                        length += XPRESS_MIN_MATCH_LEN;
 116
 117                        if (offset > (size_t)(out_next - out_begin))
 118                                goto invalid;
 119
 120                        if (length > (size_t)(out_end - out_next))
 121                                goto invalid;
 122
 123                        out_next = lz_copy(out_next, length, offset, out_end,
 124                                           XPRESS_MIN_MATCH_LEN);
 125                }
 126        }
 127        return 0;
 128
 129invalid:
 130        return -1;
 131}
 132
 133/*
 134 * xpress_free_decompressor - Free an XPRESS decompressor
 135 *
 136 * @decompressor:       A decompressor that was allocated with
 137 *                      xpress_allocate_decompressor(), or NULL.
 138 */
 139void xpress_free_decompressor(struct xpress_decompressor *decompressor)
 140{
 141        kfree(decompressor);
 142}
 143