diff options
Diffstat (limited to 'fs/ntfs3/lib')
| -rw-r--r-- | fs/ntfs3/lib/decompress_common.c | 319 | ||||
| -rw-r--r-- | fs/ntfs3/lib/decompress_common.h | 343 | ||||
| -rw-r--r-- | fs/ntfs3/lib/lib.h | 32 | ||||
| -rw-r--r-- | fs/ntfs3/lib/lzx_decompress.c | 670 | ||||
| -rw-r--r-- | fs/ntfs3/lib/xpress_decompress.c | 142 |
5 files changed, 1506 insertions, 0 deletions
diff --git a/fs/ntfs3/lib/decompress_common.c b/fs/ntfs3/lib/decompress_common.c new file mode 100644 index 000000000..e96652240 --- /dev/null +++ b/fs/ntfs3/lib/decompress_common.c @@ -0,0 +1,319 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * decompress_common.c - Code shared by the XPRESS and LZX decompressors + * + * Copyright (C) 2015 Eric Biggers + */ + +#include "decompress_common.h" + +/* + * make_huffman_decode_table() - + * + * Build a decoding table for a canonical prefix code, or "Huffman code". + * + * This is an internal function, not part of the library API! + * + * This takes as input the length of the codeword for each symbol in the + * alphabet and produces as output a table that can be used for fast + * decoding of prefix-encoded symbols using read_huffsym(). + * + * Strictly speaking, a canonical prefix code might not be a Huffman + * code. But this algorithm will work either way; and in fact, since + * Huffman codes are defined in terms of symbol frequencies, there is no + * way for the decompressor to know whether the code is a true Huffman + * code or not until all symbols have been decoded. + * + * Because the prefix code is assumed to be "canonical", it can be + * reconstructed directly from the codeword lengths. A prefix code is + * canonical if and only if a longer codeword never lexicographically + * precedes a shorter codeword, and the lexicographic ordering of + * codewords of the same length is the same as the lexicographic ordering + * of the corresponding symbols. Consequently, we can sort the symbols + * primarily by codeword length and secondarily by symbol value, then + * reconstruct the prefix code by generating codewords lexicographically + * in that order. + * + * This function does not, however, generate the prefix code explicitly. + * Instead, it directly builds a table for decoding symbols using the + * code. The basic idea is this: given the next 'max_codeword_len' bits + * in the input, we can look up the decoded symbol by indexing a table + * containing 2**max_codeword_len entries. A codeword with length + * 'max_codeword_len' will have exactly one entry in this table, whereas + * a codeword shorter than 'max_codeword_len' will have multiple entries + * in this table. Precisely, a codeword of length n will be represented + * by 2**(max_codeword_len - n) entries in this table. The 0-based index + * of each such entry will contain the corresponding codeword as a prefix + * when zero-padded on the left to 'max_codeword_len' binary digits. + * + * That's the basic idea, but we implement two optimizations regarding + * the format of the decode table itself: + * + * - For many compression formats, the maximum codeword length is too + * long for it to be efficient to build the full decoding table + * whenever a new prefix code is used. Instead, we can build the table + * using only 2**table_bits entries, where 'table_bits' is some number + * less than or equal to 'max_codeword_len'. Then, only codewords of + * length 'table_bits' and shorter can be directly looked up. For + * longer codewords, the direct lookup instead produces the root of a + * binary tree. Using this tree, the decoder can do traditional + * bit-by-bit decoding of the remainder of the codeword. Child nodes + * are allocated in extra entries at the end of the table; leaf nodes + * contain symbols. Note that the long-codeword case is, in general, + * not performance critical, since in Huffman codes the most frequently + * used symbols are assigned the shortest codeword lengths. + * + * - When we decode a symbol using a direct lookup of the table, we still + * need to know its length so that the bitstream can be advanced by the + * appropriate number of bits. The simple solution is to simply retain + * the 'lens' array and use the decoded symbol as an index into it. + * However, this requires two separate array accesses in the fast path. + * The optimization is to store the length directly in the decode + * table. We use the bottom 11 bits for the symbol and the top 5 bits + * for the length. In addition, to combine this optimization with the + * previous one, we introduce a special case where the top 2 bits of + * the length are both set if the entry is actually the root of a + * binary tree. + * + * @decode_table: + * The array in which to create the decoding table. This must have + * a length of at least ((2**table_bits) + 2 * num_syms) entries. + * + * @num_syms: + * The number of symbols in the alphabet; also, the length of the + * 'lens' array. Must be less than or equal to 2048. + * + * @table_bits: + * The order of the decode table size, as explained above. Must be + * less than or equal to 13. + * + * @lens: + * An array of length @num_syms, indexable by symbol, that gives the + * length of the codeword, in bits, for that symbol. The length can + * be 0, which means that the symbol does not have a codeword + * assigned. + * + * @max_codeword_len: + * The longest codeword length allowed in the compression format. + * All entries in 'lens' must be less than or equal to this value. + * This must be less than or equal to 23. + * + * @working_space + * A temporary array of length '2 * (max_codeword_len + 1) + + * num_syms'. + * + * Returns 0 on success, or -1 if the lengths do not form a valid prefix + * code. + */ +int make_huffman_decode_table(u16 decode_table[], const u32 num_syms, + const u32 table_bits, const u8 lens[], + const u32 max_codeword_len, + u16 working_space[]) +{ + const u32 table_num_entries = 1 << table_bits; + u16 * const len_counts = &working_space[0]; + u16 * const offsets = &working_space[1 * (max_codeword_len + 1)]; + u16 * const sorted_syms = &working_space[2 * (max_codeword_len + 1)]; + int left; + void *decode_table_ptr; + u32 sym_idx; + u32 codeword_len; + u32 stores_per_loop; + u32 decode_table_pos; + u32 len; + u32 sym; + + /* Count how many symbols have each possible codeword length. + * Note that a length of 0 indicates the corresponding symbol is not + * used in the code and therefore does not have a codeword. + */ + for (len = 0; len <= max_codeword_len; len++) + len_counts[len] = 0; + for (sym = 0; sym < num_syms; sym++) + len_counts[lens[sym]]++; + + /* We can assume all lengths are <= max_codeword_len, but we + * cannot assume they form a valid prefix code. A codeword of + * length n should require a proportion of the codespace equaling + * (1/2)^n. The code is valid if and only if the codespace is + * exactly filled by the lengths, by this measure. + */ + left = 1; + for (len = 1; len <= max_codeword_len; len++) { + left <<= 1; + left -= len_counts[len]; + if (left < 0) { + /* The lengths overflow the codespace; that is, the code + * is over-subscribed. + */ + return -1; + } + } + + if (left) { + /* The lengths do not fill the codespace; that is, they form an + * incomplete set. + */ + if (left == (1 << max_codeword_len)) { + /* The code is completely empty. This is arguably + * invalid, but in fact it is valid in LZX and XPRESS, + * so we must allow it. By definition, no symbols can + * be decoded with an empty code. Consequently, we + * technically don't even need to fill in the decode + * table. However, to avoid accessing uninitialized + * memory if the algorithm nevertheless attempts to + * decode symbols using such a code, we zero out the + * decode table. + */ + memset(decode_table, 0, + table_num_entries * sizeof(decode_table[0])); + return 0; + } + return -1; + } + + /* Sort the symbols primarily by length and secondarily by symbol order. + */ + + /* Initialize 'offsets' so that offsets[len] for 1 <= len <= + * max_codeword_len is the number of codewords shorter than 'len' bits. + */ + offsets[1] = 0; + for (len = 1; len < max_codeword_len; len++) + offsets[len + 1] = offsets[len] + len_counts[len]; + + /* Use the 'offsets' array to sort the symbols. Note that we do not + * include symbols that are not used in the code. Consequently, fewer + * than 'num_syms' entries in 'sorted_syms' may be filled. + */ + for (sym = 0; sym < num_syms; sym++) + if (lens[sym]) + sorted_syms[offsets[lens[sym]]++] = sym; + + /* Fill entries for codewords with length <= table_bits + * --- that is, those short enough for a direct mapping. + * + * The table will start with entries for the shortest codeword(s), which + * have the most entries. From there, the number of entries per + * codeword will decrease. + */ + decode_table_ptr = decode_table; + sym_idx = 0; + codeword_len = 1; + stores_per_loop = (1 << (table_bits - codeword_len)); + for (; stores_per_loop != 0; codeword_len++, stores_per_loop >>= 1) { + u32 end_sym_idx = sym_idx + len_counts[codeword_len]; + + for (; sym_idx < end_sym_idx; sym_idx++) { + u16 entry; + u16 *p; + u32 n; + + entry = ((u32)codeword_len << 11) | sorted_syms[sym_idx]; + p = (u16 *)decode_table_ptr; + n = stores_per_loop; + + do { + *p++ = entry; + } while (--n); + + decode_table_ptr = p; + } + } + + /* If we've filled in the entire table, we are done. Otherwise, + * there are codewords longer than table_bits for which we must + * generate binary trees. + */ + decode_table_pos = (u16 *)decode_table_ptr - decode_table; + if (decode_table_pos != table_num_entries) { + u32 j; + u32 next_free_tree_slot; + u32 cur_codeword; + + /* First, zero out the remaining entries. This is + * necessary so that these entries appear as + * "unallocated" in the next part. Each of these entries + * will eventually be filled with the representation of + * the root node of a binary tree. + */ + j = decode_table_pos; + do { + decode_table[j] = 0; + } while (++j != table_num_entries); + + /* We allocate child nodes starting at the end of the + * direct lookup table. Note that there should be + * 2*num_syms extra entries for this purpose, although + * fewer than this may actually be needed. + */ + next_free_tree_slot = table_num_entries; + + /* Iterate through each codeword with length greater than + * 'table_bits', primarily in order of codeword length + * and secondarily in order of symbol. + */ + for (cur_codeword = decode_table_pos << 1; + codeword_len <= max_codeword_len; + codeword_len++, cur_codeword <<= 1) { + u32 end_sym_idx = sym_idx + len_counts[codeword_len]; + + for (; sym_idx < end_sym_idx; sym_idx++, cur_codeword++) { + /* 'sorted_sym' is the symbol represented by the + * codeword. + */ + u32 sorted_sym = sorted_syms[sym_idx]; + u32 extra_bits = codeword_len - table_bits; + u32 node_idx = cur_codeword >> extra_bits; + + /* Go through each bit of the current codeword + * beyond the prefix of length @table_bits and + * walk the appropriate binary tree, allocating + * any slots that have not yet been allocated. + * + * Note that the 'pointer' entry to the binary + * tree, which is stored in the direct lookup + * portion of the table, is represented + * identically to other internal (non-leaf) + * nodes of the binary tree; it can be thought + * of as simply the root of the tree. The + * representation of these internal nodes is + * simply the index of the left child combined + * with the special bits 0xC000 to distinguish + * the entry from direct mapping and leaf node + * entries. + */ + do { + /* At least one bit remains in the + * codeword, but the current node is an + * unallocated leaf. Change it to an + * internal node. + */ + if (decode_table[node_idx] == 0) { + decode_table[node_idx] = + next_free_tree_slot | 0xC000; + decode_table[next_free_tree_slot++] = 0; + decode_table[next_free_tree_slot++] = 0; + } + + /* Go to the left child if the next bit + * in the codeword is 0; otherwise go to + * the right child. + */ + node_idx = decode_table[node_idx] & 0x3FFF; + --extra_bits; + node_idx += (cur_codeword >> extra_bits) & 1; + } while (extra_bits != 0); + + /* We've traversed the tree using the entire + * codeword, and we're now at the entry where + * the actual symbol will be stored. This is + * distinguished from internal nodes by not + * having its high two bits set. + */ + decode_table[node_idx] = sorted_sym; + } + } + } + return 0; +} diff --git a/fs/ntfs3/lib/decompress_common.h b/fs/ntfs3/lib/decompress_common.h new file mode 100644 index 000000000..dd7ced000 --- /dev/null +++ b/fs/ntfs3/lib/decompress_common.h @@ -0,0 +1,343 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * decompress_common.h - Code shared by the XPRESS and LZX decompressors + * + * Copyright (C) 2015 Eric Biggers + */ + +#ifndef _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H +#define _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H + +#include <linux/string.h> +#include <linux/compiler.h> +#include <linux/types.h> +#include <linux/slab.h> +#include <asm/unaligned.h> + + +/* "Force inline" macro (not required, but helpful for performance) */ +#define forceinline __always_inline + +/* Enable whole-word match copying on selected architectures */ +#if defined(__i386__) || defined(__x86_64__) || defined(__ARM_FEATURE_UNALIGNED) +# define FAST_UNALIGNED_ACCESS +#endif + +/* Size of a machine word */ +#define WORDBYTES (sizeof(size_t)) + +static forceinline void +copy_unaligned_word(const void *src, void *dst) +{ + put_unaligned(get_unaligned((const size_t *)src), (size_t *)dst); +} + + +/* Generate a "word" with platform-dependent size whose bytes all contain the + * value 'b'. + */ +static forceinline size_t repeat_byte(u8 b) +{ + size_t v; + + v = b; + v |= v << 8; + v |= v << 16; + v |= v << ((WORDBYTES == 8) ? 32 : 0); + return v; +} + +/* Structure that encapsulates a block of in-memory data being interpreted as a + * stream of bits, optionally with interwoven literal bytes. Bits are assumed + * to be stored in little endian 16-bit coding units, with the bits ordered high + * to low. + */ +struct input_bitstream { + + /* Bits that have been read from the input buffer. The bits are + * left-justified; the next bit is always bit 31. + */ + u32 bitbuf; + + /* Number of bits currently held in @bitbuf. */ + u32 bitsleft; + + /* Pointer to the next byte to be retrieved from the input buffer. */ + const u8 *next; + + /* Pointer to just past the end of the input buffer. */ + const u8 *end; +}; + +/* Initialize a bitstream to read from the specified input buffer. */ +static forceinline void init_input_bitstream(struct input_bitstream *is, + const void *buffer, u32 size) +{ + is->bitbuf = 0; + is->bitsleft = 0; + is->next = buffer; + is->end = is->next + size; +} + +/* Ensure the bit buffer variable for the bitstream contains at least @num_bits + * bits. Following this, bitstream_peek_bits() and/or bitstream_remove_bits() + * may be called on the bitstream to peek or remove up to @num_bits bits. Note + * that @num_bits must be <= 16. + */ +static forceinline void bitstream_ensure_bits(struct input_bitstream *is, + u32 num_bits) +{ + if (is->bitsleft < num_bits) { + if (is->end - is->next >= 2) { + is->bitbuf |= (u32)get_unaligned_le16(is->next) + << (16 - is->bitsleft); + is->next += 2; + } + is->bitsleft += 16; + } +} + +/* Return the next @num_bits bits from the bitstream, without removing them. + * There must be at least @num_bits remaining in the buffer variable, from a + * previous call to bitstream_ensure_bits(). + */ +static forceinline u32 +bitstream_peek_bits(const struct input_bitstream *is, const u32 num_bits) +{ + return (is->bitbuf >> 1) >> (sizeof(is->bitbuf) * 8 - num_bits - 1); +} + +/* Remove @num_bits from the bitstream. There must be at least @num_bits + * remaining in the buffer variable, from a previous call to + * bitstream_ensure_bits(). + */ +static forceinline void +bitstream_remove_bits(struct input_bitstream *is, u32 num_bits) +{ + is->bitbuf <<= num_bits; + is->bitsleft -= num_bits; +} + +/* Remove and return @num_bits bits from the bitstream. There must be at least + * @num_bits remaining in the buffer variable, from a previous call to + * bitstream_ensure_bits(). + */ +static forceinline u32 +bitstream_pop_bits(struct input_bitstream *is, u32 num_bits) +{ + u32 bits = bitstream_peek_bits(is, num_bits); + + bitstream_remove_bits(is, num_bits); + return bits; +} + +/* Read and return the next @num_bits bits from the bitstream. */ +static forceinline u32 +bitstream_read_bits(struct input_bitstream *is, u32 num_bits) +{ + bitstream_ensure_bits(is, num_bits); + return bitstream_pop_bits(is, num_bits); +} + +/* Read and return the next literal byte embedded in the bitstream. */ +static forceinline u8 +bitstream_read_byte(struct input_bitstream *is) +{ + if (unlikely(is->end == is->next)) + return 0; + return *is->next++; +} + +/* Read and return the next 16-bit integer embedded in the bitstream. */ +static forceinline u16 +bitstream_read_u16(struct input_bitstream *is) +{ + u16 v; + + if (unlikely(is->end - is->next < 2)) + return 0; + v = get_unaligned_le16(is->next); + is->next += 2; + return v; +} + +/* Read and return the next 32-bit integer embedded in the bitstream. */ +static forceinline u32 +bitstream_read_u32(struct input_bitstream *is) +{ + u32 v; + + if (unlikely(is->end - is->next < 4)) + return 0; + v = get_unaligned_le32(is->next); + is->next += 4; + return v; +} + +/* Read into @dst_buffer an array of literal bytes embedded in the bitstream. + * Return either a pointer to the byte past the last written, or NULL if the + * read overflows the input buffer. + */ +static forceinline void *bitstream_read_bytes(struct input_bitstream *is, + void *dst_buffer, size_t count) +{ + if ((size_t)(is->end - is->next) < count) + return NULL; + memcpy(dst_buffer, is->next, count); + is->next += count; + return (u8 *)dst_buffer + count; +} + +/* Align the input bitstream on a coding-unit boundary. */ +static forceinline void bitstream_align(struct input_bitstream *is) +{ + is->bitsleft = 0; + is->bitbuf = 0; +} + +extern int make_huffman_decode_table(u16 decode_table[], const u32 num_syms, + const u32 num_bits, const u8 lens[], + const u32 max_codeword_len, + u16 working_space[]); + + +/* Reads and returns the next Huffman-encoded symbol from a bitstream. If the + * input data is exhausted, the Huffman symbol is decoded as if the missing bits + * are all zeroes. + */ +static forceinline u32 read_huffsym(struct input_bitstream *istream, + const u16 decode_table[], + u32 table_bits, + u32 max_codeword_len) +{ + u32 entry; + u32 key_bits; + + bitstream_ensure_bits(istream, max_codeword_len); + + /* Index the decode table by the next table_bits bits of the input. */ + key_bits = bitstream_peek_bits(istream, table_bits); + entry = decode_table[key_bits]; + if (entry < 0xC000) { + /* Fast case: The decode table directly provided the + * symbol and codeword length. The low 11 bits are the + * symbol, and the high 5 bits are the codeword length. + */ + bitstream_remove_bits(istream, entry >> 11); + return entry & 0x7FF; + } + /* Slow case: The codeword for the symbol is longer than + * table_bits, so the symbol does not have an entry + * directly in the first (1 << table_bits) entries of the + * decode table. Traverse the appropriate binary tree + * bit-by-bit to decode the symbol. + */ + bitstream_remove_bits(istream, table_bits); + do { + key_bits = (entry & 0x3FFF) + bitstream_pop_bits(istream, 1); + } while ((entry = decode_table[key_bits]) >= 0xC000); + return entry; +} + +/* + * Copy an LZ77 match at (dst - offset) to dst. + * + * The length and offset must be already validated --- that is, (dst - offset) + * can't underrun the output buffer, and (dst + length) can't overrun the output + * buffer. Also, the length cannot be 0. + * + * @bufend points to the byte past the end of the output buffer. This function + * won't write any data beyond this position. + * + * Returns dst + length. + */ +static forceinline u8 *lz_copy(u8 *dst, u32 length, u32 offset, const u8 *bufend, + u32 min_length) +{ + const u8 *src = dst - offset; + + /* + * Try to copy one machine word at a time. On i386 and x86_64 this is + * faster than copying one byte at a time, unless the data is + * near-random and all the matches have very short lengths. Note that + * since this requires unaligned memory accesses, it won't necessarily + * be faster on every architecture. + * + * Also note that we might copy more than the length of the match. For + * example, if a word is 8 bytes and the match is of length 5, then + * we'll simply copy 8 bytes. This is okay as long as we don't write + * beyond the end of the output buffer, hence the check for (bufend - + * end >= WORDBYTES - 1). + */ +#ifdef FAST_UNALIGNED_ACCESS + u8 * const end = dst + length; + + if (bufend - end >= (ptrdiff_t)(WORDBYTES - 1)) { + + if (offset >= WORDBYTES) { + /* The source and destination words don't overlap. */ + + /* To improve branch prediction, one iteration of this + * loop is unrolled. Most matches are short and will + * fail the first check. But if that check passes, then + * it becomes increasing likely that the match is long + * and we'll need to continue copying. + */ + + copy_unaligned_word(src, dst); + src += WORDBYTES; + dst += WORDBYTES; + + if (dst < end) { + do { + copy_unaligned_word(src, dst); + src += WORDBYTES; + dst += WORDBYTES; + } while (dst < end); + } + return end; + } else if (offset == 1) { + + /* Offset 1 matches are equivalent to run-length + * encoding of the previous byte. This case is common + * if the data contains many repeated bytes. + */ + size_t v = repeat_byte(*(dst - 1)); + + do { + put_unaligned(v, (size_t *)dst); + src += WORDBYTES; + dst += WORDBYTES; + } while (dst < end); + return end; + } + /* + * We don't bother with special cases for other 'offset < + * WORDBYTES', which are usually rarer than 'offset == 1'. Extra + * checks will just slow things down. Actually, it's possible + * to handle all the 'offset < WORDBYTES' cases using the same + * code, but it still becomes more complicated doesn't seem any + * faster overall; it definitely slows down the more common + * 'offset == 1' case. + */ + } +#endif /* FAST_UNALIGNED_ACCESS */ + + /* Fall back to a bytewise copy. */ + + if (min_length >= 2) { + *dst++ = *src++; + length--; + } + if (min_length >= 3) { + *dst++ = *src++; + length--; + } + do { + *dst++ = *src++; + } while (--length); + + return dst; +} + +#endif /* _LINUX_NTFS3_LIB_DECOMPRESS_COMMON_H */ diff --git a/fs/ntfs3/lib/lib.h b/fs/ntfs3/lib/lib.h new file mode 100644 index 000000000..90309a5ae --- /dev/null +++ b/fs/ntfs3/lib/lib.h @@ -0,0 +1,32 @@ +/* SPDX-License-Identifier: GPL-2.0-or-later */ +/* + * Adapted for linux kernel by Alexander Mamaev: + * - remove implementations of get_unaligned_ + * - assume GCC is always defined + * - ISO C90 + * - linux kernel code style + */ + +#ifndef _LINUX_NTFS3_LIB_LIB_H +#define _LINUX_NTFS3_LIB_LIB_H + +#include <linux/types.h> + +/* globals from xpress_decompress.c */ +struct xpress_decompressor *xpress_allocate_decompressor(void); +void xpress_free_decompressor(struct xpress_decompressor *d); +int xpress_decompress(struct xpress_decompressor *__restrict d, + const void *__restrict compressed_data, + size_t compressed_size, + void *__restrict uncompressed_data, + size_t uncompressed_size); + +/* globals from lzx_decompress.c */ +struct lzx_decompressor *lzx_allocate_decompressor(void); +void lzx_free_decompressor(struct lzx_decompressor *d); +int lzx_decompress(struct lzx_decompressor *__restrict d, + const void *__restrict compressed_data, + size_t compressed_size, void *__restrict uncompressed_data, + size_t uncompressed_size); + +#endif /* _LINUX_NTFS3_LIB_LIB_H */ diff --git a/fs/ntfs3/lib/lzx_decompress.c b/fs/ntfs3/lib/lzx_decompress.c new file mode 100644 index 000000000..6b16f0707 --- /dev/null +++ b/fs/ntfs3/lib/lzx_decompress.c @@ -0,0 +1,670 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * lzx_decompress.c - A decompressor for the LZX compression format, which can + * be used in "System Compressed" files. This is based on the code from wimlib. + * This code only supports a window size (dictionary size) of 32768 bytes, since + * this is the only size used in System Compression. + * + * Copyright (C) 2015 Eric Biggers + */ + +#include "decompress_common.h" +#include "lib.h" + +/* Number of literal byte values */ +#define LZX_NUM_CHARS 256 + +/* The smallest and largest allowed match lengths */ +#define LZX_MIN_MATCH_LEN 2 +#define LZX_MAX_MATCH_LEN 257 + +/* Number of distinct match lengths that can be represented */ +#define LZX_NUM_LENS (LZX_MAX_MATCH_LEN - LZX_MIN_MATCH_LEN + 1) + +/* Number of match lengths for which no length symbol is required */ +#define LZX_NUM_PRIMARY_LENS 7 +#define LZX_NUM_LEN_HEADERS (LZX_NUM_PRIMARY_LENS + 1) + +/* Valid values of the 3-bit block type field */ +#define LZX_BLOCKTYPE_VERBATIM 1 +#define LZX_BLOCKTYPE_ALIGNED 2 +#define LZX_BLOCKTYPE_UNCOMPRESSED 3 + +/* Number of offset slots for a window size of 32768 */ +#define LZX_NUM_OFFSET_SLOTS 30 + +/* Number of symbols in the main code for a window size of 32768 */ +#define LZX_MAINCODE_NUM_SYMBOLS \ + (LZX_NUM_CHARS + (LZX_NUM_OFFSET_SLOTS * LZX_NUM_LEN_HEADERS)) + +/* Number of symbols in the length code */ +#define LZX_LENCODE_NUM_SYMBOLS (LZX_NUM_LENS - LZX_NUM_PRIMARY_LENS) + +/* Number of symbols in the precode */ +#define LZX_PRECODE_NUM_SYMBOLS 20 + +/* Number of bits in which each precode codeword length is represented */ +#define LZX_PRECODE_ELEMENT_SIZE 4 + +/* Number of low-order bits of each match offset that are entropy-encoded in + * aligned offset blocks + */ +#define LZX_NUM_ALIGNED_OFFSET_BITS 3 + +/* Number of symbols in the aligned offset code */ +#define LZX_ALIGNEDCODE_NUM_SYMBOLS (1 << LZX_NUM_ALIGNED_OFFSET_BITS) + +/* Mask for the match offset bits that are entropy-encoded in aligned offset + * blocks + */ +#define LZX_ALIGNED_OFFSET_BITMASK ((1 << LZX_NUM_ALIGNED_OFFSET_BITS) - 1) + +/* Number of bits in which each aligned offset codeword length is represented */ +#define LZX_ALIGNEDCODE_ELEMENT_SIZE 3 + +/* Maximum lengths (in bits) of the codewords in each Huffman code */ +#define LZX_MAX_MAIN_CODEWORD_LEN 16 +#define LZX_MAX_LEN_CODEWORD_LEN 16 +#define LZX_MAX_PRE_CODEWORD_LEN ((1 << LZX_PRECODE_ELEMENT_SIZE) - 1) +#define LZX_MAX_ALIGNED_CODEWORD_LEN ((1 << LZX_ALIGNEDCODE_ELEMENT_SIZE) - 1) + +/* The default "filesize" value used in pre/post-processing. In the LZX format + * used in cabinet files this value must be given to the decompressor, whereas + * in the LZX format used in WIM files and system-compressed files this value is + * fixed at 12000000. + */ +#define LZX_DEFAULT_FILESIZE 12000000 + +/* Assumed block size when the encoded block size begins with a 0 bit. */ +#define LZX_DEFAULT_BLOCK_SIZE 32768 + +/* Number of offsets in the recent (or "repeat") offsets queue. */ +#define LZX_NUM_RECENT_OFFSETS 3 + +/* These values are chosen for fast decompression. */ +#define LZX_MAINCODE_TABLEBITS 11 +#define LZX_LENCODE_TABLEBITS 10 +#define LZX_PRECODE_TABLEBITS 6 +#define LZX_ALIGNEDCODE_TABLEBITS 7 + +#define LZX_READ_LENS_MAX_OVERRUN 50 + +/* Mapping: offset slot => first match offset that uses that offset slot. + */ +static const u32 lzx_offset_slot_base[LZX_NUM_OFFSET_SLOTS + 1] = { + 0, 1, 2, 3, 4, /* 0 --- 4 */ + 6, 8, 12, 16, 24, /* 5 --- 9 */ + 32, 48, 64, 96, 128, /* 10 --- 14 */ + 192, 256, 384, 512, 768, /* 15 --- 19 */ + 1024, 1536, 2048, 3072, 4096, /* 20 --- 24 */ + 6144, 8192, 12288, 16384, 24576, /* 25 --- 29 */ + 32768, /* extra */ +}; + +/* Mapping: offset slot => how many extra bits must be read and added to the + * corresponding offset slot base to decode the match offset. + */ +static const u8 lzx_extra_offset_bits[LZX_NUM_OFFSET_SLOTS] = { + 0, 0, 0, 0, 1, + 1, 2, 2, 3, 3, + 4, 4, 5, 5, 6, + 6, 7, 7, 8, 8, + 9, 9, 10, 10, 11, + 11, 12, 12, 13, 13, +}; + +/* Reusable heap-allocated memory for LZX decompression */ +struct lzx_decompressor { + + /* Huffman decoding tables, and arrays that map symbols to codeword + * lengths + */ + + u16 maincode_decode_table[(1 << LZX_MAINCODE_TABLEBITS) + + (LZX_MAINCODE_NUM_SYMBOLS * 2)]; + u8 maincode_lens[LZX_MAINCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN]; + + + u16 lencode_decode_table[(1 << LZX_LENCODE_TABLEBITS) + + (LZX_LENCODE_NUM_SYMBOLS * 2)]; + u8 lencode_lens[LZX_LENCODE_NUM_SYMBOLS + LZX_READ_LENS_MAX_OVERRUN]; + + + u16 alignedcode_decode_table[(1 << LZX_ALIGNEDCODE_TABLEBITS) + + (LZX_ALIGNEDCODE_NUM_SYMBOLS * 2)]; + u8 alignedcode_lens[LZX_ALIGNEDCODE_NUM_SYMBOLS]; + + u16 precode_decode_table[(1 << LZX_PRECODE_TABLEBITS) + + (LZX_PRECODE_NUM_SYMBOLS * 2)]; + u8 precode_lens[LZX_PRECODE_NUM_SYMBOLS]; + + /* Temporary space for make_huffman_decode_table() */ + u16 working_space[2 * (1 + LZX_MAX_MAIN_CODEWORD_LEN) + + LZX_MAINCODE_NUM_SYMBOLS]; +}; + +static void undo_e8_translation(void *target, s32 input_pos) +{ + s32 abs_offset, rel_offset; + + abs_offset = get_unaligned_le32(target); + if (abs_offset >= 0) { + if (abs_offset < LZX_DEFAULT_FILESIZE) { + /* "good translation" */ + rel_offset = abs_offset - input_pos; + put_unaligned_le32(rel_offset, target); + } + } else { + if (abs_offset >= -input_pos) { + /* "compensating translation" */ + rel_offset = abs_offset + LZX_DEFAULT_FILESIZE; + put_unaligned_le32(rel_offset, target); + } + } +} + +/* + * Undo the 'E8' preprocessing used in LZX. Before compression, the + * uncompressed data was preprocessed by changing the targets of suspected x86 + * CALL instructions from relative offsets to absolute offsets. After + * match/literal decoding, the decompressor must undo the translation. + */ +static void lzx_postprocess(u8 *data, u32 size) +{ + /* + * A worthwhile optimization is to push the end-of-buffer check into the + * relatively rare E8 case. This is possible if we replace the last six + * bytes of data with E8 bytes; then we are guaranteed to hit an E8 byte + * before reaching end-of-buffer. In addition, this scheme guarantees + * that no translation can begin following an E8 byte in the last 10 + * bytes because a 4-byte offset containing E8 as its high byte is a + * large negative number that is not valid for translation. That is + * exactly what we need. + */ + u8 *tail; + u8 saved_bytes[6]; + u8 *p; + + if (size <= 10) + return; + + tail = &data[size - 6]; + memcpy(saved_bytes, tail, 6); + memset(tail, 0xE8, 6); + p = data; + for (;;) { + while (*p != 0xE8) + p++; + if (p >= tail) + break; + undo_e8_translation(p + 1, p - data); + p += 5; + } + memcpy(tail, saved_bytes, 6); +} + +/* Read a Huffman-encoded symbol using the precode. */ +static forceinline u32 read_presym(const struct lzx_decompressor *d, + struct input_bitstream *is) +{ + return read_huffsym(is, d->precode_decode_table, + LZX_PRECODE_TABLEBITS, LZX_MAX_PRE_CODEWORD_LEN); +} + +/* Read a Huffman-encoded symbol using the main code. */ +static forceinline u32 read_mainsym(const struct lzx_decompressor *d, + struct input_bitstream *is) +{ + return read_huffsym(is, d->maincode_decode_table, + LZX_MAINCODE_TABLEBITS, LZX_MAX_MAIN_CODEWORD_LEN); +} + +/* Read a Huffman-encoded symbol using the length code. */ +static forceinline u32 read_lensym(const struct lzx_decompressor *d, + struct input_bitstream *is) +{ + return read_huffsym(is, d->lencode_decode_table, + LZX_LENCODE_TABLEBITS, LZX_MAX_LEN_CODEWORD_LEN); +} + +/* Read a Huffman-encoded symbol using the aligned offset code. */ +static forceinline u32 read_alignedsym(const struct lzx_decompressor *d, + struct input_bitstream *is) +{ + return read_huffsym(is, d->alignedcode_decode_table, + LZX_ALIGNEDCODE_TABLEBITS, + LZX_MAX_ALIGNED_CODEWORD_LEN); +} + +/* + * Read the precode from the compressed input bitstream, then use it to decode + * @num_lens codeword length values. + * + * @is: The input bitstream. + * + * @lens: An array that contains the length values from the previous time + * the codeword lengths for this Huffman code were read, or all 0's + * if this is the first time. This array must have at least + * (@num_lens + LZX_READ_LENS_MAX_OVERRUN) entries. + * + * @num_lens: Number of length values to decode. + * + * Returns 0 on success, or -1 if the data was invalid. + */ +static int lzx_read_codeword_lens(struct lzx_decompressor *d, + struct input_bitstream *is, + u8 *lens, u32 num_lens) +{ + u8 *len_ptr = lens; + u8 *lens_end = lens + num_lens; + int i; + + /* Read the lengths of the precode codewords. These are given + * explicitly. + */ + for (i = 0; i < LZX_PRECODE_NUM_SYMBOLS; i++) { + d->precode_lens[i] = + bitstream_read_bits(is, LZX_PRECODE_ELEMENT_SIZE); + } + + /* Make the decoding table for the precode. */ + if (make_huffman_decode_table(d->precode_decode_table, + LZX_PRECODE_NUM_SYMBOLS, + LZX_PRECODE_TABLEBITS, + d->precode_lens, + LZX_MAX_PRE_CODEWORD_LEN, + d->working_space)) + return -1; + + /* Decode the codeword lengths. */ + do { + u32 presym; + u8 len; + + /* Read the next precode symbol. */ + presym = read_presym(d, is); + if (presym < 17) { + /* Difference from old length */ + len = *len_ptr - presym; + if ((s8)len < 0) + len += 17; + *len_ptr++ = len; + } else { + /* Special RLE values */ + + u32 run_len; + + if (presym == 17) { + /* Run of 0's */ + run_len = 4 + bitstream_read_bits(is, 4); + len = 0; + } else if (presym == 18) { + /* Longer run of 0's */ + run_len = 20 + bitstream_read_bits(is, 5); + len = 0; + } else { + /* Run of identical lengths */ + run_len = 4 + bitstream_read_bits(is, 1); + presym = read_presym(d, is); + if (presym > 17) + return -1; + len = *len_ptr - presym; + if ((s8)len < 0) + len += 17; + } + + do { + *len_ptr++ = len; + } while (--run_len); + /* Worst case overrun is when presym == 18, + * run_len == 20 + 31, and only 1 length was remaining. + * So LZX_READ_LENS_MAX_OVERRUN == 50. + * + * Overrun while reading the first half of maincode_lens + * can corrupt the previous values in the second half. + * This doesn't really matter because the resulting + * lengths will still be in range, and data that + * generates overruns is invalid anyway. + */ + } + } while (len_ptr < lens_end); + + return 0; +} + +/* + * Read the header of an LZX block and save the block type and (uncompressed) + * size in *block_type_ret and *block_size_ret, respectively. + * + * If the block is compressed, also update the Huffman decode @tables with the + * new Huffman codes. If the block is uncompressed, also update the match + * offset @queue with the new match offsets. + * + * Return 0 on success, or -1 if the data was invalid. + */ +static int lzx_read_block_header(struct lzx_decompressor *d, + struct input_bitstream *is, + int *block_type_ret, + u32 *block_size_ret, + u32 recent_offsets[]) +{ + int block_type; + u32 block_size; + int i; + + bitstream_ensure_bits(is, 4); + + /* The first three bits tell us what kind of block it is, and should be + * one of the LZX_BLOCKTYPE_* values. + */ + block_type = bitstream_pop_bits(is, 3); + + /* Read the block size. */ + if (bitstream_pop_bits(is, 1)) { + block_size = LZX_DEFAULT_BLOCK_SIZE; + } else { + block_size = 0; + block_size |= bitstream_read_bits(is, 8); + block_size <<= 8; + block_size |= bitstream_read_bits(is, 8); + } + + switch (block_type) { + + case LZX_BLOCKTYPE_ALIGNED: + + /* Read the aligned offset code and prepare its decode table. + */ + + for (i = 0; i < LZX_ALIGNEDCODE_NUM_SYMBOLS; i++) { + d->alignedcode_lens[i] = + bitstream_read_bits(is, + LZX_ALIGNEDCODE_ELEMENT_SIZE); + } + + if (make_huffman_decode_table(d->alignedcode_decode_table, + LZX_ALIGNEDCODE_NUM_SYMBOLS, + LZX_ALIGNEDCODE_TABLEBITS, + d->alignedcode_lens, + LZX_MAX_ALIGNED_CODEWORD_LEN, + d->working_space)) + return -1; + + /* Fall though, since the rest of the header for aligned offset + * blocks is the same as that for verbatim blocks. + */ + fallthrough; + + case LZX_BLOCKTYPE_VERBATIM: + + /* Read the main code and prepare its decode table. + * + * Note that the codeword lengths in the main code are encoded + * in two parts: one part for literal symbols, and one part for + * match symbols. + */ + + if (lzx_read_codeword_lens(d, is, d->maincode_lens, + LZX_NUM_CHARS)) + return -1; + + if (lzx_read_codeword_lens(d, is, + d->maincode_lens + LZX_NUM_CHARS, + LZX_MAINCODE_NUM_SYMBOLS - LZX_NUM_CHARS)) + return -1; + + if (make_huffman_decode_table(d->maincode_decode_table, + LZX_MAINCODE_NUM_SYMBOLS, + LZX_MAINCODE_TABLEBITS, + d->maincode_lens, + LZX_MAX_MAIN_CODEWORD_LEN, + d->working_space)) + return -1; + + /* Read the length code and prepare its decode table. */ + + if (lzx_read_codeword_lens(d, is, d->lencode_lens, + LZX_LENCODE_NUM_SYMBOLS)) + return -1; + + if (make_huffman_decode_table(d->lencode_decode_table, + LZX_LENCODE_NUM_SYMBOLS, + LZX_LENCODE_TABLEBITS, + d->lencode_lens, + LZX_MAX_LEN_CODEWORD_LEN, + d->working_space)) + return -1; + + break; + + case LZX_BLOCKTYPE_UNCOMPRESSED: + + /* Before reading the three recent offsets from the uncompressed + * block header, the stream must be aligned on a 16-bit + * boundary. But if the stream is *already* aligned, then the + * next 16 bits must be discarded. + */ + bitstream_ensure_bits(is, 1); + bitstream_align(is); + + recent_offsets[0] = bitstream_read_u32(is); + recent_offsets[1] = bitstream_read_u32(is); + recent_offsets[2] = bitstream_read_u32(is); + + /* Offsets of 0 are invalid. */ + if (recent_offsets[0] == 0 || recent_offsets[1] == 0 || + recent_offsets[2] == 0) + return -1; + break; + + default: + /* Unrecognized block type. */ + return -1; + } + + *block_type_ret = block_type; + *block_size_ret = block_size; + return 0; +} + +/* Decompress a block of LZX-compressed data. */ +static int lzx_decompress_block(const struct lzx_decompressor *d, + struct input_bitstream *is, + int block_type, u32 block_size, + u8 * const out_begin, u8 *out_next, + u32 recent_offsets[]) +{ + u8 * const block_end = out_next + block_size; + u32 ones_if_aligned = 0U - (block_type == LZX_BLOCKTYPE_ALIGNED); + + do { + u32 mainsym; + u32 match_len; + u32 match_offset; + u32 offset_slot; + u32 num_extra_bits; + + mainsym = read_mainsym(d, is); + if (mainsym < LZX_NUM_CHARS) { + /* Literal */ + *out_next++ = mainsym; + continue; + } + + /* Match */ + + /* Decode the length header and offset slot. */ + mainsym -= LZX_NUM_CHARS; + match_len = mainsym % LZX_NUM_LEN_HEADERS; + offset_slot = mainsym / LZX_NUM_LEN_HEADERS; + + /* If needed, read a length symbol to decode the full length. */ + if (match_len == LZX_NUM_PRIMARY_LENS) + match_len += read_lensym(d, is); + match_len += LZX_MIN_MATCH_LEN; + + if (offset_slot < LZX_NUM_RECENT_OFFSETS) { + /* Repeat offset */ + + /* Note: This isn't a real LRU queue, since using the R2 + * offset doesn't bump the R1 offset down to R2. This + * quirk allows all 3 recent offsets to be handled by + * the same code. (For R0, the swap is a no-op.) + */ + match_offset = recent_offsets[offset_slot]; + recent_offsets[offset_slot] = recent_offsets[0]; + recent_offsets[0] = match_offset; + } else { + /* Explicit offset */ + + /* Look up the number of extra bits that need to be read + * to decode offsets with this offset slot. + */ + num_extra_bits = lzx_extra_offset_bits[offset_slot]; + + /* Start with the offset slot base value. */ + match_offset = lzx_offset_slot_base[offset_slot]; + + /* In aligned offset blocks, the low-order 3 bits of + * each offset are encoded using the aligned offset + * code. Otherwise, all the extra bits are literal. + */ + + if ((num_extra_bits & ones_if_aligned) >= LZX_NUM_ALIGNED_OFFSET_BITS) { + match_offset += + bitstream_read_bits(is, num_extra_bits - + LZX_NUM_ALIGNED_OFFSET_BITS) + << LZX_NUM_ALIGNED_OFFSET_BITS; + match_offset += read_alignedsym(d, is); + } else { + match_offset += bitstream_read_bits(is, num_extra_bits); + } + + /* Adjust the offset. */ + match_offset -= (LZX_NUM_RECENT_OFFSETS - 1); + + /* Update the recent offsets. */ + recent_offsets[2] = recent_offsets[1]; + recent_offsets[1] = recent_offsets[0]; + recent_offsets[0] = match_offset; + } + + /* Validate the match, then copy it to the current position. */ + + if (match_len > (size_t)(block_end - out_next)) + return -1; + + if (match_offset > (size_t)(out_next - out_begin)) + return -1; + + out_next = lz_copy(out_next, match_len, match_offset, + block_end, LZX_MIN_MATCH_LEN); + + } while (out_next != block_end); + + return 0; +} + +/* + * lzx_allocate_decompressor - Allocate an LZX decompressor + * + * Return the pointer to the decompressor on success, or return NULL and set + * errno on failure. + */ +struct lzx_decompressor *lzx_allocate_decompressor(void) +{ + return kmalloc(sizeof(struct lzx_decompressor), GFP_NOFS); +} + +/* + * lzx_decompress - Decompress a buffer of LZX-compressed data + * + * @decompressor: A decompressor allocated with lzx_allocate_decompressor() + * @compressed_data: The buffer of data to decompress + * @compressed_size: Number of bytes of compressed data + * @uncompressed_data: The buffer in which to store the decompressed data + * @uncompressed_size: The number of bytes the data decompresses into + * + * Return 0 on success, or return -1 and set errno on failure. + */ +int lzx_decompress(struct lzx_decompressor *decompressor, + const void *compressed_data, size_t compressed_size, + void *uncompressed_data, size_t uncompressed_size) +{ + struct lzx_decompressor *d = decompressor; + u8 * const out_begin = uncompressed_data; + u8 *out_next = out_begin; + u8 * const out_end = out_begin + uncompressed_size; + struct input_bitstream is; + u32 recent_offsets[LZX_NUM_RECENT_OFFSETS] = {1, 1, 1}; + int e8_status = 0; + + init_input_bitstream(&is, compressed_data, compressed_size); + + /* Codeword lengths begin as all 0's for delta encoding purposes. */ + memset(d->maincode_lens, 0, LZX_MAINCODE_NUM_SYMBOLS); + memset(d->lencode_lens, 0, LZX_LENCODE_NUM_SYMBOLS); + + /* Decompress blocks until we have all the uncompressed data. */ + + while (out_next != out_end) { + int block_type; + u32 block_size; + + if (lzx_read_block_header(d, &is, &block_type, &block_size, + recent_offsets)) + goto invalid; + + if (block_size < 1 || block_size > (size_t)(out_end - out_next)) + goto invalid; + + if (block_type != LZX_BLOCKTYPE_UNCOMPRESSED) { + + /* Compressed block */ + + if (lzx_decompress_block(d, + &is, + block_type, + block_size, + out_begin, + out_next, + recent_offsets)) + goto invalid; + + e8_status |= d->maincode_lens[0xe8]; + out_next += block_size; + } else { + /* Uncompressed block */ + + out_next = bitstream_read_bytes(&is, out_next, + block_size); + if (!out_next) + goto invalid; + + if (block_size & 1) + bitstream_read_byte(&is); + + e8_status = 1; + } + } + + /* Postprocess the data unless it cannot possibly contain 0xe8 bytes. */ + if (e8_status) + lzx_postprocess(uncompressed_data, uncompressed_size); + + return 0; + +invalid: + return -1; +} + +/* + * lzx_free_decompressor - Free an LZX decompressor + * + * @decompressor: A decompressor that was allocated with + * lzx_allocate_decompressor(), or NULL. + */ +void lzx_free_decompressor(struct lzx_decompressor *decompressor) +{ + kfree(decompressor); +} diff --git a/fs/ntfs3/lib/xpress_decompress.c b/fs/ntfs3/lib/xpress_decompress.c new file mode 100644 index 000000000..769c6d3dd --- /dev/null +++ b/fs/ntfs3/lib/xpress_decompress.c @@ -0,0 +1,142 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * xpress_decompress.c - A decompressor for the XPRESS compression format + * (Huffman variant), which can be used in "System Compressed" files. This is + * based on the code from wimlib. + * + * Copyright (C) 2015 Eric Biggers + */ + +#include "decompress_common.h" +#include "lib.h" + +#define XPRESS_NUM_SYMBOLS 512 +#define XPRESS_MAX_CODEWORD_LEN 15 +#define XPRESS_MIN_MATCH_LEN 3 + +/* This value is chosen for fast decompression. */ +#define XPRESS_TABLEBITS 12 + +/* Reusable heap-allocated memory for XPRESS decompression */ +struct xpress_decompressor { + + /* The Huffman decoding table */ + u16 decode_table[(1 << XPRESS_TABLEBITS) + 2 * XPRESS_NUM_SYMBOLS]; + + /* An array that maps symbols to codeword lengths */ + u8 lens[XPRESS_NUM_SYMBOLS]; + + /* Temporary space for make_huffman_decode_table() */ + u16 working_space[2 * (1 + XPRESS_MAX_CODEWORD_LEN) + + XPRESS_NUM_SYMBOLS]; +}; + +/* + * xpress_allocate_decompressor - Allocate an XPRESS decompressor + * + * Return the pointer to the decompressor on success, or return NULL and set + * errno on failure. + */ +struct xpress_decompressor *xpress_allocate_decompressor(void) +{ + return kmalloc(sizeof(struct xpress_decompressor), GFP_NOFS); +} + +/* + * xpress_decompress - Decompress a buffer of XPRESS-compressed data + * + * @decompressor: A decompressor that was allocated with + * xpress_allocate_decompressor() + * @compressed_data: The buffer of data to decompress + * @compressed_size: Number of bytes of compressed data + * @uncompressed_data: The buffer in which to store the decompressed data + * @uncompressed_size: The number of bytes the data decompresses into + * + * Return 0 on success, or return -1 and set errno on failure. + */ +int xpress_decompress(struct xpress_decompressor *decompressor, + const void *compressed_data, size_t compressed_size, + void *uncompressed_data, size_t uncompressed_size) +{ + struct xpress_decompressor *d = decompressor; + const u8 * const in_begin = compressed_data; + u8 * const out_begin = uncompressed_data; + u8 *out_next = out_begin; + u8 * const out_end = out_begin + uncompressed_size; + struct input_bitstream is; + u32 i; + + /* Read the Huffman codeword lengths. */ + if (compressed_size < XPRESS_NUM_SYMBOLS / 2) + goto invalid; + for (i = 0; i < XPRESS_NUM_SYMBOLS / 2; i++) { + d->lens[i*2 + 0] = in_begin[i] & 0xF; + d->lens[i*2 + 1] = in_begin[i] >> 4; + } + + /* Build a decoding table for the Huffman code. */ + if (make_huffman_decode_table(d->decode_table, XPRESS_NUM_SYMBOLS, + XPRESS_TABLEBITS, d->lens, + XPRESS_MAX_CODEWORD_LEN, + d->working_space)) + goto invalid; + + /* Decode the matches and literals. */ + + init_input_bitstream(&is, in_begin + XPRESS_NUM_SYMBOLS / 2, + compressed_size - XPRESS_NUM_SYMBOLS / 2); + + while (out_next != out_end) { + u32 sym; + u32 log2_offset; + u32 length; + u32 offset; + + sym = read_huffsym(&is, d->decode_table, + XPRESS_TABLEBITS, XPRESS_MAX_CODEWORD_LEN); + if (sym < 256) { + /* Literal */ + *out_next++ = sym; + } else { + /* Match */ + length = sym & 0xf; + log2_offset = (sym >> 4) & 0xf; + + bitstream_ensure_bits(&is, 16); + + offset = ((u32)1 << log2_offset) | + bitstream_pop_bits(&is, log2_offset); + + if (length == 0xf) { + length += bitstream_read_byte(&is); + if (length == 0xf + 0xff) + length = bitstream_read_u16(&is); + } + length += XPRESS_MIN_MATCH_LEN; + + if (offset > (size_t)(out_next - out_begin)) + goto invalid; + + if (length > (size_t)(out_end - out_next)) + goto invalid; + + out_next = lz_copy(out_next, length, offset, out_end, + XPRESS_MIN_MATCH_LEN); + } + } + return 0; + +invalid: + return -1; +} + +/* + * xpress_free_decompressor - Free an XPRESS decompressor + * + * @decompressor: A decompressor that was allocated with + * xpress_allocate_decompressor(), or NULL. + */ +void xpress_free_decompressor(struct xpress_decompressor *decompressor) +{ + kfree(decompressor); +} |