/*
* compress.c
*
- * Functions used for compression.
+ * Generic functions for compression, wrapping around actual compression
+ * implementations.
*/
/*
- * Copyright (C) 2012 Eric Biggers
+ * Copyright (C) 2013 Eric Biggers
*
* This file is part of wimlib, a library for working with WIM files.
*
* along with wimlib; if not, see http://www.gnu.org/licenses/.
*/
-#include "compress.h"
-#include <stdlib.h>
-#include <string.h>
+#ifdef HAVE_CONFIG_H
+# include "config.h"
+#endif
-static inline void flush_bits(struct output_bitstream *ostream)
-{
- *(u16*)ostream->bit_output = cpu_to_le16(ostream->bitbuf);
- ostream->bit_output = ostream->next_bit_output;
- ostream->next_bit_output = ostream->output;
- ostream->output += 2;
- ostream->num_bytes_remaining -= 2;
-}
-
-/* Writes @num_bits bits, given by the @num_bits least significant bits of
- * @bits, to the output @ostream. */
-int bitstream_put_bits(struct output_bitstream *ostream, output_bitbuf_t bits,
- unsigned num_bits)
-{
- unsigned rem_bits;
-
- wimlib_assert(num_bits <= 16);
- if (num_bits <= ostream->free_bits) {
- ostream->bitbuf = (ostream->bitbuf << num_bits) | bits;
- ostream->free_bits -= num_bits;
- } else {
+#include "wimlib.h"
+#include "wimlib/compressor_ops.h"
+#include "wimlib/util.h"
- if (ostream->num_bytes_remaining + (ostream->output -
- ostream->bit_output) < 2)
- return 1;
+struct wimlib_compressor {
+ const struct compressor_ops *ops;
+ void *private;
+};
- /* It is tricky to output the bits correctly. The correct way
- * is to output little-endian 2-byte words, such that the bits
- * in the SECOND byte logically precede those in the FIRST byte.
- * While the byte order is little-endian, the bit order is
- * big-endian; the first bit in a byte is the high-order one.
- * Any multi-bit numbers are in bit-big-endian form, so the
- * low-order bit of a multi-bit number is the LAST bit to be
- * output. */
- rem_bits = num_bits - ostream->free_bits;
- ostream->bitbuf <<= ostream->free_bits;
- ostream->bitbuf |= bits >> rem_bits;
- flush_bits(ostream);
- ostream->free_bits = 16 - rem_bits;
- ostream->bitbuf = bits;
+static const struct compressor_ops *compressor_ops[] = {
+ [WIMLIB_COMPRESSION_TYPE_LZX] = &lzx_compressor_ops,
+ [WIMLIB_COMPRESSION_TYPE_XPRESS] = &xpress_compressor_ops,
+ [WIMLIB_COMPRESSION_TYPE_LZMS] = &lzms_compressor_ops,
+};
- }
- return 0;
-}
+static struct wimlib_compressor_params_header *
+compressor_default_params[ARRAY_LEN(compressor_ops)] = {
+};
-/* Flushes any remaining bits in the output buffer to the output byte stream. */
-int flush_output_bitstream(struct output_bitstream *ostream)
+static bool
+compressor_ctype_valid(int ctype)
{
- if (ostream->num_bytes_remaining + (ostream->output -
- ostream->bit_output) < 2)
- return 1;
- if (ostream->free_bits != 16) {
- ostream->bitbuf <<= ostream->free_bits;
- flush_bits(ostream);
- }
- return 0;
+ return (ctype >= 0 &&
+ ctype < ARRAY_LEN(compressor_ops) &&
+ compressor_ops[ctype] != NULL);
}
-/* Initializes an output bit buffer to write its output to the memory location
- * pointer to by @data. */
-void init_output_bitstream(struct output_bitstream *ostream, void *data,
- unsigned num_bytes)
+WIMLIBAPI int
+wimlib_set_default_compressor_params(enum wimlib_compression_type ctype,
+ const struct wimlib_compressor_params_header *params)
{
- wimlib_assert(num_bytes >= 4);
-
- ostream->bitbuf = 0;
- ostream->free_bits = 16;
- ostream->bit_output = (u8*)data;
- ostream->next_bit_output = (u8*)data + 2;
- ostream->output = (u8*)data + 4;
- ostream->num_bytes_remaining = num_bytes - 4;
-}
-
-/* Intermediate (non-leaf) node in a Huffman tree. */
-typedef struct HuffmanNode {
- u32 freq;
- u16 sym;
- union {
- u16 path_len;
- u16 height;
- };
- struct HuffmanNode *left_child;
- struct HuffmanNode *right_child;
-} HuffmanNode;
-
-/* Leaf node in a Huffman tree. The fields are in the same order as the
- * HuffmanNode, so it can be cast to a HuffmanNode. There are no pointers to
- * the children in the leaf node. */
-typedef struct {
- u32 freq;
- u16 sym;
- union {
- u16 path_len;
- u16 height;
- };
-} HuffmanLeafNode;
+ struct wimlib_compressor_params_header *dup;
-/* Comparator function for HuffmanLeafNodes. Sorts primarily by symbol
- * frequency and secondarily by symbol value. */
-static int cmp_leaves_by_freq(const void *__leaf1, const void *__leaf2)
-{
- const HuffmanLeafNode *leaf1 = __leaf1;
- const HuffmanLeafNode *leaf2 = __leaf2;
-
- int freq_diff = (int)leaf1->freq - (int)leaf2->freq;
-
- if (freq_diff == 0)
- return (int)leaf1->sym - (int)leaf2->sym;
- else
- return freq_diff;
-}
+ if (!compressor_ctype_valid(ctype))
+ return WIMLIB_ERR_INVALID_COMPRESSION_TYPE;
-/* Comparator function for HuffmanLeafNodes. Sorts primarily by code length and
- * secondarily by symbol value. */
-static int cmp_leaves_by_code_len(const void *__leaf1, const void *__leaf2)
-{
- const HuffmanLeafNode *leaf1 = __leaf1;
- const HuffmanLeafNode *leaf2 = __leaf2;
+ if (params != NULL &&
+ compressor_ops[ctype]->params_valid != NULL &&
+ !compressor_ops[ctype]->params_valid(params))
+ return WIMLIB_ERR_INVALID_PARAM;
- int code_len_diff = (int)leaf1->path_len - (int)leaf2->path_len;
+ dup = NULL;
+ if (params) {
+ dup = memdup(params, params->size);
+ if (dup == NULL)
+ return WIMLIB_ERR_NOMEM;
+ }
- if (code_len_diff == 0)
- return (int)leaf1->sym - (int)leaf2->sym;
- else
- return code_len_diff;
+ FREE(compressor_default_params[ctype]);
+ compressor_default_params[ctype] = dup;
+ return 0;
}
-/* Recursive function to calculate the depth of the leaves in a Huffman tree.
- * */
-static void huffman_tree_compute_path_lengths(HuffmanNode *node, u16 cur_len)
+void
+cleanup_compressor_params(void)
{
- if (node->sym == (u16)(-1)) {
- /* Intermediate node. */
- huffman_tree_compute_path_lengths(node->left_child, cur_len + 1);
- huffman_tree_compute_path_lengths(node->right_child, cur_len + 1);
- } else {
- /* Leaf node. */
- node->path_len = cur_len;
+ for (size_t i = 0; i < ARRAY_LEN(compressor_default_params); i++) {
+ FREE(compressor_default_params[i]);
+ compressor_default_params[i] = NULL;
}
}
-/* Creates a canonical Huffman code from an array of symbol frequencies.
- *
- * The algorithm used is similar to the well-known algorithm that builds a
- * Huffman tree using a minheap. In that algorithm, the leaf nodes are
- * initialized and inserted into the minheap with the frequency as the key.
- * Repeatedly, the top two nodes (nodes with the lowest frequency) are taken out
- * of the heap and made the children of a new node that has a frequency equal to
- * the sum of the two frequencies of its children. This new node is inserted
- * into the heap. When all the nodes have been removed from the heap, what
- * remains is the Huffman tree. The Huffman code for a symbol is given by the
- * path to it in the tree, where each left pointer is mapped to a 0 bit and each
- * right pointer is mapped to a 1 bit.
- *
- * The algorithm used here uses an optimization that removes the need to
- * actually use a heap. The leaf nodes are first sorted by frequency, as
- * opposed to being made into a heap. Note that this sorting step takes O(n log
- * n) time vs. O(n) time for heapifying the array, where n is the number of
- * symbols. However, the heapless method is probably faster overall, due to the
- * time saved later. In the heapless method, whenever an intermediate node is
- * created, it is not inserted into the sorted array. Instead, the intermediate
- * nodes are kept in a separate array, which is easily kept sorted because every
- * time an intermediate node is initialized, it will have a frequency at least
- * as high as that of the previous intermediate node that was initialized. So
- * whenever we want the 2 nodes, leaf or intermediate, that have the lowest
- * frequency, we check the low-frequency ends of both arrays, which is an O(1)
- * operation.
- *
- * The function builds a canonical Huffman code, not just any Huffman code. A
- * Huffman code is canonical if the codeword for each symbol numerically
- * precedes the codeword for all other symbols of the same length that are
- * numbered higher than the symbol, and additionally, all shorter codewords,
- * 0-extended, numerically precede longer codewords. A canonical Huffman code
- * is useful because it can be reconstructed by only knowing the path lengths in
- * the tree. See the make_huffman_decode_table() function to see how to
- * reconstruct a canonical Huffman code from only the lengths of the codes.
- *
- * @num_syms: The number of symbols in the alphabet.
- *
- * @max_codeword_len: The maximum allowed length of a codeword in the code.
- * Note that if the code being created runs up against
- * this restriction, the code ultimately created will be
- * suboptimal, although there are some advantages for
- * limiting the length of the codewords.
- *
- * @freq_tab: An array of length @num_syms that contains the frequencies
- * of each symbol in the uncompressed data.
- *
- * @lens: An array of length @num_syms into which the lengths of the
- * codewords for each symbol will be written.
- *
- * @codewords: An array of @num_syms short integers into which the
- * codewords for each symbol will be written. The first
- * lens[i] bits of codewords[i] will contain the codeword
- * for symbol i.
- */
-void make_canonical_huffman_code(unsigned num_syms, unsigned max_codeword_len,
- const freq_t freq_tab[], u8 lens[],
- u16 codewords[])
+WIMLIBAPI u64
+wimlib_get_compressor_needed_memory(enum wimlib_compression_type ctype,
+ size_t max_block_size,
+ const struct wimlib_compressor_params_header *extra_params)
{
- /* We require at least 2 possible symbols in the alphabet to produce a
- * valid Huffman decoding table. It is allowed that fewer than 2 symbols
- * are actually used, though. */
- wimlib_assert(num_syms >= 2);
-
- /* Initialize the lengths and codewords to 0 */
- memset(lens, 0, num_syms * sizeof(lens[0]));
- memset(codewords, 0, num_syms * sizeof(codewords[0]));
-
- /* Calculate how many symbols have non-zero frequency. These are the
- * symbols that actually appeared in the input. */
- unsigned num_used_symbols = 0;
- for (unsigned i = 0; i < num_syms; i++)
- if (freq_tab[i] != 0)
- num_used_symbols++;
+ const struct compressor_ops *ops;
+ const struct wimlib_compressor_params_header *params;
+ if (!compressor_ctype_valid(ctype))
+ return 0;
- /* It is impossible to make a code for num_used_symbols symbols if there
- * aren't enough code bits to uniquely represent all of them. */
- wimlib_assert((1 << max_codeword_len) > num_used_symbols);
+ ops = compressor_ops[ctype];
+ if (ops->get_needed_memory == NULL)
+ return 0;
- /* Initialize the array of leaf nodes with the symbols and their
- * frequencies. */
- HuffmanLeafNode leaves[num_used_symbols];
- unsigned leaf_idx = 0;
- for (unsigned i = 0; i < num_syms; i++) {
- if (freq_tab[i] != 0) {
- leaves[leaf_idx].freq = freq_tab[i];
- leaves[leaf_idx].sym = i;
- leaves[leaf_idx].height = 0;
- leaf_idx++;
- }
+ if (extra_params) {
+ params = extra_params;
+ if (ops->params_valid && !ops->params_valid(params))
+ return 0;
+ } else {
+ params = compressor_default_params[ctype];
}
- /* Deal with the special cases where num_used_symbols < 2. */
- if (num_used_symbols < 2) {
- if (num_used_symbols == 0) {
- /* If num_used_symbols is 0, there are no symbols in the
- * input, so it must be empty. This should be an error,
- * but the LZX format expects this case to succeed. All
- * the codeword lengths are simply marked as 0 (which
- * was already done.) */
- } else {
- /* If only one symbol is present, the LZX format
- * requires that the Huffman code include two codewords.
- * One is not used. Note that this doesn't make the
- * encoded data take up more room anyway, since binary
- * data itself has 2 symbols. */
+ return ops->get_needed_memory(max_block_size, params);
+}
- unsigned sym = leaves[0].sym;
- codewords[0] = 0;
- lens[0] = 1;
- if (sym == 0) {
- /* dummy symbol is 1, real symbol is 0 */
- codewords[1] = 1;
- lens[1] = 1;
- } else {
- /* dummy symbol is 0, real symbol is sym */
- codewords[sym] = 1;
- lens[sym] = 1;
+WIMLIBAPI int
+wimlib_create_compressor(enum wimlib_compression_type ctype,
+ size_t max_block_size,
+ const struct wimlib_compressor_params_header *extra_params,
+ struct wimlib_compressor **c_ret)
+{
+ struct wimlib_compressor *c;
+
+ if (c_ret == NULL)
+ return WIMLIB_ERR_INVALID_PARAM;
+
+ if (!compressor_ctype_valid(ctype))
+ return WIMLIB_ERR_INVALID_COMPRESSION_TYPE;
+
+ c = MALLOC(sizeof(*c));
+ if (c == NULL)
+ return WIMLIB_ERR_NOMEM;
+ c->ops = compressor_ops[ctype];
+ c->private = NULL;
+ if (c->ops->create_compressor) {
+ const struct wimlib_compressor_params_header *params;
+ int ret;
+
+ if (extra_params) {
+ params = extra_params;
+ if (c->ops->params_valid && !c->ops->params_valid(params)) {
+ FREE(c);
+ return WIMLIB_ERR_INVALID_PARAM;
}
- }
- return;
- }
-
- /* Otherwise, there are at least 2 symbols in the input, so we need to
- * find a real Huffman code. */
-
-
- /* Declare the array of intermediate nodes. An intermediate node is not
- * associated with a symbol. Instead, it represents some binary code
- * prefix that is shared between at least 2 codewords. There can be at
- * most num_used_symbols - 1 intermediate nodes when creating a Huffman
- * code. This is because if there were at least num_used_symbols nodes,
- * the code would be suboptimal because there would be at least one
- * unnecessary intermediate node.
- *
- * The worst case (greatest number of intermediate nodes) would be if
- * all the intermediate nodes were chained together. This results in
- * num_used_symbols - 1 intermediate nodes. If num_used_symbols is at
- * least 17, this configuration would not be allowed because the LZX
- * format constrains codes to 16 bits or less each. However, it is
- * still possible for there to be more than 16 intermediate nodes, as
- * long as no leaf has a depth of more than 16. */
- HuffmanNode inodes[num_used_symbols - 1];
-
-
- /* Pointer to the leaf node of lowest frequency that hasn't already been
- * added as the child of some intermediate note. */
- HuffmanLeafNode *cur_leaf;
-
- /* Pointer past the end of the array of leaves. */
- HuffmanLeafNode *end_leaf = &leaves[num_used_symbols];
-
- /* Pointer to the intermediate node of lowest frequency. */
- HuffmanNode *cur_inode;
-
- /* Pointer to the next unallocated intermediate node. */
- HuffmanNode *next_inode;
-
- /* Only jump back to here if the maximum length of the codewords allowed
- * by the LZX format (16 bits) is exceeded. */
-try_building_tree_again:
-
- /* Sort the leaves from those that correspond to the least frequent
- * symbol, to those that correspond to the most frequent symbol. If two
- * leaves have the same frequency, they are sorted by symbol. */
- qsort(leaves, num_used_symbols, sizeof(leaves[0]), cmp_leaves_by_freq);
-
- cur_leaf = &leaves[0];
- cur_inode = &inodes[0];
- next_inode = &inodes[0];
-
- /* The following loop takes the two lowest frequency nodes of those
- * remaining and makes them the children of the next available
- * intermediate node. It continues until all the leaf nodes and
- * intermediate nodes have been used up, or the maximum allowed length
- * for the codewords is exceeded. For the latter case, we must adjust
- * the frequencies to be more equal and then execute this loop again. */
- while (1) {
-
- /* Lowest frequency node. */
- HuffmanNode *f1;
-
- /* Second lowest frequency node. */
- HuffmanNode *f2;
-
- /* Get the lowest and second lowest frequency nodes from the
- * remaining leaves or from the intermediate nodes. */
-
- if (cur_leaf != end_leaf && (cur_inode == next_inode ||
- cur_leaf->freq <= cur_inode->freq)) {
- f1 = (HuffmanNode*)cur_leaf++;
- } else if (cur_inode != next_inode) {
- f1 = cur_inode++;
- }
-
- if (cur_leaf != end_leaf && (cur_inode == next_inode ||
- cur_leaf->freq <= cur_inode->freq)) {
- f2 = (HuffmanNode*)cur_leaf++;
- } else if (cur_inode != next_inode) {
- f2 = cur_inode++;
} else {
- /* All nodes used up! */
- break;
+ params = compressor_default_params[ctype];
}
-
- /* next_inode becomes the parent of f1 and f2. */
-
- next_inode->freq = f1->freq + f2->freq;
- next_inode->sym = (u16)(-1); /* Invalid symbol. */
- next_inode->left_child = f1;
- next_inode->right_child = f2;
-
- /* We need to keep track of the height so that we can detect if
- * the length of a codeword has execeed max_codeword_len. The
- * parent node has a height one higher than the maximum height
- * of its children. */
- next_inode->height = max(f1->height, f2->height) + 1;
-
- /* Check to see if the code length of the leaf farthest away
- * from next_inode has exceeded the maximum code length. */
- if (next_inode->height > max_codeword_len) {
- /* The code lengths can be made more uniform by making
- * the frequencies more uniform. Divide all the
- * frequencies by 2, leaving 1 as the minimum frequency.
- * If this keeps happening, the symbol frequencies will
- * approach equality, which makes their Huffman
- * codewords approach the length
- * log_2(num_used_symbols).
- * */
- for (unsigned i = 0; i < num_used_symbols; i++)
- if (leaves[i].freq > 1)
- leaves[i].freq >>= 1;
- goto try_building_tree_again;
+ ret = c->ops->create_compressor(max_block_size,
+ params, &c->private);
+ if (ret) {
+ FREE(c);
+ return ret;
}
- next_inode++;
}
+ *c_ret = c;
+ return 0;
+}
- /* The Huffman tree is now complete, and its height is no more than
- * max_codeword_len. */
-
- HuffmanNode *root = next_inode - 1;
- wimlib_assert(root->height <= max_codeword_len);
-
- /* Compute the path lengths for the leaf nodes. */
- huffman_tree_compute_path_lengths(root, 0);
-
- /* Sort the leaf nodes primarily by code length and secondarily by
- * symbol. */
- qsort(leaves, num_used_symbols, sizeof(leaves[0]), cmp_leaves_by_code_len);
-
- u16 cur_codeword = 0;
- unsigned cur_codeword_len = 0;
- for (unsigned i = 0; i < num_used_symbols; i++) {
-
- /* Each time a codeword becomes one longer, the current codeword
- * is left shifted by one place. This is part of the procedure
- * for enumerating the canonical Huffman code. Additionally,
- * whenever a codeword is used, 1 is added to the current
- * codeword. */
-
- unsigned len_diff = leaves[i].path_len - cur_codeword_len;
- cur_codeword <<= len_diff;
- cur_codeword_len += len_diff;
-
- u16 sym = leaves[i].sym;
- codewords[sym] = cur_codeword;
- lens[sym] = cur_codeword_len;
+WIMLIBAPI size_t
+wimlib_compress(const void *uncompressed_data, size_t uncompressed_size,
+ void *compressed_data, size_t compressed_size_avail,
+ struct wimlib_compressor *c)
+{
+ return c->ops->compress(uncompressed_data, uncompressed_size,
+ compressed_data, compressed_size_avail,
+ c->private);
+}
- cur_codeword++;
+WIMLIBAPI void
+wimlib_free_compressor(struct wimlib_compressor *c)
+{
+ if (c) {
+ if (c->ops->free_compressor)
+ c->ops->free_compressor(c->private);
+ FREE(c);
}
}
git://wimlib.net / wimlib / blobdiff