| /* cairo - a vector graphics library with display and print output |
| * |
| * Copyright © 2006 Red Hat, Inc. |
| * |
| * This library is free software; you can redistribute it and/or |
| * modify it either under the terms of the GNU Lesser General Public |
| * License version 2.1 as published by the Free Software Foundation |
| * (the "LGPL") or, at your option, under the terms of the Mozilla |
| * Public License Version 1.1 (the "MPL"). If you do not alter this |
| * notice, a recipient may use your version of this file under either |
| * the MPL or the LGPL. |
| * |
| * You should have received a copy of the LGPL along with this library |
| * in the file COPYING-LGPL-2.1; if not, write to the Free Software |
| * Foundation, Inc., 51 Franklin Street, Suite 500, Boston, MA 02110-1335, USA |
| * You should have received a copy of the MPL along with this library |
| * in the file COPYING-MPL-1.1 |
| * |
| * The contents of this file are subject to the Mozilla Public License |
| * Version 1.1 (the "License"); you may not use this file except in |
| * compliance with the License. You may obtain a copy of the License at |
| * http://www.mozilla.org/MPL/ |
| * |
| * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY |
| * OF ANY KIND, either express or implied. See the LGPL or the MPL for |
| * the specific language governing rights and limitations. |
| * |
| * The Original Code is the cairo graphics library. |
| * |
| * The Initial Developer of the Original Code is University of Southern |
| * California. |
| * |
| * Contributor(s): |
| * Carl D. Worth <cworth@cworth.org> |
| */ |
| |
| #include "cairoint.h" |
| #include "cairo-error-private.h" |
| |
| typedef struct _lzw_buf { |
| cairo_status_t status; |
| |
| unsigned char *data; |
| int data_size; |
| int num_data; |
| uint32_t pending; |
| unsigned int pending_bits; |
| } lzw_buf_t; |
| |
| /* An lzw_buf_t is a simple, growable chunk of memory for holding |
| * variable-size objects of up to 16 bits each. |
| * |
| * Initialize an lzw_buf_t to the given size in bytes. |
| * |
| * To store objects into the lzw_buf_t, call _lzw_buf_store_bits and |
| * when finished, call _lzw_buf_store_pending, (which flushes out the |
| * last few bits that hadn't yet made a complete byte yet). |
| * |
| * Instead of returning failure from any functions, lzw_buf_t provides |
| * a status value that the caller can query, (and should query at |
| * least once when done with the object). The status value will be |
| * either %CAIRO_STATUS_SUCCESS or %CAIRO_STATUS_NO_MEMORY; |
| */ |
| static void |
| _lzw_buf_init (lzw_buf_t *buf, int size) |
| { |
| if (size == 0) |
| size = 16; |
| |
| buf->status = CAIRO_STATUS_SUCCESS; |
| buf->data_size = size; |
| buf->num_data = 0; |
| buf->pending = 0; |
| buf->pending_bits = 0; |
| |
| buf->data = malloc (size); |
| if (unlikely (buf->data == NULL)) { |
| buf->data_size = 0; |
| buf->status = _cairo_error (CAIRO_STATUS_NO_MEMORY); |
| return; |
| } |
| } |
| |
| /* Increase the buffer size by doubling. |
| * |
| * Returns %CAIRO_STATUS_SUCCESS or %CAIRO_STATUS_NO_MEMORY |
| */ |
| static cairo_status_t |
| _lzw_buf_grow (lzw_buf_t *buf) |
| { |
| int new_size = buf->data_size * 2; |
| unsigned char *new_data; |
| |
| if (buf->status) |
| return buf->status; |
| |
| new_data = NULL; |
| /* check for integer overflow */ |
| if (new_size / 2 == buf->data_size) |
| new_data = realloc (buf->data, new_size); |
| |
| if (unlikely (new_data == NULL)) { |
| free (buf->data); |
| buf->data_size = 0; |
| buf->status = _cairo_error (CAIRO_STATUS_NO_MEMORY); |
| return buf->status; |
| } |
| |
| buf->data = new_data; |
| buf->data_size = new_size; |
| |
| return CAIRO_STATUS_SUCCESS; |
| } |
| |
| /* Store the lowest num_bits bits of values into buf. |
| * |
| * Note: The bits of value above size_in_bits must be 0, (so don't lie |
| * about the size). |
| * |
| * See also _lzw_buf_store_pending which must be called after the last |
| * call to _lzw_buf_store_bits. |
| * |
| * Sets buf->status to either %CAIRO_STATUS_SUCCESS or %CAIRO_STATUS_NO_MEMORY. |
| */ |
| static void |
| _lzw_buf_store_bits (lzw_buf_t *buf, uint16_t value, int num_bits) |
| { |
| cairo_status_t status; |
| |
| assert (value <= (1 << num_bits) - 1); |
| |
| if (buf->status) |
| return; |
| |
| buf->pending = (buf->pending << num_bits) | value; |
| buf->pending_bits += num_bits; |
| |
| while (buf->pending_bits >= 8) { |
| if (buf->num_data >= buf->data_size) { |
| status = _lzw_buf_grow (buf); |
| if (unlikely (status)) |
| return; |
| } |
| buf->data[buf->num_data++] = buf->pending >> (buf->pending_bits - 8); |
| buf->pending_bits -= 8; |
| } |
| } |
| |
| /* Store the last remaining pending bits into the buffer. |
| * |
| * Note: This function must be called after the last call to |
| * _lzw_buf_store_bits. |
| * |
| * Sets buf->status to either %CAIRO_STATUS_SUCCESS or %CAIRO_STATUS_NO_MEMORY. |
| */ |
| static void |
| _lzw_buf_store_pending (lzw_buf_t *buf) |
| { |
| cairo_status_t status; |
| |
| if (buf->status) |
| return; |
| |
| if (buf->pending_bits == 0) |
| return; |
| |
| assert (buf->pending_bits < 8); |
| |
| if (buf->num_data >= buf->data_size) { |
| status = _lzw_buf_grow (buf); |
| if (unlikely (status)) |
| return; |
| } |
| |
| buf->data[buf->num_data++] = buf->pending << (8 - buf->pending_bits); |
| buf->pending_bits = 0; |
| } |
| |
| /* LZW defines a few magic code values */ |
| #define LZW_CODE_CLEAR_TABLE 256 |
| #define LZW_CODE_EOD 257 |
| #define LZW_CODE_FIRST 258 |
| |
| /* We pack three separate values into a symbol as follows: |
| * |
| * 12 bits (31 down to 20): CODE: code value used to represent this symbol |
| * 12 bits (19 down to 8): PREV: previous code value in chain |
| * 8 bits ( 7 down to 0): NEXT: next byte value in chain |
| */ |
| typedef uint32_t lzw_symbol_t; |
| |
| #define LZW_SYMBOL_SET(sym, prev, next) ((sym) = ((prev) << 8)|(next)) |
| #define LZW_SYMBOL_SET_CODE(sym, code, prev, next) ((sym) = ((code << 20)|(prev) << 8)|(next)) |
| #define LZW_SYMBOL_GET_CODE(sym) (((sym) >> 20)) |
| #define LZW_SYMBOL_GET_PREV(sym) (((sym) >> 8) & 0x7ff) |
| #define LZW_SYMBOL_GET_BYTE(sym) (((sym) >> 0) & 0x0ff) |
| |
| /* The PREV+NEXT fields can be seen as the key used to fetch values |
| * from the hash table, while the code is the value fetched. |
| */ |
| #define LZW_SYMBOL_KEY_MASK 0x000fffff |
| |
| /* Since code values are only stored starting with 258 we can safely |
| * use a zero value to represent free slots in the hash table. */ |
| #define LZW_SYMBOL_FREE 0x00000000 |
| |
| /* These really aren't very free for modifying. First, the PostScript |
| * specification sets the 9-12 bit range. Second, the encoding of |
| * lzw_symbol_t above also relies on 2 of LZW_BITS_MAX plus one byte |
| * fitting within 32 bits. |
| * |
| * But other than that, the LZW compression scheme could function with |
| * more bits per code. |
| */ |
| #define LZW_BITS_MIN 9 |
| #define LZW_BITS_MAX 12 |
| #define LZW_BITS_BOUNDARY(bits) ((1<<(bits))-1) |
| #define LZW_MAX_SYMBOLS (1<<LZW_BITS_MAX) |
| |
| #define LZW_SYMBOL_TABLE_SIZE 9013 |
| #define LZW_SYMBOL_MOD1 LZW_SYMBOL_TABLE_SIZE |
| #define LZW_SYMBOL_MOD2 9011 |
| |
| typedef struct _lzw_symbol_table { |
| lzw_symbol_t table[LZW_SYMBOL_TABLE_SIZE]; |
| } lzw_symbol_table_t; |
| |
| /* Initialize the hash table to entirely empty */ |
| static void |
| _lzw_symbol_table_init (lzw_symbol_table_t *table) |
| { |
| memset (table->table, 0, LZW_SYMBOL_TABLE_SIZE * sizeof (lzw_symbol_t)); |
| } |
| |
| /* Lookup a symbol in the symbol table. The PREV and NEXT fields of |
| * symbol form the key for the lookup. |
| * |
| * If successful, then this function returns %TRUE and slot_ret will be |
| * left pointing at the result that will have the CODE field of |
| * interest. |
| * |
| * If the lookup fails, then this function returns %FALSE and slot_ret |
| * will be pointing at the location in the table to which a new CODE |
| * value should be stored along with PREV and NEXT. |
| */ |
| static cairo_bool_t |
| _lzw_symbol_table_lookup (lzw_symbol_table_t *table, |
| lzw_symbol_t symbol, |
| lzw_symbol_t **slot_ret) |
| { |
| /* The algorithm here is identical to that in cairo-hash.c. We |
| * copy it here to allow for a rather more efficient |
| * implementation due to several circumstances that do not apply |
| * to the more general case: |
| * |
| * 1) We have a known bound on the total number of symbols, so we |
| * have a fixed-size table without any copying when growing |
| * |
| * 2) We never delete any entries, so we don't need to |
| * support/check for DEAD entries during lookup. |
| * |
| * 3) The object fits in 32 bits so we store each object in its |
| * entirety within the table rather than storing objects |
| * externally and putting pointers in the table, (which here |
| * would just double the storage requirements and have negative |
| * impacts on memory locality). |
| */ |
| int i, idx, step, hash = symbol & LZW_SYMBOL_KEY_MASK; |
| lzw_symbol_t candidate; |
| |
| idx = hash % LZW_SYMBOL_MOD1; |
| step = 0; |
| |
| *slot_ret = NULL; |
| for (i = 0; i < LZW_SYMBOL_TABLE_SIZE; i++) |
| { |
| candidate = table->table[idx]; |
| if (candidate == LZW_SYMBOL_FREE) |
| { |
| *slot_ret = &table->table[idx]; |
| return FALSE; |
| } |
| else /* candidate is LIVE */ |
| { |
| if ((candidate & LZW_SYMBOL_KEY_MASK) == |
| (symbol & LZW_SYMBOL_KEY_MASK)) |
| { |
| *slot_ret = &table->table[idx]; |
| return TRUE; |
| } |
| } |
| |
| if (step == 0) { |
| step = hash % LZW_SYMBOL_MOD2; |
| if (step == 0) |
| step = 1; |
| } |
| |
| idx += step; |
| if (idx >= LZW_SYMBOL_TABLE_SIZE) |
| idx -= LZW_SYMBOL_TABLE_SIZE; |
| } |
| |
| return FALSE; |
| } |
| |
| /* Compress a bytestream using the LZW algorithm. |
| * |
| * This is an original implementation based on reading the |
| * specification of the LZWDecode filter in the PostScript Language |
| * Reference. The free parameters in the LZW algorithm are set to the |
| * values mandated by PostScript, (symbols encoded with widths from 9 |
| * to 12 bits). |
| * |
| * This function returns a pointer to a newly allocated buffer holding |
| * the compressed data, or %NULL if an out-of-memory situation |
| * occurs. |
| * |
| * Notice that any one of the _lzw_buf functions called here could |
| * trigger an out-of-memory condition. But lzw_buf_t uses cairo's |
| * shutdown-on-error idiom, so it's safe to continue to call into |
| * lzw_buf without having to check for errors, (until a final check at |
| * the end). |
| */ |
| unsigned char * |
| _cairo_lzw_compress (unsigned char *data, unsigned long *size_in_out) |
| { |
| int bytes_remaining = *size_in_out; |
| lzw_buf_t buf; |
| lzw_symbol_table_t table; |
| lzw_symbol_t symbol, *slot = NULL; /* just to squelch a warning */ |
| int code_next = LZW_CODE_FIRST; |
| int code_bits = LZW_BITS_MIN; |
| int prev, next = 0; /* just to squelch a warning */ |
| |
| if (*size_in_out == 0) |
| return NULL; |
| |
| _lzw_buf_init (&buf, *size_in_out); |
| |
| _lzw_symbol_table_init (&table); |
| |
| /* The LZW header is a clear table code. */ |
| _lzw_buf_store_bits (&buf, LZW_CODE_CLEAR_TABLE, code_bits); |
| |
| while (1) { |
| |
| /* Find the longest existing code in the symbol table that |
| * matches the current input, if any. */ |
| prev = *data++; |
| bytes_remaining--; |
| if (bytes_remaining) { |
| do |
| { |
| next = *data++; |
| bytes_remaining--; |
| LZW_SYMBOL_SET (symbol, prev, next); |
| if (_lzw_symbol_table_lookup (&table, symbol, &slot)) |
| prev = LZW_SYMBOL_GET_CODE (*slot); |
| } while (bytes_remaining && *slot != LZW_SYMBOL_FREE); |
| if (*slot == LZW_SYMBOL_FREE) { |
| data--; |
| bytes_remaining++; |
| } |
| } |
| |
| /* Write the code into the output. This is either a byte read |
| * directly from the input, or a code from the last successful |
| * lookup. */ |
| _lzw_buf_store_bits (&buf, prev, code_bits); |
| |
| if (bytes_remaining == 0) |
| break; |
| |
| LZW_SYMBOL_SET_CODE (*slot, code_next++, prev, next); |
| |
| if (code_next > LZW_BITS_BOUNDARY(code_bits)) |
| { |
| code_bits++; |
| if (code_bits > LZW_BITS_MAX) { |
| _lzw_symbol_table_init (&table); |
| _lzw_buf_store_bits (&buf, LZW_CODE_CLEAR_TABLE, code_bits - 1); |
| code_bits = LZW_BITS_MIN; |
| code_next = LZW_CODE_FIRST; |
| } |
| } |
| } |
| |
| /* The LZW footer is an end-of-data code. */ |
| _lzw_buf_store_bits (&buf, LZW_CODE_EOD, code_bits); |
| |
| _lzw_buf_store_pending (&buf); |
| |
| /* See if we ever ran out of memory while writing to buf. */ |
| if (buf.status == CAIRO_STATUS_NO_MEMORY) { |
| *size_in_out = 0; |
| return NULL; |
| } |
| |
| assert (buf.status == CAIRO_STATUS_SUCCESS); |
| |
| *size_in_out = buf.num_data; |
| return buf.data; |
| } |