1 /**************************************************************************
2 *
3 * Copyright 2011 Christian König.
4 * All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
22 * ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 **************************************************************************/
27
28 /*
29 * Functions for fast bitwise access to multiple probably unaligned input buffers
30 */
31
32 #ifndef vl_vlc_h
33 #define vl_vlc_h
34
35 #include "util/u_math.h"
36
37 struct vl_vlc
38 {
39 uint64_t buffer;
40 signed invalid_bits;
41 const uint8_t *data;
42 const uint8_t *end;
43
44 const void *const *inputs;
45 const unsigned *sizes;
46 unsigned bytes_left;
47 };
48
49 struct vl_vlc_entry
50 {
51 int8_t length;
52 int8_t value;
53 };
54
55 struct vl_vlc_compressed
56 {
57 uint16_t bitcode;
58 struct vl_vlc_entry entry;
59 };
60
61 /**
62 * initalize and decompress a lookup table
63 */
64 static inline void
vl_vlc_init_table(struct vl_vlc_entry * dst,unsigned dst_size,const struct vl_vlc_compressed * src,unsigned src_size)65 vl_vlc_init_table(struct vl_vlc_entry *dst, unsigned dst_size, const struct vl_vlc_compressed *src, unsigned src_size)
66 {
67 unsigned i, bits = util_logbase2(dst_size);
68
69 assert(dst && dst_size);
70 assert(src && src_size);
71
72 for (i=0;i<dst_size;++i) {
73 dst[i].length = 0;
74 dst[i].value = 0;
75 }
76
77 for(; src_size > 0; --src_size, ++src) {
78 for(i = 0; i < (1u << (bits - src->entry.length)); ++i)
79 dst[src->bitcode >> (16 - bits) | i] = src->entry;
80 }
81 }
82
83 /**
84 * switch over to next input buffer
85 */
86 static inline void
vl_vlc_next_input(struct vl_vlc * vlc)87 vl_vlc_next_input(struct vl_vlc *vlc)
88 {
89 unsigned len = vlc->sizes[0];
90
91 assert(vlc);
92 assert(vlc->bytes_left);
93
94 if (len < vlc->bytes_left)
95 vlc->bytes_left -= len;
96 else {
97 len = vlc->bytes_left;
98 vlc->bytes_left = 0;
99 }
100
101 vlc->data = (const uint8_t *) vlc->inputs[0];
102 vlc->end = vlc->data + len;
103
104 ++vlc->inputs;
105 ++vlc->sizes;
106 }
107
108 /**
109 * align the data pointer to the next dword
110 */
111 static inline void
vl_vlc_align_data_ptr(struct vl_vlc * vlc)112 vl_vlc_align_data_ptr(struct vl_vlc *vlc)
113 {
114 /* align the data pointer */
115 while (vlc->data != vlc->end && ((uintptr_t)vlc->data) & 3) {
116 vlc->buffer |= (uint64_t)*vlc->data << (24 + vlc->invalid_bits);
117 ++vlc->data;
118 vlc->invalid_bits -= 8;
119 }
120 }
121
122 /**
123 * fill the bit buffer, so that at least 32 bits are valid
124 */
125 static inline void
vl_vlc_fillbits(struct vl_vlc * vlc)126 vl_vlc_fillbits(struct vl_vlc *vlc)
127 {
128 assert(vlc);
129
130 /* as long as the buffer needs to be filled */
131 while (vlc->invalid_bits > 0) {
132 unsigned bytes_left = vlc->end - vlc->data;
133
134 /* if this input is depleted */
135 if (bytes_left == 0) {
136
137 if (vlc->bytes_left) {
138 /* go on to next input */
139 vl_vlc_next_input(vlc);
140 vl_vlc_align_data_ptr(vlc);
141 } else
142 /* or give up since we don't have anymore inputs */
143 return;
144
145 } else if (bytes_left >= 4) {
146
147 /* enough bytes in buffer, read in a whole dword */
148 uint64_t value = *(const uint32_t*)vlc->data;
149
150 #if !UTIL_ARCH_BIG_ENDIAN
151 value = util_bswap32(value);
152 #endif
153
154 vlc->buffer |= value << vlc->invalid_bits;
155 vlc->data += 4;
156 vlc->invalid_bits -= 32;
157
158 /* buffer is now definitely filled up avoid the loop test */
159 break;
160
161 } else while (vlc->data < vlc->end) {
162
163 /* not enough bytes left in buffer, read single bytes */
164 vlc->buffer |= (uint64_t)*vlc->data << (24 + vlc->invalid_bits);
165 ++vlc->data;
166 vlc->invalid_bits -= 8;
167 }
168 }
169 }
170
171 /**
172 * initialize vlc structure and start reading from first input buffer
173 */
174 static inline void
vl_vlc_init(struct vl_vlc * vlc,unsigned num_inputs,const void * const * inputs,const unsigned * sizes)175 vl_vlc_init(struct vl_vlc *vlc, unsigned num_inputs,
176 const void *const *inputs, const unsigned *sizes)
177 {
178 unsigned i;
179
180 assert(vlc);
181 assert(num_inputs);
182
183 vlc->buffer = 0;
184 vlc->invalid_bits = 32;
185 vlc->inputs = inputs;
186 vlc->sizes = sizes;
187 vlc->bytes_left = 0;
188 vlc->data = NULL;
189 vlc->end = NULL;
190
191 for (i = 0; i < num_inputs; ++i)
192 vlc->bytes_left += sizes[i];
193
194 if (vlc->bytes_left) {
195 vl_vlc_next_input(vlc);
196 vl_vlc_align_data_ptr(vlc);
197 vl_vlc_fillbits(vlc);
198 }
199 }
200
201 /**
202 * number of bits still valid in bit buffer
203 */
204 static inline unsigned
vl_vlc_valid_bits(struct vl_vlc * vlc)205 vl_vlc_valid_bits(struct vl_vlc *vlc)
206 {
207 return 32 - vlc->invalid_bits;
208 }
209
210 /**
211 * number of bits left over all inbut buffers
212 */
213 static inline unsigned
vl_vlc_bits_left(struct vl_vlc * vlc)214 vl_vlc_bits_left(struct vl_vlc *vlc)
215 {
216 signed bytes_left = vlc->end - vlc->data;
217 bytes_left += vlc->bytes_left;
218 return bytes_left * 8 + vl_vlc_valid_bits(vlc);
219 }
220
221 /**
222 * get num_bits from bit buffer without removing them
223 */
224 static inline unsigned
vl_vlc_peekbits(struct vl_vlc * vlc,unsigned num_bits)225 vl_vlc_peekbits(struct vl_vlc *vlc, unsigned num_bits)
226 {
227 assert(vl_vlc_valid_bits(vlc) >= num_bits || vlc->data >= vlc->end);
228 return vlc->buffer >> (64 - num_bits);
229 }
230
231 /**
232 * remove num_bits from bit buffer
233 */
234 static inline void
vl_vlc_eatbits(struct vl_vlc * vlc,unsigned num_bits)235 vl_vlc_eatbits(struct vl_vlc *vlc, unsigned num_bits)
236 {
237 assert(vl_vlc_valid_bits(vlc) >= num_bits);
238
239 vlc->buffer <<= num_bits;
240 vlc->invalid_bits += num_bits;
241 }
242
243 /**
244 * get num_bits from bit buffer with removing them
245 */
246 static inline unsigned
vl_vlc_get_uimsbf(struct vl_vlc * vlc,unsigned num_bits)247 vl_vlc_get_uimsbf(struct vl_vlc *vlc, unsigned num_bits)
248 {
249 unsigned value;
250
251 assert(vl_vlc_valid_bits(vlc) >= num_bits);
252
253 value = vlc->buffer >> (64 - num_bits);
254 vl_vlc_eatbits(vlc, num_bits);
255
256 return value;
257 }
258
259 /**
260 * treat num_bits as signed value and remove them from bit buffer
261 */
262 static inline signed
vl_vlc_get_simsbf(struct vl_vlc * vlc,unsigned num_bits)263 vl_vlc_get_simsbf(struct vl_vlc *vlc, unsigned num_bits)
264 {
265 signed value;
266
267 assert(vl_vlc_valid_bits(vlc) >= num_bits);
268
269 value = ((int64_t)vlc->buffer) >> (64 - num_bits);
270 vl_vlc_eatbits(vlc, num_bits);
271
272 return value;
273 }
274
275 /**
276 * lookup a value and length in a decompressed table
277 */
278 static inline int8_t
vl_vlc_get_vlclbf(struct vl_vlc * vlc,const struct vl_vlc_entry * tbl,unsigned num_bits)279 vl_vlc_get_vlclbf(struct vl_vlc *vlc, const struct vl_vlc_entry *tbl, unsigned num_bits)
280 {
281 tbl += vl_vlc_peekbits(vlc, num_bits);
282 vl_vlc_eatbits(vlc, tbl->length);
283 return tbl->value;
284 }
285
286 /**
287 * fast forward search for a specific byte value
288 */
289 static inline bool
vl_vlc_search_byte(struct vl_vlc * vlc,unsigned num_bits,uint8_t value)290 vl_vlc_search_byte(struct vl_vlc *vlc, unsigned num_bits, uint8_t value)
291 {
292 /* make sure we are on a byte boundary */
293 assert((vl_vlc_valid_bits(vlc) % 8) == 0);
294 assert(num_bits == ~0u || (num_bits % 8) == 0);
295
296 /* deplete the bit buffer */
297 while (vl_vlc_valid_bits(vlc) > 0) {
298
299 if (vl_vlc_peekbits(vlc, 8) == value) {
300 vl_vlc_fillbits(vlc);
301 return true;
302 }
303
304 vl_vlc_eatbits(vlc, 8);
305
306 if (num_bits != ~0u) {
307 num_bits -= 8;
308 if (num_bits == 0)
309 return false;
310 }
311 }
312
313 /* deplete the byte buffers */
314 while (1) {
315
316 /* if this input is depleted */
317 if (vlc->data == vlc->end) {
318 if (vlc->bytes_left)
319 /* go on to next input */
320 vl_vlc_next_input(vlc);
321 else
322 /* or give up since we don't have anymore inputs */
323 return false;
324 }
325
326 if (*vlc->data == value) {
327 vl_vlc_align_data_ptr(vlc);
328 vl_vlc_fillbits(vlc);
329 return true;
330 }
331
332 ++vlc->data;
333 if (num_bits != ~0u) {
334 num_bits -= 8;
335 if (num_bits == 0) {
336 vl_vlc_align_data_ptr(vlc);
337 return false;
338 }
339 }
340 }
341 }
342
343 /**
344 * remove num_bits bits starting at pos from the bitbuffer
345 */
346 static inline void
vl_vlc_removebits(struct vl_vlc * vlc,unsigned pos,unsigned num_bits)347 vl_vlc_removebits(struct vl_vlc *vlc, unsigned pos, unsigned num_bits)
348 {
349 #if defined(_MSC_VER)
350 /* MSVC Compiler defines unsigned long as 4 bytes so use explicit 64 bits mask */
351 uint64_t lo = (vlc->buffer & (UINT64_MAX >> (pos + num_bits))) << num_bits;
352 uint64_t hi = (vlc->buffer & (UINT64_MAX << (64 - pos)));
353 #else
354 uint64_t lo = (vlc->buffer & (~0UL >> (pos + num_bits))) << num_bits;
355 uint64_t hi = (vlc->buffer & (~0UL << (64 - pos)));
356 #endif
357 vlc->buffer = lo | hi;
358 vlc->invalid_bits += num_bits;
359 }
360
361 /**
362 * limit the number of bits left for fetching
363 */
364 static inline void
vl_vlc_limit(struct vl_vlc * vlc,unsigned bits_left)365 vl_vlc_limit(struct vl_vlc *vlc, unsigned bits_left)
366 {
367 assert(bits_left <= vl_vlc_bits_left(vlc));
368
369 vl_vlc_fillbits(vlc);
370 if (bits_left < vl_vlc_valid_bits(vlc)) {
371 vlc->invalid_bits = 32 - bits_left;
372 vlc->buffer &= ~0L << (vlc->invalid_bits + 32);
373 vlc->end = vlc->data;
374 vlc->bytes_left = 0;
375 } else {
376 assert((bits_left - vl_vlc_valid_bits(vlc)) % 8 == 0);
377 vlc->bytes_left = (bits_left - vl_vlc_valid_bits(vlc)) / 8;
378 if (vlc->bytes_left < (vlc->end - vlc->data)) {
379 vlc->end = vlc->data + vlc->bytes_left;
380 vlc->bytes_left = 0;
381 } else
382 vlc->bytes_left -= vlc->end - vlc->data;
383 }
384 }
385
386 #endif /* vl_vlc_h */
387