src/gallium/auxiliary/vl/vl_vlc.h

   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 TUNGSTEN GRAPHICS 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 "pipe/p_compiler.h"
  36
  37 #include "util/u_math.h"
  38 #include "util/u_pointer.h"
  39 #include "util/u_debug.h"
  40
  41 struct vl_vlc
  42 {
  43    uint64_t buffer;
  44    signed invalid_bits;
  45    const uint8_t *data;
  46    const uint8_t *end;
  47
  48    unsigned          num_inputs;
  49    const void *const *inputs;
  50    const unsigned    *sizes;
  51    unsigned          bytes_left;
  52 };
  53
  54 struct vl_vlc_entry
  55 {
  56    int8_t length;
  57    int8_t value;
  58 };
  59
  60 struct vl_vlc_compressed
  61 {
  62    uint16_t bitcode;
  63    struct vl_vlc_entry entry;
  64 };
  65
  66 /**
  67  * initalize and decompress a lookup table
  68  */
  69 static INLINE void
  70 vl_vlc_init_table(struct vl_vlc_entry *dst, unsigned dst_size, const struct vl_vlc_compressed *src, unsigned src_size)
  71 {
  72    unsigned i, bits = util_logbase2(dst_size);
  73
  74    assert(dst && dst_size);
  75    assert(src && src_size);
  76
  77    for (i=0;i<dst_size;++i) {
  78       dst[i].length = 0;
  79       dst[i].value = 0;
  80    }
  81
  82    for(; src_size > 0; --src_size, ++src) {
  83       for(i=0; i<(1 << (bits - src->entry.length)); ++i)
  84          dst[src->bitcode >> (16 - bits) | i] = src->entry;
  85    }
  86 }
  87
  88 /**
  89  * switch over to next input buffer
  90  */
  91 static INLINE void
  92 vl_vlc_next_input(struct vl_vlc *vlc)
  93 {
  94    const uint8_t* data = vlc->inputs[0];
  95    unsigned len = vlc->sizes[0];
  96
  97    assert(vlc);
  98    assert(vlc->num_inputs);
  99
 100    vlc->bytes_left -= len;
 101
 102    /* align the data pointer */
 103    while (len && pointer_to_uintptr(data) & 3) {
 104       vlc->buffer |= (uint64_t)*data << (24 + vlc->invalid_bits);
 105       ++data;
 106       --len;
 107       vlc->invalid_bits -= 8;
 108    }
 109    vlc->data = data;
 110    vlc->end = data + len;
 111
 112    --vlc->num_inputs;
 113    ++vlc->inputs;
 114    ++vlc->sizes;
 115 }
 116
 117 /**
 118  * fill the bit buffer, so that at least 32 bits are valid
 119  */
 120 static INLINE void
 121 vl_vlc_fillbits(struct vl_vlc *vlc)
 122 {
 123    assert(vlc);
 124
 125    /* as long as the buffer needs to be filled */
 126    while (vlc->invalid_bits > 0) {
 127       unsigned bytes_left = vlc->end - vlc->data;
 128
 129       /* if this input is depleted */
 130       if (bytes_left == 0) {
 131
 132          if (vlc->num_inputs)
 133             /* go on to next input */
 134             vl_vlc_next_input(vlc);
 135          else
 136             /* or give up since we don't have anymore inputs */
 137             return;
 138
 139       } else if (bytes_left >= 4) {
 140
 141          /* enough bytes in buffer, read in a whole dword */
 142          uint64_t value = *(const uint32_t*)vlc->data;
 143
 144 #ifndef PIPE_ARCH_BIG_ENDIAN
 145          value = util_bswap32(value);
 146 #endif
 147
 148          vlc->buffer |= value << vlc->invalid_bits;
 149          vlc->data += 4;
 150          vlc->invalid_bits -= 32;
 151
 152          /* buffer is now definitely filled up avoid the loop test */
 153          break;
 154
 155       } else while (vlc->data < vlc->end) {
 156
 157          /* not enough bytes left in buffer, read single bytes */
 158          vlc->buffer |= (uint64_t)*vlc->data << (24 + vlc->invalid_bits);
 159          ++vlc->data;
 160          vlc->invalid_bits -= 8;
 161       }
 162    }
 163 }
 164
 165 /**
 166  * initialize vlc structure and start reading from first input buffer
 167  */
 168 static INLINE void
 169 vl_vlc_init(struct vl_vlc *vlc, unsigned num_inputs,
 170             const void *const *inputs, const unsigned *sizes)
 171 {
 172    unsigned i;
 173
 174    assert(vlc);
 175    assert(num_inputs);
 176
 177    vlc->buffer = 0;
 178    vlc->invalid_bits = 32;
 179    vlc->num_inputs = num_inputs;
 180    vlc->inputs = inputs;
 181    vlc->sizes = sizes;
 182    vlc->bytes_left = 0;
 183
 184    for (i = 0; i < num_inputs; ++i)
 185       vlc->bytes_left += sizes[i];
 186
 187    vl_vlc_next_input(vlc);
 188    vl_vlc_fillbits(vlc);
 189    vl_vlc_fillbits(vlc);
 190 }
 191
 192 /**
 193  * number of bits still valid in bit buffer
 194  */
 195 static INLINE unsigned
 196 vl_vlc_valid_bits(struct vl_vlc *vlc)
 197 {
 198    return 32 - vlc->invalid_bits;
 199 }
 200
 201 /**
 202  * number of bits left over all inbut buffers
 203  */
 204 static INLINE unsigned
 205 vl_vlc_bits_left(struct vl_vlc *vlc)
 206 {
 207    signed bytes_left = vlc->end - vlc->data;
 208    bytes_left += vlc->bytes_left;
 209    return bytes_left * 8 + vl_vlc_valid_bits(vlc);
 210 }
 211
 212 /**
 213  * get num_bits from bit buffer without removing them
 214  */
 215 static INLINE unsigned
 216 vl_vlc_peekbits(struct vl_vlc *vlc, unsigned num_bits)
 217 {
 218    assert(vl_vlc_valid_bits(vlc) >= num_bits || vlc->data >= vlc->end);
 219    return vlc->buffer >> (64 - num_bits);
 220 }
 221
 222 /**
 223  * remove num_bits from bit buffer
 224  */
 225 static INLINE void
 226 vl_vlc_eatbits(struct vl_vlc *vlc, unsigned num_bits)
 227 {
 228    assert(vl_vlc_valid_bits(vlc) >= num_bits);
 229
 230    vlc->buffer <<= num_bits;
 231    vlc->invalid_bits += num_bits;
 232 }
 233
 234 /**
 235  * get num_bits from bit buffer with removing them
 236  */
 237 static INLINE unsigned
 238 vl_vlc_get_uimsbf(struct vl_vlc *vlc, unsigned num_bits)
 239 {
 240    unsigned value;
 241
 242    assert(vl_vlc_valid_bits(vlc) >= num_bits);
 243
 244    value = vlc->buffer >> (64 - num_bits);
 245    vl_vlc_eatbits(vlc, num_bits);
 246
 247    return value;
 248 }
 249
 250 /**
 251  * treat num_bits as signed value and remove them from bit buffer
 252  */
 253 static INLINE signed
 254 vl_vlc_get_simsbf(struct vl_vlc *vlc, unsigned num_bits)
 255 {
 256    signed value;
 257
 258    assert(vl_vlc_valid_bits(vlc) >= num_bits);
 259
 260    value = ((int64_t)vlc->buffer) >> (64 - num_bits);
 261    vl_vlc_eatbits(vlc, num_bits);
 262
 263    return value;
 264 }
 265
 266 /**
 267  * lookup a value and length in a decompressed table
 268  */
 269 static INLINE int8_t
 270 vl_vlc_get_vlclbf(struct vl_vlc *vlc, const struct vl_vlc_entry *tbl, unsigned num_bits)
 271 {
 272    tbl += vl_vlc_peekbits(vlc, num_bits);
 273    vl_vlc_eatbits(vlc, tbl->length);
 274    return tbl->value;
 275 }
 276
 277 #endif /* vl_vlc_h */