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2 /******************************************************************
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3
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4 iLBC Speech Coder ANSI-C Source Code
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5
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6 packing.c
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7
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8 Copyright (C) The Internet Society (2004).
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9 All Rights Reserved.
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10
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11 ******************************************************************/
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12
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13 #include <math.h>
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14 #include <stdlib.h>
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15
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16 #include "iLBC_define.h"
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17 #include "constants.h"
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18 #include "helpfun.h"
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19 #include "string.h"
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20
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21 /*----------------------------------------------------------------*
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22 * splitting an integer into first most significant bits and
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23 * remaining least significant bits
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24 *---------------------------------------------------------------*/
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25
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26 void packsplit(int *index, /* (i) the value to split */
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27 int *firstpart, /* (o) the value specified by most
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28 significant bits */
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29 int *rest, /* (o) the value specified by least
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30 significant bits */
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31 int bitno_firstpart, /* (i) number of bits in most
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32 significant part */
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33 int bitno_total /* (i) number of bits in full range
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34 of value */
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35 )
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36 {
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37 int bitno_rest = bitno_total - bitno_firstpart;
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38
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39 *firstpart = *index >> (bitno_rest);
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40 *rest = *index - (*firstpart << (bitno_rest));
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41 }
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42
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43 /*----------------------------------------------------------------*
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44 * combining a value corresponding to msb's with a value
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45 * corresponding to lsb's
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46 *---------------------------------------------------------------*/
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47
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48 void packcombine(int *index, /* (i/o) the msb value in the
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49 combined value out */
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50 int rest, /* (i) the lsb value */
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51 int bitno_rest /* (i) the number of bits in the
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52 lsb part */
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53 )
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54 {
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55 *index = *index << bitno_rest;
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56 *index += rest;
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57 }
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58
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59 /*----------------------------------------------------------------*
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60 * packing of bits into bitstream, i.e., vector of bytes
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61 *---------------------------------------------------------------*/
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62
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63 void dopack(unsigned char **bitstream, /* (i/o) on entrance pointer to
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64 place in bitstream to pack
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65 new data, on exit pointer
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66 to place in bitstream to
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67 pack future data */
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68 int index, /* (i) the value to pack */
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69 int bitno, /* (i) the number of bits that the
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70 value will fit within */
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71 int *pos /* (i/o) write position in the
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72 current byte */
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73 )
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74 {
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75 int posLeft;
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76
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77 /* Clear the bits before starting in a new byte */
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78
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79 if ((*pos) == 0) {
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80
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81
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82
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83
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84
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85 **bitstream = 0;
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86 }
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87
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88 while (bitno > 0) {
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89
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90 /* Jump to the next byte if end of this byte is reached */
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91
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92 if (*pos == 8) {
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93 *pos = 0;
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94 (*bitstream)++;
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95 **bitstream = 0;
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96 }
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97
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98 posLeft = 8 - (*pos);
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99
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100 /* Insert index into the bitstream */
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101
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102 if (bitno <= posLeft) {
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103 **bitstream |= (unsigned char) (index << (posLeft - bitno));
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104 *pos += bitno;
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105 bitno = 0;
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106 } else {
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107 **bitstream |= (unsigned char) (index >> (bitno - posLeft));
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108
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109 *pos = 8;
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110 index -= ((index >> (bitno - posLeft)) << (bitno - posLeft));
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111
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112 bitno -= posLeft;
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113 }
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114 }
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115 }
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116
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117 /*----------------------------------------------------------------*
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118 * unpacking of bits from bitstream, i.e., vector of bytes
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119 *---------------------------------------------------------------*/
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120
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121 void unpack(unsigned char **bitstream, /* (i/o) on entrance pointer to
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122 place in bitstream to
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123 unpack new data from, on
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124 exit pointer to place in
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125 bitstream to unpack future
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126 data from */
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127 int *index, /* (o) resulting value */
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128 int bitno, /* (i) number of bits used to
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129 represent the value */
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130 int *pos /* (i/o) read position in the
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131 current byte */
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132 )
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133 {
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134 int BitsLeft;
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135
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136 *index = 0;
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137
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138 while (bitno > 0) {
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139
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140 /* move forward in bitstream when the end of the
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141 byte is reached */
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142
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143 if (*pos == 8) {
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144 *pos = 0;
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145 (*bitstream)++;
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146 }
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147
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148 BitsLeft = 8 - (*pos);
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149
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150 /* Extract bits to index */
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151
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152 if (BitsLeft >= bitno) {
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153 *index += ((((**bitstream) << (*pos)) & 0xFF) >> (8 - bitno));
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154
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155 *pos += bitno;
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156 bitno = 0;
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157 } else {
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158
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159 if ((8 - bitno) > 0) {
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160 *index += ((((**bitstream) << (*pos)) & 0xFF) >> (8 - bitno));
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161 *pos = 8;
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162 } else {
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163 *index += (((int) (((**bitstream) << (*pos)) & 0xFF)) <<
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164 (bitno - 8));
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165 *pos = 8;
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166 }
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167 bitno -= BitsLeft;
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168 }
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169 }
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170 }
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