Tristan Matthews | 0a329cc | 2013-07-17 13:20:14 -0400 | [diff] [blame] | 1 | |
| 2 | /****************************************************************** |
| 3 | |
| 4 | iLBC Speech Coder ANSI-C Source Code |
| 5 | |
| 6 | packing.c |
| 7 | |
| 8 | Copyright (C) The Internet Society (2004). |
| 9 | All Rights Reserved. |
| 10 | |
| 11 | ******************************************************************/ |
| 12 | |
| 13 | #include <math.h> |
| 14 | #include <stdlib.h> |
| 15 | |
| 16 | #include "iLBC_define.h" |
| 17 | #include "constants.h" |
| 18 | #include "helpfun.h" |
| 19 | #include "string.h" |
| 20 | |
| 21 | /*----------------------------------------------------------------* |
| 22 | * splitting an integer into first most significant bits and |
| 23 | * remaining least significant bits |
| 24 | *---------------------------------------------------------------*/ |
| 25 | |
| 26 | void packsplit( |
| 27 | int *index, /* (i) the value to split */ |
| 28 | int *firstpart, /* (o) the value specified by most |
| 29 | significant bits */ |
| 30 | int *rest, /* (o) the value specified by least |
| 31 | significant bits */ |
| 32 | |
| 33 | |
| 34 | |
| 35 | |
| 36 | |
| 37 | int bitno_firstpart, /* (i) number of bits in most |
| 38 | significant part */ |
| 39 | int bitno_total /* (i) number of bits in full range |
| 40 | of value */ |
| 41 | ){ |
| 42 | int bitno_rest = bitno_total-bitno_firstpart; |
| 43 | |
| 44 | *firstpart = *index>>(bitno_rest); |
| 45 | *rest = *index-(*firstpart<<(bitno_rest)); |
| 46 | } |
| 47 | |
| 48 | /*----------------------------------------------------------------* |
| 49 | * combining a value corresponding to msb's with a value |
| 50 | * corresponding to lsb's |
| 51 | *---------------------------------------------------------------*/ |
| 52 | |
| 53 | void packcombine( |
| 54 | int *index, /* (i/o) the msb value in the |
| 55 | combined value out */ |
| 56 | int rest, /* (i) the lsb value */ |
| 57 | int bitno_rest /* (i) the number of bits in the |
| 58 | lsb part */ |
| 59 | ){ |
| 60 | *index = *index<<bitno_rest; |
| 61 | *index += rest; |
| 62 | } |
| 63 | |
| 64 | /*----------------------------------------------------------------* |
| 65 | * packing of bits into bitstream, i.e., vector of bytes |
| 66 | *---------------------------------------------------------------*/ |
| 67 | |
| 68 | void dopack( |
| 69 | unsigned char **bitstream, /* (i/o) on entrance pointer to |
| 70 | place in bitstream to pack |
| 71 | new data, on exit pointer |
| 72 | to place in bitstream to |
| 73 | pack future data */ |
| 74 | int index, /* (i) the value to pack */ |
| 75 | int bitno, /* (i) the number of bits that the |
| 76 | value will fit within */ |
| 77 | int *pos /* (i/o) write position in the |
| 78 | current byte */ |
| 79 | ){ |
| 80 | int posLeft; |
| 81 | |
| 82 | /* Clear the bits before starting in a new byte */ |
| 83 | |
| 84 | if ((*pos)==0) { |
| 85 | |
| 86 | |
| 87 | |
| 88 | |
| 89 | |
| 90 | **bitstream=0; |
| 91 | } |
| 92 | |
| 93 | while (bitno>0) { |
| 94 | |
| 95 | /* Jump to the next byte if end of this byte is reached*/ |
| 96 | |
| 97 | if (*pos==8) { |
| 98 | *pos=0; |
| 99 | (*bitstream)++; |
| 100 | **bitstream=0; |
| 101 | } |
| 102 | |
| 103 | posLeft=8-(*pos); |
| 104 | |
| 105 | /* Insert index into the bitstream */ |
| 106 | |
| 107 | if (bitno <= posLeft) { |
| 108 | **bitstream |= (unsigned char)(index<<(posLeft-bitno)); |
| 109 | *pos+=bitno; |
| 110 | bitno=0; |
| 111 | } else { |
| 112 | **bitstream |= (unsigned char)(index>>(bitno-posLeft)); |
| 113 | |
| 114 | *pos=8; |
| 115 | index-=((index>>(bitno-posLeft))<<(bitno-posLeft)); |
| 116 | |
| 117 | bitno-=posLeft; |
| 118 | } |
| 119 | } |
| 120 | } |
| 121 | |
| 122 | /*----------------------------------------------------------------* |
| 123 | * unpacking of bits from bitstream, i.e., vector of bytes |
| 124 | *---------------------------------------------------------------*/ |
| 125 | |
| 126 | void unpack( |
| 127 | unsigned char **bitstream, /* (i/o) on entrance pointer to |
| 128 | place in bitstream to |
| 129 | unpack new data from, on |
| 130 | exit pointer to place in |
| 131 | bitstream to unpack future |
| 132 | data from */ |
| 133 | int *index, /* (o) resulting value */ |
| 134 | int bitno, /* (i) number of bits used to |
| 135 | represent the value */ |
| 136 | int *pos /* (i/o) read position in the |
| 137 | current byte */ |
| 138 | |
| 139 | |
| 140 | |
| 141 | |
| 142 | |
| 143 | ){ |
| 144 | int BitsLeft; |
| 145 | |
| 146 | *index=0; |
| 147 | |
| 148 | while (bitno>0) { |
| 149 | |
| 150 | /* move forward in bitstream when the end of the |
| 151 | byte is reached */ |
| 152 | |
| 153 | if (*pos==8) { |
| 154 | *pos=0; |
| 155 | (*bitstream)++; |
| 156 | } |
| 157 | |
| 158 | BitsLeft=8-(*pos); |
| 159 | |
| 160 | /* Extract bits to index */ |
| 161 | |
| 162 | if (BitsLeft>=bitno) { |
| 163 | *index+=((((**bitstream)<<(*pos)) & 0xFF)>>(8-bitno)); |
| 164 | |
| 165 | *pos+=bitno; |
| 166 | bitno=0; |
| 167 | } else { |
| 168 | |
| 169 | if ((8-bitno)>0) { |
| 170 | *index+=((((**bitstream)<<(*pos)) & 0xFF)>> |
| 171 | (8-bitno)); |
| 172 | *pos=8; |
| 173 | } else { |
| 174 | *index+=(((int)(((**bitstream)<<(*pos)) & 0xFF))<< |
| 175 | (bitno-8)); |
| 176 | *pos=8; |
| 177 | } |
| 178 | bitno-=BitsLeft; |
| 179 | } |
| 180 | } |
| 181 | } |
| 182 | |