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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 6 | lvd | 1 | #include <avr/io.h> |
| 2 | #include <avr/pgmspace.h> |
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| 129 | chrv | 3 | |
| 4 | #include "mytypes.h" |
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| 5 | #include "main.h" |
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| 6 | lvd | 6 | #include "depacker_dirty.h" |
| 7 | |||
| 8 | |||
| 9 | UWORD dbpos; // current position in buffer (wrappable) |
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| 10 | |||
| 11 | UBYTE bitstream; |
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| 12 | UBYTE bitcount; |
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| 13 | |||
| 14 | void depacker_dirty(void) |
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| 15 | { |
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| 16 | UBYTE j; |
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| 17 | |||
| 18 | UBYTE bits; |
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| 19 | WORD disp; |
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| 20 | |||
| 21 | |||
| 22 | dbpos=0; |
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| 23 | |||
| 24 | // get first byte of packed file and write to output |
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| 25 | put_byte(NEXT_BYTE); |
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| 26 | |||
| 27 | |||
| 28 | // second byte goes to bitstream |
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| 29 | bitstream=NEXT_BYTE; |
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| 30 | bitcount=8; |
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| 31 | |||
| 32 | |||
| 33 | // actual depacking loop! |
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| 34 | do |
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| 35 | { |
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| 36 | j=0; |
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| 37 | |||
| 38 | // get 1st bit - either OUTBYTE or beginning of LZ code |
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| 39 | if( get_bits_dirty(1) ) |
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| 40 | { // OUTBYTE |
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| 41 | put_byte(NEXT_BYTE); |
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| 42 | } |
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| 43 | else |
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| 44 | { // LZ code |
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| 45 | switch( get_bits_dirty(2) ) |
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| 46 | { |
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| 47 | case 0: // 000 |
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| 48 | repeat( 0xFFF8|get_bits_dirty(3) ,1); |
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| 49 | break; |
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| 50 | case 1: // 001 |
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| 51 | repeat( 0xFF00|NEXT_BYTE ,2); |
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| 52 | break; |
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| 53 | case 2: // 010 |
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| 54 | repeat(get_bigdisp_dirty(),3); |
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| 55 | break; |
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| 56 | case 3: // 011 |
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| 57 | // extract num of length bits |
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| 58 | do j++; while( !get_bits_dirty(1) ); |
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| 59 | |||
| 60 | if( j<8 ) // check for exit code |
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| 61 | { |
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| 62 | // get length bits itself |
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| 63 | bits=get_bits_dirty(j); |
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| 64 | disp=get_bigdisp_dirty(); |
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| 65 | repeat(disp,2+(1<<j)+bits); |
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| 66 | } |
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| 67 | break; |
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| 68 | } |
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| 69 | } |
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| 70 | |||
| 71 | } while( j<8 ); |
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| 72 | |||
| 73 | |||
| 74 | if( (DBMASK&dbpos) ) |
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| 75 | { |
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| 76 | put_buffer(DBMASK&dbpos); |
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| 77 | } |
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| 78 | |||
| 79 | } |
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| 80 | |||
| 81 | |||
| 82 | |||
| 83 | |||
| 84 | void repeat(WORD disp,UBYTE len) |
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| 85 | { // repeat len bytes with disp displacement (negative) |
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| 86 | // uses dbpos & dbuf |
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| 87 | |||
| 88 | UBYTE i; // since length is no more than 255 |
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| 89 | |||
| 90 | for(i=0;i<len;i++) |
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| 91 | { |
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| 92 | put_byte(dbuf[DBMASK&(dbpos+disp)]); |
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| 93 | } |
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| 94 | } |
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| 95 | |||
| 96 | |||
| 97 | |||
| 98 | |||
| 99 | void put_byte(UBYTE byte) |
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| 100 | { |
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| 101 | dbuf[dbpos]=byte; |
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| 102 | dbpos = DBMASK & (dbpos+1); |
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| 103 | |||
| 104 | if( !dbpos ) |
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| 105 | { |
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| 106 | put_buffer(DBSIZE); |
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| 107 | } |
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| 108 | } |
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| 109 | |||
| 110 | |||
| 111 | UBYTE get_bits_dirty(UBYTE numbits) |
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| 112 | { // gets bits in a byte-wise style, no checks |
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| 113 | // numbits must be >0 |
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| 114 | |||
| 115 | UBYTE bits; |
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| 116 | |||
| 117 | bits=0; |
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| 118 | |||
| 119 | do |
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| 120 | { |
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| 121 | if( !(bitcount--) ) |
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| 122 | { |
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| 123 | bitcount=7; |
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| 124 | bitstream=NEXT_BYTE; |
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| 125 | } |
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| 126 | |||
| 127 | bits = (bits<<1)|(bitstream>>7); // all shifts byte-wise |
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| 128 | bitstream<<=1; |
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| 129 | |||
| 130 | } while (--numbits); |
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| 131 | |||
| 132 | return bits; |
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| 133 | } |
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| 134 | |||
| 135 | WORD get_bigdisp_dirty(void) |
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| 136 | { // fetches 'big' displacement (-1..-4352) |
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| 137 | // returns negative displacement |
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| 138 | |||
| 139 | UBYTE bits; |
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| 140 | |||
| 141 | if( get_bits_dirty(1) ) |
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| 142 | { // longer displacement |
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| 143 | bits=get_bits_dirty(4); |
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| 144 | return (((0xF0|bits)-1)<<8)|NEXT_BYTE; |
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| 145 | } |
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| 146 | else |
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| 147 | { // shorter displacement |
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| 148 | return 0xFF00|NEXT_BYTE; |
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| 149 | } |
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| 150 | } |
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| 151 |