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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 1905 | serge | 1 | /* |
| 2 | getbits |
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| 3 | |||
| 4 | copyright ?-2009 by the mpg123 project - free software under the terms of the LGPL 2.1 |
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| 5 | see COPYING and AUTHORS files in distribution or http://mpg123.org |
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| 6 | initially written by Michael Hipp |
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| 7 | |||
| 8 | All code is in the header to suggest/force inlining of these small often-used functions. |
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| 9 | This indeed has some impact on performance. |
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| 10 | */ |
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| 11 | |||
| 12 | #ifndef _MPG123_GETBITS_H_ |
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| 13 | #define _MPG123_GETBITS_H_ |
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| 14 | |||
| 15 | #include "mpg123lib_intern.h" |
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| 16 | |||
| 17 | #define backbits(fr,nob) ((void)( \ |
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| 18 | fr->bitindex -= nob, \ |
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| 19 | fr->wordpointer += (fr->bitindex>>3), \ |
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| 20 | fr->bitindex &= 0x7 )) |
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| 21 | |||
| 22 | #define getbitoffset(fr) ((-fr->bitindex)&0x7) |
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| 23 | #define getbyte(fr) (*fr->wordpointer++) |
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| 24 | |||
| 25 | /* There is something wrong with that macro... the function below works also for the layer1 test case. */ |
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| 26 | #define macro_getbits(fr, nob) ( \ |
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| 27 | fr->ultmp = fr->wordpointer[0],\ |
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| 28 | fr->ultmp <<= 8, \ |
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| 29 | fr->ultmp |= fr->wordpointer[1], \ |
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| 30 | fr->ultmp <<= 8, \ |
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| 31 | fr->ultmp |= fr->wordpointer[2], \ |
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| 32 | fr->ultmp <<= fr->bitindex, \ |
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| 33 | fr->ultmp &= 0xffffff, \ |
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| 34 | fr->bitindex += nob, \ |
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| 35 | fr->ultmp >>= (24-nob), \ |
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| 36 | fr->wordpointer += (fr->bitindex>>3), \ |
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| 37 | fr->bitindex &= 7, \ |
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| 38 | fr->ultmp) |
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| 39 | |||
| 40 | static unsigned int getbits(mpg123_handle *fr, int number_of_bits) |
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| 41 | { |
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| 42 | unsigned long rval; |
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| 43 | |||
| 44 | #ifdef DEBUG_GETBITS |
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| 45 | fprintf(stderr,"g%d",number_of_bits); |
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| 46 | #endif |
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| 47 | |||
| 48 | /* This is actually slow: if(!number_of_bits) |
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| 49 | return 0; */ |
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| 50 | |||
| 51 | #if 0 |
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| 52 | check_buffer_range(number_of_bits+fr->bitindex); |
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| 53 | #endif |
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| 54 | |||
| 55 | { |
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| 56 | rval = fr->wordpointer[0]; |
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| 57 | rval <<= 8; |
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| 58 | rval |= fr->wordpointer[1]; |
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| 59 | rval <<= 8; |
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| 60 | rval |= fr->wordpointer[2]; |
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| 61 | |||
| 62 | rval <<= fr->bitindex; |
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| 63 | rval &= 0xffffff; |
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| 64 | |||
| 65 | fr->bitindex += number_of_bits; |
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| 66 | |||
| 67 | rval >>= (24-number_of_bits); |
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| 68 | |||
| 69 | fr->wordpointer += (fr->bitindex>>3); |
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| 70 | fr->bitindex &= 7; |
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| 71 | } |
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| 72 | |||
| 73 | #ifdef DEBUG_GETBITS |
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| 74 | fprintf(stderr,":%lx\n",rval); |
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| 75 | #endif |
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| 76 | |||
| 77 | return rval; |
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| 78 | } |
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| 79 | |||
| 80 | |||
| 81 | #define skipbits(fr, nob) fr->ultmp = ( \ |
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| 82 | fr->ultmp = fr->wordpointer[0], fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[1], \ |
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| 83 | fr->ultmp <<= 8, fr->ultmp |= fr->wordpointer[2], fr->ultmp <<= fr->bitindex, \ |
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| 84 | fr->ultmp &= 0xffffff, fr->bitindex += nob, \ |
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| 85 | fr->ultmp >>= (24-nob), fr->wordpointer += (fr->bitindex>>3), \ |
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| 86 | fr->bitindex &= 7 ) |
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| 87 | |||
| 88 | #define getbits_fast(fr, nob) ( \ |
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| 89 | fr->ultmp = (unsigned char) (fr->wordpointer[0] << fr->bitindex), \ |
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| 90 | fr->ultmp |= ((unsigned long) fr->wordpointer[1]< |
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| 91 | fr->ultmp <<= nob, fr->ultmp >>= 8, \ |
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| 92 | fr->bitindex += nob, fr->wordpointer += (fr->bitindex>>3), \ |
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| 93 | fr->bitindex &= 7, fr->ultmp ) |
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| 94 | |||
| 95 | #define get1bit(fr) ( \ |
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| 96 | fr->uctmp = *fr->wordpointer << fr->bitindex, fr->bitindex++, \ |
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| 97 | fr->wordpointer += (fr->bitindex>>3), fr->bitindex &= 7, fr->uctmp>>7 ) |
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| 98 | |||
| 99 | |||
| 100 | #endif |