source: buchla-68k/lib700/mangle.c@ 7c5def4

Last change on this file since 7c5def4 was b28a12e, checked in by Thomas Lopatic <thomas@…>, 7 years ago

Zero redundant declarations.

  • Property mode set to 100644
File size: 1.5 KB
Line 
1/*
2 =============================================================================
3 mangle.c -- mangle a bit stream
4 Version 2 -- 1987-08-28 -- D.N. Lynx Crowe
5 (c) Copyright 1987 - D.N. Lynx Crowe
6 =============================================================================
7*/
8
9/*
10 =============================================================================
11 mangle(bitmap, nb, ib) -- reorder the 'nb' least significant bits
12 in 'ib' according to 'bitmap'. Assumes that 'bitmap' is at least 'nb'
13 words long, and that nb <= 32. The 'bitmap' translation table contains
14 an output word for each bit in the input word, with each 'bitmap' entry
15 corresponding to the bit number matching its index. For example,
16 'bitmap[0]' contains the word which will be 'OR'ed into the output if
17 the least significant bit of the input word is set, while 'bitmap[31]'
18 corresponds to the most significant bit of the input word.
19 =============================================================================
20*/
21
22#include "ram.h"
23
24int32_t mangle(int32_t *bitmap, int16_t nb, int32_t ib)
25{
26 register int32_t bm; /* scan mask */
27 register int32_t rv; /* result value */
28 register int16_t bn; /* bit number (bitmap index) */
29
30 bm = 0x00000001L; /* setup scan mask */
31 rv = 0x00000000L; /* clear the output word */
32
33 for (bn = 0; bn < nb; bn++) { /* scan across nb bits */
34
35 if (ib & bm) /* if the input bit is 1 */
36 rv |= bitmap[bn]; /* 'OR' the bitmap into rv */
37
38 bm <<= 1; /* shift the scan mask left */
39 }
40
41 return(rv); /* return rv as the result */
42}
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