source: buchla-68k/ram/dec2fr.c@ 46d8069

Last change on this file since 46d8069 was f40a309, checked in by Thomas Lopatic <thomas@…>, 7 years ago

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1/*
2 =============================================================================
3 dec2fr.c -- Buchla 700 fractional 2's complement conversion functions
4 Version 10 -- 1987-12-06 -- D.N. Lynx Crowe
5 =============================================================================
6*/
7
8#define TESTER 0
9
10#include "stddefs.h"
11
12#define SFACT 1000L /* scale factor */
13
14static long d2f[][10] = { /* decimal to fraction table */
15
16 {0x00000000L, 0x000019A0L, 0x00003336L, 0x00004CD0L, 0x00006668L,
17 0x00008000L, 0x000099A0L, 0x0000B336L, 0x0000CCCEL, 0x0000E668L},
18
19 {0x00000000L, 0x00000290L, 0x00000520L, 0x000007B0L, 0x00000A40L,
20 0x00000CD0L, 0x00000F60L, 0x000011F0L, 0x00001480L, 0x00001710L}
21};
22
23static long f2d[] = { /* fraction to decimal table */
24
25 50000L, 25000L, 12500L, 6250L,
26 3125L, 1562L, 781L, 390L,
27 195L, 97L, 48L, 24L,
28 12L, 6L, 3L, 1L
29};
30
31/*
32
33*/
34
35/*
36 =============================================================================
37 dec2fr() -- convert an ASCII decimal string to fractional binary
38
39 The input string is 4 characters in the range 100- to 100+ inclusive.
40 The result is a 2's complement binary fractional value.
41 =============================================================================
42*/
43
44short
45dec2fr(s)
46register char *s;
47{
48 register short i;
49
50 if (s[0] EQ '1') {
51
52 if (s[1] EQ '0') {
53
54 if (s[2] EQ '0') {
55
56 if (s[3] EQ '-')
57 return(0x8000); /* -100 */
58 else
59 return(0x7FFF); /* +100 */
60
61 } else {
62
63 return(0xFFFF); /* ERROR */
64 }
65
66 } else {
67
68 return(0xFFFF); /* ERROR */
69
70 }
71
72/*
73
74*/
75
76 } else if (s[0] EQ '0') {
77
78 i = (d2f[0][s[1] - '0'] + d2f[1][s[2] - '0']) >> 1;
79
80 if (s[3] EQ '-') {
81
82 if (i)
83 return(~i); /* negative number */
84 else
85 return(0); /* zero is always 0 */
86
87 } else {
88
89 return(i); /* positive number */
90 }
91 }
92
93 return(0xFFFF); /* ERROR */
94}
95
96/*
97
98*/
99
100/*
101 =============================================================================
102 fr2dec() -- convert a 2's complement fraction to decimal ASCII notation
103
104 The input is a 2's complement binary fractional value.
105 The result string is 4 characters in the range 100- to 100+ inclusive.
106 =============================================================================
107*/
108
109char *
110fr2dec(v, s)
111register short v;
112register char *s;
113{
114 register long acc, sc;
115 register short i, p;
116
117 if (v EQ 0x7FFF) { /* +100 */
118
119 sprintf(s, "100+");
120 return(s);
121 }
122
123 if (v EQ 0x8000) { /* -100 */
124
125 sprintf(s, "100-");
126 return(s);
127 }
128
129 if (v & 0x8000) {
130
131 v = ~v; /* negative number */
132 p = '-';
133
134 } else {
135
136 p = '+'; /* positive number */
137 }
138
139 acc = 0;
140
141 for (i = 0; i LT 15; i++)
142 if (v & (1 << (14 - i)))
143 acc += f2d[i];
144
145 sc = SFACT;
146 acc /= sc;
147 sprintf(s, "%03d%c", (short)acc, p);
148 return(s);
149}
150
151/*
152
153*/
154
155#if TESTER
156
157#include "stdio.h"
158
159extern int memcmp();
160
161char t[8], v[8];
162
163/*
164 =============================================================================
165 test program for fractional two's complement conversion functions
166 =============================================================================
167*/
168
169main()
170{
171 register short i;
172 register short u;
173
174 for (i = 0; i < 101; i++) {
175
176 if (i EQ 50)
177 printf("\f");
178
179 sprintf(t, "%03d+", i);
180 u = dec2fr(t);
181
182 if (u EQ 0xFFFF) {
183
184 printf("[%s] = ERROR = ?????? ", t);
185
186 } else {
187
188 fr2dec(u, v);
189 printf("[%s] = 0x%04x = [%s]", t, u, v);
190 }
191
192 printf(" %s ", memcmp(t, v, 4) ? "<--" : " ");
193
194 sprintf(t, "%03d-", i);
195 u = dec2fr(t);
196
197 if (u EQ 0xFFFF) {
198
199 printf(" [%s] = ERROR = ??????\n", t);
200
201 } else {
202
203 fr2dec(u, v);
204 printf(" [%s] = 0x%04x = [%s]", t, u, v);
205 }
206
207 printf(" %s\n", memcmp(t, v, 4) ? "<--" : "");
208
209 }
210}
211
212#endif
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