Skip to content
Navigation Menu
{{ message }}
forked from adafruit/circuitpython
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathformatfloat.c
More file actions
429 lines (384 loc) · 12.5 KB
/
Copy pathformatfloat.c
File metadata and controls
429 lines (384 loc) · 12.5 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2013, 2014 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "py/mpconfig.h"
#if MICROPY_FLOAT_IMPL != MICROPY_FLOAT_IMPL_NONE
#include <assert.h>
#include <stdlib.h>
#include <stdint.h>
#include <math.h>
#include "py/formatfloat.h"
/***********************************************************************
Routine for converting a arbitrary floating
point number into a string.
The code in this funcion was inspired from Fred Bayer's pdouble.c.
Since pdouble.c was released as Public Domain, I'm releasing this
code as public domain as well.
The original code can be found in https://github.com/dhylands/format-float
Dave Hylands
***********************************************************************/
#if MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_FLOAT
// 1 sign bit, 8 exponent bits, and 23 mantissa bits.
// exponent values 0 and 255 are reserved, exponent can be 1 to 254.
// exponent is stored with a bias of 127.
// The min and max floats are on the order of 1x10^37 and 1x10^-37
#define FPTYPE float
#define FPCONST(x) x##F
#define FPROUND_TO_ONE 0.9999995F
#define FPDECEXP 32
#define FPMIN_BUF_SIZE 6 // +9e+99
#define FLT_SIGN_MASK 0x80000000
#define FLT_EXP_MASK 0x7F800000
#define FLT_MAN_MASK 0x007FFFFF
union floatbits {
float f;
uint32_t u;
};
static inline int fp_signbit(float x) { union floatbits fb = {x}; return fb.u & FLT_SIGN_MASK; }
#define fp_isnan(x) isnan(x)
#define fp_isinf(x) isinf(x)
static inline int fp_iszero(float x) { union floatbits fb = {x}; return fb.u == 0; }
static inline int fp_isless1(float x) { union floatbits fb = {x}; return fb.u < 0x3f800000; }
#elif MICROPY_FLOAT_IMPL == MICROPY_FLOAT_IMPL_DOUBLE
#define FPTYPE double
#define FPCONST(x) x
#define FPROUND_TO_ONE 0.999999999995
#define FPDECEXP 256
#define FPMIN_BUF_SIZE 7 // +9e+199
#define fp_signbit(x) signbit(x)
#define fp_isnan(x) isnan(x)
#define fp_isinf(x) isinf(x)
#define fp_iszero(x) (x == 0)
#define fp_isless1(x) (x < 1.0)
#endif
static const FPTYPE g_pos_pow[] = {
#if FPDECEXP > 32
1e256, 1e128, 1e64,
#endif
1e32, 1e16, 1e8, 1e4, 1e2, 1e1
};
static const FPTYPE g_neg_pow[] = {
#if FPDECEXP > 32
1e-256, 1e-128, 1e-64,
#endif
1e-32, 1e-16, 1e-8, 1e-4, 1e-2, 1e-1
};
int mp_format_float(FPTYPE f, char *buf, size_t buf_size, char fmt, int prec, char sign) {
char *s = buf;
if (buf_size <= FPMIN_BUF_SIZE) {
// FPMIN_BUF_SIZE is the minimum size needed to store any FP number.
// If the buffer does not have enough room for this (plus null terminator)
// then don't try to format the float.
if (buf_size >= 2) {
*s++ = '?';
}
if (buf_size >= 1) {
*s = '\0';
}
return buf_size >= 2;
}
if (fp_signbit(f) && !fp_isnan(f)) {
*s++ = '-';
f = -f;
} else {
if (sign) {
*s++ = sign;
}
}
// buf_remaining contains bytes available for digits and exponent.
// It is buf_size minus room for the sign and null byte.
int buf_remaining = buf_size - 1 - (s - buf);
{
char uc = fmt & 0x20;
if (fp_isinf(f)) {
*s++ = 'I' ^ uc;
*s++ = 'N' ^ uc;
*s++ = 'F' ^ uc;
goto ret;
} else if (fp_isnan(f)) {
*s++ = 'N' ^ uc;
*s++ = 'A' ^ uc;
*s++ = 'N' ^ uc;
ret:
*s = '\0';
return s - buf;
}
}
if (prec < 0) {
prec = 6;
}
char e_char = 'E' | (fmt & 0x20); // e_char will match case of fmt
fmt |= 0x20; // Force fmt to be lowercase
char org_fmt = fmt;
if (fmt == 'g' && prec == 0) {
prec = 1;
}
int e, e1;
int dec = 0;
char e_sign = '\0';
int num_digits = 0;
const FPTYPE *pos_pow = g_pos_pow;
const FPTYPE *neg_pow = g_neg_pow;
if (fp_iszero(f)) {
e = 0;
if (fmt == 'f') {
// Truncate precision to prevent buffer overflow
if (prec + 2 > buf_remaining) {
prec = buf_remaining - 2;
}
num_digits = prec + 1;
} else {
// Truncate precision to prevent buffer overflow
if (prec + 6 > buf_remaining) {
prec = buf_remaining - 6;
}
if (fmt == 'e') {
e_sign = '+';
}
}
} else if (fp_isless1(f)) {
// We need to figure out what an integer digit will be used
// in case 'f' is used (or we revert other format to it below).
// As we just tested number to be <1, this is obviously 0,
// but we can round it up to 1 below.
char first_dig = '0';
if (f >= FPROUND_TO_ONE) {
first_dig = '1';
}
// Build negative exponent
for (e = 0, e1 = FPDECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
if (*neg_pow > f) {
e += e1;
f *= *pos_pow;
}
}
char e_sign_char = '-';
if (fp_isless1(f) && f >= FPROUND_TO_ONE) {
f = FPCONST(1.0);
if (e == 0) {
e_sign_char = '+';
}
} else if (fp_isless1(f)) {
e++;
f *= FPCONST(10.0);
}
// If the user specified 'g' format, and e is <= 4, then we'll switch
// to the fixed format ('f')
if (fmt == 'f' || (fmt == 'g' && e <= 4)) {
fmt = 'f';
dec = -1;
*s++ = first_dig;
if (org_fmt == 'g') {
prec += (e - 1);
}
// truncate precision to prevent buffer overflow
if (prec + 2 > buf_remaining) {
prec = buf_remaining - 2;
}
num_digits = prec;
if (num_digits) {
*s++ = '.';
while (--e && num_digits) {
*s++ = '0';
num_digits--;
}
}
} else {
// For e & g formats, we'll be printing the exponent, so set the
// sign.
e_sign = e_sign_char;
dec = 0;
if (prec > (buf_remaining - FPMIN_BUF_SIZE)) {
prec = buf_remaining - FPMIN_BUF_SIZE;
if (fmt == 'g') {
prec++;
}
}
}
} else {
// Build positive exponent
for (e = 0, e1 = FPDECEXP; e1; e1 >>= 1, pos_pow++, neg_pow++) {
if (*pos_pow <= f) {
e += e1;
f *= *neg_pow;
}
}
// It can be that f was right on the edge of an entry in pos_pow needs to be reduced
if ((int)f >= 10) {
e += 1;
f *= FPCONST(0.1);
}
// If the user specified fixed format (fmt == 'f') and e makes the
// number too big to fit into the available buffer, then we'll
// switch to the 'e' format.
if (fmt == 'f') {
if (e >= buf_remaining) {
fmt = 'e';
} else if ((e + prec + 2) > buf_remaining) {
prec = buf_remaining - e - 2;
if (prec < 0) {
// This means no decimal point, so we can add one back
// for the decimal.
prec++;
}
}
}
if (fmt == 'e' && prec > (buf_remaining - FPMIN_BUF_SIZE)) {
prec = buf_remaining - FPMIN_BUF_SIZE;
}
if (fmt == 'g'){
// Truncate precision to prevent buffer overflow
if (prec + (FPMIN_BUF_SIZE - 1) > buf_remaining) {
prec = buf_remaining - (FPMIN_BUF_SIZE - 1);
}
}
// If the user specified 'g' format, and e is < prec, then we'll switch
// to the fixed format.
if (fmt == 'g' && e < prec) {
fmt = 'f';
prec -= (e + 1);
}
if (fmt == 'f') {
dec = e;
num_digits = prec + e + 1;
} else {
e_sign = '+';
}
}
if (prec < 0) {
// This can happen when the prec is trimmed to prevent buffer overflow
prec = 0;
}
// We now have num.f as a floating point number between >= 1 and < 10
// (or equal to zero), and e contains the absolute value of the power of
// 10 exponent. and (dec + 1) == the number of dgits before the decimal.
// For e, prec is # digits after the decimal
// For f, prec is # digits after the decimal
// For g, prec is the max number of significant digits
//
// For e & g there will be a single digit before the decimal
// for f there will be e digits before the decimal
if (fmt == 'e') {
num_digits = prec + 1;
} else if (fmt == 'g') {
if (prec == 0) {
prec = 1;
}
num_digits = prec;
}
// Print the digits of the mantissa
for (int i = 0; i < num_digits; ++i, --dec) {
int32_t d = (int32_t)f;
if (d < 0) {
*s++ = '0';
} else {
*s++ = '0' + d;
}
if (dec == 0 && prec > 0) {
*s++ = '.';
}
f -= (FPTYPE)d;
f *= FPCONST(10.0);
}
// Round
// If we print non-exponential format (i.e. 'f'), but a digit we're going
// to round by (e) is too far away, then there's nothing to round.
if ((org_fmt != 'f' || e <= num_digits) && f >= FPCONST(5.0)) {
char *rs = s;
rs--;
while (1) {
if (*rs == '.') {
rs--;
continue;
}
if (*rs < '0' || *rs > '9') {
// + or -
rs++; // So we sit on the digit to the right of the sign
break;
}
if (*rs < '9') {
(*rs)++;
break;
}
*rs = '0';
if (rs == buf) {
break;
}
rs--;
}
if (*rs == '0') {
// We need to insert a 1
if (rs[1] == '.' && fmt != 'f') {
// We're going to round 9.99 to 10.00
// Move the decimal point
rs[0] = '.';
rs[1] = '0';
if (e_sign == '-') {
e--;
if (e == 0) {
e_sign = '+';
}
} else {
e++;
}
} else {
// Need at extra digit at the end to make room for the leading '1'
s++;
}
char *ss = s;
while (ss > rs) {
*ss = ss[-1];
ss--;
}
*rs = '1';
}
}
// verify that we did not overrun the input buffer so far
assert((size_t)(s + 1 - buf) <= buf_size);
if (org_fmt == 'g' && prec > 0) {
// Remove trailing zeros and a trailing decimal point
while (s[-1] == '0') {
s--;
}
if (s[-1] == '.') {
s--;
}
}
// Append the exponent
if (e_sign) {
*s++ = e_char;
*s++ = e_sign;
if (FPMIN_BUF_SIZE == 7 && e >= 100) {
*s++ = '0' + (e / 100);
}
*s++ = '0' + ((e / 10) % 10);
*s++ = '0' + (e % 10);
}
*s = '\0';
// verify that we did not overrun the input buffer
assert((size_t)(s + 1 - buf) <= buf_size);
return s - buf;
}
#endif // MICROPY_FLOAT_IMPL != MICROPY_FLOAT_IMPL_NONE
You can’t perform that action at this time.