circuitpython/py/formatfloat.c at master · ProGamerCode/circuitpython · GitHub

History

429 lines (384 loc) · 12.5 KB

Raw

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)

* 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

circuitpython/py/formatfloat.c at master · ProGamerCode/circuitpython · GitHub

Expand file tree

Breadcrumbs

formatfloat.c

Latest commit

History

Breadcrumbs

formatfloat.c

File metadata and controls