js/src/jsdtoa.cpp@6474c204b198
js/src/jsdtoa.cpp
Wed, 31 Dec 2014 06:09:35 +0100
- author
- Michael Schloh von Bennewitz <michael@schloh.com>
- date
- Wed, 31 Dec 2014 06:09:35 +0100
- changeset 0
- 6474c204b198
- permissions
- -rw-r--r--
Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.
1 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
2 * vim: set ts=8 sts=4 et sw=4 tw=99:
3 * This Source Code Form is subject to the terms of the Mozilla Public
4 * License, v. 2.0. If a copy of the MPL was not distributed with this
5 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
7 /*
8 * Portable double to alphanumeric string and back converters.
9 */
11 #include "jsdtoa.h"
13 #include "jsprf.h"
14 #include "jstypes.h"
15 #include "jsutil.h"
17 using namespace js;
19 #ifdef IS_LITTLE_ENDIAN
20 #define IEEE_8087
21 #else
22 #define IEEE_MC68k
23 #endif
25 #ifndef Long
26 #define Long int32_t
27 #endif
29 #ifndef ULong
30 #define ULong uint32_t
31 #endif
33 /*
34 #ifndef Llong
35 #define Llong int64_t
36 #endif
38 #ifndef ULlong
39 #define ULlong uint64_t
40 #endif
41 */
43 /*
44 * MALLOC gets declared external, and that doesn't work for class members, so
45 * wrap.
46 */
47 static inline void* dtoa_malloc(size_t size) { return js_malloc(size); }
48 static inline void dtoa_free(void* p) { return js_free(p); }
50 #define NO_GLOBAL_STATE
51 #define NO_ERRNO
52 #define MALLOC dtoa_malloc
53 #define FREE dtoa_free
54 #include "dtoa.c"
56 /* Mapping of JSDToStrMode -> js_dtoa mode */
57 static const uint8_t dtoaModes[] = {
58 0, /* DTOSTR_STANDARD */
59 0, /* DTOSTR_STANDARD_EXPONENTIAL, */
60 3, /* DTOSTR_FIXED, */
61 2, /* DTOSTR_EXPONENTIAL, */
62 2}; /* DTOSTR_PRECISION */
64 double
65 js_strtod_harder(DtoaState *state, const char *s00, char **se, int *err)
66 {
67 double retval;
68 if (err)
69 *err = 0;
70 retval = _strtod(state, s00, se);
71 return retval;
72 }
74 char *
75 js_dtostr(DtoaState *state, char *buffer, size_t bufferSize, JSDToStrMode mode, int precision,
76 double dinput)
77 {
78 U d;
79 int decPt; /* Offset of decimal point from first digit */
80 int sign; /* Nonzero if the sign bit was set in d */
81 int nDigits; /* Number of significand digits returned by js_dtoa */
82 char *numBegin; /* Pointer to the digits returned by js_dtoa */
83 char *numEnd = 0; /* Pointer past the digits returned by js_dtoa */
85 JS_ASSERT(bufferSize >= (size_t)(mode <= DTOSTR_STANDARD_EXPONENTIAL
86 ? DTOSTR_STANDARD_BUFFER_SIZE
87 : DTOSTR_VARIABLE_BUFFER_SIZE(precision)));
89 /*
90 * Change mode here rather than below because the buffer may not be large
91 * enough to hold a large integer.
92 */
93 if (mode == DTOSTR_FIXED && (dinput >= 1e21 || dinput <= -1e21))
94 mode = DTOSTR_STANDARD;
96 dval(d) = dinput;
97 numBegin = dtoa(PASS_STATE d, dtoaModes[mode], precision, &decPt, &sign, &numEnd);
98 if (!numBegin) {
99 return nullptr;
100 }
102 nDigits = numEnd - numBegin;
103 JS_ASSERT((size_t) nDigits <= bufferSize - 2);
104 if ((size_t) nDigits > bufferSize - 2) {
105 return nullptr;
106 }
108 js_memcpy(buffer + 2, numBegin, nDigits);
109 freedtoa(PASS_STATE numBegin);
110 numBegin = buffer + 2; /* +2 leaves space for sign and/or decimal point */
111 numEnd = numBegin + nDigits;
112 *numEnd = '\0';
114 /* If Infinity, -Infinity, or NaN, return the string regardless of mode. */
115 if (decPt != 9999) {
116 bool exponentialNotation = false;
117 int minNDigits = 0; /* Min number of significant digits required */
118 char *p;
119 char *q;
121 switch (mode) {
122 case DTOSTR_STANDARD:
123 if (decPt < -5 || decPt > 21)
124 exponentialNotation = true;
125 else
126 minNDigits = decPt;
127 break;
129 case DTOSTR_FIXED:
130 if (precision >= 0)
131 minNDigits = decPt + precision;
132 else
133 minNDigits = decPt;
134 break;
136 case DTOSTR_EXPONENTIAL:
137 JS_ASSERT(precision > 0);
138 minNDigits = precision;
139 /* Fall through */
140 case DTOSTR_STANDARD_EXPONENTIAL:
141 exponentialNotation = true;
142 break;
144 case DTOSTR_PRECISION:
145 JS_ASSERT(precision > 0);
146 minNDigits = precision;
147 if (decPt < -5 || decPt > precision)
148 exponentialNotation = true;
149 break;
150 }
152 /* If the number has fewer than minNDigits, end-pad it with zeros. */
153 if (nDigits < minNDigits) {
154 p = numBegin + minNDigits;
155 nDigits = minNDigits;
156 do {
157 *numEnd++ = '0';
158 } while (numEnd != p);
159 *numEnd = '\0';
160 }
162 if (exponentialNotation) {
163 /* Insert a decimal point if more than one significand digit */
164 if (nDigits != 1) {
165 numBegin--;
166 numBegin[0] = numBegin[1];
167 numBegin[1] = '.';
168 }
169 JS_snprintf(numEnd, bufferSize - (numEnd - buffer), "e%+d", decPt-1);
170 } else if (decPt != nDigits) {
171 /* Some kind of a fraction in fixed notation */
172 JS_ASSERT(decPt <= nDigits);
173 if (decPt > 0) {
174 /* dd...dd . dd...dd */
175 p = --numBegin;
176 do {
177 *p = p[1];
178 p++;
179 } while (--decPt);
180 *p = '.';
181 } else {
182 /* 0 . 00...00dd...dd */
183 p = numEnd;
184 numEnd += 1 - decPt;
185 q = numEnd;
186 JS_ASSERT(numEnd < buffer + bufferSize);
187 *numEnd = '\0';
188 while (p != numBegin)
189 *--q = *--p;
190 for (p = numBegin + 1; p != q; p++)
191 *p = '0';
192 *numBegin = '.';
193 *--numBegin = '0';
194 }
195 }
196 }
198 /* If negative and neither -0.0 nor NaN, output a leading '-'. */
199 if (sign &&
200 !(word0(d) == Sign_bit && word1(d) == 0) &&
201 !((word0(d) & Exp_mask) == Exp_mask &&
202 (word1(d) || (word0(d) & Frac_mask)))) {
203 *--numBegin = '-';
204 }
205 return numBegin;
206 }
209 /* Let b = floor(b / divisor), and return the remainder. b must be nonnegative.
210 * divisor must be between 1 and 65536.
211 * This function cannot run out of memory. */
212 static uint32_t
213 divrem(Bigint *b, uint32_t divisor)
214 {
215 int32_t n = b->wds;
216 uint32_t remainder = 0;
217 ULong *bx;
218 ULong *bp;
220 JS_ASSERT(divisor > 0 && divisor <= 65536);
222 if (!n)
223 return 0; /* b is zero */
224 bx = b->x;
225 bp = bx + n;
226 do {
227 ULong a = *--bp;
228 ULong dividend = remainder << 16 | a >> 16;
229 ULong quotientHi = dividend / divisor;
230 ULong quotientLo;
232 remainder = dividend - quotientHi*divisor;
233 JS_ASSERT(quotientHi <= 0xFFFF && remainder < divisor);
234 dividend = remainder << 16 | (a & 0xFFFF);
235 quotientLo = dividend / divisor;
236 remainder = dividend - quotientLo*divisor;
237 JS_ASSERT(quotientLo <= 0xFFFF && remainder < divisor);
238 *bp = quotientHi << 16 | quotientLo;
239 } while (bp != bx);
240 /* Decrease the size of the number if its most significant word is now zero. */
241 if (bx[n-1] == 0)
242 b->wds--;
243 return remainder;
244 }
246 /* Return floor(b/2^k) and set b to be the remainder. The returned quotient must be less than 2^32. */
247 static uint32_t quorem2(Bigint *b, int32_t k)
248 {
249 ULong mask;
250 ULong result;
251 ULong *bx, *bxe;
252 int32_t w;
253 int32_t n = k >> 5;
254 k &= 0x1F;
255 mask = (1<<k) - 1;
257 w = b->wds - n;
258 if (w <= 0)
259 return 0;
260 JS_ASSERT(w <= 2);
261 bx = b->x;
262 bxe = bx + n;
263 result = *bxe >> k;
264 *bxe &= mask;
265 if (w == 2) {
266 JS_ASSERT(!(bxe[1] & ~mask));
267 if (k)
268 result |= bxe[1] << (32 - k);
269 }
270 n++;
271 while (!*bxe && bxe != bx) {
272 n--;
273 bxe--;
274 }
275 b->wds = n;
276 return result;
277 }
280 /* "-0.0000...(1073 zeros after decimal point)...0001\0" is the longest string that we could produce,
281 * which occurs when printing -5e-324 in binary. We could compute a better estimate of the size of
282 * the output string and malloc fewer bytes depending on d and base, but why bother? */
283 #define DTOBASESTR_BUFFER_SIZE 1078
284 #define BASEDIGIT(digit) ((char)(((digit) >= 10) ? 'a' - 10 + (digit) : '0' + (digit)))
286 char *
287 js_dtobasestr(DtoaState *state, int base, double dinput)
288 {
289 U d;
290 char *buffer; /* The output string */
291 char *p; /* Pointer to current position in the buffer */
292 char *pInt; /* Pointer to the beginning of the integer part of the string */
293 char *q;
294 uint32_t digit;
295 U di; /* d truncated to an integer */
296 U df; /* The fractional part of d */
298 JS_ASSERT(base >= 2 && base <= 36);
300 dval(d) = dinput;
301 buffer = (char*) js_malloc(DTOBASESTR_BUFFER_SIZE);
302 if (!buffer)
303 return nullptr;
304 p = buffer;
306 if (dval(d) < 0.0
307 #if defined(XP_WIN)
308 && !((word0(d) & Exp_mask) == Exp_mask && ((word0(d) & Frac_mask) || word1(d))) /* Visual C++ doesn't know how to compare against NaN */
309 #endif
310 ) {
311 *p++ = '-';
312 dval(d) = -dval(d);
313 }
315 /* Check for Infinity and NaN */
316 if ((word0(d) & Exp_mask) == Exp_mask) {
317 strcpy(p, !word1(d) && !(word0(d) & Frac_mask) ? "Infinity" : "NaN");
318 return buffer;
319 }
321 /* Output the integer part of d with the digits in reverse order. */
322 pInt = p;
323 dval(di) = floor(dval(d));
324 if (dval(di) <= 4294967295.0) {
325 uint32_t n = (uint32_t)dval(di);
326 if (n)
327 do {
328 uint32_t m = n / base;
329 digit = n - m*base;
330 n = m;
331 JS_ASSERT(digit < (uint32_t)base);
332 *p++ = BASEDIGIT(digit);
333 } while (n);
334 else *p++ = '0';
335 } else {
336 int e;
337 int bits; /* Number of significant bits in di; not used. */
338 Bigint *b = d2b(PASS_STATE di, &e, &bits);
339 if (!b)
340 goto nomem1;
341 b = lshift(PASS_STATE b, e);
342 if (!b) {
343 nomem1:
344 Bfree(PASS_STATE b);
345 js_free(buffer);
346 return nullptr;
347 }
348 do {
349 digit = divrem(b, base);
350 JS_ASSERT(digit < (uint32_t)base);
351 *p++ = BASEDIGIT(digit);
352 } while (b->wds);
353 Bfree(PASS_STATE b);
354 }
355 /* Reverse the digits of the integer part of d. */
356 q = p-1;
357 while (q > pInt) {
358 char ch = *pInt;
359 *pInt++ = *q;
360 *q-- = ch;
361 }
363 dval(df) = dval(d) - dval(di);
364 if (dval(df) != 0.0) {
365 /* We have a fraction. */
366 int e, bbits;
367 int32_t s2, done;
368 Bigint *b, *s, *mlo, *mhi;
370 b = s = mlo = mhi = nullptr;
372 *p++ = '.';
373 b = d2b(PASS_STATE df, &e, &bbits);
374 if (!b) {
375 nomem2:
376 Bfree(PASS_STATE b);
377 Bfree(PASS_STATE s);
378 if (mlo != mhi)
379 Bfree(PASS_STATE mlo);
380 Bfree(PASS_STATE mhi);
381 js_free(buffer);
382 return nullptr;
383 }
384 JS_ASSERT(e < 0);
385 /* At this point df = b * 2^e. e must be less than zero because 0 < df < 1. */
387 s2 = -(int32_t)(word0(d) >> Exp_shift1 & Exp_mask>>Exp_shift1);
388 #ifndef Sudden_Underflow
389 if (!s2)
390 s2 = -1;
391 #endif
392 s2 += Bias + P;
393 /* 1/2^s2 = (nextDouble(d) - d)/2 */
394 JS_ASSERT(-s2 < e);
395 mlo = i2b(PASS_STATE 1);
396 if (!mlo)
397 goto nomem2;
398 mhi = mlo;
399 if (!word1(d) && !(word0(d) & Bndry_mask)
400 #ifndef Sudden_Underflow
401 && word0(d) & (Exp_mask & Exp_mask << 1)
402 #endif
403 ) {
404 /* The special case. Here we want to be within a quarter of the last input
405 significant digit instead of one half of it when the output string's value is less than d. */
406 s2 += Log2P;
407 mhi = i2b(PASS_STATE 1<<Log2P);
408 if (!mhi)
409 goto nomem2;
410 }
411 b = lshift(PASS_STATE b, e + s2);
412 if (!b)
413 goto nomem2;
414 s = i2b(PASS_STATE 1);
415 if (!s)
416 goto nomem2;
417 s = lshift(PASS_STATE s, s2);
418 if (!s)
419 goto nomem2;
420 /* At this point we have the following:
421 * s = 2^s2;
422 * 1 > df = b/2^s2 > 0;
423 * (d - prevDouble(d))/2 = mlo/2^s2;
424 * (nextDouble(d) - d)/2 = mhi/2^s2. */
426 done = false;
427 do {
428 int32_t j, j1;
429 Bigint *delta;
431 b = multadd(PASS_STATE b, base, 0);
432 if (!b)
433 goto nomem2;
434 digit = quorem2(b, s2);
435 if (mlo == mhi) {
436 mlo = mhi = multadd(PASS_STATE mlo, base, 0);
437 if (!mhi)
438 goto nomem2;
439 }
440 else {
441 mlo = multadd(PASS_STATE mlo, base, 0);
442 if (!mlo)
443 goto nomem2;
444 mhi = multadd(PASS_STATE mhi, base, 0);
445 if (!mhi)
446 goto nomem2;
447 }
449 /* Do we yet have the shortest string that will round to d? */
450 j = cmp(b, mlo);
451 /* j is b/2^s2 compared with mlo/2^s2. */
452 delta = diff(PASS_STATE s, mhi);
453 if (!delta)
454 goto nomem2;
455 j1 = delta->sign ? 1 : cmp(b, delta);
456 Bfree(PASS_STATE delta);
457 /* j1 is b/2^s2 compared with 1 - mhi/2^s2. */
459 #ifndef ROUND_BIASED
460 if (j1 == 0 && !(word1(d) & 1)) {
461 if (j > 0)
462 digit++;
463 done = true;
464 } else
465 #endif
466 if (j < 0 || (j == 0
467 #ifndef ROUND_BIASED
468 && !(word1(d) & 1)
469 #endif
470 )) {
471 if (j1 > 0) {
472 /* Either dig or dig+1 would work here as the least significant digit.
473 Use whichever would produce an output value closer to d. */
474 b = lshift(PASS_STATE b, 1);
475 if (!b)
476 goto nomem2;
477 j1 = cmp(b, s);
478 if (j1 > 0) /* The even test (|| (j1 == 0 && (digit & 1))) is not here because it messes up odd base output
479 * such as 3.5 in base 3. */
480 digit++;
481 }
482 done = true;
483 } else if (j1 > 0) {
484 digit++;
485 done = true;
486 }
487 JS_ASSERT(digit < (uint32_t)base);
488 *p++ = BASEDIGIT(digit);
489 } while (!done);
490 Bfree(PASS_STATE b);
491 Bfree(PASS_STATE s);
492 if (mlo != mhi)
493 Bfree(PASS_STATE mlo);
494 Bfree(PASS_STATE mhi);
495 }
496 JS_ASSERT(p < buffer + DTOBASESTR_BUFFER_SIZE);
497 *p = '\0';
498 return buffer;
499 }
501 DtoaState *
502 js_NewDtoaState()
503 {
504 return newdtoa();
505 }
507 void
508 js_DestroyDtoaState(DtoaState *state)
509 {
510 destroydtoa(state);
511 }
