The Tor Browser: js/src/jsdtoa.cpp@6474c204b198 (annotated)

js/src/jsdtoa.cpp@6474c204b198 (annotated)

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.

 /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
  * vim: set ts=8 sts=4 et sw=4 tw=99:
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 /*
  * Portable double to alphanumeric string and back converters.
  */
 #include "jsdtoa.h"
 #include "jsprf.h"
 #include "jstypes.h"
 #include "jsutil.h"
 using namespace js;
 #ifdef IS_LITTLE_ENDIAN
 #define IEEE_8087
 #else
 #define IEEE_MC68k
 #endif
 #ifndef Long
 #define Long int32_t
 #endif
 #ifndef ULong
 #define ULong uint32_t
 #endif
 /*
 #ifndef Llong
 #define Llong int64_t
 #endif
 #ifndef ULlong
 #define ULlong uint64_t
 #endif
 */
 /*
  * MALLOC gets declared external, and that doesn't work for class members, so
  * wrap.
  */
 static inline void* dtoa_malloc(size_t size) { return js_malloc(size); }
 static inline void dtoa_free(void* p) { return js_free(p); }
 #define NO_GLOBAL_STATE
 #define NO_ERRNO
 #define MALLOC dtoa_malloc
 #define FREE dtoa_free
 #include "dtoa.c"
 /* Mapping of JSDToStrMode -> js_dtoa mode */
 static const uint8_t dtoaModes[] = {
 ,   /* DTOSTR_STANDARD */
 ,   /* DTOSTR_STANDARD_EXPONENTIAL, */
 ,   /* DTOSTR_FIXED, */
 ,   /* DTOSTR_EXPONENTIAL, */
 };  /* DTOSTR_PRECISION */
 double
 js_strtod_harder(DtoaState *state, const char *s00, char **se, int *err)
 {
     double retval;
     if (err)
         *err = 0;
     retval = _strtod(state, s00, se);
     return retval;
 }
 char *
 js_dtostr(DtoaState *state, char *buffer, size_t bufferSize, JSDToStrMode mode, int precision,
           double dinput)
 {
     U d;
     int decPt;        /* Offset of decimal point from first digit */
     int sign;         /* Nonzero if the sign bit was set in d */
     int nDigits;      /* Number of significand digits returned by js_dtoa */
     char *numBegin;   /* Pointer to the digits returned by js_dtoa */
     char *numEnd = 0; /* Pointer past the digits returned by js_dtoa */
     JS_ASSERT(bufferSize >= (size_t)(mode <= DTOSTR_STANDARD_EXPONENTIAL
                                     ? DTOSTR_STANDARD_BUFFER_SIZE
                                     : DTOSTR_VARIABLE_BUFFER_SIZE(precision)));
     /*
      * Change mode here rather than below because the buffer may not be large
      * enough to hold a large integer.
      */
     if (mode == DTOSTR_FIXED && (dinput >= 1e21 || dinput <= -1e21))
         mode = DTOSTR_STANDARD;
     dval(d) = dinput;
     numBegin = dtoa(PASS_STATE d, dtoaModes[mode], precision, &decPt, &sign, &numEnd);
     if (!numBegin) {
         return nullptr;
     }
     nDigits = numEnd - numBegin;
     JS_ASSERT((size_t) nDigits <= bufferSize - 2);
     if ((size_t) nDigits > bufferSize - 2) {
         return nullptr;
     }
     js_memcpy(buffer + 2, numBegin, nDigits);
     freedtoa(PASS_STATE numBegin);
     numBegin = buffer + 2; /* +2 leaves space for sign and/or decimal point */
     numEnd = numBegin + nDigits;
     *numEnd = '\0';
     /* If Infinity, -Infinity, or NaN, return the string regardless of mode. */
     if (decPt != 9999) {
         bool exponentialNotation = false;
         int minNDigits = 0;  /* Min number of significant digits required */
         char *p;
         char *q;
         switch (mode) {
             case DTOSTR_STANDARD:
                 if (decPt < -5 || decPt > 21)
                     exponentialNotation = true;
                 else
                     minNDigits = decPt;
                 break;
             case DTOSTR_FIXED:
                 if (precision >= 0)
                     minNDigits = decPt + precision;
                 else
                     minNDigits = decPt;
                 break;
             case DTOSTR_EXPONENTIAL:
                 JS_ASSERT(precision > 0);
                 minNDigits = precision;
                 /* Fall through */
             case DTOSTR_STANDARD_EXPONENTIAL:
                 exponentialNotation = true;
                 break;
             case DTOSTR_PRECISION:
                 JS_ASSERT(precision > 0);
                 minNDigits = precision;
                 if (decPt < -5 || decPt > precision)
                     exponentialNotation = true;
                 break;
         }
         /* If the number has fewer than minNDigits, end-pad it with zeros. */
         if (nDigits < minNDigits) {
             p = numBegin + minNDigits;
             nDigits = minNDigits;
             do {
                 *numEnd++ = '0';
             } while (numEnd != p);
             *numEnd = '\0';
         }
         if (exponentialNotation) {
             /* Insert a decimal point if more than one significand digit */
             if (nDigits != 1) {
                 numBegin--;
                 numBegin[0] = numBegin[1];
                 numBegin[1] = '.';
             }
             JS_snprintf(numEnd, bufferSize - (numEnd - buffer), "e%+d", decPt-1);
         } else if (decPt != nDigits) {
             /* Some kind of a fraction in fixed notation */
             JS_ASSERT(decPt <= nDigits);
             if (decPt > 0) {
                 /* dd...dd . dd...dd */
                 p = --numBegin;
                 do {
                     *p = p[1];
                     p++;
                 } while (--decPt);
                 *p = '.';
             } else {
                 /* 0 . 00...00dd...dd */
                 p = numEnd;
                 numEnd += 1 - decPt;
                 q = numEnd;
                 JS_ASSERT(numEnd < buffer + bufferSize);
                 *numEnd = '\0';
                 while (p != numBegin)
                     *--q = *--p;
                 for (p = numBegin + 1; p != q; p++)
                     *p = '0';
                 *numBegin = '.';
                 *--numBegin = '0';
             }
         }
     }
     /* If negative and neither -0.0 nor NaN, output a leading '-'. */
     if (sign &&
             !(word0(d) == Sign_bit && word1(d) == 0) &&
             !((word0(d) & Exp_mask) == Exp_mask &&
               (word1(d) || (word0(d) & Frac_mask)))) {
         *--numBegin = '-';
     }
     return numBegin;
 }
 /* Let b = floor(b / divisor), and return the remainder.  b must be nonnegative.
  * divisor must be between 1 and 65536.
  * This function cannot run out of memory. */
 static uint32_t
 divrem(Bigint *b, uint32_t divisor)
 {
     int32_t n = b->wds;
     uint32_t remainder = 0;
     ULong *bx;
     ULong *bp;
     JS_ASSERT(divisor > 0 && divisor <= 65536);
     if (!n)
         return 0; /* b is zero */
     bx = b->x;
     bp = bx + n;
     do {
         ULong a = *--bp;
         ULong dividend = remainder << 16 | a >> 16;
         ULong quotientHi = dividend / divisor;
         ULong quotientLo;
         remainder = dividend - quotientHi*divisor;
         JS_ASSERT(quotientHi <= 0xFFFF && remainder < divisor);
         dividend = remainder << 16 | (a & 0xFFFF);
         quotientLo = dividend / divisor;
         remainder = dividend - quotientLo*divisor;
         JS_ASSERT(quotientLo <= 0xFFFF && remainder < divisor);
         *bp = quotientHi << 16 | quotientLo;
     } while (bp != bx);
     /* Decrease the size of the number if its most significant word is now zero. */
     if (bx[n-1] == 0)
         b->wds--;
     return remainder;
 }
 /* Return floor(b/2^k) and set b to be the remainder.  The returned quotient must be less than 2^32. */
 static uint32_t quorem2(Bigint *b, int32_t k)
 {
     ULong mask;
     ULong result;
     ULong *bx, *bxe;
     int32_t w;
     int32_t n = k >> 5;
     k &= 0x1F;
     mask = (1<<k) - 1;
     w = b->wds - n;
     if (w <= 0)
         return 0;
     JS_ASSERT(w <= 2);
     bx = b->x;
     bxe = bx + n;
     result = *bxe >> k;
     *bxe &= mask;
     if (w == 2) {
         JS_ASSERT(!(bxe[1] & ~mask));
         if (k)
             result |= bxe[1] << (32 - k);
     }
     n++;
     while (!*bxe && bxe != bx) {
         n--;
         bxe--;
     }
     b->wds = n;
     return result;
 }
 /* "-0.0000...(1073 zeros after decimal point)...0001\0" is the longest string that we could produce,
  * which occurs when printing -5e-324 in binary.  We could compute a better estimate of the size of
  * the output string and malloc fewer bytes depending on d and base, but why bother? */
 #define DTOBASESTR_BUFFER_SIZE 1078
 #define BASEDIGIT(digit) ((char)(((digit) >= 10) ? 'a' - 10 + (digit) : '0' + (digit)))
 char *
 js_dtobasestr(DtoaState *state, int base, double dinput)
 {
     U d;
     char *buffer;        /* The output string */
     char *p;             /* Pointer to current position in the buffer */
     char *pInt;          /* Pointer to the beginning of the integer part of the string */
     char *q;
     uint32_t digit;
     U di;                /* d truncated to an integer */
     U df;                /* The fractional part of d */
     JS_ASSERT(base >= 2 && base <= 36);
     dval(d) = dinput;
     buffer = (char*) js_malloc(DTOBASESTR_BUFFER_SIZE);
     if (!buffer)
         return nullptr;
     p = buffer;
     if (dval(d) < 0.0
 #if defined(XP_WIN)
         && !((word0(d) & Exp_mask) == Exp_mask && ((word0(d) & Frac_mask) || word1(d))) /* Visual C++ doesn't know how to compare against NaN */
 #endif
        ) {
         *p++ = '-';
         dval(d) = -dval(d);
     }
     /* Check for Infinity and NaN */
     if ((word0(d) & Exp_mask) == Exp_mask) {
         strcpy(p, !word1(d) && !(word0(d) & Frac_mask) ? "Infinity" : "NaN");
         return buffer;
     }
     /* Output the integer part of d with the digits in reverse order. */
     pInt = p;
     dval(di) = floor(dval(d));
     if (dval(di) <= 4294967295.0) {
         uint32_t n = (uint32_t)dval(di);
         if (n)
             do {
                 uint32_t m = n / base;
                 digit = n - m*base;
                 n = m;
                 JS_ASSERT(digit < (uint32_t)base);
                 *p++ = BASEDIGIT(digit);
             } while (n);
         else *p++ = '0';
     } else {
         int e;
         int bits;  /* Number of significant bits in di; not used. */
         Bigint *b = d2b(PASS_STATE di, &e, &bits);
         if (!b)
             goto nomem1;
         b = lshift(PASS_STATE b, e);
         if (!b) {
           nomem1:
             Bfree(PASS_STATE b);
             js_free(buffer);
             return nullptr;
         }
         do {
             digit = divrem(b, base);
             JS_ASSERT(digit < (uint32_t)base);
             *p++ = BASEDIGIT(digit);
         } while (b->wds);
         Bfree(PASS_STATE b);
     }
     /* Reverse the digits of the integer part of d. */
     q = p-1;
     while (q > pInt) {
         char ch = *pInt;
         *pInt++ = *q;
         *q-- = ch;
     }
     dval(df) = dval(d) - dval(di);
     if (dval(df) != 0.0) {
         /* We have a fraction. */
         int e, bbits;
         int32_t s2, done;
         Bigint *b, *s, *mlo, *mhi;
         b = s = mlo = mhi = nullptr;
         *p++ = '.';
         b = d2b(PASS_STATE df, &e, &bbits);
         if (!b) {
           nomem2:
             Bfree(PASS_STATE b);
             Bfree(PASS_STATE s);
             if (mlo != mhi)
                 Bfree(PASS_STATE mlo);
             Bfree(PASS_STATE mhi);
             js_free(buffer);
             return nullptr;
         }
         JS_ASSERT(e < 0);
         /* At this point df = b * 2^e.  e must be less than zero because 0 < df < 1. */
         s2 = -(int32_t)(word0(d) >> Exp_shift1 & Exp_mask>>Exp_shift1);
 #ifndef Sudden_Underflow
         if (!s2)
             s2 = -1;
 #endif
         s2 += Bias + P;
         /* 1/2^s2 = (nextDouble(d) - d)/2 */
         JS_ASSERT(-s2 < e);
         mlo = i2b(PASS_STATE 1);
         if (!mlo)
             goto nomem2;
         mhi = mlo;
         if (!word1(d) && !(word0(d) & Bndry_mask)
 #ifndef Sudden_Underflow
             && word0(d) & (Exp_mask & Exp_mask << 1)
 #endif
             ) {
             /* The special case.  Here we want to be within a quarter of the last input
                significant digit instead of one half of it when the output string's value is less than d.  */
             s2 += Log2P;
             mhi = i2b(PASS_STATE 1<<Log2P);
             if (!mhi)
                 goto nomem2;
         }
         b = lshift(PASS_STATE b, e + s2);
         if (!b)
             goto nomem2;
         s = i2b(PASS_STATE 1);
         if (!s)
             goto nomem2;
         s = lshift(PASS_STATE s, s2);
         if (!s)
             goto nomem2;
         /* At this point we have the following:
          *   s = 2^s2;
          *   1 > df = b/2^s2 > 0;
          *   (d - prevDouble(d))/2 = mlo/2^s2;
          *   (nextDouble(d) - d)/2 = mhi/2^s2. */
         done = false;
         do {
             int32_t j, j1;
             Bigint *delta;
             b = multadd(PASS_STATE b, base, 0);
             if (!b)
                 goto nomem2;
             digit = quorem2(b, s2);
             if (mlo == mhi) {
                 mlo = mhi = multadd(PASS_STATE mlo, base, 0);
                 if (!mhi)
                     goto nomem2;
             }
             else {
                 mlo = multadd(PASS_STATE mlo, base, 0);
                 if (!mlo)
                     goto nomem2;
                 mhi = multadd(PASS_STATE mhi, base, 0);
                 if (!mhi)
                     goto nomem2;
             }
             /* Do we yet have the shortest string that will round to d? */
             j = cmp(b, mlo);
             /* j is b/2^s2 compared with mlo/2^s2. */
             delta = diff(PASS_STATE s, mhi);
             if (!delta)
                 goto nomem2;
             j1 = delta->sign ? 1 : cmp(b, delta);
             Bfree(PASS_STATE delta);
             /* j1 is b/2^s2 compared with 1 - mhi/2^s2. */
 #ifndef ROUND_BIASED
             if (j1 == 0 && !(word1(d) & 1)) {
                 if (j > 0)
                     digit++;
                 done = true;
             } else
 #endif
             if (j < 0 || (j == 0
 #ifndef ROUND_BIASED
                 && !(word1(d) & 1)
 #endif
                 )) {
                 if (j1 > 0) {
                     /* Either dig or dig+1 would work here as the least significant digit.
                        Use whichever would produce an output value closer to d. */
                     b = lshift(PASS_STATE b, 1);
                     if (!b)
                         goto nomem2;
                     j1 = cmp(b, s);
                     if (j1 > 0) /* The even test (|| (j1 == 0 && (digit & 1))) is not here because it messes up odd base output
                                  * such as 3.5 in base 3.  */
                         digit++;
                 }
                 done = true;
             } else if (j1 > 0) {
                 digit++;
                 done = true;
             }
             JS_ASSERT(digit < (uint32_t)base);
             *p++ = BASEDIGIT(digit);
         } while (!done);
         Bfree(PASS_STATE b);
         Bfree(PASS_STATE s);
         if (mlo != mhi)
             Bfree(PASS_STATE mlo);
         Bfree(PASS_STATE mhi);
     }
     JS_ASSERT(p < buffer + DTOBASESTR_BUFFER_SIZE);
     *p = '\0';
     return buffer;
 }
 DtoaState *
 js_NewDtoaState()
 {
     return newdtoa();
 }
 void
 js_DestroyDtoaState(DtoaState *state)
 {
     destroydtoa(state);
 }

The Tor Browser / annotate

js/src/jsdtoa.cpp@6474c204b198 (annotated)

js/src/jsdtoa.cpp