Extract string->double and double->string conversions for use in the preparser.

src/conversions-inl.h

-// Copyright 2006-2008 the V8 project authors. All rights reserved.
+// Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
 //       with the distribution.
 //     * Neither the name of Google Inc. nor the names of its
 //       contributors may be used to endorse or promote products derived
 //       from this software without specific prior written permission.
 //
 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 #ifndef V8_CONVERSIONS_INL_H_
 #define V8_CONVERSIONS_INL_H_
 
+#include <limits.h>        // Required for INT_MAX etc.
 #include <math.h>
-#include <float.h>         // required for DBL_MAX and on Win32 for finite()
+#include <float.h>         // Required for DBL_MAX and on Win32 for finite()
 #include <stdarg.h>
 
 // ----------------------------------------------------------------------------
 // Extra POSIX/ANSI functions for Win32/MSVC.
 
 #include "conversions.h"
+#include "strtod.h"
 #include "platform.h"
 
 namespace v8 {
 namespace internal {
 
 // The fast double-to-unsigned-int conversion routine does not guarantee
 // rounding towards zero, or any reasonable value if the argument is larger
 // than what fits in an unsigned 32-bit integer.
 static inline unsigned int FastD2UI(double x) {
   // There is no unsigned version of lrint, so there is no fast path
@@ skipping 21 matching lines @@
 }
 
 
 static inline double DoubleToInteger(double x) {
   if (isnan(x)) return 0;
   if (!isfinite(x) || x == 0) return x;
   return (x >= 0) ? floor(x) : ceil(x);
 }
 
 
-int32_t NumberToInt32(Object* number) {
-  if (number->IsSmi()) return Smi::cast(number)->value();
-  return DoubleToInt32(number->Number());
-}
-
-
-uint32_t NumberToUint32(Object* number) {
-  if (number->IsSmi()) return Smi::cast(number)->value();
-  return DoubleToUint32(number->Number());
-}
-
-
 int32_t DoubleToInt32(double x) {
   int32_t i = FastD2I(x);
   if (FastI2D(i) == x) return i;
   static const double two32 = 4294967296.0;
   static const double two31 = 2147483648.0;
   if (!isfinite(x) || x == 0) return 0;
   if (x < 0 || x >= two32) x = modulo(x, two32);
   x = (x >= 0) ? floor(x) : ceil(x) + two32;
   return (int32_t) ((x >= two31) ? x - two32 : x);
 }
 
 
+template <class Iterator, class EndMark>
+static bool SubStringEquals(Iterator* current,
+                            EndMark end,
+                            const char* substring) {
+  ASSERT(**current == *substring);
+  for (substring++; *substring != '\0'; substring++) {
+    ++*current;
+    if (*current == end || **current != *substring) return false;
+  }
+  ++*current;
+  return true;
+}
+
+
+// Returns true if a nonspace character has been found and false if the
+// end was been reached before finding a nonspace character.
+template <class Iterator, class EndMark>
+static inline bool AdvanceToNonspace(UnicodeCache* unicode_cache,
+                                     Iterator* current,
+                                     EndMark end) {
+  while (*current != end) {
+    if (!unicode_cache->IsWhiteSpace(**current)) return true;
+    ++*current;
+  }
+  return false;
+}
+
+
+// Parsing integers with radix 2, 4, 8, 16, 32. Assumes current != end.
+template <int radix_log_2, class Iterator, class EndMark>
+static double InternalStringToIntDouble(UnicodeCache* unicode_cache,
+                                        Iterator current,
+                                        EndMark end,
+                                        bool negative,
+                                        bool allow_trailing_junk) {
+  ASSERT(current != end);
+
+  // Skip leading 0s.
+  while (*current == '0') {
+    ++current;
+    if (current == end) return SignedZero(negative);
+  }
+
+  int64_t number = 0;
+  int exponent = 0;
+  const int radix = (1 << radix_log_2);
+
+  do {
+    int digit;
+    if (*current >= '0' && *current <= '9' && *current < '0' + radix) {
+      digit = static_cast<char>(*current) - '0';
+    } else if (radix > 10 && *current >= 'a' && *current < 'a' + radix - 10) {
+      digit = static_cast<char>(*current) - 'a' + 10;
+    } else if (radix > 10 && *current >= 'A' && *current < 'A' + radix - 10) {
+      digit = static_cast<char>(*current) - 'A' + 10;
+    } else {
+      if (allow_trailing_junk ||
+          !AdvanceToNonspace(unicode_cache, &current, end)) {
+        break;
+      } else {
+        return JUNK_STRING_VALUE;
+      }
+    }
+
+    number = number * radix + digit;
+    int overflow = static_cast<int>(number >> 53);
+    if (overflow != 0) {
+      // Overflow occurred. Need to determine which direction to round the
+      // result.
+      int overflow_bits_count = 1;
+      while (overflow > 1) {
+        overflow_bits_count++;
+        overflow >>= 1;
+      }
+
+      int dropped_bits_mask = ((1 << overflow_bits_count) - 1);
+      int dropped_bits = static_cast<int>(number) & dropped_bits_mask;
+      number >>= overflow_bits_count;
+      exponent = overflow_bits_count;
+
+      bool zero_tail = true;
+      while (true) {
+        ++current;
+        if (current == end || !isDigit(*current, radix)) break;
+        zero_tail = zero_tail && *current == '0';
+        exponent += radix_log_2;
+      }
+
+      if (!allow_trailing_junk &&
+          AdvanceToNonspace(unicode_cache, &current, end)) {
+        return JUNK_STRING_VALUE;
+      }
+
+      int middle_value = (1 << (overflow_bits_count - 1));
+      if (dropped_bits > middle_value) {
+        number++;  // Rounding up.
+      } else if (dropped_bits == middle_value) {
+        // Rounding to even to consistency with decimals: half-way case rounds
+        // up if significant part is odd and down otherwise.
+        if ((number & 1) != 0 || !zero_tail) {
+          number++;  // Rounding up.
+        }
+      }
+
+      // Rounding up may cause overflow.
+      if ((number & ((int64_t)1 << 53)) != 0) {
+        exponent++;
+        number >>= 1;
+      }
+      break;
+    }
+    ++current;
+  } while (current != end);
+
+  ASSERT(number < ((int64_t)1 << 53));
+  ASSERT(static_cast<int64_t>(static_cast<double>(number)) == number);
+
+  if (exponent == 0) {
+    if (negative) {
+      if (number == 0) return -0.0;
+      number = -number;
+    }
+    return static_cast<double>(number);
+  }
+
+  ASSERT(number != 0);
+  // The double could be constructed faster from number (mantissa), exponent
+  // and sign. Assuming it's a rare case more simple code is used.
+  return static_cast<double>(negative ? -number : number) * pow(2.0, exponent);
+}
+
+
+template <class Iterator, class EndMark>
+static double InternalStringToInt(UnicodeCache* unicode_cache,
+                                  Iterator current,
+                                  EndMark end,
+                                  int radix) {
+  const bool allow_trailing_junk = true;
+  const double empty_string_val = JUNK_STRING_VALUE;
+
+  if (!AdvanceToNonspace(unicode_cache, &current, end)) {
+    return empty_string_val;
+  }
+
+  bool negative = false;
+  bool leading_zero = false;
+
+  if (*current == '+') {
+    // Ignore leading sign; skip following spaces.
+    ++current;
+    if (current == end) {
+      return JUNK_STRING_VALUE;
+    }
+  } else if (*current == '-') {
+    ++current;
+    if (current == end) {
+      return JUNK_STRING_VALUE;
+    }
+    negative = true;
+  }
+
+  if (radix == 0) {
+    // Radix detection.
+    if (*current == '0') {
+      ++current;
+      if (current == end) return SignedZero(negative);
+      if (*current == 'x' || *current == 'X') {
+        radix = 16;
+        ++current;
+        if (current == end) return JUNK_STRING_VALUE;
+      } else {
+        radix = 8;
+        leading_zero = true;
+      }
+    } else {
+      radix = 10;
+    }
+  } else if (radix == 16) {
+    if (*current == '0') {
+      // Allow "0x" prefix.
+      ++current;
+      if (current == end) return SignedZero(negative);
+      if (*current == 'x' || *current == 'X') {
+        ++current;
+        if (current == end) return JUNK_STRING_VALUE;
+      } else {
+        leading_zero = true;
+      }
+    }
+  }
+
+  if (radix < 2 || radix > 36) return JUNK_STRING_VALUE;
+
+  // Skip leading zeros.
+  while (*current == '0') {
+    leading_zero = true;
+    ++current;
+    if (current == end) return SignedZero(negative);
+  }
+
+  if (!leading_zero && !isDigit(*current, radix)) {
+    return JUNK_STRING_VALUE;
+  }
+
+  if (IsPowerOf2(radix)) {
+    switch (radix) {
+      case 2:
+        return InternalStringToIntDouble<1>(
+            unicode_cache, current, end, negative, allow_trailing_junk);
+      case 4:
+        return InternalStringToIntDouble<2>(
+            unicode_cache, current, end, negative, allow_trailing_junk);
+      case 8:
+        return InternalStringToIntDouble<3>(
+            unicode_cache, current, end, negative, allow_trailing_junk);
+
+      case 16:
+        return InternalStringToIntDouble<4>(
+            unicode_cache, current, end, negative, allow_trailing_junk);
+
+      case 32:
+        return InternalStringToIntDouble<5>(
+            unicode_cache, current, end, negative, allow_trailing_junk);
+      default:
+        UNREACHABLE();
+    }
+  }
+
+  if (radix == 10) {
+    // Parsing with strtod.
+    const int kMaxSignificantDigits = 309;  // Doubles are less than 1.8e308.
+    // The buffer may contain up to kMaxSignificantDigits + 1 digits and a zero
+    // end.
+    const int kBufferSize = kMaxSignificantDigits + 2;
+    char buffer[kBufferSize];
+    int buffer_pos = 0;
+    while (*current >= '0' && *current <= '9') {
+      if (buffer_pos <= kMaxSignificantDigits) {
+        // If the number has more than kMaxSignificantDigits it will be parsed
+        // as infinity.
+        ASSERT(buffer_pos < kBufferSize);
+        buffer[buffer_pos++] = static_cast<char>(*current);
+      }
+      ++current;
+      if (current == end) break;
+    }
+
+    if (!allow_trailing_junk &&
+        AdvanceToNonspace(unicode_cache, &current, end)) {
+      return JUNK_STRING_VALUE;
+    }
+
+    ASSERT(buffer_pos < kBufferSize);
+    buffer[buffer_pos] = '\0';
+    Vector<const char> buffer_vector(buffer, buffer_pos);
+    return negative ? -Strtod(buffer_vector, 0) : Strtod(buffer_vector, 0);
+  }
+
+  // The following code causes accumulating rounding error for numbers greater
+  // than ~2^56. It's explicitly allowed in the spec: "if R is not 2, 4, 8, 10,
+  // 16, or 32, then mathInt may be an implementation-dependent approximation to
+  // the mathematical integer value" (15.1.2.2).
+
+  int lim_0 = '0' + (radix < 10 ? radix : 10);
+  int lim_a = 'a' + (radix - 10);
+  int lim_A = 'A' + (radix - 10);
+
+  // NOTE: The code for computing the value may seem a bit complex at
+  // first glance. It is structured to use 32-bit multiply-and-add
+  // loops as long as possible to avoid loosing precision.
+
+  double v = 0.0;
+  bool done = false;
+  do {
+    // Parse the longest part of the string starting at index j
+    // possible while keeping the multiplier, and thus the part
+    // itself, within 32 bits.
+    unsigned int part = 0, multiplier = 1;
+    while (true) {
+      int d;
+      if (*current >= '0' && *current < lim_0) {
+        d = *current - '0';
+      } else if (*current >= 'a' && *current < lim_a) {
+        d = *current - 'a' + 10;
+      } else if (*current >= 'A' && *current < lim_A) {
+        d = *current - 'A' + 10;
+      } else {
+        done = true;
+        break;
+      }
+
+      // Update the value of the part as long as the multiplier fits
+      // in 32 bits. When we can't guarantee that the next iteration
+      // will not overflow the multiplier, we stop parsing the part
+      // by leaving the loop.
+      const unsigned int kMaximumMultiplier = 0xffffffffU / 36;
+      uint32_t m = multiplier * radix;
+      if (m > kMaximumMultiplier) break;
+      part = part * radix + d;
+      multiplier = m;
+      ASSERT(multiplier > part);
+
+      ++current;
+      if (current == end) {
+        done = true;
+        break;
+      }
+    }
+
+    // Update the value and skip the part in the string.
+    v = v * multiplier + part;
+  } while (!done);
+
+  if (!allow_trailing_junk &&
+      AdvanceToNonspace(unicode_cache, &current, end)) {
+    return JUNK_STRING_VALUE;
+  }
+
+  return negative ? -v : v;
+}
+
+
+// Converts a string to a double value. Assumes the Iterator supports
+// the following operations:
+// 1. current == end (other ops are not allowed), current != end.
+// 2. *current - gets the current character in the sequence.
+// 3. ++current (advances the position).
+template <class Iterator, class EndMark>
+static double InternalStringToDouble(UnicodeCache* unicode_cache,
+                                     Iterator current,
+                                     EndMark end,
+                                     int flags,
+                                     double empty_string_val) {
+  // To make sure that iterator dereferencing is valid the following
+  // convention is used:
+  // 1. Each '++current' statement is followed by check for equality to 'end'.
+  // 2. If AdvanceToNonspace returned false then current == end.
+  // 3. If 'current' becomes be equal to 'end' the function returns or goes to
+  // 'parsing_done'.
+  // 4. 'current' is not dereferenced after the 'parsing_done' label.
+  // 5. Code before 'parsing_done' may rely on 'current != end'.
+  if (!AdvanceToNonspace(unicode_cache, &current, end)) {
+    return empty_string_val;
+  }
+
+  const bool allow_trailing_junk = (flags & ALLOW_TRAILING_JUNK) != 0;
+
+  // The longest form of simplified number is: "-<significant digits>'.1eXXX\0".
+  const int kBufferSize = kMaxSignificantDigits + 10;
+  char buffer[kBufferSize];  // NOLINT: size is known at compile time.
+  int buffer_pos = 0;
+
+  // Exponent will be adjusted if insignificant digits of the integer part
+  // or insignificant leading zeros of the fractional part are dropped.
+  int exponent = 0;
+  int significant_digits = 0;
+  int insignificant_digits = 0;
+  bool nonzero_digit_dropped = false;
+  bool fractional_part = false;
+
+  bool negative = false;
+
+  if (*current == '+') {
+    // Ignore leading sign.
+    ++current;
+    if (current == end) return JUNK_STRING_VALUE;
+  } else if (*current == '-') {
+    ++current;
+    if (current == end) return JUNK_STRING_VALUE;
+    negative = true;
+  }
+
+  static const char kInfinitySymbol[] = "Infinity";
+  if (*current == kInfinitySymbol[0]) {
+    if (!SubStringEquals(&current, end, kInfinitySymbol)) {
+      return JUNK_STRING_VALUE;
+    }
+
+    if (!allow_trailing_junk &&
+        AdvanceToNonspace(unicode_cache, &current, end)) {
+      return JUNK_STRING_VALUE;
+    }
+
+    ASSERT(buffer_pos == 0);
+    return negative ? -V8_INFINITY : V8_INFINITY;
+  }
+
+  bool leading_zero = false;
+  if (*current == '0') {
+    ++current;
+    if (current == end) return SignedZero(negative);
+
+    leading_zero = true;
+
+    // It could be hexadecimal value.
+    if ((flags & ALLOW_HEX) && (*current == 'x' || *current == 'X')) {
+      ++current;
+      if (current == end || !isDigit(*current, 16)) {
+        return JUNK_STRING_VALUE;  // "0x".
+      }
+
+      return InternalStringToIntDouble<4>(unicode_cache,
+                                          current,
+                                          end,
+                                          negative,
+                                          allow_trailing_junk);
+    }
+
+    // Ignore leading zeros in the integer part.
+    while (*current == '0') {
+      ++current;
+      if (current == end) return SignedZero(negative);
+    }
+  }
+
+  bool octal = leading_zero && (flags & ALLOW_OCTALS) != 0;
+
+  // Copy significant digits of the integer part (if any) to the buffer.
+  while (*current >= '0' && *current <= '9') {
+    if (significant_digits < kMaxSignificantDigits) {
+      ASSERT(buffer_pos < kBufferSize);
+      buffer[buffer_pos++] = static_cast<char>(*current);
+      significant_digits++;
+      // Will later check if it's an octal in the buffer.
+    } else {
+      insignificant_digits++;  // Move the digit into the exponential part.
+      nonzero_digit_dropped = nonzero_digit_dropped || *current != '0';
+    }
+    octal = octal && *current < '8';
+    ++current;
+    if (current == end) goto parsing_done;
+  }
+
+  if (significant_digits == 0) {
+    octal = false;
+  }
+
+  if (*current == '.') {
+    if (octal && !allow_trailing_junk) return JUNK_STRING_VALUE;
+    if (octal) goto parsing_done;
+
+    ++current;
+    if (current == end) {
+      if (significant_digits == 0 && !leading_zero) {
+        return JUNK_STRING_VALUE;
+      } else {
+        goto parsing_done;
+      }
+    }
+
+    if (significant_digits == 0) {
+      // octal = false;
+      // Integer part consists of 0 or is absent. Significant digits start after
+      // leading zeros (if any).
+      while (*current == '0') {
+        ++current;
+        if (current == end) return SignedZero(negative);
+        exponent--;  // Move this 0 into the exponent.
+      }
+    }
+
+    // We don't emit a '.', but adjust the exponent instead.
+    fractional_part = true;
+
+    // There is a fractional part.
+    while (*current >= '0' && *current <= '9') {
+      if (significant_digits < kMaxSignificantDigits) {
+        ASSERT(buffer_pos < kBufferSize);
+        buffer[buffer_pos++] = static_cast<char>(*current);
+        significant_digits++;
+        exponent--;
+      } else {
+        // Ignore insignificant digits in the fractional part.
+        nonzero_digit_dropped = nonzero_digit_dropped || *current != '0';
+      }
+      ++current;
+      if (current == end) goto parsing_done;
+    }
+  }
+
+  if (!leading_zero && exponent == 0 && significant_digits == 0) {
+    // If leading_zeros is true then the string contains zeros.
+    // If exponent < 0 then string was [+-]\.0*...
+    // If significant_digits != 0 the string is not equal to 0.
+    // Otherwise there are no digits in the string.
+    return JUNK_STRING_VALUE;
+  }
+
+  // Parse exponential part.
+  if (*current == 'e' || *current == 'E') {
+    if (octal) return JUNK_STRING_VALUE;
+    ++current;
+    if (current == end) {
+      if (allow_trailing_junk) {
+        goto parsing_done;
+      } else {
+        return JUNK_STRING_VALUE;
+      }
+    }
+    char sign = '+';
+    if (*current == '+' || *current == '-') {
+      sign = static_cast<char>(*current);
+      ++current;
+      if (current == end) {
+        if (allow_trailing_junk) {
+          goto parsing_done;
+        } else {
+          return JUNK_STRING_VALUE;
+        }
+      }
+    }
+
+    if (current == end || *current < '0' || *current > '9') {
+      if (allow_trailing_junk) {
+        goto parsing_done;
+      } else {
+        return JUNK_STRING_VALUE;
+      }
+    }
+
+    const int max_exponent = INT_MAX / 2;
+    ASSERT(-max_exponent / 2 <= exponent && exponent <= max_exponent / 2);
+    int num = 0;
+    do {
+      // Check overflow.
+      int digit = *current - '0';
+      if (num >= max_exponent / 10
+          && !(num == max_exponent / 10 && digit <= max_exponent % 10)) {
+        num = max_exponent;
+      } else {
+        num = num * 10 + digit;
+      }
+      ++current;
+    } while (current != end && *current >= '0' && *current <= '9');
+
+    exponent += (sign == '-' ? -num : num);
+  }
+
+  if (!allow_trailing_junk &&
+      AdvanceToNonspace(unicode_cache, &current, end)) {
+    return JUNK_STRING_VALUE;
+  }
+
+  parsing_done:
+  exponent += insignificant_digits;
+
+  if (octal) {
+    return InternalStringToIntDouble<3>(unicode_cache,
+                                        buffer,
+                                        buffer + buffer_pos,
+                                        negative,
+                                        allow_trailing_junk);
+  }
+
+  if (nonzero_digit_dropped) {
+    buffer[buffer_pos++] = '1';
+    exponent--;
+  }
+
+  ASSERT(buffer_pos < kBufferSize);
+  buffer[buffer_pos] = '\0';
+
+  double converted = Strtod(Vector<const char>(buffer, buffer_pos), exponent);
+  return negative ? -converted : converted;
+}
+
 } }  // namespace v8::internal
 
 #endif  // V8_CONVERSIONS_INL_H_