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Unified Diff: src/conversions.cc

Issue 1096002: StringToDouble rewritten not using String::Get and memory allocations.... (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: '' Created 10 years, 9 months ago
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Index: src/conversions.cc
===================================================================
--- src/conversions.cc (revision 4210)
+++ src/conversions.cc (working copy)
@@ -26,6 +26,7 @@
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include <stdarg.h>
+#include <limits.h>
#include "v8.h"
@@ -92,74 +93,66 @@
}
-static inline void ReleaseCString(const char* original, const char* str) {
-}
+namespace {
+// C++-style iterator adaptor for StringInputBuffer
+// (unlike C++ iterators the end-marker has different type).
+class StringInputBufferIterator {
+ public:
+ class EndMarker {};
-static inline void ReleaseCString(String* original, const char* str) {
- DeleteArray(const_cast<char *>(str));
-}
+ explicit StringInputBufferIterator(StringInputBuffer* buffer);
+ int operator*() const;
+ void operator++();
+ bool operator==(EndMarker const&) const { return end_; }
+ bool operator!=(EndMarker const& m) const { return !end_; }
-static inline bool IsSpace(const char* str, int index) {
- ASSERT(index >= 0 && index < StrLength(str));
- return Scanner::kIsWhiteSpace.get(str[index]);
-}
+ private:
+ StringInputBuffer* const buffer_;
+ int current_;
+ bool end_;
+};
-static inline bool IsSpace(String* str, int index) {
- return Scanner::kIsWhiteSpace.get(str->Get(index));
+StringInputBufferIterator::StringInputBufferIterator(
+ StringInputBuffer* buffer) : buffer_(buffer) {
+ ++(*this);
}
+int StringInputBufferIterator::operator*() const {
+ return current_;
+}
-static inline bool SubStringEquals(const char* str,
- int index,
- const char* other) {
- return strncmp(str + index, other, strlen(other)) != 0;
+
+void StringInputBufferIterator::operator++() {
+ end_ = !buffer_->has_more();
+ if (!end_) {
+ current_ = buffer_->GetNext();
+ }
}
+}
-static inline bool SubStringEquals(String* str, int index, const char* other) {
- HandleScope scope;
- int str_length = str->length();
- int other_length = StrLength(other);
- int end = index + other_length < str_length ?
- index + other_length :
- str_length;
- Handle<String> substring =
- Factory::NewSubString(Handle<String>(str), index, end);
- return substring->IsEqualTo(Vector<const char>(other, other_length));
+static inline void ReleaseCString(const char* original, const char* str) {
}
-// Check if a string should be parsed as an octal number. The string
-// can be either a char* or a String*.
-template<class S>
-static bool ShouldParseOctal(S* s, int i) {
- int index = i;
- int len = GetLength(s);
- if (index < len && GetChar(s, index) != '0') return false;
+static inline void ReleaseCString(String* original, const char* str) {
+ DeleteArray(const_cast<char *>(str));
+}
- // If the first real character (following '0') is not an octal
- // digit, bail out early. This also takes care of numbers of the
- // forms 0.xxx and 0exxx by not allowing the first 0 to be
- // interpreted as an octal.
- index++;
- if (index < len) {
- int d = GetChar(s, index) - '0';
- if (d < 0 || d > 7) return false;
- } else {
- return false;
- }
- // Traverse all digits (including the first). If there is an octal
- // prefix which is not a part of a longer decimal prefix, we return
- // true. Otherwise, false is returned.
- while (index < len) {
- int d = GetChar(s, index++) - '0';
- if (d == 8 || d == 9) return false;
- if (d < 0 || d > 7) return true;
+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;
}
@@ -262,95 +255,365 @@
static const double JUNK_STRING_VALUE = OS::nan_value();
-// Convert a string to a double value. The string can be either a
-// char* or a String*.
-template<class S>
-static double InternalStringToDouble(S* str,
+// Returns true if a nonspace found and false if the end has reached.
+template <class Iterator, class EndMark>
+static inline bool AdvanceToNonspace(Iterator* current, EndMark end) {
+ while (*current != end) {
+ if (!Scanner::kIsWhiteSpace.get(**current)) return true;
+ ++*current;
+ }
+ return false;
+}
+
+
+template <class Iterator, class EndMark>
+static double InternalHexidecimalStringToDouble(Iterator current,
+ EndMark end,
+ char* buffer,
+ bool allow_trailing_junk) {
+ ASSERT(current != end);
+ // We reuse the buffer of InternalStringToDouble. Since hexidecimal
+ // numbers may have much less digits than decimal the buffer won't overflow.
+ int significant_digits = 0;
+ int insignificant_digits = 0;
+ bool leading_zero = false;
+ // Hexidecomal may have (52) / 4 + 1 significant digit. Mean of 2
Erik Corry 2010/03/25 12:26:16 Hexidecomal -> Hexadecimal digit -> digits I can't
Florian Loitsch 2010/03/25 13:51:35 Maybe the following explanation is easier to under
+ // hexidecimal may have n + 1.
Erik Corry 2010/03/25 12:26:16 hexidecimal -> hexadecimal
+ const int max_significant_digits = (52) / 4 + 2;
Erik Corry 2010/03/25 12:26:16 I don't see the point in putting 52 in brackets he
+ int buffer_pos = 0;
+ bool nonzero_digit_dropped = false;
+
+ // Skip leading 0s.
+ while (*current == '0') {
+ leading_zero = true;
+ ++current;
+ if (current == end) return 0;
+ }
+
+ int begin_pos = buffer_pos;
+ while ((*current >= '0' && *current <= '9')
+ || (*current >= 'a' && *current <= 'f')
+ || (*current >= 'A' && *current <= 'F')) {
+ if (significant_digits <= max_significant_digits) {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = *current;
+ significant_digits++;
+ } else {
+ insignificant_digits++;
+ nonzero_digit_dropped = nonzero_digit_dropped || *current != '0';
+ }
+ ++current;
+ if (current == end) break;
+ }
+
+ if (!allow_trailing_junk && AdvanceToNonspace(&current, end)) {
+ return JUNK_STRING_VALUE;
+ }
+
+ if (significant_digits == 0) {
+ return leading_zero ? 0 : JUNK_STRING_VALUE;
+ }
+
+ if (nonzero_digit_dropped) {
+ ASSERT(insignificant_digits > 0);
+ insignificant_digits--;
+ buffer[buffer_pos++] = '1';
+ }
+
+ buffer[buffer_pos] = '\0';
+
+ double result;
+ StringToInt(buffer, begin_pos, 16, &result);
+ if (insignificant_digits > 0) {
+ // Multiplying by power of 2 doesn't cause a loss of precision.
Erik Corry 2010/03/25 12:26:16 power -> a power
+ result *= pow(16.0, insignificant_digits);
+ }
+ return result;
+}
+
+
+// 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(Iterator current,
+ EndMark end,
int flags,
double empty_string_val) {
- double result = 0.0;
- int index = 0;
+ // To make sure that iterator unreferencing is valid the following
Erik Corry 2010/03/25 12:26:16 unreferencing -> dereferencing
+ // 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 unreferenced after the 'parsing_done' label.
Erik Corry 2010/03/25 12:26:16 and here
+ // 5. Code before 'parsing_done' may rely on 'current != end'.
+ if (!AdvanceToNonspace(&current, end)) return empty_string_val;
- int len = GetLength(str);
+ const bool allow_trailing_junk = (flags & ALLOW_TRAILING_JUNK) != 0;
- // Skip leading spaces.
- while ((index < len) && IsSpace(str, index)) index++;
+ // Insignificant digits will be removed.
+ const int max_significant_digits = 772;
Erik Corry 2010/03/25 12:26:16 Name as a constant. Is it possible to provide a o
+ // The longest form of simplified number is: "-<significant digits>'.1eXXX\0".
+ const int buffer_size = max_significant_digits + 10;
Erik Corry 2010/03/25 12:26:16 Name as a constant.
+ char buffer[buffer_size]; // NOLINT: size is known at compile time.
+ int buffer_pos = 0;
- // Is the string empty?
- if (index >= len) return empty_string_val;
+ // 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;
- // Get the first character.
- uint16_t first = GetChar(str, index);
+ double signed_zero = 0.0;
- // Numbers can only start with '-', '+', '.', 'I' (Infinity), or a digit.
- if (first != '-' && first != '+' && first != '.' && first != 'I' &&
- (first > '9' || first < '0')) {
- return JUNK_STRING_VALUE;
+ if (*current == '+') {
+ // Ignore leading sign; Skip following spaces.
Erik Corry 2010/03/25 12:26:16 Skip -> skip
+ ++current;
+ if (!AdvanceToNonspace(&current, end)) return JUNK_STRING_VALUE;
+ } else if (*current == '-') {
+ buffer[buffer_pos++] = '-';
+ ++current;
+ if (!AdvanceToNonspace(&current, end)) return JUNK_STRING_VALUE;
+ signed_zero = -0.0;
}
- // Compute sign of result based on first character.
- int sign = 1;
- if (first == '-') {
- sign = -1;
- index++;
- // String only containing a '-' are junk chars.
- if (index == len) return JUNK_STRING_VALUE;
+ static const char infinity_symbol[] = "Infinity";
Erik Corry 2010/03/25 12:26:16 Name as a constant.
+ if (*current == infinity_symbol[0]) {
+ if (!SubStringEquals(&current, end, infinity_symbol)) {
+ return JUNK_STRING_VALUE;
+ }
+
+ if (!allow_trailing_junk && AdvanceToNonspace(&current, end)) {
+ return JUNK_STRING_VALUE;
+ }
+
+ return (buffer_pos > 0 && buffer[0] == '-') ? -V8_INFINITY : V8_INFINITY;
}
- // do we have a hex number?
- // (since the string is 0-terminated, it's ok to look one char beyond the end)
- if ((flags & ALLOW_HEX) != 0 &&
- (index + 1) < len &&
- GetChar(str, index) == '0' &&
- (GetChar(str, index + 1) == 'x' || GetChar(str, index + 1) == 'X')) {
- index += 2;
- index = StringToInt(str, index, 16, &result);
- } else if ((flags & ALLOW_OCTALS) != 0 && ShouldParseOctal(str, index)) {
- // NOTE: We optimistically try to parse the number as an octal (if
- // we're allowed to), even though this is not as dictated by
- // ECMA-262. The reason for doing this is compatibility with IE and
- // Firefox.
- index = StringToInt(str, index, 8, &result);
- } else {
- const char* cstr = GetCString(str, index);
- const char* end;
- // Optimistically parse the number and then, if that fails,
- // check if it might have been {+,-,}Infinity.
- result = gay_strtod(cstr, &end);
- ReleaseCString(str, cstr);
- if (result != 0.0 || end != cstr) {
- // It appears that strtod worked
- index += static_cast<int>(end - cstr);
+ bool leading_zero = false;
+ if (*current == '0') {
+ ++current;
+ if (current == end) return signed_zero;
+
+ leading_zero = true;
+
+ // It could be hexadecimal value.
+ if ((flags & ALLOW_HEX) && (*current == 'x' || *current == 'X')) {
+ ++current;
+ if (current == end) return JUNK_STRING_VALUE; // "0x".
+
+ double result = InternalHexidecimalStringToDouble(current,
Erik Corry 2010/03/25 12:26:16 Hexi -> Hexa
+ end,
+ buffer + buffer_pos,
+ allow_trailing_junk);
+ return (buffer_pos > 0 && buffer[0] == '-') ? -result : result;
Erik Corry 2010/03/25 12:26:16 Should this be buffer[buffer_pos - 1]?
Florian Loitsch 2010/03/25 13:51:35 lgtm.
+ }
+
+ // Ignore leading zeros in the integer part.
+ while (*current == '0') {
+ ++current;
+ if (current == end) return signed_zero;
+ }
+ }
+
+ 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 < max_significant_digits) {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = *current;
+ significant_digits++;
+ // Will later check if it's an octal in the buffer.
} else {
- // Check for {+,-,}Infinity
- bool is_negative = (GetChar(str, index) == '-');
- if (GetChar(str, index) == '+' || GetChar(str, index) == '-')
- index++;
- if (!SubStringEquals(str, index, "Infinity"))
+ 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 (*current == '.') {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = '.';
+ ++current;
+ if (current == end) {
+ if (significant_digits == 0 && !leading_zero) {
return JUNK_STRING_VALUE;
- result = is_negative ? -V8_INFINITY : V8_INFINITY;
- index += 8;
+ } 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 signed_zero;
+ exponent--; // Move this 0 into the exponent.
+ }
+ }
+
+ // There is the fractional part.
+ while (*current >= '0' && *current <= '9') {
+ if (significant_digits < max_significant_digits) {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = *current;
+ significant_digits++;
+ } else {
+ // Ignore insignificant digits in the fractional part.
+ nonzero_digit_dropped = nonzero_digit_dropped || *current != '0';
+ }
+ ++current;
+ if (current == end) goto parsing_done;
+ }
}
- if ((flags & ALLOW_TRAILING_JUNK) == 0) {
- // skip trailing spaces
- while ((index < len) && IsSpace(str, index)) index++;
- // string ending with junk?
- if (index < len) return JUNK_STRING_VALUE;
+ 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 is no digits in the string.
+ return JUNK_STRING_VALUE;
}
- return sign * result;
+ // 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 = *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(&current, end)) {
+ return JUNK_STRING_VALUE;
+ }
+
+ parsing_done:
+ exponent += insignificant_digits;
+
+ if (octal) {
+ buffer[buffer_pos] = '\0';
+ // ALLOW_OCTALS has set and there is no '8' and '9' in insignificant
Erik Corry 2010/03/25 12:26:16 '8' and '9' -> '8' or '9'
Florian Loitsch 2010/03/25 13:51:35 ALLOW_OCTALS is set ...
+ // digits. Check significant digits now.
+ char sign = '+';
+ const char* s = buffer;
+ if (*s == '-' || *s == '+') sign = *s++;
+
+ double result;
+ s += StringToInt(s, 0, 8, &result);
+ if (!allow_trailing_junk && *s != '\0') return JUNK_STRING_VALUE;
+
+ if (sign == '-') result = -result;
+ if (insignificant_digits > 0) {
+ result *= pow(8.0, insignificant_digits);
+ }
+ return result;
+ }
+
+ if (nonzero_digit_dropped) {
+ if (insignificant_digits) buffer[buffer_pos++] = '.';
+ buffer[buffer_pos++] = '1';
+ }
+
+ if (exponent != 0) {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = 'e';
+ if (exponent < 0) {
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos++] = '-';
+ exponent = -exponent;
+ }
+ if (exponent > 999) exponent = 999; // Result will be Infinity or 0 or -0.
+
+ const int exp_digits = 3;
+ for (int i = 0; i < exp_digits; i++) {
+ buffer[buffer_pos + exp_digits - 1 - i] = '0' + exponent % 10;
+ exponent /= 10;
+ }
+ ASSERT(exponent == 0);
+ buffer_pos += exp_digits;
+ }
+
+ ASSERT(buffer_pos < buffer_size);
+ buffer[buffer_pos] = '\0';
+
+ return gay_strtod(buffer, NULL);
}
-
double StringToDouble(String* str, int flags, double empty_string_val) {
- return InternalStringToDouble(str, flags, empty_string_val);
+ StringShape shape(str);
+ if (shape.IsSequentialAscii()) {
+ const char* begin = SeqAsciiString::cast(str)->GetChars();
+ const char* end = begin + str->length();
+ return InternalStringToDouble(begin, end, flags, empty_string_val);
+ } else if (shape.IsSequentialTwoByte()) {
+ const uc16* begin = SeqTwoByteString::cast(str)->GetChars();
+ const uc16* end = begin + str->length();
+ return InternalStringToDouble(begin, end, flags, empty_string_val);
+ } else {
+ StringInputBuffer buffer(str);
+ return InternalStringToDouble(StringInputBufferIterator(&buffer),
+ StringInputBufferIterator::EndMarker(),
+ flags,
+ empty_string_val);
+ }
}
double StringToDouble(const char* str, int flags, double empty_string_val) {
- return InternalStringToDouble(str, flags, empty_string_val);
+ const char* end = str + StrLength(str);
+
+ return InternalStringToDouble(str, end, flags, empty_string_val);
}
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