about summary refs log tree commit diff
path: root/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
diff options
context:
space:
mode:
Diffstat (limited to 'third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc')
-rw-r--r--third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc504
1 files changed, 0 insertions, 504 deletions
diff --git a/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc b/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
deleted file mode 100644
index fd6d9480fc..0000000000
--- a/third_party/abseil_cpp/absl/strings/internal/charconv_parse.cc
+++ /dev/null
@@ -1,504 +0,0 @@
-// Copyright 2018 The Abseil Authors.
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      https://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-#include "absl/strings/internal/charconv_parse.h"
-#include "absl/strings/charconv.h"
-
-#include <cassert>
-#include <cstdint>
-#include <limits>
-
-#include "absl/strings/internal/memutil.h"
-
-namespace absl {
-ABSL_NAMESPACE_BEGIN
-namespace {
-
-// ParseFloat<10> will read the first 19 significant digits of the mantissa.
-// This number was chosen for multiple reasons.
-//
-// (a) First, for whatever integer type we choose to represent the mantissa, we
-// want to choose the largest possible number of decimal digits for that integer
-// type.  We are using uint64_t, which can express any 19-digit unsigned
-// integer.
-//
-// (b) Second, we need to parse enough digits that the binary value of any
-// mantissa we capture has more bits of resolution than the mantissa
-// representation in the target float.  Our algorithm requires at least 3 bits
-// of headway, but 19 decimal digits give a little more than that.
-//
-// The following static assertions verify the above comments:
-constexpr int kDecimalMantissaDigitsMax = 19;
-
-static_assert(std::numeric_limits<uint64_t>::digits10 ==
-                  kDecimalMantissaDigitsMax,
-              "(a) above");
-
-// IEEE doubles, which we assume in Abseil, have 53 binary bits of mantissa.
-static_assert(std::numeric_limits<double>::is_iec559, "IEEE double assumed");
-static_assert(std::numeric_limits<double>::radix == 2, "IEEE double fact");
-static_assert(std::numeric_limits<double>::digits == 53, "IEEE double fact");
-
-// The lowest valued 19-digit decimal mantissa we can read still contains
-// sufficient information to reconstruct a binary mantissa.
-static_assert(1000000000000000000u > (uint64_t(1) << (53 + 3)), "(b) above");
-
-// ParseFloat<16> will read the first 15 significant digits of the mantissa.
-//
-// Because a base-16-to-base-2 conversion can be done exactly, we do not need
-// to maximize the number of scanned hex digits to improve our conversion.  What
-// is required is to scan two more bits than the mantissa can represent, so that
-// we always round correctly.
-//
-// (One extra bit does not suffice to perform correct rounding, since a number
-// exactly halfway between two representable floats has unique rounding rules,
-// so we need to differentiate between a "halfway between" number and a "closer
-// to the larger value" number.)
-constexpr int kHexadecimalMantissaDigitsMax = 15;
-
-// The minimum number of significant bits that will be read from
-// kHexadecimalMantissaDigitsMax hex digits.  We must subtract by three, since
-// the most significant digit can be a "1", which only contributes a single
-// significant bit.
-constexpr int kGuaranteedHexadecimalMantissaBitPrecision =
-    4 * kHexadecimalMantissaDigitsMax - 3;
-
-static_assert(kGuaranteedHexadecimalMantissaBitPrecision >
-                  std::numeric_limits<double>::digits + 2,
-              "kHexadecimalMantissaDigitsMax too small");
-
-// We also impose a limit on the number of significant digits we will read from
-// an exponent, to avoid having to deal with integer overflow.  We use 9 for
-// this purpose.
-//
-// If we read a 9 digit exponent, the end result of the conversion will
-// necessarily be infinity or zero, depending on the sign of the exponent.
-// Therefore we can just drop extra digits on the floor without any extra
-// logic.
-constexpr int kDecimalExponentDigitsMax = 9;
-static_assert(std::numeric_limits<int>::digits10 >= kDecimalExponentDigitsMax,
-              "int type too small");
-
-// To avoid incredibly large inputs causing integer overflow for our exponent,
-// we impose an arbitrary but very large limit on the number of significant
-// digits we will accept.  The implementation refuses to match a string with
-// more consecutive significant mantissa digits than this.
-constexpr int kDecimalDigitLimit = 50000000;
-
-// Corresponding limit for hexadecimal digit inputs.  This is one fourth the
-// amount of kDecimalDigitLimit, since each dropped hexadecimal digit requires
-// a binary exponent adjustment of 4.
-constexpr int kHexadecimalDigitLimit = kDecimalDigitLimit / 4;
-
-// The largest exponent we can read is 999999999 (per
-// kDecimalExponentDigitsMax), and the largest exponent adjustment we can get
-// from dropped mantissa digits is 2 * kDecimalDigitLimit, and the sum of these
-// comfortably fits in an integer.
-//
-// We count kDecimalDigitLimit twice because there are independent limits for
-// numbers before and after the decimal point.  (In the case where there are no
-// significant digits before the decimal point, there are independent limits for
-// post-decimal-point leading zeroes and for significant digits.)
-static_assert(999999999 + 2 * kDecimalDigitLimit <
-                  std::numeric_limits<int>::max(),
-              "int type too small");
-static_assert(999999999 + 2 * (4 * kHexadecimalDigitLimit) <
-                  std::numeric_limits<int>::max(),
-              "int type too small");
-
-// Returns true if the provided bitfield allows parsing an exponent value
-// (e.g., "1.5e100").
-bool AllowExponent(chars_format flags) {
-  bool fixed = (flags & chars_format::fixed) == chars_format::fixed;
-  bool scientific =
-      (flags & chars_format::scientific) == chars_format::scientific;
-  return scientific || !fixed;
-}
-
-// Returns true if the provided bitfield requires an exponent value be present.
-bool RequireExponent(chars_format flags) {
-  bool fixed = (flags & chars_format::fixed) == chars_format::fixed;
-  bool scientific =
-      (flags & chars_format::scientific) == chars_format::scientific;
-  return scientific && !fixed;
-}
-
-const int8_t kAsciiToInt[256] = {
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0,  1,  2,  3,  4,  5,  6,  7,  8,
-    9,  -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, 10, 11, 12, 13, 14, 15, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
-    -1, -1, -1, -1, -1, -1, -1, -1, -1};
-
-// Returns true if `ch` is a digit in the given base
-template <int base>
-bool IsDigit(char ch);
-
-// Converts a valid `ch` to its digit value in the given base.
-template <int base>
-unsigned ToDigit(char ch);
-
-// Returns true if `ch` is the exponent delimiter for the given base.
-template <int base>
-bool IsExponentCharacter(char ch);
-
-// Returns the maximum number of significant digits we will read for a float
-// in the given base.
-template <int base>
-constexpr int MantissaDigitsMax();
-
-// Returns the largest consecutive run of digits we will accept when parsing a
-// number in the given base.
-template <int base>
-constexpr int DigitLimit();
-
-// Returns the amount the exponent must be adjusted by for each dropped digit.
-// (For decimal this is 1, since the digits are in base 10 and the exponent base
-// is also 10, but for hexadecimal this is 4, since the digits are base 16 but
-// the exponent base is 2.)
-template <int base>
-constexpr int DigitMagnitude();
-
-template <>
-bool IsDigit<10>(char ch) {
-  return ch >= '0' && ch <= '9';
-}
-template <>
-bool IsDigit<16>(char ch) {
-  return kAsciiToInt[static_cast<unsigned char>(ch)] >= 0;
-}
-
-template <>
-unsigned ToDigit<10>(char ch) {
-  return ch - '0';
-}
-template <>
-unsigned ToDigit<16>(char ch) {
-  return kAsciiToInt[static_cast<unsigned char>(ch)];
-}
-
-template <>
-bool IsExponentCharacter<10>(char ch) {
-  return ch == 'e' || ch == 'E';
-}
-
-template <>
-bool IsExponentCharacter<16>(char ch) {
-  return ch == 'p' || ch == 'P';
-}
-
-template <>
-constexpr int MantissaDigitsMax<10>() {
-  return kDecimalMantissaDigitsMax;
-}
-template <>
-constexpr int MantissaDigitsMax<16>() {
-  return kHexadecimalMantissaDigitsMax;
-}
-
-template <>
-constexpr int DigitLimit<10>() {
-  return kDecimalDigitLimit;
-}
-template <>
-constexpr int DigitLimit<16>() {
-  return kHexadecimalDigitLimit;
-}
-
-template <>
-constexpr int DigitMagnitude<10>() {
-  return 1;
-}
-template <>
-constexpr int DigitMagnitude<16>() {
-  return 4;
-}
-
-// Reads decimal digits from [begin, end) into *out.  Returns the number of
-// digits consumed.
-//
-// After max_digits has been read, keeps consuming characters, but no longer
-// adjusts *out.  If a nonzero digit is dropped this way, *dropped_nonzero_digit
-// is set; otherwise, it is left unmodified.
-//
-// If no digits are matched, returns 0 and leaves *out unchanged.
-//
-// ConsumeDigits does not protect against overflow on *out; max_digits must
-// be chosen with respect to type T to avoid the possibility of overflow.
-template <int base, typename T>
-std::size_t ConsumeDigits(const char* begin, const char* end, int max_digits,
-                          T* out, bool* dropped_nonzero_digit) {
-  if (base == 10) {
-    assert(max_digits <= std::numeric_limits<T>::digits10);
-  } else if (base == 16) {
-    assert(max_digits * 4 <= std::numeric_limits<T>::digits);
-  }
-  const char* const original_begin = begin;
-
-  // Skip leading zeros, but only if *out is zero.
-  // They don't cause an overflow so we don't have to count them for
-  // `max_digits`.
-  while (!*out && end != begin && *begin == '0') ++begin;
-
-  T accumulator = *out;
-  const char* significant_digits_end =
-      (end - begin > max_digits) ? begin + max_digits : end;
-  while (begin < significant_digits_end && IsDigit<base>(*begin)) {
-    // Do not guard against *out overflow; max_digits was chosen to avoid this.
-    // Do assert against it, to detect problems in debug builds.
-    auto digit = static_cast<T>(ToDigit<base>(*begin));
-    assert(accumulator * base >= accumulator);
-    accumulator *= base;
-    assert(accumulator + digit >= accumulator);
-    accumulator += digit;
-    ++begin;
-  }
-  bool dropped_nonzero = false;
-  while (begin < end && IsDigit<base>(*begin)) {
-    dropped_nonzero = dropped_nonzero || (*begin != '0');
-    ++begin;
-  }
-  if (dropped_nonzero && dropped_nonzero_digit != nullptr) {
-    *dropped_nonzero_digit = true;
-  }
-  *out = accumulator;
-  return begin - original_begin;
-}
-
-// Returns true if `v` is one of the chars allowed inside parentheses following
-// a NaN.
-bool IsNanChar(char v) {
-  return (v == '_') || (v >= '0' && v <= '9') || (v >= 'a' && v <= 'z') ||
-         (v >= 'A' && v <= 'Z');
-}
-
-// Checks the range [begin, end) for a strtod()-formatted infinity or NaN.  If
-// one is found, sets `out` appropriately and returns true.
-bool ParseInfinityOrNan(const char* begin, const char* end,
-                        strings_internal::ParsedFloat* out) {
-  if (end - begin < 3) {
-    return false;
-  }
-  switch (*begin) {
-    case 'i':
-    case 'I': {
-      // An infinity string consists of the characters "inf" or "infinity",
-      // case insensitive.
-      if (strings_internal::memcasecmp(begin + 1, "nf", 2) != 0) {
-        return false;
-      }
-      out->type = strings_internal::FloatType::kInfinity;
-      if (end - begin >= 8 &&
-          strings_internal::memcasecmp(begin + 3, "inity", 5) == 0) {
-        out->end = begin + 8;
-      } else {
-        out->end = begin + 3;
-      }
-      return true;
-    }
-    case 'n':
-    case 'N': {
-      // A NaN consists of the characters "nan", case insensitive, optionally
-      // followed by a parenthesized sequence of zero or more alphanumeric
-      // characters and/or underscores.
-      if (strings_internal::memcasecmp(begin + 1, "an", 2) != 0) {
-        return false;
-      }
-      out->type = strings_internal::FloatType::kNan;
-      out->end = begin + 3;
-      // NaN is allowed to be followed by a parenthesized string, consisting of
-      // only the characters [a-zA-Z0-9_].  Match that if it's present.
-      begin += 3;
-      if (begin < end && *begin == '(') {
-        const char* nan_begin = begin + 1;
-        while (nan_begin < end && IsNanChar(*nan_begin)) {
-          ++nan_begin;
-        }
-        if (nan_begin < end && *nan_begin == ')') {
-          // We found an extra NaN specifier range
-          out->subrange_begin = begin + 1;
-          out->subrange_end = nan_begin;
-          out->end = nan_begin + 1;
-        }
-      }
-      return true;
-    }
-    default:
-      return false;
-  }
-}
-}  // namespace
-
-namespace strings_internal {
-
-template <int base>
-strings_internal::ParsedFloat ParseFloat(const char* begin, const char* end,
-                                         chars_format format_flags) {
-  strings_internal::ParsedFloat result;
-
-  // Exit early if we're given an empty range.
-  if (begin == end) return result;
-
-  // Handle the infinity and NaN cases.
-  if (ParseInfinityOrNan(begin, end, &result)) {
-    return result;
-  }
-
-  const char* const mantissa_begin = begin;
-  while (begin < end && *begin == '0') {
-    ++begin;  // skip leading zeros
-  }
-  uint64_t mantissa = 0;
-
-  int exponent_adjustment = 0;
-  bool mantissa_is_inexact = false;
-  std::size_t pre_decimal_digits = ConsumeDigits<base>(
-      begin, end, MantissaDigitsMax<base>(), &mantissa, &mantissa_is_inexact);
-  begin += pre_decimal_digits;
-  int digits_left;
-  if (pre_decimal_digits >= DigitLimit<base>()) {
-    // refuse to parse pathological inputs
-    return result;
-  } else if (pre_decimal_digits > MantissaDigitsMax<base>()) {
-    // We dropped some non-fraction digits on the floor.  Adjust our exponent
-    // to compensate.
-    exponent_adjustment =
-        static_cast<int>(pre_decimal_digits - MantissaDigitsMax<base>());
-    digits_left = 0;
-  } else {
-    digits_left =
-        static_cast<int>(MantissaDigitsMax<base>() - pre_decimal_digits);
-  }
-  if (begin < end && *begin == '.') {
-    ++begin;
-    if (mantissa == 0) {
-      // If we haven't seen any nonzero digits yet, keep skipping zeros.  We
-      // have to adjust the exponent to reflect the changed place value.
-      const char* begin_zeros = begin;
-      while (begin < end && *begin == '0') {
-        ++begin;
-      }
-      std::size_t zeros_skipped = begin - begin_zeros;
-      if (zeros_skipped >= DigitLimit<base>()) {
-        // refuse to parse pathological inputs
-        return result;
-      }
-      exponent_adjustment -= static_cast<int>(zeros_skipped);
-    }
-    std::size_t post_decimal_digits = ConsumeDigits<base>(
-        begin, end, digits_left, &mantissa, &mantissa_is_inexact);
-    begin += post_decimal_digits;
-
-    // Since `mantissa` is an integer, each significant digit we read after
-    // the decimal point requires an adjustment to the exponent. "1.23e0" will
-    // be stored as `mantissa` == 123 and `exponent` == -2 (that is,
-    // "123e-2").
-    if (post_decimal_digits >= DigitLimit<base>()) {
-      // refuse to parse pathological inputs
-      return result;
-    } else if (post_decimal_digits > digits_left) {
-      exponent_adjustment -= digits_left;
-    } else {
-      exponent_adjustment -= post_decimal_digits;
-    }
-  }
-  // If we've found no mantissa whatsoever, this isn't a number.
-  if (mantissa_begin == begin) {
-    return result;
-  }
-  // A bare "." doesn't count as a mantissa either.
-  if (begin - mantissa_begin == 1 && *mantissa_begin == '.') {
-    return result;
-  }
-
-  if (mantissa_is_inexact) {
-    // We dropped significant digits on the floor.  Handle this appropriately.
-    if (base == 10) {
-      // If we truncated significant decimal digits, store the full range of the
-      // mantissa for future big integer math for exact rounding.
-      result.subrange_begin = mantissa_begin;
-      result.subrange_end = begin;
-    } else if (base == 16) {
-      // If we truncated hex digits, reflect this fact by setting the low
-      // ("sticky") bit.  This allows for correct rounding in all cases.
-      mantissa |= 1;
-    }
-  }
-  result.mantissa = mantissa;
-
-  const char* const exponent_begin = begin;
-  result.literal_exponent = 0;
-  bool found_exponent = false;
-  if (AllowExponent(format_flags) && begin < end &&
-      IsExponentCharacter<base>(*begin)) {
-    bool negative_exponent = false;
-    ++begin;
-    if (begin < end && *begin == '-') {
-      negative_exponent = true;
-      ++begin;
-    } else if (begin < end && *begin == '+') {
-      ++begin;
-    }
-    const char* const exponent_digits_begin = begin;
-    // Exponent is always expressed in decimal, even for hexadecimal floats.
-    begin += ConsumeDigits<10>(begin, end, kDecimalExponentDigitsMax,
-                               &result.literal_exponent, nullptr);
-    if (begin == exponent_digits_begin) {
-      // there were no digits where we expected an exponent.  We failed to read
-      // an exponent and should not consume the 'e' after all.  Rewind 'begin'.
-      found_exponent = false;
-      begin = exponent_begin;
-    } else {
-      found_exponent = true;
-      if (negative_exponent) {
-        result.literal_exponent = -result.literal_exponent;
-      }
-    }
-  }
-
-  if (!found_exponent && RequireExponent(format_flags)) {
-    // Provided flags required an exponent, but none was found.  This results
-    // in a failure to scan.
-    return result;
-  }
-
-  // Success!
-  result.type = strings_internal::FloatType::kNumber;
-  if (result.mantissa > 0) {
-    result.exponent = result.literal_exponent +
-                      (DigitMagnitude<base>() * exponent_adjustment);
-  } else {
-    result.exponent = 0;
-  }
-  result.end = begin;
-  return result;
-}
-
-template ParsedFloat ParseFloat<10>(const char* begin, const char* end,
-                                    chars_format format_flags);
-template ParsedFloat ParseFloat<16>(const char* begin, const char* end,
-                                    chars_format format_flags);
-
-}  // namespace strings_internal
-ABSL_NAMESPACE_END
-}  // namespace absl