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Diffstat (limited to 'third_party/abseil_cpp/absl/strings/numbers.cc')
| -rw-r--r-- | third_party/abseil_cpp/absl/strings/numbers.cc | 965 |
1 files changed, 965 insertions, 0 deletions
diff --git a/third_party/abseil_cpp/absl/strings/numbers.cc b/third_party/abseil_cpp/absl/strings/numbers.cc new file mode 100644 index 000000000000..68c26dd6f8c1 --- /dev/null +++ b/third_party/abseil_cpp/absl/strings/numbers.cc @@ -0,0 +1,965 @@ +// Copyright 2017 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. + +// This file contains string processing functions related to +// numeric values. + +#include "absl/strings/numbers.h" + +#include <algorithm> +#include <cassert> +#include <cfloat> // for DBL_DIG and FLT_DIG +#include <cmath> // for HUGE_VAL +#include <cstdint> +#include <cstdio> +#include <cstdlib> +#include <cstring> +#include <iterator> +#include <limits> +#include <memory> +#include <utility> + +#include "absl/base/attributes.h" +#include "absl/base/internal/bits.h" +#include "absl/base/internal/raw_logging.h" +#include "absl/strings/ascii.h" +#include "absl/strings/charconv.h" +#include "absl/strings/escaping.h" +#include "absl/strings/internal/memutil.h" +#include "absl/strings/match.h" +#include "absl/strings/str_cat.h" + +namespace absl { +ABSL_NAMESPACE_BEGIN + +bool SimpleAtof(absl::string_view str, float* out) { + *out = 0.0; + str = StripAsciiWhitespace(str); + if (!str.empty() && str[0] == '+') { + str.remove_prefix(1); + } + auto result = absl::from_chars(str.data(), str.data() + str.size(), *out); + if (result.ec == std::errc::invalid_argument) { + return false; + } + if (result.ptr != str.data() + str.size()) { + // not all non-whitespace characters consumed + return false; + } + // from_chars() with DR 3081's current wording will return max() on + // overflow. SimpleAtof returns infinity instead. + if (result.ec == std::errc::result_out_of_range) { + if (*out > 1.0) { + *out = std::numeric_limits<float>::infinity(); + } else if (*out < -1.0) { + *out = -std::numeric_limits<float>::infinity(); + } + } + return true; +} + +bool SimpleAtod(absl::string_view str, double* out) { + *out = 0.0; + str = StripAsciiWhitespace(str); + if (!str.empty() && str[0] == '+') { + str.remove_prefix(1); + } + auto result = absl::from_chars(str.data(), str.data() + str.size(), *out); + if (result.ec == std::errc::invalid_argument) { + return false; + } + if (result.ptr != str.data() + str.size()) { + // not all non-whitespace characters consumed + return false; + } + // from_chars() with DR 3081's current wording will return max() on + // overflow. SimpleAtod returns infinity instead. + if (result.ec == std::errc::result_out_of_range) { + if (*out > 1.0) { + *out = std::numeric_limits<double>::infinity(); + } else if (*out < -1.0) { + *out = -std::numeric_limits<double>::infinity(); + } + } + return true; +} + +bool SimpleAtob(absl::string_view str, bool* out) { + ABSL_RAW_CHECK(out != nullptr, "Output pointer must not be nullptr."); + if (EqualsIgnoreCase(str, "true") || EqualsIgnoreCase(str, "t") || + EqualsIgnoreCase(str, "yes") || EqualsIgnoreCase(str, "y") || + EqualsIgnoreCase(str, "1")) { + *out = true; + return true; + } + if (EqualsIgnoreCase(str, "false") || EqualsIgnoreCase(str, "f") || + EqualsIgnoreCase(str, "no") || EqualsIgnoreCase(str, "n") || + EqualsIgnoreCase(str, "0")) { + *out = false; + return true; + } + return false; +} + +// ---------------------------------------------------------------------- +// FastIntToBuffer() overloads +// +// Like the Fast*ToBuffer() functions above, these are intended for speed. +// Unlike the Fast*ToBuffer() functions, however, these functions write +// their output to the beginning of the buffer. The caller is responsible +// for ensuring that the buffer has enough space to hold the output. +// +// Returns a pointer to the end of the string (i.e. the null character +// terminating the string). +// ---------------------------------------------------------------------- + +namespace { + +// Used to optimize printing a decimal number's final digit. +const char one_ASCII_final_digits[10][2] { + {'0', 0}, {'1', 0}, {'2', 0}, {'3', 0}, {'4', 0}, + {'5', 0}, {'6', 0}, {'7', 0}, {'8', 0}, {'9', 0}, +}; + +} // namespace + +char* numbers_internal::FastIntToBuffer(uint32_t i, char* buffer) { + uint32_t digits; + // The idea of this implementation is to trim the number of divides to as few + // as possible, and also reducing memory stores and branches, by going in + // steps of two digits at a time rather than one whenever possible. + // The huge-number case is first, in the hopes that the compiler will output + // that case in one branch-free block of code, and only output conditional + // branches into it from below. + if (i >= 1000000000) { // >= 1,000,000,000 + digits = i / 100000000; // 100,000,000 + i -= digits * 100000000; + PutTwoDigits(digits, buffer); + buffer += 2; + lt100_000_000: + digits = i / 1000000; // 1,000,000 + i -= digits * 1000000; + PutTwoDigits(digits, buffer); + buffer += 2; + lt1_000_000: + digits = i / 10000; // 10,000 + i -= digits * 10000; + PutTwoDigits(digits, buffer); + buffer += 2; + lt10_000: + digits = i / 100; + i -= digits * 100; + PutTwoDigits(digits, buffer); + buffer += 2; + lt100: + digits = i; + PutTwoDigits(digits, buffer); + buffer += 2; + *buffer = 0; + return buffer; + } + + if (i < 100) { + digits = i; + if (i >= 10) goto lt100; + memcpy(buffer, one_ASCII_final_digits[i], 2); + return buffer + 1; + } + if (i < 10000) { // 10,000 + if (i >= 1000) goto lt10_000; + digits = i / 100; + i -= digits * 100; + *buffer++ = '0' + digits; + goto lt100; + } + if (i < 1000000) { // 1,000,000 + if (i >= 100000) goto lt1_000_000; + digits = i / 10000; // 10,000 + i -= digits * 10000; + *buffer++ = '0' + digits; + goto lt10_000; + } + if (i < 100000000) { // 100,000,000 + if (i >= 10000000) goto lt100_000_000; + digits = i / 1000000; // 1,000,000 + i -= digits * 1000000; + *buffer++ = '0' + digits; + goto lt1_000_000; + } + // we already know that i < 1,000,000,000 + digits = i / 100000000; // 100,000,000 + i -= digits * 100000000; + *buffer++ = '0' + digits; + goto lt100_000_000; +} + +char* numbers_internal::FastIntToBuffer(int32_t i, char* buffer) { + uint32_t u = i; + if (i < 0) { + *buffer++ = '-'; + // We need to do the negation in modular (i.e., "unsigned") + // arithmetic; MSVC++ apprently warns for plain "-u", so + // we write the equivalent expression "0 - u" instead. + u = 0 - u; + } + return numbers_internal::FastIntToBuffer(u, buffer); +} + +char* numbers_internal::FastIntToBuffer(uint64_t i, char* buffer) { + uint32_t u32 = static_cast<uint32_t>(i); + if (u32 == i) return numbers_internal::FastIntToBuffer(u32, buffer); + + // Here we know i has at least 10 decimal digits. + uint64_t top_1to11 = i / 1000000000; + u32 = static_cast<uint32_t>(i - top_1to11 * 1000000000); + uint32_t top_1to11_32 = static_cast<uint32_t>(top_1to11); + + if (top_1to11_32 == top_1to11) { + buffer = numbers_internal::FastIntToBuffer(top_1to11_32, buffer); + } else { + // top_1to11 has more than 32 bits too; print it in two steps. + uint32_t top_8to9 = static_cast<uint32_t>(top_1to11 / 100); + uint32_t mid_2 = static_cast<uint32_t>(top_1to11 - top_8to9 * 100); + buffer = numbers_internal::FastIntToBuffer(top_8to9, buffer); + PutTwoDigits(mid_2, buffer); + buffer += 2; + } + + // We have only 9 digits now, again the maximum uint32_t can handle fully. + uint32_t digits = u32 / 10000000; // 10,000,000 + u32 -= digits * 10000000; + PutTwoDigits(digits, buffer); + buffer += 2; + digits = u32 / 100000; // 100,000 + u32 -= digits * 100000; + PutTwoDigits(digits, buffer); + buffer += 2; + digits = u32 / 1000; // 1,000 + u32 -= digits * 1000; + PutTwoDigits(digits, buffer); + buffer += 2; + digits = u32 / 10; + u32 -= digits * 10; + PutTwoDigits(digits, buffer); + buffer += 2; + memcpy(buffer, one_ASCII_final_digits[u32], 2); + return buffer + 1; +} + +char* numbers_internal::FastIntToBuffer(int64_t i, char* buffer) { + uint64_t u = i; + if (i < 0) { + *buffer++ = '-'; + u = 0 - u; + } + return numbers_internal::FastIntToBuffer(u, buffer); +} + +// Given a 128-bit number expressed as a pair of uint64_t, high half first, +// return that number multiplied by the given 32-bit value. If the result is +// too large to fit in a 128-bit number, divide it by 2 until it fits. +static std::pair<uint64_t, uint64_t> Mul32(std::pair<uint64_t, uint64_t> num, + uint32_t mul) { + uint64_t bits0_31 = num.second & 0xFFFFFFFF; + uint64_t bits32_63 = num.second >> 32; + uint64_t bits64_95 = num.first & 0xFFFFFFFF; + uint64_t bits96_127 = num.first >> 32; + + // The picture so far: each of these 64-bit values has only the lower 32 bits + // filled in. + // bits96_127: [ 00000000 xxxxxxxx ] + // bits64_95: [ 00000000 xxxxxxxx ] + // bits32_63: [ 00000000 xxxxxxxx ] + // bits0_31: [ 00000000 xxxxxxxx ] + + bits0_31 *= mul; + bits32_63 *= mul; + bits64_95 *= mul; + bits96_127 *= mul; + + // Now the top halves may also have value, though all 64 of their bits will + // never be set at the same time, since they are a result of a 32x32 bit + // multiply. This makes the carry calculation slightly easier. + // bits96_127: [ mmmmmmmm | mmmmmmmm ] + // bits64_95: [ | mmmmmmmm mmmmmmmm | ] + // bits32_63: | [ mmmmmmmm | mmmmmmmm ] + // bits0_31: | [ | mmmmmmmm mmmmmmmm ] + // eventually: [ bits128_up | ...bits64_127.... | ..bits0_63... ] + + uint64_t bits0_63 = bits0_31 + (bits32_63 << 32); + uint64_t bits64_127 = bits64_95 + (bits96_127 << 32) + (bits32_63 >> 32) + + (bits0_63 < bits0_31); + uint64_t bits128_up = (bits96_127 >> 32) + (bits64_127 < bits64_95); + if (bits128_up == 0) return {bits64_127, bits0_63}; + + int shift = 64 - base_internal::CountLeadingZeros64(bits128_up); + uint64_t lo = (bits0_63 >> shift) + (bits64_127 << (64 - shift)); + uint64_t hi = (bits64_127 >> shift) + (bits128_up << (64 - shift)); + return {hi, lo}; +} + +// Compute num * 5 ^ expfive, and return the first 128 bits of the result, +// where the first bit is always a one. So PowFive(1, 0) starts 0b100000, +// PowFive(1, 1) starts 0b101000, PowFive(1, 2) starts 0b110010, etc. +static std::pair<uint64_t, uint64_t> PowFive(uint64_t num, int expfive) { + std::pair<uint64_t, uint64_t> result = {num, 0}; + while (expfive >= 13) { + // 5^13 is the highest power of five that will fit in a 32-bit integer. + result = Mul32(result, 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5); + expfive -= 13; + } + constexpr int powers_of_five[13] = { + 1, + 5, + 5 * 5, + 5 * 5 * 5, + 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5, + 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5 * 5}; + result = Mul32(result, powers_of_five[expfive & 15]); + int shift = base_internal::CountLeadingZeros64(result.first); + if (shift != 0) { + result.first = (result.first << shift) + (result.second >> (64 - shift)); + result.second = (result.second << shift); + } + return result; +} + +struct ExpDigits { + int32_t exponent; + char digits[6]; +}; + +// SplitToSix converts value, a positive double-precision floating-point number, +// into a base-10 exponent and 6 ASCII digits, where the first digit is never +// zero. For example, SplitToSix(1) returns an exponent of zero and a digits +// array of {'1', '0', '0', '0', '0', '0'}. If value is exactly halfway between +// two possible representations, e.g. value = 100000.5, then "round to even" is +// performed. +static ExpDigits SplitToSix(const double value) { + ExpDigits exp_dig; + int exp = 5; + double d = value; + // First step: calculate a close approximation of the output, where the + // value d will be between 100,000 and 999,999, representing the digits + // in the output ASCII array, and exp is the base-10 exponent. It would be + // faster to use a table here, and to look up the base-2 exponent of value, + // however value is an IEEE-754 64-bit number, so the table would have 2,000 + // entries, which is not cache-friendly. + if (d >= 999999.5) { + if (d >= 1e+261) exp += 256, d *= 1e-256; + if (d >= 1e+133) exp += 128, d *= 1e-128; + if (d >= 1e+69) exp += 64, d *= 1e-64; + if (d >= 1e+37) exp += 32, d *= 1e-32; + if (d >= 1e+21) exp += 16, d *= 1e-16; + if (d >= 1e+13) exp += 8, d *= 1e-8; + if (d >= 1e+9) exp += 4, d *= 1e-4; + if (d >= 1e+7) exp += 2, d *= 1e-2; + if (d >= 1e+6) exp += 1, d *= 1e-1; + } else { + if (d < 1e-250) exp -= 256, d *= 1e256; + if (d < 1e-122) exp -= 128, d *= 1e128; + if (d < 1e-58) exp -= 64, d *= 1e64; + if (d < 1e-26) exp -= 32, d *= 1e32; + if (d < 1e-10) exp -= 16, d *= 1e16; + if (d < 1e-2) exp -= 8, d *= 1e8; + if (d < 1e+2) exp -= 4, d *= 1e4; + if (d < 1e+4) exp -= 2, d *= 1e2; + if (d < 1e+5) exp -= 1, d *= 1e1; + } + // At this point, d is in the range [99999.5..999999.5) and exp is in the + // range [-324..308]. Since we need to round d up, we want to add a half + // and truncate. + // However, the technique above may have lost some precision, due to its + // repeated multiplication by constants that each may be off by half a bit + // of precision. This only matters if we're close to the edge though. + // Since we'd like to know if the fractional part of d is close to a half, + // we multiply it by 65536 and see if the fractional part is close to 32768. + // (The number doesn't have to be a power of two,but powers of two are faster) + uint64_t d64k = d * 65536; + int dddddd; // A 6-digit decimal integer. + if ((d64k % 65536) == 32767 || (d64k % 65536) == 32768) { + // OK, it's fairly likely that precision was lost above, which is + // not a surprise given only 52 mantissa bits are available. Therefore + // redo the calculation using 128-bit numbers. (64 bits are not enough). + + // Start out with digits rounded down; maybe add one below. + dddddd = static_cast<int>(d64k / 65536); + + // mantissa is a 64-bit integer representing M.mmm... * 2^63. The actual + // value we're representing, of course, is M.mmm... * 2^exp2. + int exp2; + double m = std::frexp(value, &exp2); + uint64_t mantissa = m * (32768.0 * 65536.0 * 65536.0 * 65536.0); + // std::frexp returns an m value in the range [0.5, 1.0), however we + // can't multiply it by 2^64 and convert to an integer because some FPUs + // throw an exception when converting an number higher than 2^63 into an + // integer - even an unsigned 64-bit integer! Fortunately it doesn't matter + // since m only has 52 significant bits anyway. + mantissa <<= 1; + exp2 -= 64; // not needed, but nice for debugging + + // OK, we are here to compare: + // (dddddd + 0.5) * 10^(exp-5) vs. mantissa * 2^exp2 + // so we can round up dddddd if appropriate. Those values span the full + // range of 600 orders of magnitude of IEE 64-bit floating-point. + // Fortunately, we already know they are very close, so we don't need to + // track the base-2 exponent of both sides. This greatly simplifies the + // the math since the 2^exp2 calculation is unnecessary and the power-of-10 + // calculation can become a power-of-5 instead. + + std::pair<uint64_t, uint64_t> edge, val; + if (exp >= 6) { + // Compare (dddddd + 0.5) * 5 ^ (exp - 5) to mantissa + // Since we're tossing powers of two, 2 * dddddd + 1 is the + // same as dddddd + 0.5 + edge = PowFive(2 * dddddd + 1, exp - 5); + + val.first = mantissa; + val.second = 0; + } else { + // We can't compare (dddddd + 0.5) * 5 ^ (exp - 5) to mantissa as we did + // above because (exp - 5) is negative. So we compare (dddddd + 0.5) to + // mantissa * 5 ^ (5 - exp) + edge = PowFive(2 * dddddd + 1, 0); + + val = PowFive(mantissa, 5 - exp); + } + // printf("exp=%d %016lx %016lx vs %016lx %016lx\n", exp, val.first, + // val.second, edge.first, edge.second); + if (val > edge) { + dddddd++; + } else if (val == edge) { + dddddd += (dddddd & 1); + } + } else { + // Here, we are not close to the edge. + dddddd = static_cast<int>((d64k + 32768) / 65536); + } + if (dddddd == 1000000) { + dddddd = 100000; + exp += 1; + } + exp_dig.exponent = exp; + + int two_digits = dddddd / 10000; + dddddd -= two_digits * 10000; + numbers_internal::PutTwoDigits(two_digits, &exp_dig.digits[0]); + + two_digits = dddddd / 100; + dddddd -= two_digits * 100; + numbers_internal::PutTwoDigits(two_digits, &exp_dig.digits[2]); + + numbers_internal::PutTwoDigits(dddddd, &exp_dig.digits[4]); + return exp_dig; +} + +// Helper function for fast formatting of floating-point. +// The result is the same as "%g", a.k.a. "%.6g". +size_t numbers_internal::SixDigitsToBuffer(double d, char* const buffer) { + static_assert(std::numeric_limits<float>::is_iec559, + "IEEE-754/IEC-559 support only"); + + char* out = buffer; // we write data to out, incrementing as we go, but + // FloatToBuffer always returns the address of the buffer + // passed in. + + if (std::isnan(d)) { + strcpy(out, "nan"); // NOLINT(runtime/printf) + return 3; + } + if (d == 0) { // +0 and -0 are handled here + if (std::signbit(d)) *out++ = '-'; + *out++ = '0'; + *out = 0; + return out - buffer; + } + if (d < 0) { + *out++ = '-'; + d = -d; + } + if (std::isinf(d)) { + strcpy(out, "inf"); // NOLINT(runtime/printf) + return out + 3 - buffer; + } + + auto exp_dig = SplitToSix(d); + int exp = exp_dig.exponent; + const char* digits = exp_dig.digits; + out[0] = '0'; + out[1] = '.'; + switch (exp) { + case 5: + memcpy(out, &digits[0], 6), out += 6; + *out = 0; + return out - buffer; + case 4: + memcpy(out, &digits[0], 5), out += 5; + if (digits[5] != '0') { + *out++ = '.'; + *out++ = digits[5]; + } + *out = 0; + return out - buffer; + case 3: + memcpy(out, &digits[0], 4), out += 4; + if ((digits[5] | digits[4]) != '0') { + *out++ = '.'; + *out++ = digits[4]; + if (digits[5] != '0') *out++ = digits[5]; + } + *out = 0; + return out - buffer; + case 2: + memcpy(out, &digits[0], 3), out += 3; + *out++ = '.'; + memcpy(out, &digits[3], 3); + out += 3; + while (out[-1] == '0') --out; + if (out[-1] == '.') --out; + *out = 0; + return out - buffer; + case 1: + memcpy(out, &digits[0], 2), out += 2; + *out++ = '.'; + memcpy(out, &digits[2], 4); + out += 4; + while (out[-1] == '0') --out; + if (out[-1] == '.') --out; + *out = 0; + return out - buffer; + case 0: + memcpy(out, &digits[0], 1), out += 1; + *out++ = '.'; + memcpy(out, &digits[1], 5); + out += 5; + while (out[-1] == '0') --out; + if (out[-1] == '.') --out; + *out = 0; + return out - buffer; + case -4: + out[2] = '0'; + ++out; + ABSL_FALLTHROUGH_INTENDED; + case -3: + out[2] = '0'; + ++out; + ABSL_FALLTHROUGH_INTENDED; + case -2: + out[2] = '0'; + ++out; + ABSL_FALLTHROUGH_INTENDED; + case -1: + out += 2; + memcpy(out, &digits[0], 6); + out += 6; + while (out[-1] == '0') --out; + *out = 0; + return out - buffer; + } + assert(exp < -4 || exp >= 6); + out[0] = digits[0]; + assert(out[1] == '.'); + out += 2; + memcpy(out, &digits[1], 5), out += 5; + while (out[-1] == '0') --out; + if (out[-1] == '.') --out; + *out++ = 'e'; + if (exp > 0) { + *out++ = '+'; + } else { + *out++ = '-'; + exp = -exp; + } + if (exp > 99) { + int dig1 = exp / 100; + exp -= dig1 * 100; + *out++ = '0' + dig1; + } + PutTwoDigits(exp, out); + out += 2; + *out = 0; + return out - buffer; +} + +namespace { +// Represents integer values of digits. +// Uses 36 to indicate an invalid character since we support +// bases up to 36. +static const int8_t kAsciiToInt[256] = { + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, // 16 36s. + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 0, 1, 2, 3, 4, 5, + 6, 7, 8, 9, 36, 36, 36, 36, 36, 36, 36, 10, 11, 12, 13, 14, 15, 16, 17, + 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, + 36, 36, 36, 36, 36, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, + 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, + 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36, 36}; + +// Parse the sign and optional hex or oct prefix in text. +inline bool safe_parse_sign_and_base(absl::string_view* text /*inout*/, + int* base_ptr /*inout*/, + bool* negative_ptr /*output*/) { + if (text->data() == nullptr) { + return false; + } + + const char* start = text->data(); + const char* end = start + text->size(); + int base = *base_ptr; + + // Consume whitespace. + while (start < end && absl::ascii_isspace(start[0])) { + ++start; + } + while (start < end && absl::ascii_isspace(end[-1])) { + --end; + } + if (start >= end) { + return false; + } + + // Consume sign. + *negative_ptr = (start[0] == '-'); + if (*negative_ptr || start[0] == '+') { + ++start; + if (start >= end) { + return false; + } + } + + // Consume base-dependent prefix. + // base 0: "0x" -> base 16, "0" -> base 8, default -> base 10 + // base 16: "0x" -> base 16 + // Also validate the base. + if (base == 0) { + if (end - start >= 2 && start[0] == '0' && + (start[1] == 'x' || start[1] == 'X')) { + base = 16; + start += 2; + if (start >= end) { + // "0x" with no digits after is invalid. + return false; + } + } else if (end - start >= 1 && start[0] == '0') { + base = 8; + start += 1; + } else { + base = 10; + } + } else if (base == 16) { + if (end - start >= 2 && start[0] == '0' && + (start[1] == 'x' || start[1] == 'X')) { + start += 2; + if (start >= end) { + // "0x" with no digits after is invalid. + return false; + } + } + } else if (base >= 2 && base <= 36) { + // okay + } else { + return false; + } + *text = absl::string_view(start, end - start); + *base_ptr = base; + return true; +} + +// Consume digits. +// +// The classic loop: +// +// for each digit +// value = value * base + digit +// value *= sign +// +// The classic loop needs overflow checking. It also fails on the most +// negative integer, -2147483648 in 32-bit two's complement representation. +// +// My improved loop: +// +// if (!negative) +// for each digit +// value = value * base +// value = value + digit +// else +// for each digit +// value = value * base +// value = value - digit +// +// Overflow checking becomes simple. + +// Lookup tables per IntType: +// vmax/base and vmin/base are precomputed because division costs at least 8ns. +// TODO(junyer): Doing this per base instead (i.e. an array of structs, not a +// struct of arrays) would probably be better in terms of d-cache for the most +// commonly used bases. +template <typename IntType> +struct LookupTables { + ABSL_CONST_INIT static const IntType kVmaxOverBase[]; + ABSL_CONST_INIT static const IntType kVminOverBase[]; +}; + +// An array initializer macro for X/base where base in [0, 36]. +// However, note that lookups for base in [0, 1] should never happen because +// base has been validated to be in [2, 36] by safe_parse_sign_and_base(). +#define X_OVER_BASE_INITIALIZER(X) \ + { \ + 0, 0, X / 2, X / 3, X / 4, X / 5, X / 6, X / 7, X / 8, X / 9, X / 10, \ + X / 11, X / 12, X / 13, X / 14, X / 15, X / 16, X / 17, X / 18, \ + X / 19, X / 20, X / 21, X / 22, X / 23, X / 24, X / 25, X / 26, \ + X / 27, X / 28, X / 29, X / 30, X / 31, X / 32, X / 33, X / 34, \ + X / 35, X / 36, \ + } + +// uint128& operator/=(uint128) is not constexpr, so hardcode the resulting +// array to avoid a static initializer. +template <> +const uint128 LookupTables<uint128>::kVmaxOverBase[] = { + 0, + 0, + MakeUint128(9223372036854775807u, 18446744073709551615u), + MakeUint128(6148914691236517205u, 6148914691236517205u), + MakeUint128(4611686018427387903u, 18446744073709551615u), + MakeUint128(3689348814741910323u, 3689348814741910323u), + MakeUint128(3074457345618258602u, 12297829382473034410u), + MakeUint128(2635249153387078802u, 5270498306774157604u), + MakeUint128(2305843009213693951u, 18446744073709551615u), + MakeUint128(2049638230412172401u, 14347467612885206812u), + MakeUint128(1844674407370955161u, 11068046444225730969u), + MakeUint128(1676976733973595601u, 8384883669867978007u), + MakeUint128(1537228672809129301u, 6148914691236517205u), + MakeUint128(1418980313362273201u, 4256940940086819603u), + MakeUint128(1317624576693539401u, 2635249153387078802u), + MakeUint128(1229782938247303441u, 1229782938247303441u), + MakeUint128(1152921504606846975u, 18446744073709551615u), + MakeUint128(1085102592571150095u, 1085102592571150095u), + MakeUint128(1024819115206086200u, 16397105843297379214u), + MakeUint128(970881267037344821u, 16504981539634861972u), + MakeUint128(922337203685477580u, 14757395258967641292u), + MakeUint128(878416384462359600u, 14054662151397753612u), + MakeUint128(838488366986797800u, 13415813871788764811u), + MakeUint128(802032351030850070u, 4812194106185100421u), + MakeUint128(768614336404564650u, 12297829382473034410u), + MakeUint128(737869762948382064u, 11805916207174113034u), + MakeUint128(709490156681136600u, 11351842506898185609u), + MakeUint128(683212743470724133u, 17080318586768103348u), + MakeUint128(658812288346769700u, 10540996613548315209u), + MakeUint128(636094623231363848u, 15266270957552732371u), + MakeUint128(614891469123651720u, 9838263505978427528u), + MakeUint128(595056260442243600u, 9520900167075897608u), + MakeUint128(576460752303423487u, 18446744073709551615u), + MakeUint128(558992244657865200u, 8943875914525843207u), + MakeUint128(542551296285575047u, 9765923333140350855u), + MakeUint128(527049830677415760u, 8432797290838652167u), + MakeUint128(512409557603043100u, 8198552921648689607u), +}; + +template <typename IntType> +const IntType LookupTables<IntType>::kVmaxOverBase[] = + X_OVER_BASE_INITIALIZER(std::numeric_limits<IntType>::max()); + +template <typename IntType> +const IntType LookupTables<IntType>::kVminOverBase[] = + X_OVER_BASE_INITIALIZER(std::numeric_limits<IntType>::min()); + +#undef X_OVER_BASE_INITIALIZER + +template <typename IntType> +inline bool safe_parse_positive_int(absl::string_view text, int base, + IntType* value_p) { + IntType value = 0; + const IntType vmax = std::numeric_limits<IntType>::max(); + assert(vmax > 0); + assert(base >= 0); + assert(vmax >= static_cast<IntType>(base)); + const IntType vmax_over_base = LookupTables<IntType>::kVmaxOverBase[base]; + assert(base < 2 || + std::numeric_limits<IntType>::max() / base == vmax_over_base); + const char* start = text.data(); + const char* end = start + text.size(); + // loop over digits + for (; start < end; ++start) { + unsigned char c = static_cast<unsigned char>(start[0]); + int digit = kAsciiToInt[c]; + if (digit >= base) { + *value_p = value; + return false; + } + if (value > vmax_over_base) { + *value_p = vmax; + return false; + } + value *= base; + if (value > vmax - digit) { + *value_p = vmax; + return false; + } + value += digit; + } + *value_p = value; + return true; +} + +template <typename IntType> +inline bool safe_parse_negative_int(absl::string_view text, int base, + IntType* value_p) { + IntType value = 0; + const IntType vmin = std::numeric_limits<IntType>::min(); + assert(vmin < 0); + assert(vmin <= 0 - base); + IntType vmin_over_base = LookupTables<IntType>::kVminOverBase[base]; + assert(base < 2 || + std::numeric_limits<IntType>::min() / base == vmin_over_base); + // 2003 c++ standard [expr.mul] + // "... the sign of the remainder is implementation-defined." + // Although (vmin/base)*base + vmin%base is always vmin. + // 2011 c++ standard tightens the spec but we cannot rely on it. + // TODO(junyer): Handle this in the lookup table generation. + if (vmin % base > 0) { + vmin_over_base += 1; + } + const char* start = text.data(); + const char* end = start + text.size(); + // loop over digits + for (; start < end; ++start) { + unsigned char c = static_cast<unsigned char>(start[0]); + int digit = kAsciiToInt[c]; + if (digit >= base) { + *value_p = value; + return false; + } + if (value < vmin_over_base) { + *value_p = vmin; + return false; + } + value *= base; + if (value < vmin + digit) { + *value_p = vmin; + return false; + } + value -= digit; + } + *value_p = value; + return true; +} + +// Input format based on POSIX.1-2008 strtol +// http://pubs.opengroup.org/onlinepubs/9699919799/functions/strtol.html +template <typename IntType> +inline bool safe_int_internal(absl::string_view text, IntType* value_p, + int base) { + *value_p = 0; + bool negative; + if (!safe_parse_sign_and_base(&text, &base, &negative)) { + return false; + } + if (!negative) { + return safe_parse_positive_int(text, base, value_p); + } else { + return safe_parse_negative_int(text, base, value_p); + } +} + +template <typename IntType> +inline bool safe_uint_internal(absl::string_view text, IntType* value_p, + int base) { + *value_p = 0; + bool negative; + if (!safe_parse_sign_and_base(&text, &base, &negative) || negative) { + return false; + } + return safe_parse_positive_int(text, base, value_p); +} +} // anonymous namespace + +namespace numbers_internal { + +// Digit conversion. +ABSL_CONST_INIT ABSL_DLL const char kHexChar[] = + "0123456789abcdef"; + +ABSL_CONST_INIT ABSL_DLL const char kHexTable[513] = + "000102030405060708090a0b0c0d0e0f" + "101112131415161718191a1b1c1d1e1f" + "202122232425262728292a2b2c2d2e2f" + "303132333435363738393a3b3c3d3e3f" + "404142434445464748494a4b4c4d4e4f" + "505152535455565758595a5b5c5d5e5f" + "606162636465666768696a6b6c6d6e6f" + "707172737475767778797a7b7c7d7e7f" + "808182838485868788898a8b8c8d8e8f" + "909192939495969798999a9b9c9d9e9f" + "a0a1a2a3a4a5a6a7a8a9aaabacadaeaf" + "b0b1b2b3b4b5b6b7b8b9babbbcbdbebf" + "c0c1c2c3c4c5c6c7c8c9cacbcccdcecf" + "d0d1d2d3d4d5d6d7d8d9dadbdcdddedf" + "e0e1e2e3e4e5e6e7e8e9eaebecedeeef" + "f0f1f2f3f4f5f6f7f8f9fafbfcfdfeff"; + +ABSL_CONST_INIT ABSL_DLL const char two_ASCII_digits[100][2] = { + {'0', '0'}, {'0', '1'}, {'0', '2'}, {'0', '3'}, {'0', '4'}, {'0', '5'}, + {'0', '6'}, {'0', '7'}, {'0', '8'}, {'0', '9'}, {'1', '0'}, {'1', '1'}, + {'1', '2'}, {'1', '3'}, {'1', '4'}, {'1', '5'}, {'1', '6'}, {'1', '7'}, + {'1', '8'}, {'1', '9'}, {'2', '0'}, {'2', '1'}, {'2', '2'}, {'2', '3'}, + {'2', '4'}, {'2', '5'}, {'2', '6'}, {'2', '7'}, {'2', '8'}, {'2', '9'}, + {'3', '0'}, {'3', '1'}, {'3', '2'}, {'3', '3'}, {'3', '4'}, {'3', '5'}, + {'3', '6'}, {'3', '7'}, {'3', '8'}, {'3', '9'}, {'4', '0'}, {'4', '1'}, + {'4', '2'}, {'4', '3'}, {'4', '4'}, {'4', '5'}, {'4', '6'}, {'4', '7'}, + {'4', '8'}, {'4', '9'}, {'5', '0'}, {'5', '1'}, {'5', '2'}, {'5', '3'}, + {'5', '4'}, {'5', '5'}, {'5', '6'}, {'5', '7'}, {'5', '8'}, {'5', '9'}, + {'6', '0'}, {'6', '1'}, {'6', '2'}, {'6', '3'}, {'6', '4'}, {'6', '5'}, + {'6', '6'}, {'6', '7'}, {'6', '8'}, {'6', '9'}, {'7', '0'}, {'7', '1'}, + {'7', '2'}, {'7', '3'}, {'7', '4'}, {'7', '5'}, {'7', '6'}, {'7', '7'}, + {'7', '8'}, {'7', '9'}, {'8', '0'}, {'8', '1'}, {'8', '2'}, {'8', '3'}, + {'8', '4'}, {'8', '5'}, {'8', '6'}, {'8', '7'}, {'8', '8'}, {'8', '9'}, + {'9', '0'}, {'9', '1'}, {'9', '2'}, {'9', '3'}, {'9', '4'}, {'9', '5'}, + {'9', '6'}, {'9', '7'}, {'9', '8'}, {'9', '9'}}; + +bool safe_strto32_base(absl::string_view text, int32_t* value, int base) { + return safe_int_internal<int32_t>(text, value, base); +} + +bool safe_strto64_base(absl::string_view text, int64_t* value, int base) { + return safe_int_internal<int64_t>(text, value, base); +} + +bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base) { + return safe_uint_internal<uint32_t>(text, value, base); +} + +bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base) { + return safe_uint_internal<uint64_t>(text, value, base); +} + +bool safe_strtou128_base(absl::string_view text, uint128* value, int base) { + return safe_uint_internal<absl::uint128>(text, value, base); +} + +} // namespace numbers_internal +ABSL_NAMESPACE_END +} // namespace absl |