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Diffstat (limited to 'absl/time/duration.cc')
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diff --git a/absl/time/duration.cc b/absl/time/duration.cc new file mode 100644 index 0000000..07d1082 --- /dev/null +++ b/absl/time/duration.cc @@ -0,0 +1,864 @@ +// 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 +// +// http://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. + +// The implementation of the absl::Duration class, which is declared in +// //absl/time.h. This class behaves like a numeric type; it has no public +// methods and is used only through the operators defined here. +// +// Implementation notes: +// +// An absl::Duration is represented as +// +// rep_hi_ : (int64_t) Whole seconds +// rep_lo_ : (uint32_t) Fractions of a second +// +// The seconds value (rep_hi_) may be positive or negative as appropriate. +// The fractional seconds (rep_lo_) is always a positive offset from rep_hi_. +// The API for Duration guarantees at least nanosecond resolution, which +// means rep_lo_ could have a max value of 1B - 1 if it stored nanoseconds. +// However, to utilize more of the available 32 bits of space in rep_lo_, +// we instead store quarters of a nanosecond in rep_lo_ resulting in a max +// value of 4B - 1. This allows us to correctly handle calculations like +// 0.5 nanos + 0.5 nanos = 1 nano. The following example shows the actual +// Duration rep using quarters of a nanosecond. +// +// 2.5 sec = {rep_hi_=2, rep_lo_=2000000000} // lo = 4 * 500000000 +// -2.5 sec = {rep_hi_=-3, rep_lo_=2000000000} +// +// Infinite durations are represented as Durations with the rep_lo_ field set +// to all 1s. +// +// +InfiniteDuration: +// rep_hi_ : kint64max +// rep_lo_ : ~0U +// +// -InfiniteDuration: +// rep_hi_ : kint64min +// rep_lo_ : ~0U +// +// Arithmetic overflows/underflows to +/- infinity and saturates. + +#include <algorithm> +#include <cassert> +#include <cctype> +#include <cerrno> +#include <cmath> +#include <cstdint> +#include <cstdlib> +#include <cstring> +#include <ctime> +#include <functional> +#include <limits> +#include <string> + +#include "absl/numeric/int128.h" +#include "absl/time/time.h" + +namespace absl { + +namespace { + +using time_internal::kTicksPerNanosecond; +using time_internal::kTicksPerSecond; + +constexpr int64_t kint64max = std::numeric_limits<int64_t>::max(); +constexpr int64_t kint64min = std::numeric_limits<int64_t>::min(); + +// Can't use std::isinfinite() because it doesn't exist on windows. +inline bool IsFinite(double d) { + return d != std::numeric_limits<double>::infinity() && + d != -std::numeric_limits<double>::infinity(); +} + +// Can't use std::round() because it is only available in C++11. +// Note that we ignore the possibility of floating-point over/underflow. +template <typename Double> +inline double Round(Double d) { + return d < 0 ? std::ceil(d - 0.5) : std::floor(d + 0.5); +} + +// *sec may be positive or negative. *ticks must be in the range +// -kTicksPerSecond < *ticks < kTicksPerSecond. If *ticks is negative it +// will be normalized to a positive value by adjusting *sec accordingly. +inline void NormalizeTicks(int64_t* sec, int64_t* ticks) { + if (*ticks < 0) { + --*sec; + *ticks += kTicksPerSecond; + } +} + +// Makes a uint128 from the absolute value of the given scalar. +inline uint128 MakeU128(int64_t a) { + uint128 u128 = 0; + if (a < 0) { + ++u128; + ++a; // Makes it safe to negate 'a' + a = -a; + } + u128 += static_cast<uint64_t>(a); + return u128; +} + +// Makes a uint128 count of ticks out of the absolute value of the Duration. +inline uint128 MakeU128Ticks(Duration d) { + int64_t rep_hi = time_internal::GetRepHi(d); + uint32_t rep_lo = time_internal::GetRepLo(d); + if (rep_hi < 0) { + ++rep_hi; + rep_hi = -rep_hi; + rep_lo = kTicksPerSecond - rep_lo; + } + uint128 u128 = static_cast<uint64_t>(rep_hi); + u128 *= static_cast<uint64_t>(kTicksPerSecond); + u128 += rep_lo; + return u128; +} + +// Breaks a uint128 of ticks into a Duration. +inline Duration MakeDurationFromU128(uint128 u128, bool is_neg) { + int64_t rep_hi; + uint32_t rep_lo; + const uint64_t h64 = Uint128High64(u128); + const uint64_t l64 = Uint128Low64(u128); + if (h64 == 0) { // fastpath + const uint64_t hi = l64 / kTicksPerSecond; + rep_hi = static_cast<int64_t>(hi); + rep_lo = static_cast<uint32_t>(l64 - hi * kTicksPerSecond); + } else { + // kMaxRepHi64 is the high 64 bits of (2^63 * kTicksPerSecond). + // Any positive tick count whose high 64 bits are >= kMaxRepHi64 + // is not representable as a Duration. A negative tick count can + // have its high 64 bits == kMaxRepHi64 but only when the low 64 + // bits are all zero, otherwise it is not representable either. + const uint64_t kMaxRepHi64 = 0x77359400UL; + if (h64 >= kMaxRepHi64) { + if (is_neg && h64 == kMaxRepHi64 && l64 == 0) { + // Avoid trying to represent -kint64min below. + return time_internal::MakeDuration(kint64min); + } + return is_neg ? -InfiniteDuration() : InfiniteDuration(); + } + const uint128 kTicksPerSecond128 = static_cast<uint64_t>(kTicksPerSecond); + const uint128 hi = u128 / kTicksPerSecond128; + rep_hi = static_cast<int64_t>(Uint128Low64(hi)); + rep_lo = + static_cast<uint32_t>(Uint128Low64(u128 - hi * kTicksPerSecond128)); + } + if (is_neg) { + rep_hi = -rep_hi; + if (rep_lo != 0) { + --rep_hi; + rep_lo = kTicksPerSecond - rep_lo; + } + } + return time_internal::MakeDuration(rep_hi, rep_lo); +} + +// Convert int64_t to uint64_t in twos-complement system. +inline uint64_t EncodeTwosComp(int64_t v) { return static_cast<uint64_t>(v); } + +// Convert uint64_t to int64_t in twos-complement system. +inline int64_t DecodeTwosComp(uint64_t v) { + if (v <= kint64max) return static_cast<int64_t>(v); + return static_cast<int64_t>(v - kint64max - 1) + kint64min; +} + +// Note: The overflow detection in this function is done using greater/less *or +// equal* because kint64max/min is too large to be represented exactly in a +// double (which only has 53 bits of precision). In order to avoid assigning to +// rep->hi a double value that is too large for an int64_t (and therefore is +// undefined), we must consider computations that equal kint64max/min as a +// double as overflow cases. +inline bool SafeAddRepHi(double a_hi, double b_hi, Duration* d) { + double c = a_hi + b_hi; + if (c >= kint64max) { + *d = InfiniteDuration(); + return false; + } + if (c <= kint64min) { + *d = -InfiniteDuration(); + return false; + } + *d = time_internal::MakeDuration(c, time_internal::GetRepLo(*d)); + return true; +} + +// A functor that's similar to std::multiplies<T>, except this returns the max +// T value instead of overflowing. This is only defined for uint128. +template <typename Ignored> +struct SafeMultiply { + uint128 operator()(uint128 a, uint128 b) const { + // b hi is always zero because it originated as an int64_t. + assert(Uint128High64(b) == 0); + // Fastpath to avoid the expensive overflow check with division. + if (Uint128High64(a) == 0) { + return (((Uint128Low64(a) | Uint128Low64(b)) >> 32) == 0) + ? static_cast<uint128>(Uint128Low64(a) * Uint128Low64(b)) + : a * b; + } + return b == 0 ? b : (a > kuint128max / b) ? kuint128max : a * b; + } +}; + +// Scales (i.e., multiplies or divides, depending on the Operation template) +// the Duration d by the int64_t r. +template <template <typename> class Operation> +inline Duration ScaleFixed(Duration d, int64_t r) { + const uint128 a = MakeU128Ticks(d); + const uint128 b = MakeU128(r); + const uint128 q = Operation<uint128>()(a, b); + const bool is_neg = (time_internal::GetRepHi(d) < 0) != (r < 0); + return MakeDurationFromU128(q, is_neg); +} + +// Scales (i.e., multiplies or divides, depending on the Operation template) +// the Duration d by the double r. +template <template <typename> class Operation> +inline Duration ScaleDouble(Duration d, double r) { + Operation<double> op; + double hi_doub = op(time_internal::GetRepHi(d), r); + double lo_doub = op(time_internal::GetRepLo(d), r); + + double hi_int = 0; + double hi_frac = std::modf(hi_doub, &hi_int); + + // Moves hi's fractional bits to lo. + lo_doub /= kTicksPerSecond; + lo_doub += hi_frac; + + double lo_int = 0; + double lo_frac = std::modf(lo_doub, &lo_int); + + // Rolls lo into hi if necessary. + int64_t lo64 = Round(lo_frac * kTicksPerSecond); + + Duration ans; + if (!SafeAddRepHi(hi_int, lo_int, &ans)) return ans; + int64_t hi64 = time_internal::GetRepHi(ans); + if (!SafeAddRepHi(hi64, lo64 / kTicksPerSecond, &ans)) return ans; + hi64 = time_internal::GetRepHi(ans); + lo64 %= kTicksPerSecond; + NormalizeTicks(&hi64, &lo64); + return time_internal::MakeDuration(hi64, lo64); +} + +// Tries to divide num by den as fast as possible by looking for common, easy +// cases. If the division was done, the quotient is in *q and the remainder is +// in *rem and true will be returned. +inline bool IDivFastPath(const Duration num, const Duration den, int64_t* q, + Duration* rem) { + // Bail if num or den is an infinity. + if (time_internal::IsInfiniteDuration(num) || + time_internal::IsInfiniteDuration(den)) + return false; + + int64_t num_hi = time_internal::GetRepHi(num); + uint32_t num_lo = time_internal::GetRepLo(num); + int64_t den_hi = time_internal::GetRepHi(den); + uint32_t den_lo = time_internal::GetRepLo(den); + + if (den_hi == 0 && den_lo == kTicksPerNanosecond) { + // Dividing by 1ns + if (num_hi >= 0 && num_hi < (kint64max - kTicksPerSecond) / 1000000000) { + *q = num_hi * 1000000000 + num_lo / kTicksPerNanosecond; + *rem = time_internal::MakeDuration(0, num_lo % den_lo); + return true; + } + } else if (den_hi == 0 && den_lo == 100 * kTicksPerNanosecond) { + // Dividing by 100ns (common when converting to Universal time) + if (num_hi >= 0 && num_hi < (kint64max - kTicksPerSecond) / 10000000) { + *q = num_hi * 10000000 + num_lo / (100 * kTicksPerNanosecond); + *rem = time_internal::MakeDuration(0, num_lo % den_lo); + return true; + } + } else if (den_hi == 0 && den_lo == 1000 * kTicksPerNanosecond) { + // Dividing by 1us + if (num_hi >= 0 && num_hi < (kint64max - kTicksPerSecond) / 1000000) { + *q = num_hi * 1000000 + num_lo / (1000 * kTicksPerNanosecond); + *rem = time_internal::MakeDuration(0, num_lo % den_lo); + return true; + } + } else if (den_hi == 0 && den_lo == 1000000 * kTicksPerNanosecond) { + // Dividing by 1ms + if (num_hi >= 0 && num_hi < (kint64max - kTicksPerSecond) / 1000) { + *q = num_hi * 1000 + num_lo / (1000000 * kTicksPerNanosecond); + *rem = time_internal::MakeDuration(0, num_lo % den_lo); + return true; + } + } else if (den_hi > 0 && den_lo == 0) { + // Dividing by positive multiple of 1s + if (num_hi >= 0) { + if (den_hi == 1) { + *q = num_hi; + *rem = time_internal::MakeDuration(0, num_lo); + return true; + } + *q = num_hi / den_hi; + *rem = time_internal::MakeDuration(num_hi % den_hi, num_lo); + return true; + } + if (num_lo != 0) { + num_hi += 1; + } + int64_t quotient = num_hi / den_hi; + int64_t rem_sec = num_hi % den_hi; + if (rem_sec > 0) { + rem_sec -= den_hi; + quotient += 1; + } + if (num_lo != 0) { + rem_sec -= 1; + } + *q = quotient; + *rem = time_internal::MakeDuration(rem_sec, num_lo); + return true; + } + + return false; +} + +} // namespace + +namespace time_internal { + +// The 'satq' argument indicates whether the quotient should saturate at the +// bounds of int64_t. If it does saturate, the difference will spill over to +// the remainder. If it does not saturate, the remainder remain accurate, +// but the returned quotient will over/underflow int64_t and should not be used. +int64_t IDivDuration(bool satq, const Duration num, const Duration den, + Duration* rem) { + int64_t q = 0; + if (IDivFastPath(num, den, &q, rem)) { + return q; + } + + const bool num_neg = num < ZeroDuration(); + const bool den_neg = den < ZeroDuration(); + const bool quotient_neg = num_neg != den_neg; + + if (time_internal::IsInfiniteDuration(num) || den == ZeroDuration()) { + *rem = num_neg ? -InfiniteDuration() : InfiniteDuration(); + return quotient_neg ? kint64min : kint64max; + } + if (time_internal::IsInfiniteDuration(den)) { + *rem = num; + return 0; + } + + const uint128 a = MakeU128Ticks(num); + const uint128 b = MakeU128Ticks(den); + uint128 quotient128 = a / b; + + if (satq) { + // Limits the quotient to the range of int64_t. + if (quotient128 > uint128(static_cast<uint64_t>(kint64max))) { + quotient128 = quotient_neg ? uint128(static_cast<uint64_t>(kint64min)) + : uint128(static_cast<uint64_t>(kint64max)); + } + } + + const uint128 remainder128 = a - quotient128 * b; + *rem = MakeDurationFromU128(remainder128, num_neg); + + if (!quotient_neg || quotient128 == 0) { + return Uint128Low64(quotient128) & kint64max; + } + // The quotient needs to be negated, but we need to carefully handle + // quotient128s with the top bit on. + return -static_cast<int64_t>(Uint128Low64(quotient128 - 1) & kint64max) - 1; +} + +} // namespace time_internal + +// +// Additive operators. +// + +Duration& Duration::operator+=(Duration rhs) { + if (time_internal::IsInfiniteDuration(*this)) return *this; + if (time_internal::IsInfiniteDuration(rhs)) return *this = rhs; + const int64_t orig_rep_hi = rep_hi_; + rep_hi_ = + DecodeTwosComp(EncodeTwosComp(rep_hi_) + EncodeTwosComp(rhs.rep_hi_)); + if (rep_lo_ >= kTicksPerSecond - rhs.rep_lo_) { + rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) + 1); + rep_lo_ -= kTicksPerSecond; + } + rep_lo_ += rhs.rep_lo_; + if (rhs.rep_hi_ < 0 ? rep_hi_ > orig_rep_hi : rep_hi_ < orig_rep_hi) { + return *this = rhs.rep_hi_ < 0 ? -InfiniteDuration() : InfiniteDuration(); + } + return *this; +} + +Duration& Duration::operator-=(Duration rhs) { + if (time_internal::IsInfiniteDuration(*this)) return *this; + if (time_internal::IsInfiniteDuration(rhs)) { + return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration(); + } + const int64_t orig_rep_hi = rep_hi_; + rep_hi_ = + DecodeTwosComp(EncodeTwosComp(rep_hi_) - EncodeTwosComp(rhs.rep_hi_)); + if (rep_lo_ < rhs.rep_lo_) { + rep_hi_ = DecodeTwosComp(EncodeTwosComp(rep_hi_) - 1); + rep_lo_ += kTicksPerSecond; + } + rep_lo_ -= rhs.rep_lo_; + if (rhs.rep_hi_ < 0 ? rep_hi_ < orig_rep_hi : rep_hi_ > orig_rep_hi) { + return *this = rhs.rep_hi_ >= 0 ? -InfiniteDuration() : InfiniteDuration(); + } + return *this; +} + +// +// Multiplicative operators. +// + +Duration& Duration::operator*=(int64_t r) { + if (time_internal::IsInfiniteDuration(*this)) { + const bool is_neg = (r < 0) != (rep_hi_ < 0); + return *this = is_neg ? -InfiniteDuration() : InfiniteDuration(); + } + return *this = ScaleFixed<SafeMultiply>(*this, r); +} + +Duration& Duration::operator*=(double r) { + if (time_internal::IsInfiniteDuration(*this) || !IsFinite(r)) { + const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0); + return *this = is_neg ? -InfiniteDuration() : InfiniteDuration(); + } + return *this = ScaleDouble<std::multiplies>(*this, r); +} + +Duration& Duration::operator/=(int64_t r) { + if (time_internal::IsInfiniteDuration(*this) || r == 0) { + const bool is_neg = (r < 0) != (rep_hi_ < 0); + return *this = is_neg ? -InfiniteDuration() : InfiniteDuration(); + } + return *this = ScaleFixed<std::divides>(*this, r); +} + +Duration& Duration::operator/=(double r) { + if (time_internal::IsInfiniteDuration(*this) || r == 0.0) { + const bool is_neg = (std::signbit(r) != 0) != (rep_hi_ < 0); + return *this = is_neg ? -InfiniteDuration() : InfiniteDuration(); + } + return *this = ScaleDouble<std::divides>(*this, r); +} + +Duration& Duration::operator%=(Duration rhs) { + time_internal::IDivDuration(false, *this, rhs, this); + return *this; +} + +double FDivDuration(Duration num, Duration den) { + // Arithmetic with infinity is sticky. + if (time_internal::IsInfiniteDuration(num) || den == ZeroDuration()) { + return (num < ZeroDuration()) == (den < ZeroDuration()) + ? std::numeric_limits<double>::infinity() + : -std::numeric_limits<double>::infinity(); + } + if (time_internal::IsInfiniteDuration(den)) return 0.0; + + double a = + static_cast<double>(time_internal::GetRepHi(num)) * kTicksPerSecond + + time_internal::GetRepLo(num); + double b = + static_cast<double>(time_internal::GetRepHi(den)) * kTicksPerSecond + + time_internal::GetRepLo(den); + return a / b; +} + +// +// Trunc/Floor/Ceil. +// + +Duration Trunc(Duration d, Duration unit) { + return d - (d % unit); +} + +Duration Floor(const Duration d, const Duration unit) { + const absl::Duration td = Trunc(d, unit); + return td <= d ? td : td - AbsDuration(unit); +} + +Duration Ceil(const Duration d, const Duration unit) { + const absl::Duration td = Trunc(d, unit); + return td >= d ? td : td + AbsDuration(unit); +} + +// +// Factory functions. +// + +Duration DurationFromTimespec(timespec ts) { + if (static_cast<uint64_t>(ts.tv_nsec) < 1000 * 1000 * 1000) { + int64_t ticks = ts.tv_nsec * kTicksPerNanosecond; + return time_internal::MakeDuration(ts.tv_sec, ticks); + } + return Seconds(ts.tv_sec) + Nanoseconds(ts.tv_nsec); +} + +Duration DurationFromTimeval(timeval tv) { + if (static_cast<uint64_t>(tv.tv_usec) < 1000 * 1000) { + int64_t ticks = tv.tv_usec * 1000 * kTicksPerNanosecond; + return time_internal::MakeDuration(tv.tv_sec, ticks); + } + return Seconds(tv.tv_sec) + Microseconds(tv.tv_usec); +} + +// +// Conversion to other duration types. +// + +int64_t ToInt64Nanoseconds(Duration d) { + if (time_internal::GetRepHi(d) >= 0 && + time_internal::GetRepHi(d) >> 33 == 0) { + return (time_internal::GetRepHi(d) * 1000 * 1000 * 1000) + + (time_internal::GetRepLo(d) / kTicksPerNanosecond); + } + return d / Nanoseconds(1); +} +int64_t ToInt64Microseconds(Duration d) { + if (time_internal::GetRepHi(d) >= 0 && + time_internal::GetRepHi(d) >> 43 == 0) { + return (time_internal::GetRepHi(d) * 1000 * 1000) + + (time_internal::GetRepLo(d) / (kTicksPerNanosecond * 1000)); + } + return d / Microseconds(1); +} +int64_t ToInt64Milliseconds(Duration d) { + if (time_internal::GetRepHi(d) >= 0 && + time_internal::GetRepHi(d) >> 53 == 0) { + return (time_internal::GetRepHi(d) * 1000) + + (time_internal::GetRepLo(d) / (kTicksPerNanosecond * 1000 * 1000)); + } + return d / Milliseconds(1); +} +int64_t ToInt64Seconds(Duration d) { + int64_t hi = time_internal::GetRepHi(d); + if (time_internal::IsInfiniteDuration(d)) return hi; + if (hi < 0 && time_internal::GetRepLo(d) != 0) ++hi; + return hi; +} +int64_t ToInt64Minutes(Duration d) { + int64_t hi = time_internal::GetRepHi(d); + if (time_internal::IsInfiniteDuration(d)) return hi; + if (hi < 0 && time_internal::GetRepLo(d) != 0) ++hi; + return hi / 60; +} +int64_t ToInt64Hours(Duration d) { + int64_t hi = time_internal::GetRepHi(d); + if (time_internal::IsInfiniteDuration(d)) return hi; + if (hi < 0 && time_internal::GetRepLo(d) != 0) ++hi; + return hi / (60 * 60); +} + +double ToDoubleNanoseconds(Duration d) { + return FDivDuration(d, Nanoseconds(1)); +} +double ToDoubleMicroseconds(Duration d) { + return FDivDuration(d, Microseconds(1)); +} +double ToDoubleMilliseconds(Duration d) { + return FDivDuration(d, Milliseconds(1)); +} +double ToDoubleSeconds(Duration d) { + return FDivDuration(d, Seconds(1)); +} +double ToDoubleMinutes(Duration d) { + return FDivDuration(d, Minutes(1)); +} +double ToDoubleHours(Duration d) { + return FDivDuration(d, Hours(1)); +} + +timespec ToTimespec(Duration d) { + timespec ts; + if (!time_internal::IsInfiniteDuration(d)) { + int64_t rep_hi = time_internal::GetRepHi(d); + uint32_t rep_lo = time_internal::GetRepLo(d); + if (rep_hi < 0) { + // Tweak the fields so that unsigned division of rep_lo + // maps to truncation (towards zero) for the timespec. + rep_lo += kTicksPerNanosecond - 1; + if (rep_lo >= kTicksPerSecond) { + rep_hi += 1; + rep_lo -= kTicksPerSecond; + } + } + ts.tv_sec = rep_hi; + if (ts.tv_sec == rep_hi) { // no time_t narrowing + ts.tv_nsec = rep_lo / kTicksPerNanosecond; + return ts; + } + } + if (d >= ZeroDuration()) { + ts.tv_sec = std::numeric_limits<time_t>::max(); + ts.tv_nsec = 1000 * 1000 * 1000 - 1; + } else { + ts.tv_sec = std::numeric_limits<time_t>::min(); + ts.tv_nsec = 0; + } + return ts; +} + +timeval ToTimeval(Duration d) { + timeval tv; + timespec ts = ToTimespec(d); + if (ts.tv_sec < 0) { + // Tweak the fields so that positive division of tv_nsec + // maps to truncation (towards zero) for the timeval. + ts.tv_nsec += 1000 - 1; + if (ts.tv_nsec >= 1000 * 1000 * 1000) { + ts.tv_sec += 1; + ts.tv_nsec -= 1000 * 1000 * 1000; + } + } + tv.tv_sec = ts.tv_sec; + if (tv.tv_sec != ts.tv_sec) { // narrowing + if (ts.tv_sec < 0) { + tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::min(); + tv.tv_usec = 0; + } else { + tv.tv_sec = std::numeric_limits<decltype(tv.tv_sec)>::max(); + tv.tv_usec = 1000 * 1000 - 1; + } + return tv; + } + tv.tv_usec = static_cast<int>(ts.tv_nsec / 1000); // suseconds_t + return tv; +} + +// +// To/From std::string formatting. +// + +namespace { + +// Formats a positive 64-bit integer in the given field width. Note that +// it is up to the caller of Format64() to ensure that there is sufficient +// space before ep to hold the conversion. +char* Format64(char* ep, int width, int64_t v) { + do { + --width; + *--ep = "0123456789"[v % 10]; + } while (v /= 10); + while (--width >= 0) *--ep = '0'; // zero pad + return ep; +} + +// Helpers for FormatDuration() that format 'n' and append it to 'out' +// followed by the given 'unit'. If 'n' formats to "0", nothing is +// appended (not even the unit). + +// A type that encapsulates how to display a value of a particular unit. For +// values that are displayed with fractional parts, the precision indicates +// where to round the value. The precision varies with the display unit because +// a Duration can hold only quarters of a nanosecond, so displaying information +// beyond that is just noise. +// +// For example, a microsecond value of 42.00025xxxxx should not display beyond 5 +// fractional digits, because it is in the noise of what a Duration can +// represent. +struct DisplayUnit { + const char* abbr; + int prec; + double pow10; +}; +const DisplayUnit kDisplayNano = {"ns", 2, 1e2}; +const DisplayUnit kDisplayMicro = {"us", 5, 1e5}; +const DisplayUnit kDisplayMilli = {"ms", 8, 1e8}; +const DisplayUnit kDisplaySec = {"s", 11, 1e11}; +const DisplayUnit kDisplayMin = {"m", -1, 0.0}; // prec ignored +const DisplayUnit kDisplayHour = {"h", -1, 0.0}; // prec ignored + +void AppendNumberUnit(std::string* out, int64_t n, DisplayUnit unit) { + char buf[sizeof("2562047788015216")]; // hours in max duration + char* const ep = buf + sizeof(buf); + char* bp = Format64(ep, 0, n); + if (*bp != '0' || bp + 1 != ep) { + out->append(bp, ep - bp); + out->append(unit.abbr); + } +} + +// Note: unit.prec is limited to double's digits10 value (typically 15) so it +// always fits in buf[]. +void AppendNumberUnit(std::string* out, double n, DisplayUnit unit) { + const int buf_size = std::numeric_limits<double>::digits10; + const int prec = std::min(buf_size, unit.prec); + char buf[buf_size]; // also large enough to hold integer part + char* ep = buf + sizeof(buf); + double d = 0; + int64_t frac_part = Round(std::modf(n, &d) * unit.pow10); + int64_t int_part = d; + if (int_part != 0 || frac_part != 0) { + char* bp = Format64(ep, 0, int_part); // always < 1000 + out->append(bp, ep - bp); + if (frac_part != 0) { + out->push_back('.'); + bp = Format64(ep, prec, frac_part); + while (ep[-1] == '0') --ep; + out->append(bp, ep - bp); + } + out->append(unit.abbr); + } +} + +} // namespace + +// From Go's doc at http://golang.org/pkg/time/#Duration.String +// [FormatDuration] returns a std::string representing the duration in the +// form "72h3m0.5s". Leading zero units are omitted. As a special +// case, durations less than one second format use a smaller unit +// (milli-, micro-, or nanoseconds) to ensure that the leading digit +// is non-zero. The zero duration formats as 0, with no unit. +std::string FormatDuration(Duration d) { + const Duration min_duration = Seconds(kint64min); + if (d == min_duration) { + // Avoid needing to negate kint64min by directly returning what the + // following code should produce in that case. + return "-2562047788015215h30m8s"; + } + std::string s; + if (d < ZeroDuration()) { + s.append("-"); + d = -d; + } + if (d == InfiniteDuration()) { + s.append("inf"); + } else if (d < Seconds(1)) { + // Special case for durations with a magnitude < 1 second. The duration + // is printed as a fraction of a single unit, e.g., "1.2ms". + if (d < Microseconds(1)) { + AppendNumberUnit(&s, FDivDuration(d, Nanoseconds(1)), kDisplayNano); + } else if (d < Milliseconds(1)) { + AppendNumberUnit(&s, FDivDuration(d, Microseconds(1)), kDisplayMicro); + } else { + AppendNumberUnit(&s, FDivDuration(d, Milliseconds(1)), kDisplayMilli); + } + } else { + AppendNumberUnit(&s, IDivDuration(d, Hours(1), &d), kDisplayHour); + AppendNumberUnit(&s, IDivDuration(d, Minutes(1), &d), kDisplayMin); + AppendNumberUnit(&s, FDivDuration(d, Seconds(1)), kDisplaySec); + } + if (s.empty() || s == "-") { + s = "0"; + } + return s; +} + +namespace { + +// A helper for ParseDuration() that parses a leading number from the given +// std::string and stores the result in *n. The given std::string pointer is modified +// to point to the first unconsumed char. +bool ConsumeDurationNumber(const char** start, double* n) { + const char* s = *start; + char* end = nullptr; + errno = 0; + *n = strtod(s, &end); + *start = end; + return !std::isspace(*s) && errno == 0 && end != s && *n >= 0; +} + +// A helper for ParseDuration() that parses a leading unit designator (e.g., +// ns, us, ms, s, m, h) from the given std::string and stores the resulting unit +// in "*unit". The given std::string pointer is modified to point to the first +// unconsumed char. +bool ConsumeDurationUnit(const char** start, Duration* unit) { + const char *s = *start; + bool ok = true; + if (strncmp(s, "ns", 2) == 0) { + s += 2; + *unit = Nanoseconds(1); + } else if (strncmp(s, "us", 2) == 0) { + s += 2; + *unit = Microseconds(1); + } else if (strncmp(s, "ms", 2) == 0) { + s += 2; + *unit = Milliseconds(1); + } else if (strncmp(s, "s", 1) == 0) { + s += 1; + *unit = Seconds(1); + } else if (strncmp(s, "m", 1) == 0) { + s += 1; + *unit = Minutes(1); + } else if (strncmp(s, "h", 1) == 0) { + s += 1; + *unit = Hours(1); + } else { + ok = false; + } + *start = s; + return ok; +} + +} // namespace + +// From Go's doc at http://golang.org/pkg/time/#ParseDuration +// [ParseDuration] parses a duration std::string. A duration std::string is +// a possibly signed sequence of decimal numbers, each with optional +// fraction and a unit suffix, such as "300ms", "-1.5h" or "2h45m". +// Valid time units are "ns", "us" "ms", "s", "m", "h". +bool ParseDuration(const std::string& dur_string, Duration* d) { + const char* start = dur_string.c_str(); + int sign = 1; + + if (*start == '-' || *start == '+') { + sign = *start == '-' ? -1 : 1; + ++start; + } + + // Can't parse a duration from an empty std::string. + if (*start == '\0') { + return false; + } + + // Special case for a std::string of "0". + if (*start == '0' && *(start + 1) == '\0') { + *d = ZeroDuration(); + return true; + } + + if (strcmp(start, "inf") == 0) { + *d = sign * InfiniteDuration(); + return true; + } + + Duration dur; + while (*start != '\0') { + double n = 0; + Duration unit; + if (!ConsumeDurationNumber(&start, &n) || + !ConsumeDurationUnit(&start, &unit)) { + return false; + } + dur += sign * n * unit; + } + *d = dur; + return true; +} + +// TODO(b/63899288) copybara strip once dependencies are removed. +bool ParseFlag(const std::string& text, Duration* dst, std::string* /* err */) { + return ParseDuration(text, dst); +} + +std::string UnparseFlag(Duration d) { + return FormatDuration(d); +} + +} // namespace absl |