chromium/base/time/time_delta_from_string.cc

// Copyright 2021 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "base/time/time_delta_from_string.h"

#include <limits>
#include <string_view>
#include <utility>

#include "base/strings/string_util.h"
#include "base/time/time.h"

namespace base {

namespace {

// Strips the |expected| prefix from the start of the given string, returning
// |true| if the strip operation succeeded or false otherwise.
//
// Example:
//
//   std::string_view input("abc");
//   EXPECT_TRUE(ConsumePrefix(input, "a"));
//   EXPECT_EQ(input, "bc");
//
// Adapted from absl::ConsumePrefix():
// https://cs.chromium.org/chromium/src/third_party/abseil-cpp/absl/strings/strip.h?l=45&rcl=2c22e9135f107a4319582ae52e2e3e6b201b6b7c
bool ConsumePrefix(std::string_view& str, std::string_view expected) { … }

// Utility struct used by ConsumeDurationNumber() to parse decimal numbers.
// A ParsedDecimal represents the number `int_part` + `frac_part`/`frac_scale`,
// where:
//  (i)  0 <= `frac_part` < `frac_scale` (implies `frac_part`/`frac_scale` < 1)
//  (ii) `frac_scale` is 10^[number of digits after the decimal point]
//
// Example:
//  -42 => {.int_part = -42, .frac_part = 0, .frac_scale = 1}
//  1.23 => {.int_part = 1, .frac_part = 23, .frac_scale = 100}
struct ParsedDecimal { … };

// A helper for FromString() that tries to parse a leading number from the given
// std::string_view. |number_string| is modified to start from the first
// unconsumed char.
//
// Adapted from absl:
// https://cs.chromium.org/chromium/src/third_party/abseil-cpp/absl/time/duration.cc?l=807&rcl=2c22e9135f107a4319582ae52e2e3e6b201b6b7c
constexpr std::optional<ParsedDecimal> ConsumeDurationNumber(
    std::string_view& number_string) { … }

// A helper for FromString() that tries to parse a leading unit designator
// (e.g., ns, us, ms, s, m, h, d) from the given std::string_view. |unit_string|
// is modified to start from the first unconsumed char.
//
// Adapted from absl:
// https://cs.chromium.org/chromium/src/third_party/abseil-cpp/absl/time/duration.cc?l=841&rcl=2c22e9135f107a4319582ae52e2e3e6b201b6b7c
std::optional<TimeDelta> ConsumeDurationUnit(std::string_view& unit_string) { … }

}  // namespace

std::optional<TimeDelta> TimeDeltaFromString(std::string_view duration_string) { … }

}  // namespace base