--- /dev/null
+//
+// 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.
+//
+// -----------------------------------------------------------------------------
+// File: numbers.h
+// -----------------------------------------------------------------------------
+//
+// This package contains functions for converting strings to numbers. For
+// converting numbers to strings, use `StrCat()` or `StrAppend()` in str_cat.h,
+// which automatically detect and convert most number values appropriately.
+
+#ifndef ABSL_STRINGS_NUMBERS_H_
+#define ABSL_STRINGS_NUMBERS_H_
+
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
+#include <ctime>
+#include <limits>
+#include <string>
+#include <type_traits>
+
+#include "absl/base/macros.h"
+#include "absl/base/port.h"
+#include "absl/numeric/int128.h"
+#include "absl/strings/string_view.h"
+
+namespace absl {
+
+// SimpleAtoi()
+//
+// Converts the given string into an integer value, returning `true` if
+// successful. The string must reflect a base-10 integer (optionally followed or
+// preceded by ASCII whitespace) whose value falls within the range of the
+// integer type. If any errors are encountered, this function returns `false`,
+// leaving `out` in an unspecified state.
+template <typename int_type>
+ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out);
+
+// SimpleAtof()
+//
+// Converts the given string (optionally followed or preceded by ASCII
+// whitespace) into a float, which may be rounded on overflow or underflow.
+// See https://en.cppreference.com/w/c/string/byte/strtof for details about the
+// allowed formats for `str`. If any errors are encountered, this function
+// returns `false`, leaving `out` in an unspecified state.
+ABSL_MUST_USE_RESULT bool SimpleAtof(absl::string_view str, float* out);
+
+// SimpleAtod()
+//
+// Converts the given string (optionally followed or preceded by ASCII
+// whitespace) into a double, which may be rounded on overflow or underflow.
+// See https://en.cppreference.com/w/c/string/byte/strtof for details about the
+// allowed formats for `str`. If any errors are encountered, this function
+// returns `false`, leaving `out` in an unspecified state.
+ABSL_MUST_USE_RESULT bool SimpleAtod(absl::string_view str, double* out);
+
+// SimpleAtob()
+//
+// Converts the given string into a boolean, returning `true` if successful.
+// The following case-insensitive strings are interpreted as boolean `true`:
+// "true", "t", "yes", "y", "1". The following case-insensitive strings
+// are interpreted as boolean `false`: "false", "f", "no", "n", "0". If any
+// errors are encountered, this function returns `false`, leaving `out` in an
+// unspecified state.
+ABSL_MUST_USE_RESULT bool SimpleAtob(absl::string_view str, bool* out);
+
+} // namespace absl
+
+// End of public API. Implementation details follow.
+
+namespace absl {
+namespace numbers_internal {
+
+// safe_strto?() functions for implementing SimpleAtoi()
+bool safe_strto32_base(absl::string_view text, int32_t* value, int base);
+bool safe_strto64_base(absl::string_view text, int64_t* value, int base);
+bool safe_strtou32_base(absl::string_view text, uint32_t* value, int base);
+bool safe_strtou64_base(absl::string_view text, uint64_t* value, int base);
+
+static const int kFastToBufferSize = 32;
+static const int kSixDigitsToBufferSize = 16;
+
+// Helper function for fast formatting of floating-point values.
+// The result is the same as printf's "%g", a.k.a. "%.6g"; that is, six
+// significant digits are returned, trailing zeros are removed, and numbers
+// outside the range 0.0001-999999 are output using scientific notation
+// (1.23456e+06). This routine is heavily optimized.
+// Required buffer size is `kSixDigitsToBufferSize`.
+size_t SixDigitsToBuffer(double d, char* buffer);
+
+// These functions are intended for speed. All functions take an output buffer
+// as an argument and return a pointer to the last byte they wrote, which is the
+// terminating '\0'. At most `kFastToBufferSize` bytes are written.
+char* FastIntToBuffer(int32_t, char*);
+char* FastIntToBuffer(uint32_t, char*);
+char* FastIntToBuffer(int64_t, char*);
+char* FastIntToBuffer(uint64_t, char*);
+
+// For enums and integer types that are not an exact match for the types above,
+// use templates to call the appropriate one of the four overloads above.
+template <typename int_type>
+char* FastIntToBuffer(int_type i, char* buffer) {
+ static_assert(sizeof(i) <= 64 / 8,
+ "FastIntToBuffer works only with 64-bit-or-less integers.");
+ // TODO(jorg): This signed-ness check is used because it works correctly
+ // with enums, and it also serves to check that int_type is not a pointer.
+ // If one day something like std::is_signed<enum E> works, switch to it.
+ if (static_cast<int_type>(1) - 2 < 0) { // Signed
+ if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
+ return FastIntToBuffer(static_cast<int64_t>(i), buffer);
+ } else { // 32-bit or less
+ return FastIntToBuffer(static_cast<int32_t>(i), buffer);
+ }
+ } else { // Unsigned
+ if (sizeof(i) > 32 / 8) { // 33-bit to 64-bit
+ return FastIntToBuffer(static_cast<uint64_t>(i), buffer);
+ } else { // 32-bit or less
+ return FastIntToBuffer(static_cast<uint32_t>(i), buffer);
+ }
+ }
+}
+
+// Implementation of SimpleAtoi, generalized to support arbitrary base (used
+// with base different from 10 elsewhere in Abseil implementation).
+template <typename int_type>
+ABSL_MUST_USE_RESULT bool safe_strtoi_base(absl::string_view s, int_type* out,
+ int base) {
+ static_assert(sizeof(*out) == 4 || sizeof(*out) == 8,
+ "SimpleAtoi works only with 32-bit or 64-bit integers.");
+ static_assert(!std::is_floating_point<int_type>::value,
+ "Use SimpleAtof or SimpleAtod instead.");
+ bool parsed;
+ // TODO(jorg): This signed-ness check is used because it works correctly
+ // with enums, and it also serves to check that int_type is not a pointer.
+ // If one day something like std::is_signed<enum E> works, switch to it.
+ if (static_cast<int_type>(1) - 2 < 0) { // Signed
+ if (sizeof(*out) == 64 / 8) { // 64-bit
+ int64_t val;
+ parsed = numbers_internal::safe_strto64_base(s, &val, base);
+ *out = static_cast<int_type>(val);
+ } else { // 32-bit
+ int32_t val;
+ parsed = numbers_internal::safe_strto32_base(s, &val, base);
+ *out = static_cast<int_type>(val);
+ }
+ } else { // Unsigned
+ if (sizeof(*out) == 64 / 8) { // 64-bit
+ uint64_t val;
+ parsed = numbers_internal::safe_strtou64_base(s, &val, base);
+ *out = static_cast<int_type>(val);
+ } else { // 32-bit
+ uint32_t val;
+ parsed = numbers_internal::safe_strtou32_base(s, &val, base);
+ *out = static_cast<int_type>(val);
+ }
+ }
+ return parsed;
+}
+
+} // namespace numbers_internal
+
+// SimpleAtoi()
+//
+// Converts a string to an integer, using `safe_strto?()` functions for actual
+// parsing, returning `true` if successful. The `safe_strto?()` functions apply
+// strict checking; the string must be a base-10 integer, optionally followed or
+// preceded by ASCII whitespace, with a value in the range of the corresponding
+// integer type.
+template <typename int_type>
+ABSL_MUST_USE_RESULT bool SimpleAtoi(absl::string_view s, int_type* out) {
+ return numbers_internal::safe_strtoi_base(s, out, 10);
+}
+
+} // namespace absl
+
+#endif // ABSL_STRINGS_NUMBERS_H_
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