Add string_number_conversion and its test

util/stdlib/string_number_conversion.h

Index: util/stdlib/string_number_conversion.h
diff --git a/util/stdlib/string_number_conversion.h b/util/stdlib/string_number_conversion.h
new file mode 100644
index 0000000000000000000000000000000000000000..dbc4611e9f3a34251f1fa3d4b384991f60086dd9
--- /dev/null
+++ b/util/stdlib/string_number_conversion.h
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+// Copyright 2014 The Crashpad Authors. All rights reserved.
+//
+// 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.
+
+#ifndef CRASHPAD_UTIL_STDLIB_STRING_NUMBER_CONVERSION_H_
+#define CRASHPAD_UTIL_STDLIB_STRING_NUMBER_CONVERSION_H_
+
+#include "base/strings/string_piece.h"
+
+namespace crashpad {
+
+// Convert between strings and numbers.
+//
+// These functions will only set *number if a perfect conversion can be
+// performed. A perfect conversion contains no leading or trailing characters
+// (including whitespace) other than the number to convert, and does not
+// overflow the targeted data type. If a perfect conversion is possible, *number
+// is set and these functions return true. Otherwise, they return false.
+//
+// The interface in base/strings/string_number_conversions.h doesn’t allow
+// arbitrary bases based on whether the string begins with prefixes such as "0x"
+// as strtol does with base = 0. The functions here are implemented on the
+// strtol family with base = 0, and thus do accept such input.
+
+//! \{
+//! \brief Convert a string to a number.
+//!
+//! A conversion will only be performed if it can be done perfectly: if \a
+//! string contains no leading or trailing characters (including whitespace)
+//! other than the number to convert, and does not overflow the targeted data
+//! type.
+//!
+//! \param[in] string The string to convert to a number. As in `strtol()` with a
+//!     `base` parameter of `0`, the string is treated as decimal unless it
+//!     begins with a `"0x"` or `"0X"` prefix, in which case it is treated as
+//!     hexadecimal, or a `"0"` prefix, in which case it is treated as octal.
+//! \param[out] number The converted number. This will only be set if a perfect
+//!     conversion can be performed.
+//!
+//! \return `true` if a perfect conversion could be performed, with \a number
+//!     set appropriately. `false` if a perfect conversion was not possible.
+//!
+//! \note The interface in `base/strings/string_number_conversions.h` doesn’t
+//!     allow arbitrary bases based on whether the string begins with a prefix
+//!     indicating its base. The functions here are provided for situations
+//!     where such prefix recognition is desirable.
+bool StringToNumber(const base::StringPiece& string, int* number);
+bool StringToNumber(const base::StringPiece& string, unsigned int* number);
+//! \}
+
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_STDLIB_STRING_NUMBER_CONVERSION_H_