parseNumberFromString* functions

A uniform interface for parsing numbers out of strings, with implementations for
the standard integer types.  Extension to double should be straightforward.  Tests
included.

1 files changed, 74 insertions, 0 deletions

diff --git a/src/mongo/base/parse_number.h b/src/mongo/base/parse_number.h
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+/*    Copyright 2012 10gen Inc.
+ *
+ *    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.
+ */
+
+/**
+ * Utility functions for parsing numbers from strings.
+ */
+
+#pragma once
+
+#include <string>
+
+#include "mongo/base/status.h"
+
+namespace mongo {
+
+    /**
+     * Parse a number out of a string.
+     *
+     * Parses "stringValue", interpreting it as a number of the given "base".  On success, stores
+     * the parsed value into "*result" and returns Status::OK().
+     *
+     * Valid values for "base" are 2-36, with 0 meaning "choose the base by inspecting the prefix
+     * on the number", as in strtol.  Returns Status::BadValue if an illegal value is supplied for
+     * "base".
+     *
+     * The entirety of the string must consist of digits in the given base, except optionally the
+     * first character may be "+" or "-", and hexadecimal numbers may begin "0x".  Same as strtol,
+     * without the property of stripping whitespace at the beginning, and fails to parse if there
+     * are non-digit characters at the end of the string.
+     *
+     * See parse_number.cpp for the available instantiations, and add any new instantiations there.
+     */
+    template <typename NumberType>
+    Status parseNumberFromStringWithBase(const char* stringValue, int base, NumberType* result);
+
+    /**
+     * Equivalent to parseNumberFromStringWithBase(stringValue, 0, result);
+     */
+    template <typename NumberType>
+    static inline Status parseNumberFromString(const char* stringValue, NumberType* result) {
+        return parseNumberFromStringWithBase(stringValue, 0, result);
+    }
+
+    /**
+     * Same as parseNumberFromStringWithBase, above, but taking a std::string instead of a c-style
+     * string.
+     */
+    template <typename NumberType>
+    static inline Status parseNumberFromStringWithBase(
+            const std::string& stringValue, int base, NumberType* result) {
+        return parseNumberFromStringWithBase(stringValue.c_str(), base, result);
+    }
+
+    /**
+     * Same as parseNumberFromString, above, but taking a std::string instead of a c-style string.
+     */
+    template <typename NumberType>
+    static inline Status parseNumberFromString(const std::string& stringValue, NumberType* result) {
+        return parseNumberFromString(stringValue.c_str(), result);
+    }
+
+}  // namespace mongo