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78 lines
2.8 KiB
C++
78 lines
2.8 KiB
C++
// stringdata.h
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/* Copyright 2010 10gen Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef BSON_STRINDATA_HEADER
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#define BSON_STRINDATA_HEADER
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#include <string>
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#include <cstring>
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namespace mongo {
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using std::string;
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// A StringData object wraps a 'const string&' or a 'const char*' without
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// copying its contents. The most common usage is as a function argument that
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// takes any of the two forms of strings above. Fundamentally, this class tries
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// go around the fact that string literals in C++ are char[N]'s.
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//
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// Note that the object StringData wraps around must be alive while the StringDAta
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// is.
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class StringData {
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public:
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// Construct a StringData explicilty, for the case where the lenght of
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// string is not known. 'c' must be a pointer to a null-terminated string.
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StringData( const char* c )
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: _data(c), _size((unsigned) strlen(c)) {}
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// Construct a StringData explicitly, for the case where the length of the string
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// is already known. 'c' must be a pointer to a null-terminated string, and strlenOfc
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// must be the length that std::strlen(c) would return, a.k.a the index of the
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// terminator in c.
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StringData( const char* c, size_t strlenOfc )
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: _data(c), _size((unsigned) strlenOfc) {}
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// Construct a StringData explicitly, for the case of a std::string.
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StringData( const string& s )
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: _data(s.c_str()), _size((unsigned) s.size()) {}
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// Construct a StringData explicitly, for the case of a literal whose size is
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// known at compile time.
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struct LiteralTag {};
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template<size_t N>
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StringData( const char (&val)[N], LiteralTag )
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: _data(&val[0]), _size(N-1) {}
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// accessors
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const char* const data() const { return _data; }
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const unsigned size() const { return _size; }
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private:
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// There are two assumptions we use bellow.
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// '_data' *always* finishes with a null terminator
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// 'size' does *not* account for the null terminator
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// These assumptions may make it easier to minimize changes to existing code.
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const char* const _data;
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const unsigned _size;
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};
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} // namespace mongo
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#endif // BSON_STRINGDATA_HEADER
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