ClickHouse/dbms/src/IO/Operators.h

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#pragma once
#include <IO/ReadBuffer.h>
#include <IO/WriteBuffer.h>
#include <IO/ReadHelpers.h>
#include <IO/WriteHelpers.h>
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#include <functional>
namespace DB
{
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/** Implements the ability to write and read data in/from WriteBuffer/ReadBuffer
* with the help of << and >> operators and also manipulators,
* providing a way of using, similar to iostreams.
*
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* It is neither a subset nor an extension of iostreams.
*
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* Example usage:
*
* DB::WriteBufferFromFileDescriptor buf(STDOUT_FILENO);
* buf << DB::double_quote << "Hello, world!" << '\n' << DB::flush;
*
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* Outputs `char` type (usually it's Int8) as a symbol, not as a number.
*/
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/// Manipulators.
enum EscapeManip { escape }; /// For strings - escape special characters. In the rest, as usual.
enum QuoteManip { quote }; /// For strings, dates, datetimes - enclose in single quotes with escaping. In the rest, as usual.
enum DoubleQuoteManip { double_quote }; /// For strings, dates, datetimes - enclose in double quotes with escaping. In the rest, as usual.
enum BinaryManip { binary }; /// Output in binary format.
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struct EscapeManipWriteBuffer : std::reference_wrapper<WriteBuffer> { using std::reference_wrapper<WriteBuffer>::reference_wrapper; };
struct QuoteManipWriteBuffer : std::reference_wrapper<WriteBuffer> { using std::reference_wrapper<WriteBuffer>::reference_wrapper; };
struct DoubleQuoteManipWriteBuffer : std::reference_wrapper<WriteBuffer> { using std::reference_wrapper<WriteBuffer>::reference_wrapper; };
struct BinaryManipWriteBuffer : std::reference_wrapper<WriteBuffer> { using std::reference_wrapper<WriteBuffer>::reference_wrapper; };
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struct EscapeManipReadBuffer : std::reference_wrapper<ReadBuffer> { using std::reference_wrapper<ReadBuffer>::reference_wrapper; };
struct QuoteManipReadBuffer : std::reference_wrapper<ReadBuffer> { using std::reference_wrapper<ReadBuffer>::reference_wrapper; };
struct DoubleQuoteManipReadBuffer : std::reference_wrapper<ReadBuffer> { using std::reference_wrapper<ReadBuffer>::reference_wrapper; };
struct BinaryManipReadBuffer : std::reference_wrapper<ReadBuffer> { using std::reference_wrapper<ReadBuffer>::reference_wrapper; };
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template <typename T> WriteBuffer & operator<< (WriteBuffer & buf, const T & x) { writeText(x, buf); return buf; }
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/// If you do not use the manipulators, the string is displayed without an escape, as is.
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template <> inline WriteBuffer & operator<< (WriteBuffer & buf, const String & x) { writeString(x, buf); return buf; }
template <> inline WriteBuffer & operator<< (WriteBuffer & buf, const char & x) { writeChar(x, buf); return buf; }
inline WriteBuffer & operator<< (WriteBuffer & buf, const char * x) { writeCString(x, buf); return buf; }
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inline EscapeManipWriteBuffer operator<< (WriteBuffer & buf, EscapeManip) { return buf; }
inline QuoteManipWriteBuffer operator<< (WriteBuffer & buf, QuoteManip) { return buf; }
inline DoubleQuoteManipWriteBuffer operator<< (WriteBuffer & buf, DoubleQuoteManip) { return buf; }
inline BinaryManipWriteBuffer operator<< (WriteBuffer & buf, BinaryManip) { return buf; }
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template <typename T> WriteBuffer & operator<< (EscapeManipWriteBuffer buf, const T & x) { writeText(x, buf.get()); return buf; }
template <typename T> WriteBuffer & operator<< (QuoteManipWriteBuffer buf, const T & x) { writeQuoted(x, buf.get()); return buf; }
template <typename T> WriteBuffer & operator<< (DoubleQuoteManipWriteBuffer buf, const T & x) { writeDoubleQuoted(x, buf.get()); return buf; }
template <typename T> WriteBuffer & operator<< (BinaryManipWriteBuffer buf, const T & x) { writeBinary(x, buf.get()); return buf; }
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inline WriteBuffer & operator<< (EscapeManipWriteBuffer buf, const char * x) { writeAnyEscapedString<'\''>(x, x + strlen(x), buf.get()); return buf; }
inline WriteBuffer & operator<< (QuoteManipWriteBuffer buf, const char * x) { writeAnyQuotedString<'\''>(x, x + strlen(x), buf.get()); return buf; }
inline WriteBuffer & operator<< (DoubleQuoteManipWriteBuffer buf, const char * x) { writeAnyQuotedString<'"'>(x, x + strlen(x), buf.get()); return buf; }
inline WriteBuffer & operator<< (BinaryManipWriteBuffer buf, const char * x) { writeStringBinary(x, buf.get()); return buf; }
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/// The manipulator calls the WriteBuffer method `next` - this makes the buffer reset. For nested buffers, the reset is not recursive.
enum FlushManip { flush };
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inline WriteBuffer & operator<< (WriteBuffer & buf, FlushManip) { buf.next(); return buf; }
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template <typename T> ReadBuffer & operator>> (ReadBuffer & buf, T & x) { readText(x, buf); return buf; }
template <> inline ReadBuffer & operator>> (ReadBuffer & buf, String & x) { readString(x, buf); return buf; }
template <> inline ReadBuffer & operator>> (ReadBuffer & buf, char & x) { readChar(x, buf); return buf; }
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/// If you specify a string literal for reading, this will mean - make sure there is a sequence of bytes and skip it.
inline ReadBuffer & operator>> (ReadBuffer & buf, const char * x) { assertString(x, buf); return buf; }
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inline EscapeManipReadBuffer operator>> (ReadBuffer & buf, EscapeManip) { return buf; }
inline QuoteManipReadBuffer operator>> (ReadBuffer & buf, QuoteManip) { return buf; }
inline DoubleQuoteManipReadBuffer operator>> (ReadBuffer & buf, DoubleQuoteManip) { return buf; }
inline BinaryManipReadBuffer operator>> (ReadBuffer & buf, BinaryManip) { return buf; }
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template <typename T> ReadBuffer & operator>> (EscapeManipReadBuffer buf, T & x) { readText(x, buf.get()); return buf; }
template <typename T> ReadBuffer & operator>> (QuoteManipReadBuffer buf, T & x) { readQuoted(x, buf.get()); return buf; }
template <typename T> ReadBuffer & operator>> (DoubleQuoteManipReadBuffer buf, T & x) { readDoubleQuoted(x, buf.get()); return buf; }
template <typename T> ReadBuffer & operator>> (BinaryManipReadBuffer buf, T & x) { readBinary(x, buf.get()); return buf; }
}