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#pragma once
#include <util/generic/fwd.h>
#include <util/generic/noncopyable.h>
#include <util/system/defaults.h>
class IOutputStream;
/**
* @addtogroup Streams_Base
* @{
*/
/**
* Abstract input stream.
*/
class IInputStream: public TNonCopyable {
public:
IInputStream() noexcept;
virtual ~IInputStream();
IInputStream(IInputStream&&) noexcept {
}
IInputStream& operator=(IInputStream&&) noexcept {
return *this;
}
/**
* Reads some data from the stream. Note that this function might read less
* data than what was requested. Use `Load` function if you want to read as
* much data as possible.
*
* @param buf Buffer to read into.
* @param len Number of bytes to read.
* @returns Number of bytes that were actually read.
* A return value of zero signals end of stream.
*/
inline size_t Read(void* buf, size_t len) {
if (len == 0) {
return 0;
}
return DoRead(buf, len);
}
/**
* Reads one character from the stream.
*
* @param[out] c Character to read.
* @returns Whether the character was read.
* A return value of false signals the end
* of stream.
*/
inline bool ReadChar(char& c) {
return DoRead(&c, 1) > 0;
}
/**
* Reads all characters from the stream until the given character is
* encountered, and stores them into the given string. The character itself
* is read from the stream, but not stored in the string.
*
* @param[out] st String to read into.
* @param ch Character to stop at.
* @returns Total number of characters read from the stream.
* A return value of zero signals end of stream.
*/
inline size_t ReadTo(TString& st, char ch) {
return DoReadTo(st, ch);
}
/**
* Reads the requested amount of data from the stream. Unlike `Read`, this
* function stops only when the requested amount of data is read, or when
* end of stream is reached.
*
* @param buf Buffer to read into.
* @param len Number of bytes to read.
* @returns Number of bytes that were actually read.
* A return value different from `len`
* signals end of stream.
*/
size_t Load(void* buf, size_t len);
/**
* Reads the requested amount of data from the stream, or fails with an
* exception if unable to do so.
*
* @param buf Buffer to read into.
* @param len Number of bytes to read.
* @see Load
*/
void LoadOrFail(void* buf, size_t len);
/**
* Reads all data from this stream and returns it as a string.
*
* @returns Contents of this stream as a string.
*/
TString ReadAll();
/**
* Reads all data from this stream and writes it into a provided output
* stream.
*
* @param out Output stream to use.
* @returns Total number of characters read from the stream.
*/
ui64 ReadAll(IOutputStream& out);
/**
* Reads all data from the stream until the first occurrence of '\n'. Also
* handles Windows line breaks correctly.
*
* @returns Next line read from this stream,
* excluding the line terminator.
* @throws yexception If no data could be read from a stream
* because end of stream has already been
* reached.
*/
TString ReadLine();
/**
* Reads all characters from the stream until the given character is
* encountered and returns them as a string. The character itself is read
* from the stream, but not stored in the string.
*
* @param ch Character to stop at.
* @returns String containing all the characters read.
* @throws yexception If no data could be read from a stream
* because end of stream has already been
* reached.
*/
TString ReadTo(char ch);
/**
* Reads all data from the stream until the first occurrence of '\n' and
* stores it into provided string. Also handles Windows line breaks correctly.
*
* @param[out] st String to store read characters into,
* excluding the line terminator.
* @returns Total number of characters read from the stream.
* A return value of zero signals end of stream.
*/
size_t ReadLine(TString& st);
/**
* Reads UTF8 encoded characters from the stream the first occurrence of '\n',
* converts them into wide ones, and stores into provided string. Also handles
* Windows line breaks correctly.
*
* @param[out] w Wide string to store read characters into,
* excluding the line terminator.
* @returns Total number of characters read from the stream.
* A return value of zero signals end of stream.
*/
size_t ReadLine(TUtf16String& w);
/**
* Skips some data from the stream without reading / copying it. Note that
* this function might skip less data than what was requested.
*
* @param len Number of bytes to skip.
* @returns Number of bytes that were actually skipped.
* A return value of zero signals end of stream.
*/
size_t Skip(size_t len);
protected:
/**
* Reads some data from the stream. Might read less data than what was
* requested.
*
* @param buf Buffer to read into.
* @param len Number of bytes to read.
* @returns Number of bytes that were actually read.
* A return value of zero signals end of stream.
* @throws yexception If IO error occurs.
*/
virtual size_t DoRead(void* buf, size_t len) = 0;
/**
* Skips some data from the stream. Might skip less data than what was
* requested.
*
* @param len Number of bytes to skip.
* @returns Number of bytes that were actually skipped.
* A return value of zero signals end of stream.
* @throws yexception If IO error occurs.
*/
virtual size_t DoSkip(size_t len);
/**
* Reads all characters from the stream until the given character is
* encountered, and stores them into the given string. The character itself
* is read from the stream, but not stored in the string.
*
* Provided string is cleared only if there is data in the stream.
*
* @param[out] st String to read into.
* @param ch Character to stop at.
* @returns Total number of characters read from the stream.
* A return value of zero signals end of stream.
* @throws yexception If IO error occurs.
*/
virtual size_t DoReadTo(TString& st, char ch);
/**
* Reads all data from this stream and writes it into a provided output
* stream.
*
* @param out Output stream to use.
* @returns Total number of characters read from
* this stream.
* @throws yexception If IO error occurs.
*/
virtual ui64 DoReadAll(IOutputStream& out);
};
/**
* Transfers all data from the given input stream into the given output stream.
*
* @param in Input stream.
* @param out Output stream.
*/
ui64 TransferData(IInputStream* in, IOutputStream* out);
/**
* `operator>>` for `IInputStream` by default delegates to this function.
*
* Note that while `operator>>` uses overloading (and thus argument-dependent
* lookup), `In` uses template specializations. This makes it possible to
* have a single `In` declaration, and then just provide specializations in
* cpp files, letting the linker figure everything else out. This approach
* reduces compilation times.
*
* However, if the flexibility of overload resolution is needed, then one should
* just overload `operator>>`.
*
* @param in Input stream to read from.
* @param[out] value Value to read.
* @throws `yexception` on invalid input or end of stream.
* @see Out(IOutputStream&, T&)
*/
template <typename T>
void In(IInputStream& in, T& value);
/**
* Reads a value from the stream.
*
* @param in Input stream to read from.
* @param[out] value Value to read.
* @returns Input stream.
* @throws `yexception` on invalid input or end of stream.
* @see operator<<(IOutputStream&, T&)
*/
template <typename T>
inline IInputStream& operator>>(IInputStream& in Y_LIFETIME_BOUND, T& value) {
In<T>(in, value);
return in;
}
namespace NPrivate {
IInputStream& StdInStream() noexcept;
} // namespace NPrivate
/**
* Standard input stream.
*/
#define Cin (::NPrivate::StdInStream())
/** @} */
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