ClickHouse/contrib/libpoco/Foundation/include/Poco/Buffer.h

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C++

//
// Buffer.h
//
// $Id: //poco/1.4/Foundation/include/Poco/Buffer.h#2 $
//
// Library: Foundation
// Package: Core
// Module: Buffer
//
// Definition of the Buffer class.
//
// Copyright (c) 2012, Applied Informatics Software Engineering GmbH.
// and Contributors.
//
// SPDX-License-Identifier: BSL-1.0
//
#ifndef Foundation_Buffer_INCLUDED
#define Foundation_Buffer_INCLUDED
#include "Poco/Foundation.h"
#include "Poco/Exception.h"
#include <cstring>
#include <cstddef>
namespace Poco {
template <class T>
class Buffer
/// A buffer class that allocates a buffer of a given type and size
/// in the constructor and deallocates the buffer in the destructor.
///
/// This class is useful everywhere where a temporary buffer
/// is needed.
{
public:
Buffer(std::size_t capacity):
_capacity(capacity),
_used(capacity),
_ptr(0),
_ownMem(true)
/// Creates and allocates the Buffer.
{
if (capacity > 0)
{
_ptr = new T[capacity];
}
}
Buffer(T* pMem, std::size_t length):
_capacity(length),
_used(length),
_ptr(pMem),
_ownMem(false)
/// Creates the Buffer. Length argument specifies the length
/// of the supplied memory pointed to by pMem in the number
/// of elements of type T. Supplied pointer is considered
/// blank and not owned by Buffer, so in this case Buffer
/// only acts as a wrapper around externally supplied
/// (and lifetime-managed) memory.
{
}
Buffer(const T* pMem, std::size_t length):
_capacity(length),
_used(length),
_ptr(0),
_ownMem(true)
/// Creates and allocates the Buffer; copies the contents of
/// the supplied memory into the buffer. Length argument specifies
/// the length of the supplied memory pointed to by pMem in the
/// number of elements of type T.
{
if (_capacity > 0)
{
_ptr = new T[_capacity];
std::memcpy(_ptr, pMem, _used * sizeof(T));
}
}
Buffer(const Buffer& other):
/// Copy constructor.
_capacity(other._used),
_used(other._used),
_ptr(0),
_ownMem(true)
{
if (_used)
{
_ptr = new T[_used];
std::memcpy(_ptr, other._ptr, _used * sizeof(T));
}
}
Buffer& operator = (const Buffer& other)
/// Assignment operator.
{
if (this != &other)
{
Buffer tmp(other);
swap(tmp);
}
return *this;
}
~Buffer()
/// Destroys the Buffer.
{
if (_ownMem) delete [] _ptr;
}
void resize(std::size_t newCapacity, bool preserveContent = true)
/// Resizes the buffer capacity and size. If preserveContent is true,
/// the content of the old buffer is copied over to the
/// new buffer. The new capacity can be larger or smaller than
/// the current one; if it is smaller, capacity will remain intact.
/// Size will always be set to the new capacity.
///
/// Buffers only wrapping externally owned storage can not be
/// resized. If resize is attempted on those, IllegalAccessException
/// is thrown.
{
if (!_ownMem) throw Poco::InvalidAccessException("Cannot resize buffer which does not own its storage.");
if (newCapacity > _capacity)
{
T* ptr = new T[newCapacity];
if (preserveContent)
{
std::memcpy(ptr, _ptr, _used * sizeof(T));
}
delete [] _ptr;
_ptr = ptr;
_capacity = newCapacity;
}
_used = newCapacity;
}
void setCapacity(std::size_t newCapacity, bool preserveContent = true)
/// Sets the buffer capacity. If preserveContent is true,
/// the content of the old buffer is copied over to the
/// new buffer. The new capacity can be larger or smaller than
/// the current one; size will be set to the new capacity only if
/// new capacity is smaller than the current size, otherwise it will
/// remain intact.
///
/// Buffers only wrapping externally owned storage can not be
/// resized. If resize is attempted on those, IllegalAccessException
/// is thrown.
{
if (!_ownMem) throw Poco::InvalidAccessException("Cannot resize buffer which does not own its storage.");
if (newCapacity != _capacity)
{
T* ptr = 0;
if (newCapacity > 0)
{
ptr = new T[newCapacity];
if (preserveContent)
{
std::size_t newSz = _used < newCapacity ? _used : newCapacity;
std::memcpy(ptr, _ptr, newSz * sizeof(T));
}
}
delete [] _ptr;
_ptr = ptr;
_capacity = newCapacity;
if (newCapacity < _used) _used = newCapacity;
}
}
void assign(const T* buf, std::size_t sz)
/// Assigns the argument buffer to this buffer.
/// If necessary, resizes the buffer.
{
if (0 == sz) return;
if (sz > _capacity) resize(sz, false);
std::memcpy(_ptr, buf, sz * sizeof(T));
_used = sz;
}
void append(const T* buf, std::size_t sz)
/// Resizes this buffer and appends the argument buffer.
{
if (0 == sz) return;
resize(_used + sz, true);
std::memcpy(_ptr + _used - sz, buf, sz * sizeof(T));
}
void append(T val)
/// Resizes this buffer by one element and appends the argument value.
{
resize(_used + 1, true);
_ptr[_used - 1] = val;
}
void append(const Buffer& buf)
/// Resizes this buffer and appends the argument buffer.
{
append(buf.begin(), buf.size());
}
std::size_t capacity() const
/// Returns the allocated memory size in elements.
{
return _capacity;
}
std::size_t capacityBytes() const
/// Returns the allocated memory size in bytes.
{
return _capacity * sizeof(T);
}
void swap(Buffer& other)
/// Swaps the buffer with another one.
{
using std::swap;
swap(_ptr, other._ptr);
swap(_capacity, other._capacity);
swap(_used, other._used);
}
bool operator == (const Buffer& other) const
/// Compare operator.
{
if (this != &other)
{
if (_used == other._used)
{
if (std::memcmp(_ptr, other._ptr, _used * sizeof(T)) == 0)
{
return true;
}
}
return false;
}
return true;
}
bool operator != (const Buffer& other) const
/// Compare operator.
{
return !(*this == other);
}
void clear()
/// Sets the contents of the buffer to zero.
{
std::memset(_ptr, 0, _used * sizeof(T));
}
std::size_t size() const
/// Returns the used size of the buffer in elements.
{
return _used;
}
std::size_t sizeBytes() const
/// Returns the used size of the buffer in bytes.
{
return _used * sizeof(T);
}
T* begin()
/// Returns a pointer to the beginning of the buffer.
{
return _ptr;
}
const T* begin() const
/// Returns a pointer to the beginning of the buffer.
{
return _ptr;
}
T* end()
/// Returns a pointer to end of the buffer.
{
return _ptr + _used;
}
const T* end() const
/// Returns a pointer to the end of the buffer.
{
return _ptr + _used;
}
bool empty() const
/// Return true if buffer is empty.
{
return 0 == _used;
}
T& operator [] (std::size_t index)
{
poco_assert (index < _used);
return _ptr[index];
}
const T& operator [] (std::size_t index) const
{
poco_assert (index < _used);
return _ptr[index];
}
private:
Buffer();
std::size_t _capacity;
std::size_t _used;
T* _ptr;
bool _ownMem;
};
} // namespace Poco
#endif // Foundation_Buffer_INCLUDED