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// SPDX-FileCopyrightText: Copyright (c) Ken Martin, Will Schroeder, Bill Lorensen
// SPDX-License-Identifier: BSD-3-Clause
#ifndef vtkResourceStream_h
#define vtkResourceStream_h
#include "vtkIOCoreModule.h" // For export macro
#include "vtkObject.h"
#include <cstdlib> // for std::size_t
#include <memory> // for std::unique_ptr
VTK_ABI_NAMESPACE_BEGIN
/**
* @brief Abstract class used for custom streams
*
* vtkResourceStream provides a high-level interface for manipulating
* custom streams. This class is designed to be used instead of "SetFileName"
* and "SetInputString" or similar that exists in most of reader or reader-like
* classes in VTK.
*
* vtkResourceStream only support unformatted input, user must use external
* solution to format the input, such as sscanf or scnlib, fast_float or strtoX
*
* vtkResourceStream **may** be support seeking, code that uses
* vtkResourceStream should take in account this, and support for both seekable
* stream and not seekable streams, if possible. `stream.SupportSeek()` can be
* used for support checking.
*/
class VTKIOCORE_EXPORT vtkResourceStream : public vtkObject
{
struct vtkInternals;
public:
enum class SeekDirection
{
Begin = 0,
Current = 1,
End = 2
};
vtkTypeMacro(vtkResourceStream, vtkObject);
void PrintSelf(ostream& os, vtkIndent indent) override;
/**
* @brief Read data form the stream
*
* Read at most `bytes` bytes from input stream.
* If this function reads less that `bytes` bytes, then EndOfStream must
* return true.
*
* @param buffer User provided storage buffer, may be nullptr if bytes == 0
* @param bytes Maximum amount of bytes to read.
* @return The number of bytes read, may be 0.
*/
virtual std::size_t Read(void* buffer, std::size_t bytes) = 0;
/**
* @brief Check if the stream reached an end.
*
* The stream may be out of range (EOF) if a Seek call move before stream
* begin (0), or after stream end (max) Seek on an EndOfStream stream may
* restore it back to a valid state. Read on an invalid stream must do
* nothing and return 0.
*
* @return Return true if the stream reached the end of input, false
* otherwise.
*/
virtual bool EndOfStream() = 0;
/**
* @brief Move the stream cursor position
*
* Base version does nothing and returns 0.
* This function does not check if the position is out of range.
* EndOfFile() result must only change after a call of Read with
* non-zero size.
*
* @return Current position in stream.
*/
virtual vtkTypeInt64 Seek(vtkTypeInt64 pos, SeekDirection dir);
/**
* @brief Get the stream cursor position
*
* Base version calls `Seek(0, std::ios_base::cur)`.
* If seeking is unsupported, return 0.
* Subclasses may reimplement it to provide a more efficient version.
*
* @return Current position in stream.
*/
virtual vtkTypeInt64 Tell();
/**
* @brief Check if stream supports Seek and Tell functions
*
* @return true if Seek and Tell functions are supported.
*/
bool SupportSeek() const;
protected:
/**
* @brief Constructor
*
* Only constructor, subclasses must fill the vtkResourceStreamInfo and pass it
* to this constructor.
*
* @param supportSeek true is Seek and Tell are supported
*/
vtkResourceStream(bool supportSeek);
~vtkResourceStream() override;
vtkResourceStream(const vtkResourceStream&) = delete;
vtkResourceStream& operator=(const vtkResourceStream&) = delete;
private:
std::unique_ptr<vtkInternals> Impl;
};
VTK_ABI_NAMESPACE_END
#endif
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