io/CMemoryStream.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */
#pragma once

#include <mrpt/core/safe_pointers.h>
#include <mrpt/io/CStream.h>

namespace mrpt
{
namespace io
{
/** This CStream derived class allow using a memory buffer as a CStream.
 *  This class is useful for storing any required set of variables or objects,
 *   and then read them to other objects, or storing them to a file, for
 * example.
 *
 * \sa CStream
 * \ingroup mrpt_io_grp
 */
class CMemoryStream : public CStream
{
   public:
    size_t Read(void* Buffer, size_t Count) override;
    size_t Write(const void* Buffer, size_t Count) override;

   protected:
    /** Internal data */
    void_ptr_noncopy m_memory{nullptr};
    uint64_t m_size{0}, m_position{0}, m_bytesWritten{0};
    uint64_t m_alloc_block_size{0x1000};
    /** If the memory block does not belong to the object. */
    bool m_read_only{false};
    /** Resizes the internal buffer size. */
    void resize(uint64_t newSize);

   public:
    /** Default constructor */
    CMemoryStream() = default;
    /** Constructor to initilize the data in the stream from a block of memory
     * (which is copied), and sets the current stream position at the beginning
     * of the data.
     * \sa assignMemoryNotOwn */
    CMemoryStream(const void* data, const uint64_t nBytesInData);

    /** Initilize the data in the stream from a block of memory which is NEITHER
     * OWNED NOR COPIED by the object, so it must exist during the whole live of
     * the object.
     *  After assigning a block of data with this method, the object becomes
     * "read-only", so further attempts to change the size of the buffer will
     * raise an exception.
     *  This method resets the write and read positions to the beginning. */
    void assignMemoryNotOwn(const void* data, const uint64_t nBytesInData);

    /** Destructor */
    ~CMemoryStream() override;

    /** Clears the memory buffer. */
    void clear();

    // See docs in base class
    uint64_t Seek(
        int64_t Offset, CStream::TSeekOrigin Origin = sFromBeginning) override;
    /** Returns the total size of the internal buffer  */
    uint64_t getTotalBytesCount() const override;
    /** Method for getting the current cursor position, where 0 is the first
     * byte and TotalBytesCount-1 the last one */
    uint64_t getPosition() const override;

    /** Method for getting a pointer to the raw stored data. The lenght in bytes
     * is given by getTotalBytesCount */
    void* getRawBufferData();
    const void* getRawBufferData() const;

    /** Saves the entire buffer to a file \return true on success, false on
     * error */
    bool saveBufferToFile(const std::string& file_name);

    /** Loads the entire buffer from a file * \return true on success, false on
     * error */
    bool loadBufferFromFile(const std::string& file_name);

    /** Change the size of the additional memory block that is reserved whenever
     * the current block runs too short (default=0x10000 bytes) */
    void setAllocBlockSize(uint64_t alloc_block_size)
    {
        ASSERT_(alloc_block_size > 0);
        m_alloc_block_size = alloc_block_size;
    }
};  // End of class def.

namespace internal
{
struct TFreeFnDataForZMQ
{
    CMemoryStream* buf{nullptr};
    bool do_free{true};
    TFreeFnDataForZMQ() = default;
};
/** Used in mrpt_send_to_zmq(). `hint` points to a `TFreeFnDataForZMQ` struct,
 * to be freed here. */
void free_fn_for_zmq(void* data, void* hint);
}  // namespace internal
}  // namespace io
}  // namespace mrpt