SqMod/source/Base/Buffer.hpp

#ifndef _BASE_BUFFER_HPP_
#define _BASE_BUFFER_HPP_

// ------------------------------------------------------------------------------------------------
#include <assert.h>

// ------------------------------------------------------------------------------------------------
namespace SqMod {

// ------------------------------------------------------------------------------------------------
class Memory;
class Buffer;

/* ------------------------------------------------------------------------------------------------
 * A counted reference to a memory manager instance.
*/
class MemRef
{
private:

    // --------------------------------------------------------------------------------------------
    static MemRef s_Mem;

    // --------------------------------------------------------------------------------------------
    typedef unsigned int Counter;

    // --------------------------------------------------------------------------------------------
    Memory*     m_Ptr; /* The memory manager instance. */
    Counter*    m_Ref; /* Reference count to the managed instance. */

    /* --------------------------------------------------------------------------------------------
     * Grab a strong reference to a memory manager.
    */
    void Grab();

    /* --------------------------------------------------------------------------------------------
     * Drop a strong reference to a memory manager.
    */
    void Drop();

public:

    /* --------------------------------------------------------------------------------------------
     * Get a reference to the global memory manager instance.
    */
    static const MemRef & Get();

    /* --------------------------------------------------------------------------------------------
     * Default constructor (null).
    */
    MemRef()
        : m_Ptr(s_Mem.m_Ptr), m_Ref(s_Mem.m_Ref)
    {
        Grab();
    }

    /* --------------------------------------------------------------------------------------------
     * Copy constructor.
    */
    MemRef(const MemRef & o)
        : m_Ptr(o.m_Ptr), m_Ref(o.m_Ref)

    {
        Grab();
    }

    /* --------------------------------------------------------------------------------------------
     * Destructor.
    */
    ~MemRef()
    {
        Drop();
    }

    /* --------------------------------------------------------------------------------------------
     * Copy assignment operator.
    */
    MemRef & operator = (const MemRef & o)
    {
        if (m_Ptr != o.m_Ptr)
        {
            Drop();
            m_Ptr = o.m_Ptr;
            m_Ref = o.m_Ref;
            Grab();
        }
        return *this;
    }

    /* --------------------------------------------------------------------------------------------
     * Perform an equality comparison between two memory managers.
    */
    bool operator == (const MemRef & o) const
    {
        return (m_Ptr == o.m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Perform an inequality comparison between two memory managers.
    */
    bool operator != (const MemRef & o) const
    {
        return (m_Ptr != o.m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Implicit conversion to boolean for use in boolean operations.
    */
    operator bool () const
    {
        return m_Ptr;
    }

    /* --------------------------------------------------------------------------------------------
     * Member operator for dereferencing the managed pointer.
    */
    Memory * operator -> () const
    {
        assert(m_Ptr != NULL);
        return m_Ptr;
    }

    /* --------------------------------------------------------------------------------------------
     * Indirection operator for obtaining a reference of the managed pointer.
    */
    Memory & operator * () const
    {
        assert(m_Ptr != NULL);
        return *m_Ptr;
    }
};

// ------------------------------------------------------------------------------------------------
void ThrowMemExcept(const char * msg, ...);

/* ------------------------------------------------------------------------------------------------
 * Reusable buffer memory for quick allocations.
*/
class Buffer
{
public:

    // --------------------------------------------------------------------------------------------
    typedef char            Value; /* The type of value used to represent a byte. */

    // --------------------------------------------------------------------------------------------
    typedef Value &         Reference; /* A reference to the stored value type. */
    typedef const Value &   ConstRef; /* A const reference to the stored value type. */

    // --------------------------------------------------------------------------------------------
    typedef Value *         Pointer; /* A pointer to the stored value type. */
    typedef const Value *   ConstPtr; /* A const pointer to the stored value type. */

    // --------------------------------------------------------------------------------------------
    typedef unsigned int    SzType; /* The type used to represent size in general. */

    /* --------------------------------------------------------------------------------------------
     * Default constructor (null). Not null of a previous buffer was marked as movable.
    */
    Buffer()
        : m_Ptr(s_Ptr)
        , m_Cap(s_Cap)
        , m_Mem(MemRef::Get())
    {
        s_Ptr = NULL;
        s_Cap = 0;
    }

    /* --------------------------------------------------------------------------------------------
     * Explicit size constructor.
    */
    Buffer(SzType n)
        : m_Ptr(NULL)
        , m_Cap(0)
        , m_Mem(MemRef::Get())
    {
        Request(n < 8 ? 8 : n);
    }

    /* --------------------------------------------------------------------------------------------
     * Copy constructor.
    */
    Buffer(const Buffer & o);

    /* --------------------------------------------------------------------------------------------
     * Destructor.
    */
    ~Buffer();

    /* --------------------------------------------------------------------------------------------
     * Copy assignment operator.
    */
    Buffer & operator = (const Buffer & o);

    /* --------------------------------------------------------------------------------------------
     * Equality comparison operator.
    */
    bool operator == (const Buffer & o) const
    {
        return (m_Cap == o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Inequality comparison operator.
    */
    bool operator != (const Buffer & o) const
    {
        return (m_Cap != o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Less than comparison operator.
    */
    bool operator < (const Buffer & o) const
    {
        return (m_Cap < o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Greater than comparison operator.
    */
    bool operator > (const Buffer & o) const
    {
        return (m_Cap > o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Less than or equal comparison operator.
    */
    bool operator <= (const Buffer & o) const
    {
        return (m_Cap <= o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Greater than or equal comparison operator.
    */
    bool operator >= (const Buffer & o) const
    {
        return (m_Cap >= o.m_Cap);
    }

    /* --------------------------------------------------------------------------------------------
     * Implicit conversion to boolean.
    */
    operator bool () const
    {
        return m_Ptr;
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > T * Get()
    {
        return reinterpret_cast< T * >(m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > const T * Get() const
    {
        return reinterpret_cast< const T * >(m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the a certain element.
    */
    template < typename T > T & At(SzType n)
    {
        assert(n < m_Cap);
        return reinterpret_cast< T * >(m_Ptr)[n];
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the a certain element.
    */
    template < typename T > const T & At(SzType n) const
    {
        assert(n < m_Cap);
        return reinterpret_cast< const T * >(m_Ptr)[n];
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > T * Begin()
    {
        return reinterpret_cast< T * >(m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > const T * Begin() const
    {
        return reinterpret_cast< const T * >(m_Ptr);
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > T * End()
    {
        return reinterpret_cast< T * >(m_Ptr) + (m_Cap / sizeof(T));
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer casted as a different type.
    */
    template < typename T > const T * End() const
    {
        return reinterpret_cast< const T * >(m_Ptr) + (m_Cap / sizeof(T));
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer.
    */
    Pointer Data()
    {
        return m_Ptr;
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the internal buffer.
    */
    ConstPtr Data() const
    {
        return m_Ptr;
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve maximum elements it can hold for a certain type.
    */
    template < typename T > static SzType Max()
    {
        return (0xFFFFFFFF / sizeof(T));
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the current buffer capacity in element count.
    */
    template < typename T > SzType Size() const
    {
        return (m_Cap / sizeof(T));
    }

    /* --------------------------------------------------------------------------------------------
     * Retrieve the current buffer capacity in byte count.
    */
    SzType Capacity() const
    {
        return m_Cap;
    }

    /* --------------------------------------------------------------------------------------------
     * Makes sure there is enough capacity to hold the specified element count.
    */
    template < typename T > Buffer Adjust(SzType n)
    {
        if (n < 8)
        {
            n = 8;
        }
        // See if the requested capacity doesn't exceed the limit
        if (n > Max< T >())
        {
            ThrowMemExcept("Requested buffer of (%u) elements exceeds the (%u) limit", n, Max< T >());
        }
        // Is there an existing buffer?
        else if (n && !m_Cap)
        {
            // Request the memory
            Request(n * sizeof(T));
        }
        // Should the size be increased?
        else if (n > m_Cap)
        {
            // Backup the current memory
            Move();
            // Request the memory
            Request(n * sizeof(T));
        }
        // Return an empty buffer or the backup (if any)
        return Buffer();
    }

    /* --------------------------------------------------------------------------------------------
     * Release the managed memory.
    */
    void Reset()
    {
        if (m_Ptr)
        {
            Release();
        }
    }

    /* --------------------------------------------------------------------------------------------
     * Swap the contents of two buffers.
    */
    void Swap(Buffer & o)
    {
        Pointer p = m_Ptr;
        SzType n = m_Cap;
        m_Ptr = o.m_Ptr;
        m_Cap = o.m_Cap;
        o.m_Ptr = p;
        o.m_Cap = n;
    }

    /* --------------------------------------------------------------------------------------------
     * Write a portion of a buffet to the internal buffer.
    */
    SzType Write(SzType pos, ConstPtr data, SzType size);

    /* --------------------------------------------------------------------------------------------
     * Write a formatted string to the internal buffer.
    */
    SzType WriteF(SzType pos, const char * fmt, ...);

    /* --------------------------------------------------------------------------------------------
     * Write a formatted string to the internal buffer.
    */
    SzType WriteF(SzType pos, const char * fmt, va_list args);

protected:

    /* --------------------------------------------------------------------------------------------
     * Request the memory specified in the capacity.
    */
    void Request(SzType n);

    /* --------------------------------------------------------------------------------------------
     * Release the managed memory buffer.
    */
    void Release();

    /* --------------------------------------------------------------------------------------------
     * Moves the internal buffer to the global members to be taken over by the next instance.
    */
    void Move()
    {
        s_Ptr = m_Ptr;
        s_Cap = m_Cap;
        m_Ptr = NULL;
        m_Cap = 0;
    }

private:

    // --------------------------------------------------------------------------------------------
    Pointer     m_Ptr; /* Pointer to the memory buffer. */
    SzType      m_Cap; /* The total size of the buffer. */

    // --------------------------------------------------------------------------------------------
    MemRef      m_Mem;

    // --------------------------------------------------------------------------------------------
    static Pointer  s_Ptr; /* Pointer to a moved memory buffer. */
    static SzType   s_Cap; /* The total size of the moved buffer. */
};

} // Namespace:: SqMod

#endif // _BASE_BUFFER_HPP_