endian.hpp

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#ifndef LIBJIMAGE_ENDIAN_HPP
#define LIBJIMAGE_ENDIAN_HPP

#include "inttypes.hpp"

// Selectable endian handling. Endian handlers are used when accessing values
// that are of unknown (until runtime) endian.  The only requirement of the values
// accessed are that they are aligned to proper size boundaries (no misalignment.)
// To select an endian handler, one should call Endian::get_handler(big_endian);
// Where big_endian is true if big endian is required and false otherwise.  The
// native endian handler can be fetched with Endian::get_native_handler();
// To retrieve a value using the approprate endian, use one of the overloaded
// calls to get. To set a value, then use one of the overloaded set calls.
// Ex.
//          s4 value; // Imported value;
//          ...
//          Endian* endian = Endian::get_handler(true);  // Use big endian
//          s4 corrected = endian->get(value);
//          endian->set(value, 1);
//
class Endian {
public:
    virtual u2 get(u2 x) = 0;
    virtual u4 get(u4 x) = 0;
    virtual u8 get(u8 x) = 0;
    virtual s2 get(s2 x) = 0;
    virtual s4 get(s4 x) = 0;
    virtual s8 get(s8 x) = 0;

    virtual void set(u2& x, u2 y) = 0;
    virtual void set(u4& x, u4 y) = 0;
    virtual void set(u8& x, u8 y) = 0;
    virtual void set(s2& x, s2 y) = 0;
    virtual void set(s4& x, s4 y) = 0;
    virtual void set(s8& x, s8 y) = 0;

    // Quick little endian test.
    static bool is_little_endian() { u4 x = 1; return *(u1 *)&x != 0; }

    // Quick big endian test.
    static bool is_big_endian() { return !is_little_endian(); }

    // Select an appropriate endian handler.
    static Endian* get_handler(bool big_endian);

    // Return the native endian handler.
    static Endian* get_native_handler();

    // get platform u2 from Java Big endian
    static u2 get_java(u1* x);
    // set platform u2 to Java Big endian
    static void set_java(u1* p, u2 x);
};

// Normal endian handling.
class NativeEndian : public Endian {
private:
    static NativeEndian _native;

public:
    u2 get(u2 x);
    u4 get(u4 x);
    u8 get(u8 x);
    s2 get(s2 x);
    s4 get(s4 x);
    s8 get(s8 x);

    void set(u2& x, u2 y);
    void set(u4& x, u4 y);
    void set(u8& x, u8 y);
    void set(s2& x, s2 y);
    void set(s4& x, s4 y);
    void set(s8& x, s8 y);

    static Endian* get_native() { return &_native; }
};

// Swapping endian handling.
class SwappingEndian : public Endian {
private:
    static SwappingEndian _swapping;

public:
    u2 get(u2 x);
    u4 get(u4 x);
    u8 get(u8 x);
    s2 get(s2 x);
    s4 get(s4 x);
    s8 get(s8 x);

    void set(u2& x, u2 y);
    void set(u4& x, u4 y);
    void set(u8& x, u8 y);
    void set(s2& x, s2 y);
    void set(s4& x, s4 y);
    void set(s8& x, s8 y);

    static Endian* get_swapping() { return &_swapping; }
};
#endif // LIBJIMAGE_ENDIAN_HPP