types.h

DIY自己的MP3的参考价值极高的代码。含有详细的解释

/**************************************************************************
**
**  Revision History
**
**  when         what  who	why
**
**  2002-03-15   1.0   Jesper   initial release
**  2002-07-06   1.1   MIS	added conversion structures
**
*********************************************************************** */


#ifndef __TYPES_H__
#define __TYPES_H__


#define MAX_U16  65535
#define MAX_S16  32767

//
// basic unsigned types
//
typedef unsigned char  u08;
typedef unsigned short u16;
typedef unsigned long  u32;

//
// basic signed types
//
typedef char  s08;
typedef short s16;
typedef long  s32;

#ifndef NULL
#define NULL    0
#endif

// Make an unsigned copy of div function
typedef struct {
	unsigned quot;
	unsigned rem;
} udiv_t;
extern udiv_t udiv(unsigned, unsigned) __asm__("__udivmodhi4") __ATTR_CONST__;

// This structures are used to simplify code, compiler doesn't optimize 
// well shifts
struct u16bytes
{
	u08 low, high;
};

union u16convert
{
	u16 value;
	struct u16bytes bytes;
};

struct u32bytes
{
	u08 byte1, byte2, byte3, byte4;
};

struct u32words
{
	u16 low, high;
};

union u32convert 
{
	u32 value;
	struct u32bytes bytes;
	struct u32words words;
};


#endif