jas_fix.h

用C语言实现的JPEG编码

#define JAS_FIX_MUL			JAS_FIX_MUL_OFLOW
#endif

/* Calculate the product of two fixed-point numbers without overflow
  checking. */
#define	JAS_FIX_MUL_FAST(fix_t, fracbits, bigfix_t, x, y) \
	JAS_CAST(fix_t, (JAS_CAST(bigfix_t, x) * JAS_CAST(bigfix_t, y)) >> \
	  (fracbits))

/* Calculate the product of two fixed-point numbers with overflow
  checking. */
#define JAS_FIX_MUL_OFLOW(fix_t, fracbits, bigfix_t, x, y) \
	((JAS_CAST(bigfix_t, x) * JAS_CAST(bigfix_t, y) >> (fracbits)) == \
	  JAS_CAST(fix_t, (JAS_CAST(bigfix_t, x) * JAS_CAST(bigfix_t, y) >> \
	  (fracbits))) ? \
	  JAS_CAST(fix_t, (JAS_CAST(bigfix_t, x) * JAS_CAST(bigfix_t, y) >> \
	  (fracbits))) : JAS_FIX_OFLOW())

/* Calculate the product of a fixed-point number and an int. */
#if !defined(DEBUG_OVERFLOW)
#define	JAS_FIX_MULBYINT	JAS_FIX_MULBYINT_FAST
#else
#define	JAS_FIX_MULBYINT	JAS_FIX_MULBYINT_OFLOW
#endif

/* Calculate the product of a fixed-point number and an int without overflow
  checking. */
#define	JAS_FIX_MULBYINT_FAST(fix_t, fracbits, x, y) \
	JAS_CAST(fix_t, ((x) * (y)))

/* Calculate the product of a fixed-point number and an int with overflow
  checking. */
#define	JAS_FIX_MULBYINT_OFLOW(fix_t, fracbits, x, y) \
	JAS_FIX_MULBYINT_FAST(fix_t, fracbits, x, y)

/* Calculate the quotient of two fixed-point numbers. */
#if !defined(DEBUG_OVERFLOW)
#define JAS_FIX_DIV			JAS_FIX_DIV_FAST
#else
#define JAS_FIX_DIV			JAS_FIX_DIV_UFLOW
#endif

/* Calculate the quotient of two fixed-point numbers without underflow
  checking. */
#define	JAS_FIX_DIV_FAST(fix_t, fracbits, bigfix_t, x, y) \
	JAS_CAST(fix_t, (JAS_CAST(bigfix_t, x) << (fracbits)) / (y))

/* Calculate the quotient of two fixed-point numbers with underflow
  checking. */
#define JAS_FIX_DIV_UFLOW(fix_t, fracbits, bigfix_t, x, y) \
	JAS_FIX_DIV_FAST(fix_t, fracbits, bigfix_t, x, y)

/* Negate a fixed-point number. */
#if !defined(DEBUG_OVERFLOW)
#define	JAS_FIX_NEG			JAS_FIX_NEG_FAST
#else
#define	JAS_FIX_NEG			JAS_FIX_NEG_OFLOW
#endif

/* Negate a fixed-point number without overflow checking. */
#define	JAS_FIX_NEG_FAST(fix_t, fracbits, x) \
	(-(x))

/* Negate a fixed-point number with overflow checking. */
/* Yes, overflow is actually possible for two's complement representations,
  although highly unlikely to occur. */
#define	JAS_FIX_NEG_OFLOW(fix_t, fracbits, x) \
	(((x) < 0) ? (-(x) > 0 || JAS_FIX_OFLOW(), -(x)) : (-(x)))

/* Perform an arithmetic shift left of a fixed-point number. */
#if !defined(DEBUG_OVERFLOW)
#define	JAS_FIX_ASL			JAS_FIX_ASL_FAST
#else
#define	JAS_FIX_ASL			JAS_FIX_ASL_OFLOW
#endif

/* Perform an arithmetic shift left of a fixed-point number without overflow
  checking. */
#define	JAS_FIX_ASL_FAST(fix_t, fracbits, x, n) \
	((x) << (n))

/* Perform an arithmetic shift left of a fixed-point number with overflow
  checking. */
#define	JAS_FIX_ASL_OFLOW(fix_t, fracbits, x, n) \
	((((x) << (n)) >> (n)) == (x) || JAS_FIX_OFLOW(), (x) << (n))

/* Perform an arithmetic shift right of a fixed-point number. */
#if !defined(DEBUG_OVERFLOW)
#define	JAS_FIX_ASR			JAS_FIX_ASR_FAST
#else
#define	JAS_FIX_ASR			JAS_FIX_ASR_UFLOW
#endif

/* Perform an arithmetic shift right of a fixed-point number without underflow
  checking. */
#define	JAS_FIX_ASR_FAST(fix_t, fracbits, x, n) \
	((x) >> (n))

/* Perform an arithmetic shift right of a fixed-point number with underflow
  checking. */
#define	JAS_FIX_ASR_UFLOW(fix_t, fracbits, x, n) \
	JAS_FIX_ASR_FAST(fix_t, fracbits, x, n)

/******************************************************************************\
* Other basic arithmetic operations.
\******************************************************************************/

/* Calculate the difference between two fixed-point numbers. */
#define JAS_FIX_SUB(fix_t, fracbits, x, y) \
	JAS_FIX_ADD(fix_t, fracbits, x, JAS_FIX_NEG(fix_t, fracbits, y))

/* Add one fixed-point number to another. */
#define JAS_FIX_PLUSEQ(fix_t, fracbits, x, y) \
	((x) = JAS_FIX_ADD(fix_t, fracbits, x, y))

/* Subtract one fixed-point number from another. */
#define JAS_FIX_MINUSEQ(fix_t, fracbits, x, y) \
	((x) = JAS_FIX_SUB(fix_t, fracbits, x, y))

/* Multiply one fixed-point number by another. */
#define	JAS_FIX_MULEQ(fix_t, fracbits, bigfix_t, x, y) \
	((x) = JAS_FIX_MUL(fix_t, fracbits, bigfix_t, x, y))

/******************************************************************************\
* Miscellaneous operations.
\******************************************************************************/

/* Calculate the absolute value of a fixed-point number. */
#define	JAS_FIX_ABS(fix_t, fracbits, x) \
	(((x) >= 0) ? (x) : (JAS_FIX_NEG(fix_t, fracbits, x)))

/* Is a fixed-point number an integer? */
#define	JAS_FIX_ISINT(fix_t, fracbits, x) \
	(JAS_FIX_FLOOR(fix_t, fracbits, x) == (x))

/* Get the sign of a fixed-point number. */
#define JAS_FIX_SGN(fix_t, fracbits, x) \
	((x) >= 0 ? 1 : (-1))

/******************************************************************************\
* Relational operations.
\******************************************************************************/

/* Compare two fixed-point numbers. */
#define JAS_FIX_CMP(fix_t, fracbits, x, y) \
	((x) > (y) ? 1 : (((x) == (y)) ? 0 : (-1)))

/* Less than. */
#define	JAS_FIX_LT(fix_t, fracbits, x, y) \
	((x) < (y))

/* Less than or equal. */
#define	JAS_FIX_LTE(fix_t, fracbits, x, y) \
	((x) <= (y))

/* Greater than. */
#define	JAS_FIX_GT(fix_t, fracbits, x, y) \
	((x) > (y))

/* Greater than or equal. */
#define	JAS_FIX_GTE(fix_t, fracbits, x, y) \
	((x) >= (y))

/******************************************************************************\
* Rounding functions.
\******************************************************************************/

/* Round a fixed-point number to the nearest integer. */
#define	JAS_FIX_ROUND(fix_t, fracbits, x) \
	(((x) < 0) ? JAS_FIX_FLOOR(fix_t, fracbits, JAS_FIX_ADD(fix_t, fracbits, \
	  (x), JAS_FIX_HALF(fix_t, fracbits))) : \
	  JAS_FIX_NEG(fix_t, fracbits, JAS_FIX_FLOOR(fix_t, fracbits, \
	  JAS_FIX_ADD(fix_t, fracbits, (-(x)), JAS_FIX_HALF(fix_t, fracbits)))))

/* Round a fixed-point number to the nearest integer in the direction of
  negative infinity (i.e., the floor function). */
#define	JAS_FIX_FLOOR(fix_t, fracbits, x) \
	((x) & (~((JAS_CAST(fix_t, 1) << (fracbits)) - 1)))

/* Round a fixed-point number to the nearest integer in the direction
  of zero. */
#define JAS_FIX_TRUNC(fix_t, fracbits, x) \
	(((x) >= 0) ? JAS_FIX_FLOOR(fix_t, fracbits, x) : \
	  JAS_FIX_CEIL(fix_t, fracbits, x))

/******************************************************************************\
* The below macros are for internal library use only.  Do not invoke them
* directly in application code.
\******************************************************************************/

/* Handle overflow. */
#define	JAS_FIX_OFLOW() \
	fprintf(stderr, "overflow error: file %s, line %d\n", __FILE__, __LINE__)

/* Handle underflow. */
#define	JAS_FIX_UFLOW() \
	fprintf(stderr, "underflow error: file %s, line %d\n", __FILE__, __LINE__)

#ifdef __cplusplus
}
#endif

#endif