Fixed-Point math routines

Files
file	Fxp.h
	Function and macro definitions for fixed point math.
file	Fxp_trig.c
	Fixed-point trigenometry tables and routines.
Classes
class	Angle
	Class used to handle fixed-point angles. More...
class	SfxpCoord
	Class used to handle fixed-point x/y coordinates. More...
Fixed point integer definitions
#define	SFXP_BITS   10
	Defines the number of bits precision of fixed point #s.
#define	SFXP_SCALAR   (1<<SFXP_BITS)
	2^SFXP_BITS
#define	TO_SFXP(x)   (((Sint32)(x))<<SFXP_BITS)
	Convert from integer to signed fixed point.
#define	FROM_SFXP(x)   ((Sint32)((x+((SFXP_SCALAR>>1)))>>SFXP_BITS))
	Convert from signed fixed point to integer.
#define	F_TO_SFXP(x)   ((Sfxp)((x)*SFXP_SCALAR))
	Convert from float to signed fixed point.
#define	SFXP_TO_F(x)   ( ((FxpFloat)(x)) / ((FxpFloat)SFXP_SCALAR) )
	Convert from signed fixed point to floating point.
#define	MUL_SFXP(x, y)   FROM_SFXP(((Sint64)(x))*((Sint64)(y)))
	Multiplies two signed fixed point numbers.
#define	DIV_SFXP(x, y)   ((Sfxp)((TO_SFXP((Sint64)(x)))/y))
	Divides two signed fixed point numbers, x/y.
typedef Sint32	Sfxp
	Definition for the signed fixed-point type.
Fixed point angle definitions
#define	AFXP_BITSIZE   (sizeof(Afxp)*8)
	# of bits in angle type
#define	AFXP_MAX   (1<<AFXP_BITSIZE)
	Maximum value of angle type, 2^AFXP_BITSIZE.
#define	AFXP_BITS   8
	Defines the bits precision in a fixed-point angle.
#define	FXP_PI   3.14159f
	Any more digits than this would be superfluous.
#define	DEG_TO_AFXP(x)   ((Afxp)((x)*( ((double)AFXP_MAX) /360.)))
	Convert degrees to fixed-point angles.
#define	RAD_TO_AFXP(x)   DEG_TO_AFXP((x)*(180./3.14159))
	Convert radians to fixed point angles.
#define	AFXP_TO_DEG(x)   ((x)*(360./AFXP_MAX))
	Convert fixed point angles to degrees.
typedef Uint16	Afxp
	Type definition for the fixed-point angular type.
Fixed Point Trigenometry
DECLSPEC void SDLCALL	FXP_Init ()
	Initializes fixed-point trig tables.
DECLSPEC Sfxp SDLCALL	FXP_Sin (Afxp a)
	Returns fixed-point sin value.
DECLSPEC Afxp SDLCALL	FXP_Asin (Sfxp val)
	Returns fixed-point inverse-sin value.
DECLSPEC Sfxp SDLCALL	FXP_Cos (Afxp a)
	Returns fixed-point cos value.
DECLSPEC Afxp SDLCALL	FXP_Acos (Sfxp val)
	Returns fixed-point inverse-cos value.
DECLSPEC Sfxp SDLCALL	FXP_Tan (Afxp a)
	Returns fixed-point tan value.
DECLSPEC Afxp SDLCALL	FXP_Atan (Sfxp val)
	Returns fixed-point inverse-tan value.
DECLSPEC Afxp SDLCALL	FXP_Traj (Sfxp y, Sfxp x)
	Returns the angle of the vector, valid at any angle.
Defines
#define	TABLE_SIZE   2048
	# of elements in trig tables
#define	TABLEPOS_TO_ANGLE(n)   ((Afxp)((AFXP_MAX*n)/TABLE_SIZE))
	Converts a table-index to an angle.
#define	ANGLE_TO_TABLEPOS(a)   (((TABLE_SIZE*(int)a)/AFXP_MAX)%TABLE_SIZE)
	Converts an angle to a table pos.
#define	AVERAGE(x, y)   ((x+y)/2)
	Returns average of two values.
Typedefs
typedef float	FxpFloat
	The floating point type used converting to/from floating point.
Functions
int	FindInTable (Sfxp val, int min, int max, const Sfxp table[TABLE_SIZE])
	Binary search for specified area, sorted in increasing order.
int	FXP_DumpTrig (const char *fname)
	Prints contents of trig tables to a C file.
Variables
const Sfxp	__SIN_TABLE []
	Table of sin values vs angle.
const Sfxp	__COS_TABLE []
	Table of cos values vs angle.
const Sfxp	__TAN_TABLE []
	Table of tan values vs angle.

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Detailed Description

Contains routines and macros for platform-independent fixed-point math and triginometry.

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Function Documentation

Afxp FXP_Traj (  Sfxp  y, Sfxp  x )

Unlike Tan, this returns the correct angle in the range from 0 to 360 degrees. Definition at line 258 of file Fxp_trig.c. References Afxp, DEG_TO_AFXP, DIV_SFXP, FXP_Atan(), and Sfxp. Referenced by TestFxp(), and SfxpCoord::Trajectory().

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