rand.h File Reference

#include <types.h>
#include <stdint.h>

Go to the source code of this file.

Macros
#define	RAND_MAX   255
#define	RANDW_MAX   65535

Functions
void	initrand (uint16_t seed) OLDCALL
uint8_t	rand () OLDCALL
uint16_t	randw () OLDCALL
void	initarand (uint16_t seed) OLDCALL
uint8_t	arand () OLDCALL

Variables
uint16_t	__rand_seed

Detailed Description

Random generator using the linear congruential method

Author

Luc Van den Borre

Macro Definition Documentation

RAND_MAX

#define RAND_MAX   255

RANDW_MAX

#define RANDW_MAX   65535

Function Documentation

initrand()

void initrand

(

uint16_t

seed

)

Initalise the pseudo-random number generator.

Parameters

seed	The value for initializing the random number generator.

The seed should be different each time, otherwise the same pseudo-random sequence will be generated.

The DIV Register (DIV_REG) is sometimes used as a seed, particularly if read at some variable point in time (such as when the player presses a button).

Only needs to be called once to initialize, but may be called again to re-initialize with the same or a different seed.

See also

rand(), randw()

rand()

uint8_t rand

(

)

Returns a random byte (8 bit) value.

initrand() should be used to initialize the random number generator before using rand()

randw()

uint16_t randw

(

)

Returns a random word (16 bit) value.

initrand() should be used to initialize the random number generator before using rand()

initarand()

void initarand

(

uint16_t

seed

)

Random generator using the linear lagged additive method

Parameters

seed	The value for initializing the random number generator.

Note: initarand() calls initrand() with the same seed value, and uses rand() to initialize the random generator.

See also

initrand() for suggestions about seed values, arand()

arand()

uint8_t arand

(

)

Returns a random number generated with the linear lagged additive method.

initarand() should be used to initialize the random number generator before using arand()

Variable Documentation

__rand_seed

uint16_t __rand_seed

extern

The random number seed is stored in __rand_seed and can be saved and restored if needed.

// Save
some_uint16 = __rand_seed;
...
// Restore
__rand_seed = some_uint16;