prng.c File Reference

#include "prng.h"
#include "LPC17xx.h"

Go to the source code of this file.

Functions
void	PRNG_Set (u32 seed)
	Initializes the PRNG by seeding it with the given seed. Use PRNG_USE_AUTO_SEED to seed it automatically using an HW entropy source.
void	PRNG_Release (void)
	Releases the HW entropy sources used to seed the PRNG.
u32	PRNG_Next (void)
	Generates the next pseudo-random number.
u32	PRNG_Range (u32 min, u32 max)
	Generates a pseudo-random number in the given range, inclusive.

Variables
_PRIVATE u32	prng_state = 0

Function Documentation

PRNG_Next()

u32 PRNG_Next

(

void

)

Generates the next pseudo-random number.

Returns

The PRN

Definition at line 38 of file prng.c.

{
    // A simple linear congruential generator (LCG) for pseudo-random numbers
    prng_state = (1103515245 * prng_state + 12345) & 0x7FFFFFFF;
    return prng_state;
}

PRNG_Range()

u32 PRNG_Range	(	u32	min,
		u32	max
	)

Generates a pseudo-random number in the given range, inclusive.

Parameters

min	Lower bound
max	Upper bound

Returns

The PRN

Definition at line 49 of file prng.c.

{
    if (min > max)
    {
        // Swap min and max if inputs are invalid
        u32 temp = min;
        min = max;
        max = temp;
    }
 
    u32 range = max - min + 1;
    return (PRNG_Next() % range) + min;
}

PRNG_Release()

void PRNG_Release

(

void

)

Releases the HW entropy sources used to seed the PRNG.

Definition at line 29 of file prng.c.

{
    // Stopping SysTick
    SysTick->CTRL = 0;
    prng_state = 0;
}

PRNG_Set()

void PRNG_Set

(

u32

seed

)

Initializes the PRNG by seeding it with the given seed. Use PRNG_USE_AUTO_SEED to seed it automatically using an HW entropy source.

Parameters

seed	The seed to use.

Definition at line 7 of file prng.c.

{
    if (seed == (u32)PRNG_USE_AUTO_SEED)
    {
        // Starting SysTick if it's not already running
        if (!(SysTick->CTRL & SysTick_CTRL_ENABLE_Msk))
        {
            SysTick->LOAD = 0xFFFFFF; // Set the maximum value for a 24-bit counter
            SysTick->VAL = 0;         // Reset the counter
            SysTick->CTRL = SysTick_CTRL_CLKSOURCE_Msk | SysTick_CTRL_ENABLE_Msk; // Enable the counter
        }
 
        // Use SysTick counter as a hardware entropy source for automatic seeding
        prng_state = SysTick->VAL ^ (SysTick->VAL << 16) ^ (SysTick->LOAD);
        return;
    }
 
    // Use the provided seed
    prng_state = seed;
}

Variable Documentation

prng_state

_PRIVATE u32 prng_state = 0

Definition at line 5 of file prng.c.