bottleros/Kernel/utils/memManagerBuddy.c

#ifdef BUDDY
// #include <stdio.h>
#include <stdlib.h>
// #include <time.h>
// #include <math.h>
#include <string.h>
#define MANAGED_MEMORY_SIZE 1024

// https://github.com/sdpetrides/BuddyAllocator

// char initMemoryManager(void *const restrict memoryForMemoryManager, void *const restrict managedMemory) {
//     return 1;
// }

// void * memMalloc(const size_t memoryToAllocate) {
//     return NULL;
// }

typedef struct meta {
	unsigned char allo : 1;		// 0000000_ - allocated
	unsigned char left : 1;		// 000000_0 - first or second
	unsigned char size : 6;		// ______00 - n where (2^n)-1 is the block size
} Meta;

// static char myblock[MANAGED_MEMORY_SIZE];
static char *myblock;
void initMemoryManager(void * managedMemory) {
	myblock = managedMemory;
}

void unpack(Meta * m, int pos);

/* Fills myblock with zeros and creates first metadata */
void init_block() {
	memset(&myblock, '\0', MANAGED_MEMORY_SIZE);
	memset(&myblock, 54, 1);
}

int ceil(float num) {
    int inum = (int)num;
    if (num == (float)inum) {
        return inum;
    }
    return inum + 1;
}

// unsigned int log2(unsigned int n)
// {
//     return (n > 1) ? 1 + log2(n / 2) : 0;
// }

// /* Returns log base 2 of a double d */
// double log2(double d) {
//     return log(d) / log(2);  
// }

/* Returns the level a reqSize will fit in */
int size_to_n(size_t reqSize) {
	reqSize+=1;
	double d = log2((double)reqSize);
	return (int)ceil(d);
}

/* Returns the position of the next block of the correct size */
int jump_next(int n, int pos) {
	int bits = pos>>(n);
	bits+=1;
	int ret = bits<<(n);

	if (ret == MANAGED_MEMORY_SIZE) {
		return ret;
	} else {
		return ret;
	}
	
}

/* Returns the position of the left half of a pair */
int jump_back(int n, int pos) {
	int bits = pos>>(n);
	bits-=1;
	return bits<<(n);
}

/* Fills a Meta struct with metadata at pos */
void unpack(Meta * m, int pos) {
	memset(m, myblock[pos], 1);
}

/* Returns whether position at level n is left or right partner */
int is_left(int n, int pos) {

	// Manipulate bits to set nth bit on
	int k = 1;
	k<<=(n);
	
	// Manipulate bits to zero bits above n
	unsigned int p = (unsigned int)pos;
	p<<=(31-n);
	p>>=(31-n);

	if (k == p) {
		return 0;	// Right
	} else {
		return 1;	// Left
	}
}

/*  Mergee two unallocated blocks with same size */
void merge(int pos, int pos2, int n) {
	
	// Create new meta and set size field
	char newMeta = (n+1)<<2;

	// Set left field
	if (is_left(n+1, pos)) {
		newMeta+=2;
	}

	// Add new meta
	myblock[pos] = newMeta;

	// Delete meta on right partner
	myblock[pos2] = 0;		
}

/* MYmymalloc */
void * pvPortMalloc(size_t reqSize) {

	// Check if too big
	if (reqSize > MANAGED_MEMORY_SIZE - 1) {
		// fprintf(stderr, "Error: Requested size too large\n");
        return NULL;
	}

	// Traverse heap to find block of correct size - algo(n)
	int n = size_to_n(reqSize);
	int pos = 0;
	unsigned char c = 0;
	Meta * m = memset(&c, 0, 1);
	
	while (pos < MANAGED_MEMORY_SIZE) {
		// Read metadata
		unpack(m, pos);

		// // Debugging
		// if (m->size == 0) {
		// 	exit(0);
		// }

		if (n <= m->size) {
			if (m->allo == 1) {				
				// Jump
				pos = jump_next(n, pos);
				continue;
			} else if (m->size == n) {		
				// Allocate
				myblock[pos]+=1;
				pos+=1;
				return (void*)((long int)&myblock+pos);
			} else { 						
				// Partition

				// Get partner position
				int partner = jump_next((m->size)-1, pos);

				// Set Left
				char meta_1 = 2;
				char meta_2 = 0;
				
				// Set Size
				char s = ((m->size)-1)<<2;
				meta_1 = (meta_1 | s);
				meta_2 = (meta_2 | s);

				// Fill in metadata
				myblock[pos] = meta_1;
				myblock[partner] = meta_2;

				// Continue on same position with new size of block
				continue;
			}
		} else {
			// Jump
			pos = jump_next(n, pos);
			continue;
		}
	}

    //error

	return 0;
}

/* MYmyfree */
void vPortFree(void * ptr) {
	
	// Error Checking
	if (ptr <= (void *)&myblock || ptr > (void *)(&myblock + MANAGED_MEMORY_SIZE)) {
        //error
		return;
	}

	// Get position
	// int pos = (int)(ptr-(void *)&myblock-1);
    int pos = (int)((char *)ptr-(char *)&myblock-1);

	// Check if valid metadata location
	if (pos%2 == 1 || myblock[pos] == 0) {
        //error
		return;
	}


	// Initialize variables for merge
	unsigned char c1 = 0;
	unsigned char c2 = 0;
	Meta * m1 = memset(&c1, 0, 1); 
	Meta * m2 = memset(&c2, 0, 1);
	unpack(m1,pos);

	// Change allocated field
	myblock[pos] = myblock[pos] - 1;

	while (pos >= 0 && pos <= 8196){
		// Read metadata
		unpack(m1,pos);

		if (m1->left) {	// Left Partner

			// Get position of other partner and read metadata
			int pos2 = jump_next(m1->size, pos);

			if (pos2 >= 0 && pos2 <= MANAGED_MEMORY_SIZE - 2) {
				unpack(m2,pos2);
			} else {
				break;
			}

			// Merge or break
			if (m2->allo || m2->size != m1->size) {
				break;
			} else {
				merge(pos, pos2, m1->size);
			}

		} else {		// Right Partner

			// Get position of other partner and read metadata
			int pos2 = jump_back(m2->size,pos);

			if (pos2 >= 0 && pos2 <= MANAGED_MEMORY_SIZE -2) {
				unpack(m2,pos2);
			} else {
				break;
			}

			// Merge or break
			if (m2->allo || m2->size != m1->size) {
				break;
			} else {
				merge(pos2, pos, m1->size); 
			}	
		}
	}
}

#endif