stmos/src/kernel/heap.c
2018-10-18 18:24:43 -04:00

132 lines
3.0 KiB
C

/**
* @file heap.c
* A basic memory manager
*
* Copyright (C) 2018 Clyne Sullivan
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include "heap.h"
#define HEAP_ALIGN 4
static alloc_t *free_blocks;
static void *heap_end;
void heap_init(void *buf)
{
heap_end = buf;
free_blocks = 0;
}
uint32_t heap_free(void)
{
uint32_t total = 0;
for (alloc_t *node = free_blocks; node != 0; node = node->next)
total += node->size;
return total + (0x20018000 - (uint32_t)heap_end);
}
void *malloc(uint32_t size)
{
if (size == 0)
return 0;
size = (size + sizeof(alloc_t) + HEAP_ALIGN) & ~(HEAP_ALIGN - 1);
alloc_t *node = free_blocks;
alloc_t *prev = 0;
while (node != 0) {
if (node->size >= size) {
// get out of the free chain
if (prev != 0)
prev->next = node->next;
else
free_blocks = node->next;
node->next = 0;
// split alloc if too big
if (node->size > size + 64) {
alloc_t *leftover = (alloc_t *)((uint32_t)node
+ sizeof(alloc_t) + size);
leftover->size = node->size - size - sizeof(alloc_t);
leftover->next = 0;
free((uint8_t *)leftover + sizeof(alloc_t));
node->size = size;
return (void *)((uint8_t *)node + sizeof(alloc_t));
}
return (void *)((uint8_t *)node + sizeof(alloc_t));
}
prev = node;
node = node->next;
}
node = (alloc_t *)heap_end;
node->size = size;
node->next = 0;
heap_end = (void *)((uint8_t *)heap_end + size);
return (void *)((uint8_t *)node + sizeof(alloc_t));
}
void *calloc(uint32_t count, uint32_t size)
{
uint8_t *buf = malloc(count * size);
for (uint32_t i = 0; i < count * size; i++)
buf[i] = 0;
return buf;
}
void free(void *buf)
{
if (buf == 0)
return;
alloc_t *alloc = (alloc_t *)((uint8_t *)buf - sizeof(alloc_t));
if (alloc->next != 0)
return;
// check for adjacent free'd blocks
int merged = 0;
for (alloc_t *prev = 0, *node = free_blocks; node != 0; prev = node, node = node->next) {
if ((uint32_t)node + sizeof(alloc_t) + node->size == (uint32_t)alloc) {
// block before
merged |= 1;
node->size += sizeof(alloc_t) + alloc->size;
break;
//alloc = node;
} else if ((uint32_t)buf + alloc->size == (uint32_t)node) {
// block after
merged |= 1;
alloc->size += sizeof(alloc_t) + node->size;
alloc->next = node->next;
if (prev != 0)
prev->next = alloc;
else
free_blocks = alloc;
break;
}
}
if (merged == 0) {
alloc->next = free_blocks;
free_blocks = alloc;
}
}