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