1 files changed, 224 insertions, 0 deletions
diff --git a/src/stem/heap.c b/src/stem/heap.c
new file mode 100644
index 0000000..b6d2cd4
--- /dev/null
+++ b/src/stem/heap.c
@@ -0,0 +1,224 @@
+#include "heap.h"
+#include "paging.h"
+
+#define HEAP_MAGIC 0xBAD0BEEF
+#define HEAP_MIN_SIZE 0x4000
+
+/* *******************			HEADER    	   ****************** */
+
+static void heapIdx_insert(struct heap *heap, struct heap_header *e) {
+	if ((heap->idxused + sizeof(struct heap_header*) + (size_t)heap->idx) >= heap->start_addr) return;
+
+	uint32_t iterator = 0, pos;
+	while (iterator < heap->idxused && heap->idx[iterator]->size < e->size) {
+		if (heap->idx[iterator] == e) return;
+		iterator++;
+	}
+	if (iterator == heap->idxused) {
+		heap->idx[heap->idxused++] = e;
+	} else {
+		pos = iterator;
+		iterator = heap->idxused;
+		while (iterator > pos) {
+			heap->idx[iterator] = heap->idx[iterator - 1];
+			iterator--;
+		}
+		heap->idxused++;
+		heap->idx[pos] = e;
+	}
+}
+
+static void heapIdx_remove(struct heap *heap, struct heap_header *e) {
+	uint32_t iterator;
+	for (iterator = 0; iterator < heap->idxused; iterator++) {
+		if (heap->idx[iterator] == e) break;
+	}
+	if (iterator == heap->idxused) return;
+	heap->idxused--;
+	while (iterator < heap->idxused) {
+		heap->idx[iterator] = heap->idx[iterator + 1];
+		iterator++;
+	}
+}
+
+/* ********************			CONTENTS		********************* */
+
+void heap_create(struct heap *heap, size_t start, size_t idxsize, size_t datasize, size_t maxdatasize) {
+	uint32_t i;
+
+	if (start & 0x0FFF) start = (start & 0xFFFFF000) + 0x1000;
+
+	heap->start_addr = start + idxsize;
+	heap->end_addr = start + idxsize + datasize;
+	heap->max_end = start + idxsize + maxdatasize;
+
+	for (i = start; i < heap->end_addr; i += 0x1000) {
+		page_map(pagedir_getPage(kernel_pagedir, i, 1), frame_alloc(), 0, 0);
+	}
+
+	heap->idx = (struct heap_header**)start;	
+	heap->idxused = 0;
+
+	struct heap_header *hole = (struct heap_header*) heap->start_addr;
+	hole->size = (heap->end_addr - heap->start_addr);
+	hole->magic = HEAP_MAGIC;
+	hole->is_hole = 1;
+
+	struct heap_footer *hole_footer = (struct heap_footer*)(heap->end_addr - sizeof(struct heap_footer));
+	hole_footer->header = hole;
+	hole_footer->magic = HEAP_MAGIC;
+
+	heapIdx_insert(heap, hole);
+}
+
+static uint32_t heap_expand(struct heap *heap, size_t quantity) {
+	uint32_t i;
+
+	if (quantity & 0x0FFF) {
+		quantity = (quantity & 0xFFFFF000) + 0x1000;
+	}
+
+	if (heap->end_addr + quantity > heap->max_end) return 0;
+
+	size_t newEnd = heap->end_addr + quantity;
+
+	for (i = heap->end_addr; i < newEnd; i += 0x1000) {
+		page_map(pagedir_getPage(kernel_pagedir, i, 1), frame_alloc(), 0, 0);
+	}
+
+	struct heap_footer *last_footer = (struct heap_footer*)(heap->end_addr - sizeof(struct heap_footer));
+	struct heap_header *last_header = last_footer->header;
+	if (last_header->is_hole) {
+		heapIdx_remove(heap, last_header);
+		last_header->size += quantity;
+
+		last_footer = (struct heap_footer*)(newEnd - sizeof(struct heap_footer));
+		last_footer->magic = HEAP_MAGIC;
+		last_footer->header = last_header;
+
+		heapIdx_insert(heap, last_header);
+	} else {
+		last_header = (struct heap_header*)heap->end_addr;
+		last_footer = (struct heap_footer*)(newEnd - sizeof(struct heap_footer));
+
+		last_header->is_hole = 1;
+		last_header->magic = HEAP_MAGIC;
+		last_header->size = quantity;
+
+		last_footer->magic = HEAP_MAGIC;
+		last_footer->header = last_header;
+
+		heapIdx_insert(heap, last_header);
+	}
+
+	heap->end_addr = newEnd;
+
+	return 1;
+}
+
+static void heap_contract(struct heap *heap) {
+	struct heap_footer *last_footer = (struct heap_footer*)(heap->end_addr - sizeof(struct heap_footer));
+	struct heap_header *last_header = last_footer->header;
+
+	if (last_header->is_hole == 0) return;
+
+	size_t quantity = 0;
+	while ((heap->end_addr - heap->start_addr) - quantity > HEAP_MIN_SIZE &&
+			(last_header->size - quantity) > 0x1000)
+		quantity += 0x1000;
+	if (quantity == 0) return;
+
+	size_t newEnd = heap->end_addr - quantity;
+
+	heapIdx_remove(heap, last_header);
+	last_header->size -= quantity;
+	last_footer = (struct heap_footer*)((size_t)last_footer - quantity);
+	last_footer->magic = HEAP_MAGIC;
+	last_footer->header = last_header;
+	heapIdx_insert(heap, last_header);
+
+	for (heap->end_addr -= 0x1000; heap->end_addr >= newEnd; heap->end_addr -= 0x1000) {
+		page_unmapFree(pagedir_getPage(kernel_pagedir, heap->end_addr, 0));
+	}
+}
+
+void* heap_alloc(struct heap *heap, size_t sz) {
+	size_t newsize = sz + sizeof(struct heap_header) + sizeof(struct heap_footer);
+	uint32_t iterator = 0;
+
+	while (iterator < heap->idxused) {
+		if (heap->idx[iterator]->size >= newsize) break;
+		iterator++;
+	}
+
+	if (iterator == heap->idxused) {	//No hole is big enough
+		if (heap_expand(heap, (sz & 0xFFFFF000) + 0x1000) == 0) return 0;	//FAILED
+		return heap_alloc(heap, sz);
+	}
+
+	struct heap_header *loc = heap->idx[iterator];
+	struct heap_footer *footer = (struct heap_footer*)((size_t)loc + loc->size - sizeof(struct heap_footer));
+	loc->is_hole = 0;
+	heapIdx_remove(heap, loc);
+	
+	//If we have enough space to create a USEFUL new hole next to the allocated block, do it.
+	//If we do not, we might return a block that is a few bytes bigger than neede.
+	if (loc->size > (newsize + sizeof(struct heap_header) + sizeof(struct heap_footer))) {
+		loc->size = newsize;
+
+		//Write footer for block we return
+		struct heap_footer *newfooter = (struct heap_footer*)((size_t)loc + newsize - sizeof(struct heap_footer));
+		newfooter->header = loc;
+		newfooter->magic = HEAP_MAGIC;
+
+		//Write header for new hole we create
+		struct heap_header *nextloc = (struct heap_header*)((size_t)loc + newsize);
+		nextloc->is_hole = 1;
+		nextloc->magic = HEAP_MAGIC;
+		nextloc->size = ((size_t)footer - (size_t)nextloc + sizeof(struct heap_footer));
+		footer->header = nextloc;	//Update footer
+		footer->magic = HEAP_MAGIC;
+
+		heapIdx_insert(heap, nextloc);
+	}
+
+	return (void*)((size_t)loc + sizeof(struct heap_header));
+}
+
+void heap_free(struct heap *heap, void* ptr) {
+	if (ptr == 0) return;
+	if ((size_t)ptr < heap->start_addr || (size_t)ptr > heap->end_addr) return;
+
+	struct heap_header *header = (struct heap_header*)((size_t)ptr - sizeof(struct heap_header));
+	struct heap_footer *footer = (struct heap_footer*)((size_t)header + header->size - sizeof(struct heap_footer));
+	if (header->magic != HEAP_MAGIC || footer->magic != HEAP_MAGIC) return;
+
+	//Unify left
+	struct heap_footer *prev_footer = (struct heap_footer*)((size_t)header - sizeof(struct heap_footer));
+	if (prev_footer->magic == HEAP_MAGIC && prev_footer->header->is_hole) {
+		header = prev_footer->header;
+		heapIdx_remove(heap, header);
+
+		footer->header = header;
+		header->size = ((size_t)footer - (size_t)header + sizeof(struct heap_footer));
+	}
+
+	//Unify right
+	struct heap_header *next_header = (struct heap_header*)((size_t)footer + sizeof(struct heap_footer));
+	if (next_header->magic == HEAP_MAGIC && next_header->is_hole) {
+		heapIdx_remove(heap, next_header);
+		footer = (struct heap_footer*)((size_t)footer + next_header->size);
+
+		footer->header = header;
+		header->size = ((size_t)footer - (size_t)header + sizeof(struct heap_footer));
+	}
+
+	header->is_hole = 1;
+
+	heapIdx_insert(heap, header);
+
+	if ((size_t)footer == (heap->end_addr - sizeof(struct heap_footer)) &&
+			header->size >= 0x2000 && (heap->end_addr - heap->start_addr > HEAP_MIN_SIZE)) {
+		heap_contract(heap);
+	}	
+}