Shared memory segment manager in userland

1 files changed, 100 insertions, 0 deletions

diff --git a/src/library/gc/shm.c b/src/library/gc/shm.c
new file mode 100644
index 0000000..9e19533
--- /dev/null
+++ b/src/library/gc/shm.c
@@ -0,0 +1,100 @@
+#include <gc/shm.h>
+#include <gc/mem.h>
+#include <mutex.h>
+
+struct shm_block {
+	size_t start, size;
+	int is_hole;	//1 : hole, 0 : used block
+	struct shm_block *prev, *next;
+};
+
+struct shm_block *blocks = 0;
+
+static uint32_t tMutex = MUTEX_UNLOCKED;
+
+static void shm_init() {
+	struct shm_block *b = malloc(sizeof(struct shm_block));
+	b->start = 0x80000000;
+	b->size = 0xD0000000 - 0x80000000;
+	b->is_hole = 1;
+	b->prev = b->next = 0;
+	blocks = b;
+}
+
+void* shm_alloc(size_t size) {
+	mutex_lock(&tMutex);
+	if (blocks == 0) shm_init();
+	if (size & 0xFFF) size = (size & 0xFFFFF000) + 0x1000;
+	//go through all blocks, get the one with the closest size
+	struct shm_block *block = blocks;
+	while (block) {
+		if (block->size >= size) break;
+		block = block->next;
+	}
+	if (block == 0) {
+		mutex_unlock(&tMutex);
+		return 0;
+	}
+	//if the block's size is bigger, reduce it and create a new one after
+	if (block->size > size) {
+		struct shm_block *newb = malloc(sizeof(struct shm_block));
+		newb->start = block->start + size;
+		newb->size = block->size - size;
+		newb->is_hole = 1;
+		newb->prev = block; newb->next = block->next;
+		block->size = size;
+		if (block->next != 0) block->next->prev = newb;
+		block->next = newb;
+	}
+	//mark block as used
+	block->is_hole = 0;
+	//return block's address
+	mutex_unlock(&tMutex);
+	return (void*)block->start;
+}
+
+static void unify (struct shm_block *b) {
+	if (b->next == 0 || b->is_hole == 0 || b->next->is_hole == 0) return;
+	struct shm_block *n = b->next;
+	b->size += n->size;
+	n->next->prev = b;
+	b->next = n->next;
+	free(n);
+}
+
+void shm_free(void* p) {
+	mutex_lock(&tMutex);
+	//find block
+	struct shm_block *bl = blocks;
+	while (bl) {
+		if (bl->start == (size_t)p) break;
+		bl = bl->next;
+	}
+	if (bl == 0) {
+		mutex_unlock(&tMutex);
+		return;
+	}
+	//mark it as a hole
+	bl->is_hole = 1;
+	//unify after if possible
+	if (bl->next != 0 && bl->next->is_hole == 1) unify(bl);
+	//unify before if possible
+	if (bl->prev != 0 && bl->prev->is_hole == 1) unify(bl->prev);
+	mutex_unlock(&tMutex);
+}
+
+void* shm_allocNew(size_t size) {
+	if (size & 0xFFF) size = (size & 0xFFFFF000) + 0x1000;
+
+	void* p = shm_alloc(size);
+	if (shm_create((size_t)p, size) != 0) {
+		shm_free(p);
+		return 0;
+	}
+	return p;
+}
+
+void shm_freeDel(void *p) {
+	shm_delete((size_t)p);
+	shm_free(p);
+}