add some bumpptr flavors

1 files changed, 54 insertions, 0 deletions

diff --git a/src/bump_alloc.h b/src/bump_alloc.h
new file mode 100644
index 0000000..bc9cbac
--- /dev/null
+++ b/src/bump_alloc.h
@@ -0,0 +1,54 @@
+#include <assert.h>
+#include <stddef.h> /* NULL, size_t */
+#include <stdint.h> /* uintptr_t */
+
+#ifndef MEMSIZE
+#define MEMSIZE 1024*4*1024*1024l
+#endif
+
+#define unlikely(x)     __builtin_expect((x),0)
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct {
+	uintptr_t end = 0;
+	uintptr_t ptr = 0;
+} bumpptr_t;
+
+__thread bumpptr_t* tsd = NULL;
+
+inline void init_tsd() {
+	void* mem_start = mmap(NULL, MEMSIZE, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);
+	if(mem_start == MAP_FAILED) {
+		perror("mmap");
+		return NULL;
+	}
+	tsd = (bumpptr_t*)mem_start;
+	tsd->ptr = (uintptr_t)mem_start + sizeof(bumpptr_t);
+	tsd->end = (uintptr_t)mem_start + MEMSIZE;
+}
+
+inline void* bump_up(size_t size, size_t align) {
+	assert(align % 2 == 0);
+
+	if (unlikely(tsd == NULL)) {
+		init_tsd();
+	}
+
+	// align ptr;
+	uintptr_t aligned = (tsd->ptr + align - 1) & ~(align - 1);
+
+	uintptr_t new_ptr = aligned + size;
+	if (new_ptr > mem_end)
+		return NULL;
+	else {
+		tsd->ptr = new_ptr;
+		return (void*)aligned;
+	}
+}
+
+#ifdef __cplusplus
+}
+#endif