1 files changed, 109 insertions, 0 deletions
diff --git a/arena.h b/arena.h
new file mode 100644
index 0000000..9327a5e
--- /dev/null
+++ b/arena.h
@@ -0,0 +1,109 @@
+#ifndef ARENA_IMPL
+#define ARENA_IMPL
+
+#include "common.h"
+
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <sys/mman.h>
+#include <unistd.h>
+
+#define PAGESIZE 4096
+
+#ifndef ARENA_MEMORY
+#define ARENA_MEMORY PAGESIZE
+#endif
+
+struct Arena {
+    void *memory;
+    u64 size;
+    u64 pos;
+} typedef Arena;
+
+// Create an arena
+Arena *ArenaAlloc(void);
+// Destroy an arena
+void ArenaRelease(Arena *arena);
+
+// Push bytes on to the arena | allocating
+void *ArenaPush(Arena *arena, u64 size);
+void *ArenaPushZero(Arena *arena, u64 size);
+
+#define PushArray(arena, type, count) (type *)ArenaPush((arena), sizeof(type)*(count))
+#define PushArrayZero(arena, type, count) (type *)ArenaPushZero((arena), sizeof(type) * (count))
+#define PushStruct(arena, type) PushArray((arena), (type), 1)
+#define PushStructZero(arena, type) PushArrayZero((arena), (type), 1)
+
+// Free some bytes by popping the stack
+void ArenaPop(Arena *arena, u64 size);
+// Get the number of bytes allocated
+u64 ArenaGetPos(Arena *arena);
+
+void ArenaSetPosBack(Arena *arena, u64 pos);
+void ArenaClear(Arena *arena);
+
+Arena *ArenaAlloc(void)
+{
+    // NOTE: If the arena is created here the pointer to the memory get's overwritten with size in
+    // ArenaPush, so we are forced to use malloc
+    Arena *arena = malloc(sizeof(Arena));
+
+    arena->memory = mmap(NULL, ARENA_MEMORY, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+    if (arena->memory == MAP_FAILED)
+        return NULL;
+
+    arena->pos = 0;
+    arena->size = ARENA_MEMORY;
+
+    return arena;
+}
+
+void ArenaRelease(Arena *arena)
+{
+    munmap(arena->memory, ARENA_MEMORY);
+    free(arena);
+}
+
+void *ArenaPush(Arena *arena, u64 size)
+{
+    u8 *mem;
+    mem = (u8 *)arena->memory + arena->pos;
+    arena->pos += size;
+    return mem;
+}
+
+void *ArenaPushZero(Arena *arena, u64 size)
+{
+    u8 *mem;
+    mem = (u8 *)arena->memory + arena->pos;
+    bzero(mem, size);
+    arena->pos += size;
+    return mem;
+}
+
+void ArenaPop(Arena *arena, u64 size)
+{
+    arena->pos -= size;
+}
+
+u64 ArenaGetPos(Arena *arena)
+{
+    return arena->pos;
+}
+
+void ArenaSetPosBack(Arena *arena, u64 pos)
+{
+    arena->pos -= pos;
+}
+
+void ArenaClear(Arena *arena)
+{
+    bzero(arena->memory, arena->size);
+    arena->pos = 0;
+}
+
+#endif