1 files changed, 107 insertions, 0 deletions
diff --git a/lib/arena.c b/lib/arena.c
new file mode 100644
index 0000000..bea98ef
--- /dev/null
+++ b/lib/arena.c
@@ -0,0 +1,107 @@
+#include "arena.h"
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+
+#ifdef ARENA_ASAN_INSTRUMENT
+#include <sanitizer/asan_interface.h>
+
+#define ASAN_POISON(...) __asan_poison_memory_region(__VA_ARGS__)
+#define ASAN_UNPOISON(...) __asan_unpoison_memory_region(__VA_ARGS__)
+#else
+#define ASAN_POISON(...)
+#define ASAN_UNPOISON(...)
+#endif
+
+struct vl__arena_tag {
+  size_t cap; /* number of bytes after the end of this struct we can use */
+  size_t cur;
+};
+
+#define ARENA_ALIGN (size_t)((1 << 6) - 1)
+#define ROUND_UP(_am) (((_am) + ARENA_ALIGN) & ~ARENA_ALIGN)
+
+static void *arena_addr(void *a, size_t len)
+{
+  return (void *)((uintptr_t)a + ROUND_UP(sizeof(vl_arena)) + len);
+}
+
+/* returns NULL if an arena could not be allocated */
+vl_arena *vl_arena_new(size_t cap)
+{
+  cap = ROUND_UP(cap);
+
+  vl_arena *arena = calloc(1, ROUND_UP(sizeof(vl_arena)) + cap);
+  if (!arena) return NULL;
+
+  arena->cap = cap;
+  arena->cur = 0;
+
+  ASAN_POISON(arena + 1, cap + (ROUND_UP(sizeof(vl_arena)) - sizeof(vl_arena)));
+
+  return arena;
+}
+
+/* aborts if the arena is overflowing */
+void *vl_arena_push(vl_arena *parena, size_t len)
+{
+  size_t rlen = ROUND_UP(len);
+  if (parena->cur + rlen > parena->cap) abort();
+
+  void *ret = arena_addr(parena, parena->cur);
+  parena->cur += rlen;
+
+  ASAN_UNPOISON(ret, len);
+  return ret;
+}
+
+/* resets the arena (but does not free it) */
+void vl_arena_reset(vl_arena *parena)
+{
+  parena->cur = 0;
+  ASAN_POISON(arena_addr(parena, 0), parena->cap);
+}
+
+/* frees the arena */
+void vl_arena_free(vl_arena *parena)
+{
+  free(parena);
+}
+
+char *vl_arena_strdup(vl_arena *parena, const char *str)
+{
+  size_t len = strlen(str);
+  void *out = vl_arena_push(parena, len + 1);
+  memcpy(out, str, len + 1);
+  return out;
+}
+
+char *vl_arena_sprintf(vl_arena *parena, const char *fmt, ...)
+{
+  va_list ap;
+  va_start(ap, fmt);
+
+  char *ret = vl_arena_vsprintf(parena, fmt, ap);
+
+  va_end(ap);
+  return ret;
+}
+
+char *vl_arena_vsprintf(vl_arena *parena, const char *fmt, va_list ap)
+{
+  va_list copy;
+  va_copy(copy, ap);
+
+  int desire = vsnprintf(NULL, 0, fmt, copy);
+  va_end(copy);
+
+  if (desire < 0) {
+    abort(); /* vsnprintf should never fail */
+  }
+
+  char *str = vl_arena_push(parena, (unsigned)desire + 1);
+  vsnprintf(str, (unsigned)desire + 1, fmt, ap);
+
+  return str;
+}