Split CE code into multiple files

ce/strbuf.c

@@ -0,0 +1,24 @@
+#include "strbuf.h"
+#include "arena_alloc.h"
+#include <arena.h>
+#include <stddef.h>
+
+void strbuf_append (struct strbuf* strbuf, char c) {
+  if (strbuf->items == NULL) {
+    strbuf->capacity = 256;
+    strbuf->count = 0;
+    strbuf->items = arena_malloc (&arena, strbuf->capacity);
+  } else {
+    if (strbuf->count == strbuf->capacity) {
+      size_t prev_capacity = strbuf->capacity;
+      strbuf->capacity *= 2;
+      strbuf->items = arena_realloc (&arena, strbuf->items, prev_capacity, strbuf->capacity);
+    }
+  }
+  strbuf->items[strbuf->count++] = c;
+}
+
+void strbuf_append_str (struct strbuf* strbuf, const char* s) {
+  while (*s)
+    strbuf_append (strbuf, *s++);
+}