Make typing hotpath work.

include/vase/vase.h

@@ -15,31 +15,54 @@ struct Vase {
 
   ShardPtr root;
 
-  Vase(char *data, uint32_t length)
-      : original(data, length),
-        append() {
-    root = new Petal(
-      length,
-      original.newlines.size(),
-      &original,
-      0
-    );
+  Vase(char *data, uint32_t length) : original(data, length), append() {
+    root = new Petal(length, original.newlines.size(), &original, 0);
   }
 
   uint32_t length() {
     return root.ptr->length;
   }
 
+  std::string to_string() {
+    std::string out;
+    flatten(root.ptr, out);
+    return out;
+  }
+
+  void type(uint32_t offset, char key) {
+    uint32_t pos = append.key(key);
+    ShardPtr inserted = new Petal(1, key == '\n', &append, pos);
+    auto [left, right] = split_shard(root.ptr, offset);
+    left = append_leaf(left.ptr, inserted.ptr);
+    root = concat_shard(left, right);
+  }
+
   void insert(uint32_t offset, const char *data, uint32_t len) {
     uint32_t lines = 0;
     uint32_t pos = append.append(data, len, &lines);
-
     ShardPtr inserted = new Petal(len, lines, &append, pos);
-
     auto [left, right] = split_shard(root.ptr, offset);
-
     left = append_leaf(left.ptr, inserted.ptr);
-
     root = concat_shard(left, right);
   }
+
+  void flatten(Shard *s, std::string &out) {
+    if (s->kind == Shard::ShardKind::Petal) {
+      auto *p = static_cast<Petal *>(s);
+      uint32_t remaining = p->length;
+      uint32_t pos = p->pos;
+      while (remaining) {
+        uint32_t got;
+        const char *data = p->source->read(pos, &got);
+        uint32_t take = std::min(got, remaining);
+        out.append(data, take);
+        remaining -= take;
+        pos += take;
+      }
+    } else {
+      auto *b = static_cast<Branch *>(s);
+      flatten(b->left.ptr, out);
+      flatten(b->right.ptr, out);
+    }
+  }
 };