feat(lsm): some more string functions; start of data streaming api

lsm/src/str/lsm_str.c

@@ -196,3 +196,40 @@ bool lsm_str_eq(lsm_str *s1, lsm_str *s2) {
 
   return memcmp(lsm_str_ptr(s1), lsm_str_ptr(s2), s1->len) == 0;
 }
+
+lsm_error lsm_str_append(lsm_str *s, lsm_str *s2) {
+  if (s2->len == 0) {
+    return lsm_error_ok;
+  }
+
+  uint64_t new_len = s->len + s2->len;
+
+  if (new_len <= 8) {
+    memcpy(&s->data.val[s->len], s2->data.val, s2->len);
+  } else {
+    char *buf;
+
+    if (s->len <= 8) {
+      buf = malloc(new_len * sizeof(char));
+
+      if (buf == NULL) {
+        return lsm_error_failed_alloc;
+      }
+
+      memcpy(buf, s->data.val, s->len);
+    } else {
+      buf = realloc(s->data.ptr, new_len * sizeof(char));
+
+      if (buf == NULL) {
+        return lsm_error_failed_alloc;
+      }
+    }
+
+    memcpy(&buf[s->len], lsm_str_ptr(s2), s2->len);
+    s->data.ptr = buf;
+  }
+
+  s->len += s2->len;
+
+  return lsm_error_ok;
+}