1 files changed, 75 insertions, 0 deletions
diff --git a/lib/nghttp2_ratelim.c b/lib/nghttp2_ratelim.c
new file mode 100644
index 0000000..7011655
--- /dev/null
+++ b/lib/nghttp2_ratelim.c
@@ -0,0 +1,75 @@
+/*
+ * nghttp2 - HTTP/2 C Library
+ *
+ * Copyright (c) 2023 nghttp2 contributors
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be
+ * included in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
+ * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
+ * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+ * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+#include "nghttp2_ratelim.h"
+#include "nghttp2_helper.h"
+
+void nghttp2_ratelim_init(nghttp2_ratelim *rl, uint64_t burst, uint64_t rate) {
+  rl->val = rl->burst = burst;
+  rl->rate = rate;
+  rl->tstamp = 0;
+}
+
+void nghttp2_ratelim_update(nghttp2_ratelim *rl, uint64_t tstamp) {
+  uint64_t d, gain;
+
+  if (tstamp == rl->tstamp) {
+    return;
+  }
+
+  if (tstamp > rl->tstamp) {
+    d = tstamp - rl->tstamp;
+  } else {
+    d = 1;
+  }
+
+  rl->tstamp = tstamp;
+
+  if (UINT64_MAX / d < rl->rate) {
+    rl->val = rl->burst;
+
+    return;
+  }
+
+  gain = rl->rate * d;
+
+  if (UINT64_MAX - gain < rl->val) {
+    rl->val = rl->burst;
+
+    return;
+  }
+
+  rl->val += gain;
+  rl->val = nghttp2_min(rl->val, rl->burst);
+}
+
+int nghttp2_ratelim_drain(nghttp2_ratelim *rl, uint64_t n) {
+  if (rl->val < n) {
+    return -1;
+  }
+
+  rl->val -= n;
+
+  return 0;
+}