Add examples/http_config.rs

Signed-off-by: Daniel Grimm <dgrimm@redhat.com>

Cargo.toml

@@ -60,3 +60,8 @@ crate-type = ["cdylib"]
 name = "http_body"
 path = "examples/http_body.rs"
 crate-type = ["cdylib"]
+
+[[example]]
+name = "http_config"
+path = "examples/http_config.rs"
+crate-type = ["cdylib"]

examples/http_config.rs

@@ -0,0 +1,73 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+use std::str;
+use proxy_wasm::traits::*;
+use proxy_wasm::types::*;
+
+#[no_mangle]
+pub fn _start() {
+    proxy_wasm::set_log_level(LogLevel::Trace);
+    proxy_wasm::set_root_context(|_| -> Box<dyn RootContext> {
+        Box::new(HttpConfigHeaderRootContext{
+            header_content: "".to_string(),
+        })
+    });
+}
+
+struct HttpConfigHeader{
+    header_content: String
+}
+
+impl Context for HttpConfigHeader {}
+
+impl HttpContext for HttpConfigHeader {
+
+    fn on_http_response_headers(&mut self, _num_headers: usize) -> Action {
+        self.add_http_response_header("custom-header", self.header_content.as_str());
+
+        Action::Continue
+    }
+}
+
+struct HttpConfigHeaderRootContext {
+    header_content: String
+}
+
+impl Context for HttpConfigHeaderRootContext {}
+
+impl RootContext for HttpConfigHeaderRootContext {
+
+    fn on_vm_start(&mut self, _vm_configuration_size: usize) -> bool {
+        true
+    }
+
+    fn on_configure(&mut self, _plugin_configuration_size: usize) -> bool {
+        if let Some(config_bytes) = self.get_configuration() {
+            self.header_content = str::from_utf8(config_bytes.as_ref()).unwrap().to_owned()
+        }
+        true
+    }
+
+    fn create_http_context(&self, _context_id: u32) -> Box<dyn HttpContext> {
+        Box::new(HttpConfigHeader{
+            header_content: self.header_content.clone(),
+        })
+    }
+
+    fn get_type(&self) -> ContextType {
+        ContextType::HttpContext
+    }
+
+}