Pass slice instead of Vec during map serialization.

Before:

utils::bench_serialize_map         ... bench:    66.87 ns/iter (+/- 1.33)
utils::bench_serialize_map_bytes   ... bench:    69.42 ns/iter (+/- 1.45)

After:

utils::bench_serialize_map         ... bench:    55.84 ns/iter (+/- 1.16)
utils::bench_serialize_map_bytes   ... bench:    56.03 ns/iter (+/- 1.19)

Note that this is changed only in the private functions to avoid breaking
the public API.

Signed-off-by: Piotr Sikora <[email protected]>

src/hostcalls.rs

@@ -190,7 +190,7 @@ extern "C" {
 }
 
 pub fn set_map(map_type: MapType, map: Vec<(&str, &str)>) -> Result<(), Status> {
-    let serialized_map = utils::serialize_map(map);
+    let serialized_map = utils::serialize_map(&map);
     unsafe {
         match proxy_set_header_map_pairs(map_type, serialized_map.as_ptr(), serialized_map.len()) {
             Status::Ok => Ok(()),
@@ -200,7 +200,7 @@ pub fn set_map(map_type: MapType, map: Vec<(&str, &str)>) -> Result<(), Status>
 }
 
 pub fn set_map_bytes(map_type: MapType, map: Vec<(&str, &[u8])>) -> Result<(), Status> {
-    let serialized_map = utils::serialize_map_bytes(map);
+    let serialized_map = utils::serialize_map_bytes(&map);
     unsafe {
         match proxy_set_header_map_pairs(map_type, serialized_map.as_ptr(), serialized_map.len()) {
             Status::Ok => Ok(()),
@@ -710,7 +710,7 @@ pub fn send_http_response(
     headers: Vec<(&str, &str)>,
     body: Option<&[u8]>,
 ) -> Result<(), Status> {
-    let serialized_headers = utils::serialize_map(headers);
+    let serialized_headers = utils::serialize_map(&headers);
     unsafe {
         match proxy_send_local_response(
             status_code,
@@ -733,7 +733,7 @@ pub fn send_grpc_response(
     grpc_status_message: Option<&str>,
     custom_metadata: Vec<(&str, &[u8])>,
 ) -> Result<(), Status> {
-    let serialized_custom_metadata = utils::serialize_map_bytes(custom_metadata);
+    let serialized_custom_metadata = utils::serialize_map_bytes(&custom_metadata);
     unsafe {
         match proxy_send_local_response(
             200,
@@ -773,8 +773,8 @@ pub fn dispatch_http_call(
     trailers: Vec<(&str, &str)>,
     timeout: Duration,
 ) -> Result<u32, Status> {
-    let serialized_headers = utils::serialize_map(headers);
-    let serialized_trailers = utils::serialize_map(trailers);
+    let serialized_headers = utils::serialize_map(&headers);
+    let serialized_trailers = utils::serialize_map(&trailers);
     let mut return_token: u32 = 0;
     unsafe {
         match proxy_http_call(
@@ -826,7 +826,7 @@ pub fn dispatch_grpc_call(
     timeout: Duration,
 ) -> Result<u32, Status> {
     let mut return_callout_id = 0;
-    let serialized_initial_metadata = utils::serialize_map_bytes(initial_metadata);
+    let serialized_initial_metadata = utils::serialize_map_bytes(&initial_metadata);
     unsafe {
         match proxy_grpc_call(
             upstream_name.as_ptr(),
@@ -874,7 +874,7 @@ pub fn open_grpc_stream(
     initial_metadata: Vec<(&str, &[u8])>,
 ) -> Result<u32, Status> {
     let mut return_stream_id = 0;
-    let serialized_initial_metadata = utils::serialize_map_bytes(initial_metadata);
+    let serialized_initial_metadata = utils::serialize_map_bytes(&initial_metadata);
     unsafe {
         match proxy_grpc_stream(
             upstream_name.as_ptr(),
@@ -1159,18 +1159,18 @@ mod utils {
         bytes
     }
 
-    pub(super) fn serialize_map(map: Vec<(&str, &str)>) -> Bytes {
+    pub(super) fn serialize_map(map: &[(&str, &str)]) -> Bytes {
         let mut size: usize = 4;
-        for (name, value) in &map {
+        for (name, value) in map {
             size += name.len() + value.len() + 10;
         }
         let mut bytes: Bytes = Vec::with_capacity(size);
         bytes.extend_from_slice(&map.len().to_le_bytes());
-        for (name, value) in &map {
+        for (name, value) in map {
             bytes.extend_from_slice(&name.len().to_le_bytes());
             bytes.extend_from_slice(&value.len().to_le_bytes());
         }
-        for (name, value) in &map {
+        for (name, value) in map {
             bytes.extend_from_slice(name.as_bytes());
             bytes.push(0);
             bytes.extend_from_slice(value.as_bytes());
@@ -1179,18 +1179,18 @@ mod utils {
         bytes
     }
 
-    pub(super) fn serialize_map_bytes(map: Vec<(&str, &[u8])>) -> Bytes {
+    pub(super) fn serialize_map_bytes(map: &[(&str, &[u8])]) -> Bytes {
         let mut size: usize = 4;
-        for (name, value) in &map {
+        for (name, value) in map {
             size += name.len() + value.len() + 10;
         }
         let mut bytes: Bytes = Vec::with_capacity(size);
         bytes.extend_from_slice(&map.len().to_le_bytes());
-        for (name, value) in &map {
+        for (name, value) in map {
             bytes.extend_from_slice(&name.len().to_le_bytes());
             bytes.extend_from_slice(&value.len().to_le_bytes());
         }
-        for (name, value) in &map {
+        for (name, value) in map {
             bytes.extend_from_slice(name.as_bytes());
             bytes.push(0);
             bytes.extend_from_slice(value);