Improvements to the str buffer copy.

Author: alistairjevans

ext/hyper_ruby/Cargo.toml

@@ -10,7 +10,7 @@ publish = false
 crate-type = ["cdylib"]
 
 [dependencies]
-magnus = { version = "0.6.2" }
+magnus = { version = "0.6.2", features = ["rb-sys"] }
 tokio = { version = "1", features = ["full"] }
 bytes = "1.5"
 tokio-stream = { version = "0.1", features = ["net"] }

ext/hyper_ruby/src/request.rs

@@ -5,7 +5,7 @@ use magnus::{value::{qnil, ReprValue}, RString, Value};
 use bytes::Bytes;
 use hyper::Request as HyperRequest;
 
-use rb_sys::{rb_str_cat, rb_str_resize, RSTRING_PTR, VALUE};
+use rb_sys::{rb_str_set_len, rb_str_modify, rb_str_modify_expand, rb_str_capacity, RSTRING_PTR, VALUE};
 
 // Type passed to ruby giving access to the request properties.
 #[magnus::wrap(class = "HyperRuby::Request")]
@@ -44,21 +44,32 @@ impl Request {
         buffer
     }
 
-    pub fn fill_body(&self, buffer: RString) -> usize {
+    pub fn fill_body(&self, buffer: RString) -> i64 {
         let body = self.request.body();
-        let body_len = body.len();
+        let body_len: i64 = body.len().try_into().unwrap();
 
         // Access the ruby string VALUE directly, and resize to 0 (keeping the capacity), 
         // then copy our buffer into it.
         unsafe {
             let rb_value = buffer.as_value();
             let inner: VALUE = std::ptr::read(&rb_value as *const _ as *const VALUE);
-            rb_str_resize(inner, body_len.try_into().unwrap());
+            let existing_capacity = rb_str_capacity(inner) as i64;
+
+            // If the buffer is too small, expand it.
+            if existing_capacity < body_len.try_into().unwrap() {
+                rb_str_modify_expand(inner, body_len);
+            }
+            else {
+                rb_str_modify(inner);
+            }
+
             if body_len > 0 {
                 let body_ptr = body.as_ptr() as *const c_char;
                 let rb_string_ptr = RSTRING_PTR(inner) as *mut c_char;
-                std::ptr::copy(body_ptr, rb_string_ptr, body_len);
+                std::ptr::copy(body_ptr, rb_string_ptr, body_len as usize);
             }
+
+            rb_str_set_len(inner, body_len);
         }
 
         body_len