client bugfix: handle the case when we have already buffered a \r\n\r\n

client/src/conn.rs

@@ -695,21 +695,24 @@ impl Conn {
         else {
             return Err(Error::Closed);
         };
+
         let mut len = buffer.len();
+        let mut search_start = 0;
         let finder = Finder::new(b"\r\n\r\n");
         loop {
             buffer.expand();
             let bytes = transport.read(&mut buffer[len..]).await?;
-
-            let search_start = len.saturating_sub(3);
             len += bytes;
+
             let search = finder.find(&buffer[search_start..len]);
 
             if let Some(index) = search {
                 buffer.truncate(len);
                 return Ok(search_start + index + 4);
             }
 
+            search_start = len.saturating_sub(3);
+
             if bytes == 0 {
                 if len == 0 {
                     return Err(Error::Closed);
@@ -728,11 +731,11 @@ impl Conn {
         let head_offset = self.read_head().await?;
         let mut headers = [httparse::EMPTY_HEADER; MAX_HEADERS];
         let mut httparse_res = httparse::Response::new(&mut headers);
-        if httparse_res
-            .parse(&self.buffer[..head_offset])?
-            .is_partial()
-        {
-            return Err(Error::PartialHead);
+        let parse_result = httparse_res.parse(&self.buffer[..head_offset])?;
+
+        match parse_result {
+            httparse::Status::Complete(n) if n == head_offset => {}
+            _ => return Err(Error::PartialHead),
         }
 
         self.status = httparse_res.code.map(|code| code.try_into().unwrap());

client/tests/one_hundred_continue.rs

@@ -1,5 +1,6 @@
 use async_channel::Sender;
-use indoc::formatdoc;
+use futures_lite::future;
+use indoc::{formatdoc, indoc};
 use pretty_assertions::assert_eq;
 use std::future::Future;
 use test_harness::test;
@@ -133,6 +134,81 @@ async fn empty_body_no_100_continue() -> TestResult {
     Ok(())
 }
 
+#[test(harness = harness)]
+async fn two_small_continues() -> TestResult {
+    let (transport, conn_fut) =
+        test_conn(|client| client.post("http://example.com").with_body("body")).await;
+    let expected_request = formatdoc! {"
+        POST / HTTP/1.1\r
+        Expect: 100-continue\r
+        User-Agent: {USER_AGENT}\r
+        Host: example.com\r
+        Connection: close\r
+        Content-Length: 4\r
+        \r
+    "};
+
+    assert_eq!(expected_request, transport.read_available_string().await);
+
+    for _ in 0..2 {
+        transport.write_all("HTTP/1.1 100 Continue\r\n");
+        future::yield_now().await;
+        transport.write_all("\r\n");
+        future::yield_now().await;
+    }
+    assert_eq!("body", transport.read_available_string().await);
+
+    transport.write_all(formatdoc! {"
+        HTTP/1.1 200 Ok\r
+        Date: {TEST_DATE}\r
+        Connection: close\r
+        Content-Length: 0\r
+        \r
+    "});
+    let conn = conn_fut.await.unwrap();
+    assert_eq!(Some(Status::Ok), conn.status());
+
+    Ok(())
+}
+
+#[test(harness = harness)]
+async fn little_continue_big_continue() -> TestResult {
+    let (transport, conn_fut) =
+        test_conn(|client| client.post("http://example.com").with_body("body")).await;
+
+    let expected_request = formatdoc! {"
+        POST / HTTP/1.1\r
+        Expect: 100-continue\r
+        User-Agent: {USER_AGENT}\r
+        Host: example.com\r
+        Connection: close\r
+        Content-Length: 4\r
+        \r
+    "};
+
+    assert_eq!(expected_request, transport.read_available_string().await);
+
+    transport.write_all(indoc! {"
+        HTTP/1.1 100 Continue\r
+        \r
+        HTTP/1.1 100 Continue\r
+        X-Filler: AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\r
+        \r
+    "});
+    assert_eq!("body", transport.read_available_string().await);
+
+    transport.write_all(formatdoc! {"
+        HTTP/1.1 200 Ok\r
+        Date: {TEST_DATE}\r
+        Connection: close\r
+        Content-Length: 0\r
+        \r
+    "});
+    let conn = conn_fut.await.unwrap();
+    assert_eq!(Some(Status::Ok), conn.status());
+    Ok(())
+}
+
 const TEST_DATE: &'static str = "Tue, 21 Nov 2023 21:27:21 GMT";
 
 struct TestConnector(Sender<TestTransport>);