add read_to_end to AsyncRead

stole this bit out of Calvin's PR: cbaf050

Co-authored-by: Calvin Prewitt <[email protected]>

Author: pchickey

src/io/read.rs

@@ -1,6 +1,27 @@
 use crate::io;
 
+const CHUNK_SIZE: usize = 2048;
+
 /// Read bytes from a source.
 pub trait AsyncRead {
     async fn read(&mut self, buf: &mut [u8]) -> io::Result<usize>;
+    async fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        // total bytes written to buf
+        let mut n = 0;
+
+        loop {
+            // grow buf if empty
+            if buf.len() == n {
+                buf.resize(n + CHUNK_SIZE, 0u8);
+            }
+
+            let len = self.read(&mut buf[n..]).await?;
+            if len == 0 {
+                buf.truncate(n);
+                return Ok(n);
+            }
+
+            n += len;
+        }
+    }
 }