diff --git a/src/http/h1/decode.rs b/src/http/h1/decode.rs
index 1cc4b586fb..cbb24f9839 100644
--- a/src/http/h1/decode.rs
+++ b/src/http/h1/decode.rs
@@ -1,4 +1,4 @@
-use std::cmp;
+use std::{cmp, usize};
 use std::io::{self, Read};
 
 use self::Kind::{Length, Chunked, Eof};
@@ -14,21 +14,15 @@ pub struct Decoder {
 
 impl Decoder {
     pub fn length(x: u64) -> Decoder {
-        Decoder {
-            kind: Kind::Length(x)
-        }
+        Decoder { kind: Kind::Length(x) }
     }
 
     pub fn chunked() -> Decoder {
-        Decoder {
-            kind: Kind::Chunked(None)
-        }
+        Decoder { kind: Kind::Chunked(ChunkedState::Size, 0) }
     }
 
     pub fn eof() -> Decoder {
-        Decoder {
-            kind: Kind::Eof(false)
-        }
+        Decoder { kind: Kind::Eof(false) }
     }
 }
 
@@ -37,7 +31,7 @@ enum Kind {
     /// A Reader used when a Content-Length header is passed with a positive integer.
     Length(u64),
     /// A Reader used when Transfer-Encoding is `chunked`.
-    Chunked(Option<u64>),
+    Chunked(ChunkedState, u64),
     /// A Reader used for responses that don't indicate a length or chunked.
     ///
     /// Note: This should only used for `Response`s. It is illegal for a
@@ -55,14 +49,26 @@ enum Kind {
     Eof(bool),
 }
 
+#[derive(Debug, PartialEq, Clone)]
+enum ChunkedState {
+    Size,
+    SizeLws,
+    Extension,
+    SizeLf,
+    Body,
+    BodyCr,
+    BodyLf,
+    End,
+}
+
 impl Decoder {
     pub fn is_eof(&self) -> bool {
         trace!("is_eof? {:?}", self);
         match self.kind {
             Length(0) |
-            Chunked(Some(0)) |
+            Chunked(ChunkedState::End, _) |
             Eof(true) => true,
-            _ => false
+            _ => false,
         }
     }
 }
@@ -87,183 +93,248 @@ impl Decoder {
                     }
                     Ok(num as usize)
                 }
-            },
-            Chunked(ref mut opt_remaining) => {
-                let mut rem = match *opt_remaining {
-                    Some(ref rem) => *rem,
-                    // None means we don't know the size of the next chunk
-                    None => try!(read_chunk_size(body))
-                };
-                trace!("Chunked read, remaining={:?}", rem);
-
-                if rem == 0 {
-                    *opt_remaining = Some(0);
-
-                    // chunk of size 0 signals the end of the chunked stream
-                    // if the 0 digit was missing from the stream, it would
-                    // be an InvalidInput error instead.
-                    trace!("end of chunked");
-                    return Ok(0)
-                }
-
-                let to_read = cmp::min(rem as usize, buf.len());
-                let count = try!(body.read(&mut buf[..to_read])) as u64;
-
-                if count == 0 {
-                    *opt_remaining = Some(0);
-                    return Err(io::Error::new(io::ErrorKind::Other, "early eof"));
+            }
+            Chunked(ref mut state, ref mut size) => {
+                loop {
+                    let mut read = 0;
+                    // advances the chunked state
+                    *state = try!(state.step(body, size, buf, &mut read));
+                    if *state == ChunkedState::End {
+                        trace!("end of chunked");
+                        return Ok(0);
+                    }
+                    if read > 0 {
+                        return Ok(read);
+                    }
                 }
-
-                rem -= count;
-                *opt_remaining = if rem > 0 {
-                    Some(rem)
-                } else {
-                    try!(eat(body, b"\r\n"));
-                    None
-                };
-                Ok(count as usize)
-            },
+            }
             Eof(ref mut is_eof) => {
                 match body.read(buf) {
                     Ok(0) => {
                         *is_eof = true;
                         Ok(0)
                     }
-                    other => other
+                    other => other,
                 }
-            },
+            }
         }
     }
 }
 
-fn eat<R: Read>(rdr: &mut R, bytes: &[u8]) -> io::Result<()> {
-    let mut buf = [0];
-    for &b in bytes.iter() {
-        match try!(rdr.read(&mut buf)) {
-            1 if buf[0] == b => (),
-            _ => return Err(io::Error::new(io::ErrorKind::InvalidInput,
-                                          "Invalid characters found")),
+macro_rules! byte (
+    ($rdr:ident) => ({
+        let mut buf = [0];
+        match try!($rdr.read(&mut buf)) {
+            1 => buf[0],
+            _ => return Err(io::Error::new(io::ErrorKind::UnexpectedEof,
+                                           "Unexpected eof during chunk size line")),
         }
-    }
-    Ok(())
-}
+    })
+);
 
-/// Chunked chunks start with 1*HEXDIGIT, indicating the size of the chunk.
-fn read_chunk_size<R: Read>(rdr: &mut R) -> io::Result<u64> {
-    macro_rules! byte (
-        ($rdr:ident) => ({
-            let mut buf = [0];
-            match try!($rdr.read(&mut buf)) {
-                1 => buf[0],
-                _ => return Err(io::Error::new(io::ErrorKind::InvalidInput,
-                                                  "Invalid chunk size line")),
-
-            }
+impl ChunkedState {
+    fn step<R: Read>(&self,
+                     body: &mut R,
+                     size: &mut u64,
+                     buf: &mut [u8],
+                     read: &mut usize)
+                     -> io::Result<ChunkedState> {
+        use self::ChunkedState::*;
+        Ok(match *self {
+            Size => try!(ChunkedState::read_size(body, size)),
+            SizeLws => try!(ChunkedState::read_size_lws(body)),
+            Extension => try!(ChunkedState::read_extension(body)),
+            SizeLf => try!(ChunkedState::read_size_lf(body, size)),
+            Body => try!(ChunkedState::read_body(body, size, buf, read)),
+            BodyCr => try!(ChunkedState::read_body_cr(body)),
+            BodyLf => try!(ChunkedState::read_body_lf(body)),
+            End => ChunkedState::End,
         })
-    );
-    let mut size = 0u64;
-    let radix = 16;
-    let mut in_ext = false;
-    let mut in_chunk_size = true;
-    loop {
+    }
+    fn read_size<R: Read>(rdr: &mut R, size: &mut u64) -> io::Result<ChunkedState> {
+        trace!("Read size");
+        let radix = 16;
         match byte!(rdr) {
-            b@b'0'...b'9' if in_chunk_size => {
-                size *= radix;
-                size += (b - b'0') as u64;
-            },
-            b@b'a'...b'f' if in_chunk_size => {
-                size *= radix;
-                size += (b + 10 - b'a') as u64;
-            },
-            b@b'A'...b'F' if in_chunk_size => {
-                size *= radix;
-                size += (b + 10 - b'A') as u64;
-            },
-            b'\r' => {
-                match byte!(rdr) {
-                    b'\n' => break,
-                    _ => return Err(io::Error::new(io::ErrorKind::InvalidInput,
-                                                  "Invalid chunk size line"))
-
-                }
-            },
-            // If we weren't in the extension yet, the ";" signals its start
-            b';' if !in_ext => {
-                in_ext = true;
-                in_chunk_size = false;
-            },
-            // "Linear white space" is ignored between the chunk size and the
-            // extension separator token (";") due to the "implied *LWS rule".
-            b'\t' | b' ' if !in_ext & !in_chunk_size => {},
-            // LWS can follow the chunk size, but no more digits can come
-            b'\t' | b' ' if in_chunk_size => in_chunk_size = false,
-            // We allow any arbitrary octet once we are in the extension, since
-            // they all get ignored anyway. According to the HTTP spec, valid
-            // extensions would have a more strict syntax:
-            //     (token ["=" (token | quoted-string)])
-            // but we gain nothing by rejecting an otherwise valid chunk size.
-            _ext if in_ext => {
-                //TODO: chunk extension byte;
-            },
-            // Finally, if we aren't in the extension and we're reading any
-            // other octet, the chunk size line is invalid!
+            b @ b'0'...b'9' => {
+                *size *= radix;
+                *size += (b - b'0') as u64;
+            }
+            b @ b'a'...b'f' => {
+                *size *= radix;
+                *size += (b + 10 - b'a') as u64;
+            }
+            b @ b'A'...b'F' => {
+                *size *= radix;
+                *size += (b + 10 - b'A') as u64;
+            }
+            b'\t' | b' ' => return Ok(ChunkedState::SizeLws),
+            b';' => return Ok(ChunkedState::Extension),
+            b'\r' => return Ok(ChunkedState::SizeLf),
             _ => {
                 return Err(io::Error::new(io::ErrorKind::InvalidInput,
-                                         "Invalid chunk size line"));
+                                          "Invalid chunk size line: Invalid Size"));
             }
         }
+        Ok(ChunkedState::Size)
     }
-    trace!("chunk size={:?}", size);
-    Ok(size)
-}
+    fn read_size_lws<R: Read>(rdr: &mut R) -> io::Result<ChunkedState> {
+        trace!("read_size_lws");
+        match byte!(rdr) {
+            // LWS can follow the chunk size, but no more digits can come
+            b'\t' | b' ' => Ok(ChunkedState::SizeLws),
+            b';' => Ok(ChunkedState::Extension),
+            b'\r' => return Ok(ChunkedState::SizeLf),
+            _ => {
+                Err(io::Error::new(io::ErrorKind::InvalidInput,
+                                   "Invalid chunk size linear white space"))
+            }
+        }
+    }
+    fn read_extension<R: Read>(rdr: &mut R) -> io::Result<ChunkedState> {
+        trace!("read_extension");
+        match byte!(rdr) {
+            b'\r' => return Ok(ChunkedState::SizeLf),
+            _ => return Ok(ChunkedState::Extension), // no supported extensions
+        }
+    }
+    fn read_size_lf<R: Read>(rdr: &mut R, size: &mut u64) -> io::Result<ChunkedState> {
+        trace!("Chunk size is {:?}", size);
+        match byte!(rdr) {
+            b'\n' if *size > 0 => Ok(ChunkedState::Body),
+            b'\n' if *size == 0 => Ok(ChunkedState::End),
+            _ => Err(io::Error::new(io::ErrorKind::InvalidInput, "Invalid chunk size LF")),
+        }
+    }
+    fn read_body<R: Read>(rdr: &mut R,
+                          rem: &mut u64,
+                          buf: &mut [u8],
+                          read: &mut usize)
+                          -> io::Result<ChunkedState> {
+        trace!("Chunked read, remaining={:?}", rem);
+
+        // cap remaining bytes at the max capacity of usize
+        let rem_cap = match *rem {
+            r if r > usize::MAX as u64 => usize::MAX,
+            r => r as usize,
+        };
+
+        let to_read = cmp::min(rem_cap, buf.len());
+        let count = try!(rdr.read(&mut buf[..to_read]));
+
+        trace!("to_read = {}", to_read);
+        trace!("count = {}", count);
+
+        if count == 0 {
+            *rem = 0;
+            return Err(io::Error::new(io::ErrorKind::UnexpectedEof, "early eof"));
+        }
 
+        *rem -= count as u64;
+        *read = count;
+
+        if *rem > 0 {
+            Ok(ChunkedState::Body)
+        } else {
+            Ok(ChunkedState::BodyCr)
+        }
+    }
+    fn read_body_cr<R: Read>(rdr: &mut R) -> io::Result<ChunkedState> {
+        match byte!(rdr) {
+            b'\r' => Ok(ChunkedState::BodyLf),
+            _ => Err(io::Error::new(io::ErrorKind::InvalidInput, "Invalid chunk body CR")),
+        }
+    }
+    fn read_body_lf<R: Read>(rdr: &mut R) -> io::Result<ChunkedState> {
+        match byte!(rdr) {
+            b'\n' => Ok(ChunkedState::Size),
+            _ => Err(io::Error::new(io::ErrorKind::InvalidInput, "Invalid chunk body LF")),
+        }
+    }
+}
 
 #[cfg(test)]
 mod tests {
     use std::error::Error;
     use std::io;
-    use super::{Decoder, read_chunk_size};
+    use std::io::Write;
+    use super::Decoder;
+    use super::ChunkedState;
+    use mock::Async;
 
     #[test]
     fn test_read_chunk_size() {
-        fn read(s: &str, result: u64) {
-            assert_eq!(read_chunk_size(&mut s.as_bytes()).unwrap(), result);
+        use std::io::ErrorKind::{UnexpectedEof, InvalidInput};
+
+        fn read(s: &str) -> u64 {
+            let mut state = ChunkedState::Size;
+            let mut rdr = &mut s.as_bytes();
+            let mut size = 0;
+            let mut count = 0;
+            loop {
+                let mut buf = [0u8; 10];
+                let result = state.step(&mut rdr, &mut size, &mut buf, &mut count);
+                let desc = format!("read_size failed for {:?}", s);
+                state = result.expect(desc.as_str());
+                trace!("State {:?}", state);
+                if state == ChunkedState::Body || state == ChunkedState::End {
+                    break;
+                }
+            }
+            size
         }
 
-        fn read_err(s: &str) {
-            assert_eq!(read_chunk_size(&mut s.as_bytes()).unwrap_err().kind(),
-                io::ErrorKind::InvalidInput);
+        fn read_err(s: &str, expected_err: io::ErrorKind) {
+            let mut state = ChunkedState::Size;
+            let mut rdr = &mut s.as_bytes();
+            let mut size = 0;
+            let mut count = 0;
+            loop {
+                let mut buf = [0u8; 10];
+                let result = state.step(&mut rdr, &mut size, &mut buf, &mut count);
+                state = match result {
+                    Ok(s) => s,
+                    Err(e) => {
+                        assert!(expected_err == e.kind(), "Reading {:?}, expected {:?}, but got {:?}",
+                                                          s, expected_err, e.kind());
+                        return;
+                    }
+                };
+                trace!("State {:?}", state);
+                if state == ChunkedState::Body || state == ChunkedState::End {
+                    panic!(format!("Was Ok. Expected Err for {:?}", s));
+                }
+            }
         }
 
-        read("1\r\n", 1);
-        read("01\r\n", 1);
-        read("0\r\n", 0);
-        read("00\r\n", 0);
-        read("A\r\n", 10);
-        read("a\r\n", 10);
-        read("Ff\r\n", 255);
-        read("Ff   \r\n", 255);
+        assert_eq!(1, read("1\r\n"));
+        assert_eq!(1, read("01\r\n"));
+        assert_eq!(0, read("0\r\n"));
+        assert_eq!(0, read("00\r\n"));
+        assert_eq!(10, read("A\r\n"));
+        assert_eq!(10, read("a\r\n"));
+        assert_eq!(255, read("Ff\r\n"));
+        assert_eq!(255, read("Ff   \r\n"));
         // Missing LF or CRLF
-        read_err("F\rF");
-        read_err("F");
+        read_err("F\rF", InvalidInput);
+        read_err("F", UnexpectedEof);
         // Invalid hex digit
-        read_err("X\r\n");
-        read_err("1X\r\n");
-        read_err("-\r\n");
-        read_err("-1\r\n");
+        read_err("X\r\n", InvalidInput);
+        read_err("1X\r\n", InvalidInput);
+        read_err("-\r\n", InvalidInput);
+        read_err("-1\r\n", InvalidInput);
         // Acceptable (if not fully valid) extensions do not influence the size
-        read("1;extension\r\n", 1);
-        read("a;ext name=value\r\n", 10);
-        read("1;extension;extension2\r\n", 1);
-        read("1;;;  ;\r\n", 1);
-        read("2; extension...\r\n", 2);
-        read("3   ; extension=123\r\n", 3);
-        read("3   ;\r\n", 3);
-        read("3   ;   \r\n", 3);
+        assert_eq!(1, read("1;extension\r\n"));
+        assert_eq!(10, read("a;ext name=value\r\n"));
+        assert_eq!(1, read("1;extension;extension2\r\n"));
+        assert_eq!(1, read("1;;;  ;\r\n"));
+        assert_eq!(2, read("2; extension...\r\n"));
+        assert_eq!(3, read("3   ; extension=123\r\n"));
+        assert_eq!(3, read("3   ;\r\n"));
+        assert_eq!(3, read("3   ;   \r\n"));
         // Invalid extensions cause an error
-        read_err("1 invalid extension\r\n");
-        read_err("1 A\r\n");
-        read_err("1;no CRLF");
+        read_err("1 invalid extension\r\n", InvalidInput);
+        read_err("1 A\r\n", InvalidInput);
+        read_err("1;no CRLF", UnexpectedEof);
     }
 
     #[test]
@@ -287,7 +358,108 @@ mod tests {
         let mut buf = [0u8; 10];
         assert_eq!(decoder.decode(&mut bytes, &mut buf).unwrap(), 7);
         let e = decoder.decode(&mut bytes, &mut buf).unwrap_err();
-        assert_eq!(e.kind(), io::ErrorKind::Other);
+        assert_eq!(e.kind(), io::ErrorKind::UnexpectedEof);
         assert_eq!(e.description(), "early eof");
     }
+
+    #[test]
+    fn test_read_chunked_single_read() {
+        let content = b"10\r\n1234567890abcdef\r\n0\r\n";
+        let mut mock_buf = io::Cursor::new(content);
+        let mut buf = [0u8; 16];
+        let count = Decoder::chunked().decode(&mut mock_buf, &mut buf).expect("decode");
+        assert_eq!(16, count);
+        let result = String::from_utf8(buf.to_vec()).expect("decode String");
+        assert_eq!("1234567890abcdef", &result);
+    }
+
+    #[test]
+    fn test_read_chunked_after_eof() {
+        let content = b"10\r\n1234567890abcdef\r\n0\r\n";
+        let mut mock_buf = io::Cursor::new(content);
+        let mut buf = [0u8; 50];
+        let mut decoder = Decoder::chunked();
+
+        // normal read
+        let count = decoder.decode(&mut mock_buf, &mut buf).expect("decode");
+        assert_eq!(16, count);
+        let result = String::from_utf8(buf[0..count].to_vec()).expect("decode String");
+        assert_eq!("1234567890abcdef", &result);
+
+        // eof read
+        let count = decoder.decode(&mut mock_buf, &mut buf).expect("decode");
+        assert_eq!(0, count);
+
+        // ensure read after eof also returns eof
+        let count = decoder.decode(&mut mock_buf, &mut buf).expect("decode");
+        assert_eq!(0, count);
+    }
+
+    // perform an async read using a custom buffer size and causing a blocking
+    // read at the specified byte
+    fn read_async(mut decoder: Decoder,
+                  content: &[u8],
+                  block_at: usize,
+                  read_buffer_size: usize)
+                  -> String {
+        let content_len = content.len();
+        let mock_buf = io::Cursor::new(content.clone());
+        let mut ins = Async::new(mock_buf, block_at);
+        let mut outs = vec![];
+        loop {
+            let mut buf = vec![0; read_buffer_size];
+            match decoder.decode(&mut ins, buf.as_mut_slice()) {
+                Ok(0) => break,
+                Ok(i) => outs.write(&buf[0..i]).expect("write buffer"),
+                Err(e) => {
+                    if e.kind() != io::ErrorKind::WouldBlock {
+                        break;
+                    }
+                    ins.block_in(content_len); // we only block once
+                    0 as usize
+                }
+            };
+        }
+        String::from_utf8(outs).expect("decode String")
+    }
+
+    // iterate over the different ways that this async read could go.
+    // tests every combination of buffer size that is passed in, with a blocking
+    // read at each byte along the content - The shotgun approach
+    fn all_async_cases(content: &str, expected: &str, decoder: Decoder) {
+        let content_len = content.len();
+        for block_at in 0..content_len {
+            for read_buffer_size in 1..content_len {
+                let actual = read_async(decoder.clone(),
+                                        content.as_bytes(),
+                                        block_at,
+                                        read_buffer_size);
+                assert_eq!(expected,
+                    &actual,
+                    "Failed async. Blocking at {} with read buffer size {}",
+                    block_at,
+                    read_buffer_size);
+            }
+        }
+    }
+
+    #[test]
+    fn test_read_length_async() {
+        let content = "foobar";
+        all_async_cases(content, content, Decoder::length(content.len() as u64));
+    }
+
+    #[test]
+    fn test_read_chunked_async() {
+        let content = "3\r\nfoo\r\n3\r\nbar\r\n0\r\n";
+        let expected = "foobar";
+        all_async_cases(content, expected, Decoder::chunked());
+    }
+
+    #[test]
+    fn test_read_eof_async() {
+        let content = "foobar";
+        all_async_cases(content, content, Decoder::eof());
+    }
+
 }