Chunked Encoding (Read)

You know how to read a request body using Content-Length. But what if a client wants to stream data to you, and they don’t know the final size before they start sending?

In HTTP/1.1, this is solved using Chunked Transfer Encoding (RFC 9112 Section 7.1).

When a request contains the header Transfer-Encoding: chunked, the Content-Length header is omitted. Instead, the body is sent in a series of chunks.

Each chunk follows this strict ABNF grammar:

chunk          = chunk-size [ chunk-ext ] CRLF chunk-data CRLF
chunk-size     = 1*HEXDIG

• chunk-size: A hexadecimal number indicating the size of the following chunk data.
• [ chunk-ext ]: Optional extensions that you can safely ignore for this course.
• chunk-data: The actual payload bytes of the specified size.

Example of a chunked body:

4\r\n        (Chunk size: 4 bytes in hex)
Wiki\r\n     (Chunk data: 4 bytes)
5\r\n        (Chunk size: 5 bytes in hex)
pedia\r\n    (Chunk data: 5 bytes)
0\r\n        (Final zero-length chunk terminating the stream)
\r\n         (End of chunked body)

Your Task

Create a new /lowercase route to support Transfer-Encoding: chunked.

If the client sends a chunked request, you must parse the chunk sizes (hexadecimal!), read exactly that many bytes of chunk data, skip the \r\n, and repeat until you encounter a chunk of size 0.

Finally, combine all the chunk data, lowercase it, and return it in the response (you can return it with a standard Content-Length response for now).

Important

Run the below docker command to test your solution.

docker run \
  --rm \
  --add-host host.docker.internal:host-gateway \
  codeberg.org/level0/buildit/http-server:latest \
  --addr host.docker.internal:8080 \
  --until chunked_encoding_read