Skip to content
An HTTP protocol parser in Common Lisp
Common Lisp
Find file
Latest commit adf597b May 22, 2015 @orthecreedence retiring http-parse

README.md

This library has been superceded by fast-http

http-parse had a good, long life and served many HTTP requests, but it's now time for it to stand aside and let libraries better than itself take its place. fast-http is an incredible library (and is now the core parser used in Wookie).

Use fast-http instead of http-parse. This library is retired.

http-parse

A pure-lisp library for parsing HTTP requests/responses. Right now the focus for this library is making it useful and easy to use. With time, slower parts of http-parse will be replaced to make it screaming fast.

The purpose of this library is to be able to easily parse incoming HTTP data either synchronously or asynchronously (but it was mainly built for streaming HTTP data asynchronously).

Documentation

http (class)

This is a base class extended by http-request and http-response. It holds values that both requests/responses deal with (HTTP version, headers, body).

This class, and those that extend it, are meant to be instiantiated with no parameters and passed into the make-parser function, which fills in all the details which can be read out later.

http-version

Accessor for the parsed HTTP version out of the http object.

http-headers

Accessor for the headers parsed from the HTTP request/response

http-store-body

store-body specifies whether the HTTP body should be stored (in its entirety) in the http-body accessor. If this is set after initializing a parser, it should be done so no later than the header-callback being fired, or else pieces of the body may be missing.

http-force-stream

force-stream lets the parser know that you want every TCP packet that comes in to be passed into a body callback as if it was sent via an HTTP chunk. This is an advanced option, but can be very useful in some cases. For instance, if you have a server that supports file uploads and a client doesn't know how to chunk an upload (like every browser ever), your server is going to spin its CPU and waste memory buffering the entire file and passing it around as a huge array instead of dealing with it packet by packet. This is a great way to fake HTTP chunking in your server/client.

http-body

Accessor for the full HTTP body from the request/response (although storing of the body in the http object must be explicitely asked for by passing :store-body t into make-parser.

http-request (class)

extends http

Holds values specific to an HTTP request (method, resource)

http-method

Accessor for the parsed HTTP request method as a keyword: :GET, :POST, etc.

http-resource

Accessor for the resource in the request. Parse with puri.

http-response (class)

extends http

Holds values specific to an HTTP response (status, status text).

http-status

Accessor for the HTTP response status (integer).

http-status-text

Accessor for the HTTP response status string: OK, Insufficient Privileges, etc.

make-parser (function)

(defun make-parser (http &key header-callback body-callback multipart-callback finish-callback store-body)
  => closure

This is what you've all been waiting for, folks. This function initializes an HTTP parser (a closure) which can be fed binary data in sequence and will parse an HTTP request/response as it comes in.

It accepts a class of http-request or http-response as its only required argument. It returns a closure which only has one argument: a byte array that contains pieces of an HTTP request/response. The pieces must be in order, but other than that, there is no restriction on how many times the parser can be called with new data until it is finished. In some cases (older HTTP versions), the end of an HTTP payload is marked by an EOF on the socket. If this occurs, you can pass :eof into the parser instead of a byte array to signal that it should finish up.

The parser closure returns three values: the http object passed in, a boolean indicating if the headers are finished parsing, and a boolean indicating if the HTTP body has been fully parsed.

make-parser accepts these callbacks: :header-callback, :body-callback, :multipart-callback, and :finish-callback.

  • The header callback is fired when all the headers have been parsed. It takes one argument, a plist of finished headers.
  • The body callback is called either when the entire body has been received (in the case of :content-length being present in the headers) or piece by piece as it is sent in (when the body is chunked).
  • The multipart callback, if specified, is passed into a multipart parser, which is given chunks of the body as they come in. It decodes multipart form data such that the given callback is fired for each form field present in the data. If it encounters a field that is split into multiple chunks, it will fire the callback for each of the chunks, indicating in one of the arguments whether that is the final chunk or not. This makes it possible to stream the multipart data as it comes in (for instance, to a file).
  • The finish-callback is a function with no args called when the parser has detected that the HTTP payload is completely parsed (headers, body, etc).

The :store-body keyword specifies that the parser should store the body (as a byte array) into the given http object as it is parsed. Otherwise, the best way to get the body data is via the body-callback.

;; example. anything under my-app is not included.
(let ((http (make-instance 'http-response))
      (parser (make-parser http
                           :header-callback (lambda (headers)
                                              (my-app:got-headers!!! headers))
                           :body-callback (lambda (bytes)
                                              (my-app:got-body-piece bytes)))))
  (loop for http-data = (my-app:get-http-data-from-request-i-sent-out-earlier) do
    (multiple-value-bind (http headers-finished-p body-finished-p)
        (funcall parser http-data)
      (when body-finished-p
        (my-app:close-http-stream))
      ...)))
Parser lambda definition
(lambda (byte-array) ...)
  => http, headers-finished-p, body-finished-p

As noted, if an EOF happens on the socket the HTTP data is coming in on, you may indicate this to the parser by sending in :eof instead of the byte array.

header-callback definition
(lambda (header-plist) ...)

Headers are in the form '(:host "musio.com" :content-type "text/html" ...). Headers are not reversed, they are passed in the order they occur in the HTTP payload.

body-callback definition
(lambda (byte-array last-chunk-p) ...)

Byte-array is not cumulative, it is just the new data that has been parsed from the payload. If multiple chunks are parsed at once, their body data is sent in as one call to the body-callback. Incomplete chunks are not sent in until they are completed.

last-chunk-p is true if the entire body has been processed (if a Content-Length was specified and all bytes accounted for, or if the body is chunked and the 0-byte chunk has been encountered).

multipart-callback definition

See multipart parser callback definition.

finish-callback definition
(lambda () ...)

This callback is fired when the HTTP parser is finished parsing the request/response.

make-multipart-parser (function)

(defun make-multipart-parser (headers callback))
  => closure

Returns a parser closure to deal with multipart form data. Data is fed to the parser in as many chunks as needed (or all at once) and the given callback will be fired at least once for each form field present in the multipart form data. If data for a field is spread over multiple chunks, the callback is fired for each of the chunks, along with a second argument indicating whether the current chunk is that last for that field.

headers are all the headers from a parsed HTTP payload, in plist form.

NOTE: If make-multipart-parser detects that the data being decoded is not in multipart format (determined by reading the headers), it returns nil instead of a closure.

multipart parser callback definition
(lambda (field-name field-headers field-meta body-bytes body-complete-p) ...)

This callback is fired for each form field encountered in a multipart request.

The field-name arg is a string indicating the name of the form field. The field-headers arg is a plist containing the headers for that field (generally this is Content-Disposition and sometimes Content-Type for uploads). The field-meta arg is a plist of key/value pairs found in the Content-Disposition header for the field (this is where the field-name arg comes from, and is also used to specify the filename of uploaded files). body-bytes is a byte array containing all or a chunk of that field's data, and body-complete-p indicates whether or not the body-bytes being sent into the callback is the last bit of data for that field.

Generally, this callback will be a closure that is able to track the current field it's operating on and be able to handle the case where body-bytes is spread over multiple calls if body-complete-p is nil.

Tests

Tests are under the http-parse-test package:

(ql:quickload :http-parse-test)
(http-parse-test:run-tests)

Please report any bugs you find or failing tests to the issues list.

License

MIT Licensed. Enjoy.

Something went wrong with that request. Please try again.