HTTP Request/Response Parser

An implementation for parsing an http request/response. Internally the parser does not allocate memory from the heap. The aim is for a simple function call requiring as little setup as possible.

HTTP Request

The primary struct http_request_t has the following fields:

• http_method: GET, HEAD, POST, PUT, PATCH, CONNECT, DELETE, TRACE, OPTIONS
• path: the requested path i.e /name-of/resource
• http_version: "1.1", "1"
• headers: An array of headers in key value pairings;

Example:

main.c can accept a file with an http header and will attempt the use the http_parser to parse the headers as a demonstration

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

#include "http_parser.h"

void someFunction(void) {
  char buf[BUFSIZ];
  int socket_fd, bytes;
  http_request_t req;

  while ((bytes = read(socket_fd, buf, BUFSIZ)) > 0);

  if (bytes == 0) {
    // handle error
    return;
  }

  httpParseRequest(buf, &req);

  printf("%s %s HTTP/%s\n", req.http_method, req.path, req.http_version);
	
  for (int i = 0; i < req.num_headers; ++i) {
    printf("%s: %s\n", req.headers[i].key, req.headers[i].value);
  }
}

Methods

void httpParseRequest(char *request_raw, http_request_t *req);

• buf a character array used internally
• req_raw the raw response
• req a http_response_t, which on success will be populated explicity with the HTTP Version, http Method and the path.

HTTP Response

A very simliar the request parser.

The primary struct http_response_t consists of the following fields:

• http_version - "1", "1.1", "2"
• status_code char * i.e "200", "400".
• status_text char * i.e "OK", "Bad Request"

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

#include "http_parser.h"

void someFunction(void) {
  char buf[BUFSIZ];
  int socket_fd, bytes;
  http_response_t res;

  while ((bytes = read(socket_fd, buf, BUFSIZ)) > 0);

  if (bytes == 0) {
    // handle error
    return;
  }

  httpParseResponse(buf, &res);

  printf("HTTP/%s %s %s\n", res.http_version, res.status_code, res.status_text);
	
  for (int i = 0; i < res.num_headers; ++i) {
    printf("%s: %s\n", res.headers[i].key, res.headers[i].value);
  }
}

Methods

void httpParseResponse(char *resonse_raw, http_response_t *res);

• req_raw the raw response
• req a http_response_t, which on success will be populated explicitly with the HTTP version, Status code and Status Text

Utils

As a convenience for getting a header, will return a pointer to a header or NULL.

headers_kv_t *httpFindHeader(headers_kv_t *headers, int num_headers, char *key);

Utliity for getting the response body if there is one or NULL. The "body" is a header that has been added as a convenience for getting the response body. It is the last header and can be accessed in O(1).

char *httpGetResponseBody(http_response_t *res);