http服务器的主要工作就是解析http请求，然后返回http应答。http请求从socket读入，就是一段特定格式的字符串，下面是访问huangzhimn.com首页的http请求
GET / HTTP/1.1\r\n
Host: www.huangzhimin.com\r\n
User-Agent: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.5; en-US; rv:1.9.1.7) Gecko/20091221 Firefox/3.5.7\r\n
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n
Accept-Language: en-us,en;q=0.5\r\n
Accept-Encoding: gzip,deflate\r\n
Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7\r\n
Keep-Alive: 300\r\n
Connection: keep-alive\r\n
\r\n
那么webrick是解析这段字符串的呢？之前在分析webrick主要流程的时候讲到，在http服务器从socket读取到数据时，立刻交给WEBrick::HTTPRequest类来解析，解析方法如下
def parse(socket=nil)
@socket = socket
begin
@peeraddr = socket.respond_to?(:peeraddr) ? socket.peeraddr : []
@addr = socket.respond_to?(:addr) ? socket.addr : []
rescue Errno::ENOTCONN
raise HTTPStatus::EOFError
end
read_request_line(socket)
if @http_version.major > 0
read_header(socket)
@header['cookie'].each{|cookie|
@cookies += Cookie::parse(cookie)
}
@accept = HTTPUtils.parse_qvalues(self['accept'])
@accept_charset = HTTPUtils.parse_qvalues(self['accept-charset'])
@accept_encoding = HTTPUtils.parse_qvalues(self['accept-encoding'])
@accept_language = HTTPUtils.parse_qvalues(self['accept-language'])
end
return if @request_method == "CONNECT"
return if @unparsed_uri == "*"
begin
@request_uri = parse_uri(@unparsed_uri)
@path = HTTPUtils::unescape(@request_uri.path)
@path = HTTPUtils::normalize_path(@path)
@host = @request_uri.host
@port = @request_uri.port
@query_string = @request_uri.query
@script_name = ""
@path_info = @path.dup
rescue
raise HTTPStatus::BadRequest, "bad URI `#{@unparsed_uri}'."
end
if /close/io =~ self["connection"]
@keep_alive = false
elsif /keep-alive/io =~ self["connection"]
@keep_alive = true
elsif @http_version < "1.1"
@keep_alive = false
else
@keep_alive = true
end
end
第3-8行，读取对方和自己的地址信息（host, port, id）
第10行，解析http请求的第一行数据，内容为“GET / HTTP/1.1\r\n”，具体解析方法如下
def read_request_line(socket)
@request_line = read_line(socket) if socket
@request_time = Time.now
raise HTTPStatus::EOFError unless @request_line
if /^(\S+)\s+(\S+)(?:\s+HTTP\/(\d+\.\d+))?\r?\n/mo =~ @request_line
@request_method = $1
@unparsed_uri = $2
@http_version = HTTPVersion.new($3 ? $3 : "0.9")
else
rl = @request_line.sub(/\x0d?\x0a\z/o, '')
raise HTTPStatus::BadRequest, "bad Request-Line `#{rl}'."
end
end
读取http请求的第一行，读取之后通过正则匹配获取@request_method为'GET'，@unparsed_url为'/'，@http_version为‘1.1’
第11-20行，当http版本为1.0或1.1时，对http头部进行处理
首先，读取http头，读取方法如下：
def read_header(socket)
if socket
while line = read_line(socket)
break if /\A(#{CRLF}|#{LF})\z/om =~ line
@raw_header << line
end
end
begin
@header = HTTPUtils::parse_header(@raw_header)
rescue => ex
raise HTTPStatus::BadRequest, ex.message
end
end
从socket一行一行地读取数据，直到一行为”\r\n“，并通过HTTPUTils::parse_header方法将字符串数组@raw_header转换为散列@header
接着，读取cookies，将cookie字符串解析为Cookie对象
然后是读取accept, accept-charset, accept-encoding, accept-language值，这些值都是多选的，比如“Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8\r\n”，所以通过HTTPUtils::parse_qvalues解析出来的结果是一个数组，而且按照q值来排序
第21行，当request_method为CONNECT时（用于http代理，http1.1协议新增的），不再继续
第25行，将字符串@unparsed_uri转换成正规的URI实例@parsed_uri
第26-30行，通过@parsed_uri获取@path, @host, @port和@query_string
最后，第37-45行，设置keep-alive值。
WEBrick::HTTPRequest类另外一个重要的方法是body
def body(&block)
block ||= Proc.new{|chunk| @body << chunk }
read_body(@socket, block)
@body.empty? ? nil : @body
end
def read_body(socket, block)
return unless socket
if tc = self['transfer-encoding']
case tc
when /chunked/io then read_chunked(socket, block)
else raise HTTPStatus::NotImplemented, "Transfer-Encoding: #{tc}."
end
elsif self['content-length'] || @remaining_size
@remaining_size ||= self['content-length'].to_i
while @remaining_size > 0
sz = BUFSIZE < @remaining_size ? BUFSIZE : @remaining_size
break unless buf = read_data(socket, sz)
@remaining_size -= buf.size
block.call(buf)
end
if @remaining_size > 0 && @socket.eof?
raise HTTPStatus::BadRequest, "invalid body size."
end
elsif BODY_CONTAINABLE_METHODS.member?(@request_method)
raise HTTPStatus::LengthRequired
end
return @body
end
如果http body为空，则返回nil
http body分为两种，一种是数据一次性全部传入，另一种是一段一段分批传输(chunked)。
第8-18行就是处理一次性全部传入的数据，根据header中content-length来读取指定长度的数据。
第3-7行读取chunked分段数据，读取方法为
def read_chunked(socket, block)
chunk_size, = read_chunk_size(socket)
while chunk_size > 0
data = ""
while data.size < chunk_size
tmp = read_data(socket, chunk_size-data.size) # read chunk-data
break unless tmp
data << tmp
end
if data.nil? || data.size != chunk_size
raise BadRequest, "bad chunk data size."
end
read_line(socket) # skip CRLF
block.call(data)
chunk_size, = read_chunk_size(socket)
end
read_header(socket) # trailer + CRLF
@header.delete("transfer-encoding")
@remaining_size = 0
end
chunked分段数据，第一行表明这一段数据的长度，用十六进制表示，第二行开始为需要读取的分段数据。所以读取chunked数据就是读一行chunk_size，读一行chunk data，直到读完为止。
最后看看WEBrick::HTTPRequest的meta方法，对CGI的理解很有帮助
def meta_vars
# This method provides the metavariables defined by the revision 3
# of ``The WWW Common Gateway Interface Version 1.1''.
# (http://Web.Golux.Com/coar/cgi/)
meta = Hash.new
cl = self["Content-Length"]
ct = self["Content-Type"]
meta["CONTENT_LENGTH"] = cl if cl.to_i > 0
meta["CONTENT_TYPE"] = ct.dup if ct
meta["GATEWAY_INTERFACE"] = "CGI/1.1"
meta["PATH_INFO"] = @path_info ? @path_info.dup : ""
#meta["PATH_TRANSLATED"] = nil # no plan to be provided
meta["QUERY_STRING"] = @query_string ? @query_string.dup : ""
meta["REMOTE_ADDR"] = @peeraddr[3]
meta["REMOTE_HOST"] = @peeraddr[2]
#meta["REMOTE_IDENT"] = nil # no plan to be provided
meta["REMOTE_USER"] = @user
meta["REQUEST_METHOD"] = @request_method.dup
meta["REQUEST_URI"] = @request_uri.to_s
meta["SCRIPT_NAME"] = @script_name.dup
meta["SERVER_NAME"] = @host
meta["SERVER_PORT"] = @port.to_s
meta["SERVER_PROTOCOL"] = "HTTP/" + @config[:HTTPVersion].to_s
meta["SERVER_SOFTWARE"] = @config[:ServerSoftware].dup
self.each{|key, val|
next if /^content-type$/i =~ key
next if /^content-length$/i =~ key
name = "HTTP_" + key
name.gsub!(/-/o, "_")
name.upcase!
meta[name] = val
}
meta
end
