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120 строки
4.1 KiB
Plaintext
120 строки
4.1 KiB
Plaintext
Darin Fisher
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darin@netscape.com
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8/8/2001
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HTTP DESIGN NOTES
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CLASS BREAKDOWN
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nsHttpHandler
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- implements nsIProtocolHandler
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- manages preferences
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- owns the authentication cache
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- holds references to frequently used services
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nsHttpChannel
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- implements nsIHttpChannel
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- talks to the cache
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- initiates http transactions
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- processes http response codes
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- intercepts progress notifications
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nsHttpConnection
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- implements nsIStreamListener & nsIStreamProvider
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- talks to the socket transport service
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- feeds data to its transaction object
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- routes progress notifications
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nsHttpConnectionInfo
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- identifies a connection
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nsHttpTransaction
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- implements nsIRequest
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- encapsulates a http request and response
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- parses incoming data
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nsHttpChunkedDecoder
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- owned by a transaction
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- removes chunked decoding
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nsHttpRequestHead
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- owns a nsHttpHeaderArray
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- knows how to fill a request buffer
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nsHttpResponseHead
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- owns a nsHttpHeaderArray
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- knows how to parse response lines
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- performs common header manipulations/calculations
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nsHttpHeaderArray
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- stores http "<header>:<value>" pairs
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nsHttpAuthCache
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- stores authentication credentials for http auth domains
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nsHttpBasicAuth
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- implements nsIHttpAuthenticator
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- generates BASIC auth credentials from user:pass
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ATOMS
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nsHttp:: (header namespace)
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eg. nsHttp::Content_Length
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TRANSACTION MODEL
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InitiateTransaction -> ActivateConnection -> AsyncWrite, AsyncRead
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The channel creates transactions, and passes them to the handler via
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InitiateTransaction along with a nsHttpConnectionInfo object
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identifying the requested connection. The handler either dispatches
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the transaction immediately or queues it up to be dispatched later,
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depending on whether or not the limit on the number of connections
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to the requested server has been reached. Once the transaction can
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be run, the handler looks for an idle connection or creates a new
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connection, and then (re)activates the connection, assigning it the
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new transaction.
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Once activated the connection ensures that it has a socket transport,
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and then calls AsyncWrite and AsyncRead on the socket transport. This
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begins the process of talking to the server. To minimize buffering,
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socket transport thread-proxying is completely disabled (using the flags
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DONT_PROXY_LISTENER | DONT_PROXY_PROVIDER | DONT_PROXY_OBSERVER with
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both AsyncWrite and AsyncRead). This means that the nsHttpConnection's
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OnStartRequest, OnDataAvailable, OnDataWritable, and OnStopRequest
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methods will execute on the socket transport thread.
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The transaction defines (non-virtual) OnDataReadable, OnDataWritable, and
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OnStopTransaction methods, which the connection calls in response to
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its OnDataAvailable, OnDataWritable, and OnStopRequest methods, respectively.
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The transaction owns a nsStreamListenerProxy created by the channel, which
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it uses to transfer data from the socket thread over to the client's thread.
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To mimize buffering, the transaction implements nsIInputStream, and passes
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itself to the stream listener proxy's OnDataAvailable. In this way, we
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have effectively wedged the response parsing between the socket and the
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thread proxy's buffer. When read, the transaction turns around and reads
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from the socket using the buffer passed to it. The transaction scans the
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buffer for headers, removes them as they are detected, and copies the headers
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into its nsHttpResponseHead object. The rest of the data remains in the
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buffer, and is proxied over to the client's thread to be handled first by the
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http channel and eventually by the client.
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There are several other major design factors, including:
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- transaction cancelation
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- progress notification
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- SSL tunneling
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- chunked decoding
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- thread safety
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- premature EOF detection and transaction restarting
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- pipelining (not yet implemented)
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CACHING
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<EOF>
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