http://www.ousob.com --- Legacy Redefined OuSob - File: /wwwroot/clipx/usr/include/wvstreams/wvencoderstream.h

/* -*- Mode: C++ -*- * Worldvisions Tunnel Vision Software: * Copyright (C) 1997-2002 Net Integration Technologies, Inc. * * An stream wrapper for encoders. */ #ifndef __WVENCODERSTREAM_H #define __WVENCODERSTREAM_H #include "wvstream.h" #include "wvstreamclone.h" #include "wvencoder.h" /** * WvEncoderStream chains a series of encoders on the input and * output ports of the underlying stream to effect on-the-fly data * transformations. * * Notice that the value of WvEncoderStream's auto_flush flag becomes * important when working with encoders that treat explicit buffer * flushing in a special manner. For instance, on flush() the Gzip * encoder synchronizes its output. Were auto_flush to remain true, * each incremental write to the stream would cause the Gzip encoder * to flush its dictionary thereby resulting in poor compression. * * See WvStream::auto_flush(bool). * * WARNING: it is possible to add to the readchain and/or writechain in the * middle of a session, for example to add gzip compression after first * negotiating it with the remote end. If you plan to do this, be very * careful with buffering. Never read() or getline() more bytes than * you're sure will exist with the old encoding. Even then, only ever * append things to the readchain, not prepend. (Therefore only prepend * things to the writechain.) Always flush() or flush_write() before * adding to the writechain. See also min_readsize. */ class WvEncoderStream : public WvStreamClone { bool is_closing; WvDynBuf readinbuf; WvDynBuf readoutbuf; WvDynBuf writeinbuf; //WvDynBuf writeoutbuf; public: /** Encoder chain through which input data is passed. */ WvEncoderChain readchain; /** Encoder chain through which output data is passed. */ WvEncoderChain writechain; /** * Controls the minimum number of unencoded bytes the encoder * should try to read at once from the underlying stream, * to optimize performance of block-oriented protocols. * This is not the same as queuemin() which guarantees how much * encoded input must be generated before select() returns true. * if 0, the encoder will only read whatever is specified in uread(). * * NOTE: if you plan to append a new encoder to the readchain after * doing read(), you should always use read() with only 1 byte at a * time, or some extra data will end up in inbuf and not pass through * the newly- added encoder. Remember that getline() also calls * read(). The purpose of min_readsize is to make these one-byte * read() calls more efficient, because the *underlying* stream can * still read lots of bytes, as long as we only pass single bytes down * to the WvEncoderStream. * * If you don't plan to add new encoders to readchain from now on, you * can give larger sizes to read() or getline(), and thus min_readsize * is unnecessary. */ size_t min_readsize; /** * Creates an encoder stream. * * "cloned" is the stream to wrap */ WvEncoderStream(WvStream *cloned); virtual ~WvEncoderStream(); /** * Safely shuts down the stream. * * Does the following in sequence: * * - Flushes and finishes the read chain * - Flushes and finishes the write chain * - Flushes the stream output buffers * - Closes the underlying stream */ virtual void close(); /** * Flushes the read chain through to the stream's input buffer. * * The regular stream flush() only operates on the write chain. * * Returns: true if the encoder chain returned true */ bool flush_read(); /** * Flushes the write chain through to the stream's output buffer. * * The regular stream flush() invokes this, then attempts to * synchronously push the buffered data to the stream, which * may not always be desirable since it can be quite costly. * * To simply cause the write chain to be flushed but allow * WvStreams to drain the encoded output buffer at its leisure, * use this function. * * Returns: true if the encoder chain returned true */ bool flush_write(); /** * Calls flush() then finish() on the read chain of encoders. * * Returns: true if the encoder chain returned true */ bool finish_read(); /** * Calls flush() then finish() on the write chain of encoders. * * Does not flush() the stream. * * Returns: true if the encoder chain returned true. */ bool finish_write(); /** * Defines isok() semantics for encoders. * * Returns false on error or after all data has been read from * the internal buffers and readchain.isfinished() or * ! writechain.isok(). * * Returns: true if it is still possible to read and write data */ virtual bool isok() const; virtual size_t uread(void *buf, size_t size); virtual size_t uwrite(const void *buf, size_t size); protected: bool pre_select(SelectInfo &si); virtual bool flush_internal(time_t msec_timeout); private: void checkreadisok(); void checkwriteisok(); // pulls a chunk of specified size from the underlying stream void pull(size_t size); // pushes a chunk to the underlying stream bool push(bool flush, bool finish); }; #endif // __WVENCODERSTREAM_H