/* -*- C++ -*- */

/** @file   Mem_Map_Stream.h
 *
 *  @author Douglas C. Schmidt <schmidt@cs.wustl.edu>
 *  @author Krishnakumar B <kitty@cs.wustl.edu>
 */

#ifndef _ACEXML_MEM_MAP_STREAM_H
#define _ACEXML_MEM_MAP_STREAM_H

#include /**/ "ace/pre.h"
#include "ACEXML/common/ACEXML_Export.h"

#if !defined (ACE_LACKS_PRAGMA_ONCE)
#pragma once
#endif /* ACE_LACKS_PRAGMA_ONCE */

#include "ace/SOCK_Stream.h"
#include "ace/Mem_Map.h"
#include "ace/SOCK_Connector.h"
#include "ace/Connector.h"
#include "ace/Svc_Handler.h"
#include "ACEXML/common/XML_Types.h"

typedef ACE_Svc_Handler<ACE_SOCK_STREAM, ACE_NULL_SYNCH> Svc_Handler;
typedef ACE_Connector<Svc_Handler, ACE_SOCK_CONNECTOR> Connector;

/**
 * @class ACEXML_Mem_Map_Stream
 *
 * @brief Provides a memory-mapped stream abstraction to simplify parsing
 * of tokens.
 *
 * This class makes it possible to treat an connection as a stream of
 * bytes, similar to the C library stdio streams. The contents of the
 * connection are buffered incrementally in a memory-mapped file. This
 * class maintains pointers to two positions in the stream:
 *
 *   1. The <recv> position, which keeps track of the beginning of a
 *      token that is in the stream.
 *
 *   2. The <get> position, which moves along character-by-character
 *      until the end of the token is reached.
 *
 * Once a token has been located, it can be extracted from the stream by
 * calling the <recv>. The length of the token, i.e., the <recv_len>, is
 * the length in bytes between the <get> position and the <recv> position.
 * Once the token has been extracted, the <recv> and <get> positions can be
 * updated by the <seek> method.
 */
class ACEXML_Export ACEXML_Mem_Map_Stream
{
public:
  /// Default constructor
  ACEXML_Mem_Map_Stream (void);

  /// Initialize this object.
  virtual int open (Connector *connector,
                    const ACE_INET_Addr &);

  /// Destructor.
  virtual ~ACEXML_Mem_Map_Stream (void);

  /// Returns the underlying <ACE_SOCK_Stream>.
  ACE_SOCK_Stream &stream (void);

  /**
   * Send <size> bytes in <buf> to the connected peer.  This is a
   * completely unbuffered call.
   */
  virtual ssize_t send_n (const void *buf,
                          size_t size,
                          ACE_Time_Value *tv = 0);

  /**
   * Return the next character in the stream and advance the <get>
   * position. Returns EOF when the <get> position reaches the end of the
   * HTTP stream.
   */
  virtual int get_char (void);

  /**
   *  Returns a pointer to array of at most <len> characters starting at
   *  the <recv> position. If the <recv> position + <len> extends past the
   *  EOF then <len> is set to the number of characters between the <recv>
   *  position and the EOF and both the <get> and <recv> positions are
   *  advanced by <len>. Returns 0 if the <recv> position is at the EOF.
   */
  virtual const char *recv (size_t &len);

  /**
   *  Returns a pointer to array of characters starting at the <recv>
   *  position.
   */
  virtual const char *recv (void) const;

  /**
   *  Returns the length in bytes between the <get> position and the <recv>
   *  position.
   */
  virtual size_t recv_len (void) const;

  /**
   *  Returns the no. of bytes available in the stream.
   */
  virtual size_t available (void) const;

  /**
   *  Resets the <get> and <recv> positions to the beginning of the stream.
   *  This works since all the data has been cached in the memory-mapped
   *  backing store.
   */
  virtual void rewind (void);

  /**
   *  Returns the nth character <offset> from the <get> position in the
   *  stream without advancing the <get> position. Automatically extends
   *  the backing store if necessary. Returns EOF if <offset> is past the
   *  end of the stream.
   */
  virtual int peek_char (size_t offset);

  /**
   *  Return a pointer to an array of <size> characters starting at
   *  <offset> characters from the <get> position in the stream without
   *  advancing the <get> position. Automatically extends the backing store
   *  if necessary. Returns 0 if <offset> or <offset + size> is past the
   *  end of the stream.
   */
  virtual const char *peek_str (size_t offset, size_t size);

  /**
   *  Sets the <get> and <recv> positions as follows:
   *    o  If <whence> is <SEEK_SET>, the positions are set to <offset>
   *       bytes from the start of the stream.
   *    o  If <whence> is <SEEK_CUR>, the positions are set to the
   *       current <get> position plus <offset>.
   *    o  If <whence> is <SEEK_END>, the positions are set to the size
   *       of the stream plus <offset>.
   *
   *  If offset is greater than EOF, both <get> and <recv> are set to EOF.
   *  Note special return value is returned to indicate this condition.
   */
  virtual ACE_OFF_T seek (ACE_OFF_T offset, int whence = SEEK_CUR);

  /// Returns 1 if we're at the end of the HTTP stream, else 0.
  virtual int eof (void) const;

  /// Returns the underlying service handler.
  Svc_Handler *svc_handler (void);

private:
  /**
   *  Grow the file by reading another chunk from the HTTP socket and
   *  extend the mapping to cover this chunk.  Returns -1 on failure or
   *  EOF, else 0.
   */
  int grow_file_and_remap (void);

  /**
   *  Connection to peer. The granularity is at the Svc_Handler level.
   *  The Svc_Handler has an SOCK_Stream.
   */
  Svc_Handler *svc_handler_;

  /// Memory-mapped file that we're iterating over.
  ACE_Mem_Map mem_map_;

  /// Pointer to the address where the next <recv> method will start.
  char *recv_pos_;

  /**
   *  Pointer to the address where the next <get_char> method will
   *  start.
   */
  char *get_pos_;

  /// Address at the end of the file mapping.
  char *end_of_mapping_plus1_;

};


#include /**/ "ace/post.h"


#endif /* _ACEXML_MEM_MAP_STREAM_H */
