232 lines
8.3 KiB
C
232 lines
8.3 KiB
C
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/* PSTNFram.h
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*
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* Copyright (c) 1993-1995 by DataBeam Corporation, Lexington, KY
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*
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* Abstract:
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* This function encodes and decodes functions according to the encoding
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* rules set by the T.123 communications standard for PSTN. The standard
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* states that a flag will precede each packet and a flag will be appended
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* to the end of each packet. Therefore no flags are permitted in the body
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* of the packet. Flags are replaced by an ESCAPE sequence. If an ESCAPE
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* byte is found in a packet, remove the ESCAPE, and negate the 6th bit of
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* the next byte.
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*
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* Caveats:
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* None
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*
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* Authors:
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* James W. Lawwill
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*/
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#ifndef _PSTN_FRAME_H_
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#define _PSTN_FRAME_H_
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#include "framer.h"
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/*
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** Commonly used definitions
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*/
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#define FLAG 0x7e
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#define ESCAPE 0x7d
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#define COMPLEMENT_BIT 0x20
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#define NEGATE_COMPLEMENT_BIT 0xdf
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class PSTNFrame : public PacketFrame
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{
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public:
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PSTNFrame(void);
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virtual ~PSTNFrame(void);
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PacketFrameError PacketEncode (
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PUChar source_address,
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UShort source_length,
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PUChar dest_address,
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UShort dest_length,
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DBBoolean prepend_flag,
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DBBoolean append_flag,
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PUShort packet_size);
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PacketFrameError PacketDecode (
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PUChar source_address,
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UShort source_length,
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PUChar dest_address,
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UShort dest_length,
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PUShort bytes_accepted,
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PUShort packet_size,
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DBBoolean continue_packet);
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Void GetOverhead (
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UShort original_packet_size,
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PUShort max_packet_size);
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private:
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PUChar Source_Address;
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UShort Source_Length;
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PUChar Dest_Address;
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UShort Dest_Length;
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UShort Source_Byte_Count;
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UShort Dest_Byte_Count;
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DBBoolean Escape_Found;
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DBBoolean First_Flag_Found;
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};
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typedef PSTNFrame * PPSTNFrame;
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#endif
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/*
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* PSTNFrame::PSTNFrame (
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* Void);
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*
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* Functional Description
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* This is the constructor for the PSTNFrame class. It initializes all
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* internal variables.
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*
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* Formal Parameters
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* None.
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*
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* Return Value
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* None
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*
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* Side Effects
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* None
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*
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* Caveats
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* None
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*/
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/*
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* PSTNFrame::~PSTNFrame (
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* Void);
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*
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* Functional Description
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* This is the destructor for the PSTNFrame class. It does nothing
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*
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* Formal Parameters
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* None.
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*
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* Return Value
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* None
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*
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* Side Effects
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* None
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*
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* Caveats
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* None
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*/
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/*
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* PacketFrameError PSTNFrame::PacketEncode (
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* PUChar source_address,
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* UShort source_length,
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* PUChar dest_address,
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* UShort dest_length,
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* DBBoolean prepend_flag,
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* DBBoolean append_flag,
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* PUShort packet_size);
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*
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*
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* Functional Description
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* This function encodes the passed in buffer to meet the T.123 standard.
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*
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* Formal Parameters
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* source_address (i) - Address of the buffer to encode
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* source_length (i) - Length of the buffer to encode
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* dest_address (i) - Address of the destination buffer
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* dest_length (i) - Length of the destination buffer
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* prepend_flag (i) - DBBoolean that tells us whether or not to put
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* a flag at the beginning of the packet
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* append_flag (i) - DBBoolean that tells us whether or not to put
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* a flag at the end of the packet
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* packet_size (o) - We return this to the user to tell them the new
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* size of the packet
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*
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* Return Value
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* PACKET_FRAME_NO_ERROR - No error occured
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* PACKET_FRAME_DEST_BUFFER_TOO_SMALL - The destination buffer passed
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* in was too small
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*
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* Side Effects
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* None
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*
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* Caveats
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* None
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*/
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/*
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* PacketFrameError PSTNFrame::PacketDecode (
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* PUChar source_address,
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* UShort source_length,
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* PUChar dest_address,
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* UShort dest_length,
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* PUShort bytes_accepted,
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* PUShort packet_size,
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* DBBoolean continue_packet);
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*
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* Functional Description
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* This function takes the input data and decodes it, looking for a
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* T123 packet. The user may have to call this function many times
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* before a packet is pieced together. If the user calls this function
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* and and sets either soure_address or dest_address to NULL, it uses
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* the addresses passed in, the last time this function was called. If
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* there is one source buffer to decode, the user can pass that address
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* in the first time and continue calling the function with NULL as the
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* source address until the buffer is exhausted. The user will know the
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* buffer is exhausted when the return code is simply PACKET_FRAME_NO_ERROR
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* rather than PACKET_FRAME_PACKET_DECODED.
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*
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* Formal Parameters
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* source_address (i) - Address of the buffer to decode
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* source_length (i) - Length of the buffer to decode
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* dest_address (i) - Address of the destination buffer
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* dest_length (i) - Length of the destination buffer
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* bytes_accepted (o) - We return the number of source bytes processed
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* packet_size (o) - We return the size of the packet. This is only
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* valid if the return code is
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* PACKET_FRAME_PACKET_DECODED.
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* continue_packet (i) - DBBoolean, tells us if we should start by
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* looking for the first flag. If the user wants
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* to abort the current search, use this flag.
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*
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* Return Value
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* PACKET_FRAME_NO_ERROR - No error occured, source buffer
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* exhausted
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* PACKET_FRAME_DEST_BUFFER_TOO_SMALL - The destination buffer passed
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* in was too small
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* PACKET_FRAME_PACKET_DECODED - Decoding stopped, packet decoded
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*
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* Side Effects
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* None
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*
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* Caveats
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* None
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*/
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/*
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* Void PSTNFrame::GetOverhead (
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* UShort original_packet_size,
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* PUShort max_packet_size);
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*
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* Functional Description
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* This function takes the original packet size and returns the maximum
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* size of the packet after it has been encoded. Worst case will be
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* twice as big as it was with two flags.
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*
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* Formal Parameters
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* original_packet_size (i) - Self-explanatory
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* max_packet_size (o) - Worst case size of the packet
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*
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* Return Value
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* None
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*
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* Side Effects
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* None
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*
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* Caveats
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* None
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*/
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