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 *
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 * Copyright (c) 1999-2001 Apple Computer, Inc.  All Rights Reserved. The
 * contents of this file constitute Original Code as defined in and are
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 * You may not use this file except in compliance with the License.  Please
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 * read it before using this file.
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/*
	File:		RTCPSRPacket.cpp

	Contains:	A class that writes a RTCP Sender Report
				
	Change History (most recent first):

	

*/

#include <string.h>

#include "RTCPSRPacket.h"
#include "MyAssert.h"
#include "OS.h"

RTCPSRPacket::RTCPSRPacket()
{
	// Write as much of the Sender Report as is possible
	char theTempCName[kMaxCNameLen];
	UInt32 cNameLen = RTCPSRPacket::GetACName(theTempCName);
	
	//write the SR & SDES headers
	UInt32* theSRWriter = (UInt32*)&fSenderReportBuffer;
	*theSRWriter = htonl(0x80c80006);
	theSRWriter += 7; //number of UInt32s in an SR.
	
	//SDES length is the length of the CName, plus 2 32bit words, plus the 32bit word for the SSRC
	*theSRWriter = htonl(0x81ca0000 + (cNameLen >> 2) + 1);
	::memcpy(&fSenderReportBuffer[kSenderReportSizeInBytes], theTempCName, cNameLen);
	fSenderReportSize = kSenderReportSizeInBytes + cNameLen;

/*
 SERVER INFO PACKET FORMAT
struct qtss_rtcp_struct
{
	RTCPHeader		header;
	UInt32			ssrc;		// ssrc of rtcp originator
	OSType			name;
	UInt32			senderSSRC;
	SInt16			reserved;
	SInt16			length;		// bytes of data (atoms) / 4
	// qtsi_rtcp_atom structures follow
};
*/

	//
	// Write the SERVER INFO APP packet
	UInt32* theAckInfoWriter = (UInt32*)&fSenderReportBuffer[fSenderReportSize];
	*theAckInfoWriter = htonl(0x81cc0006);
	theAckInfoWriter += 2;
	*(theAckInfoWriter++) = htonl(FOUR_CHARS_TO_INT('q', 't', 's', 'i')); // Ack Info APP name
	theAckInfoWriter++; // leave space for the ssrc (again)
	*(theAckInfoWriter++) = htonl(2); // 2 UInt32s for the 'at' field
	*(theAckInfoWriter++) = htonl(FOUR_CHARS_TO_INT( 'a', 't', 0, 4 ));
	fSenderReportWithServerInfoSize = (char*)(theAckInfoWriter+1) - fSenderReportBuffer;	
	
	UInt32* theByeWriter = (UInt32*)&fSenderReportBuffer[fSenderReportWithServerInfoSize];
	*theByeWriter = htonl(0x81cb0001);
}

UInt32 RTCPSRPacket::GetACName(char* ioCNameBuffer)
{
	static char*	sCNameBase = "QTSS";

	//clear out the whole buffer
	::memset(ioCNameBuffer, 0, kMaxCNameLen);
	
	//cName identifier
	ioCNameBuffer[0] = 1;
	
	//Unique cname is constructed from the base name and the current time
	::sprintf(&ioCNameBuffer[1], " %s%"_64BITARG_"d", sCNameBase, OS::Milliseconds() / 1000);
	UInt32 cNameLen = ::strlen(ioCNameBuffer);
	//2nd byte of CName should be length
	ioCNameBuffer[1] = cNameLen - 2;//don't count indicator or length byte

	// This function assumes that the cName is the only item in this SDES chunk
	// (see RTP rfc for details).
	// The RFC says that the item (the cName) should not be NULL terminated, but
	// the chunk *must* be NULL terminated. And padded to a 32-bit boundary.
	//
	// ::sprintf already put a NULL terminator in the cName buffer. So all we have to
	// do is pad out to the boundary.
	cNameLen += 1; //add on the NULL character
	UInt32 paddedLength = cNameLen + (4 - (cNameLen % 4));
	
	// Pad, and zero out as we pad.
	for (; cNameLen < paddedLength; cNameLen++)
		ioCNameBuffer[cNameLen] = '\0';
	
	Assert((cNameLen % 4) == 0);
	return cNameLen;
}