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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
    qtss_sprintf(&ioCNameBuffer[1], " %s%"_64BITARG_"d", sCNameBase, OS::Milliseconds() / 1000);
    UInt32 cNameLen = ::strlen(ioCNameBuffer);
    //2nd byte of CName should be length
    ioCNameBuffer[1] = (UInt8) (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.
    //
    // qtss_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;
}