Working With Private TIFF Tags

#define MY_SUBIFDTAG 0xFFFE 
L_UINT GetSubIFDOffset(LFile * pLeadFile) 
{ 
   L_UINT uTags; 
   pLEADFILETAG pTags; 
   L_INT nRet = pLeadFile->ReadTags(READFILEMETADATA_NOMEMORY, &uTags, &pTags, NULL, NULL, NULL); 
   if(nRet != SUCCESS) 
      return 0; 
   L_UINT u; 
   // find the new tag 
   for(u = 0; u < uTags; u++) 
   { 
      if(pTags[u].uTag == MY_SUBIFDTAG) 
         break; 
   } 
   if(u >= uTags) 
   { 
      pLeadFile->FreeTags(uTags, pTags, 0, NULL); 
      return 0; 
   } 
   L_UINT uOffset = (L_UINT)pTags[u].uDataOffset; 
   // I don't need the tags anymore 
   pLeadFile->FreeTags(uTags, pTags, 0, NULL); 
   return uOffset; 
} 
L_INT CreateSubIFD(L_TCHAR *pszFileName) 
{ 
   LFile LeadFile; 
   SAVEFILEOPTION SaveFileOption; 
   L_INT nRet; 
   LeadFile.SetFileName(pszFileName); 
   // get the SubIFD offset, if it exists 
   L_UINT uSubIFD = GetSubIFDOffset(&LeadFile); 
   if(uSubIFD == 0) 
   { 
      // the SubIFD does not exist, write it 
      // allocate an array of 6 bytes and set them all to 0 
#define TAG_COUNT    2        // since we will be writing two tags 
#define TAG_SIZE     12       // the number of bytes in one tag 
#define PRIVATETAG_1 0x8003   // use private tags, because LEADTOOLS will reject attempts to write tags below 0x8000 
#define PRIVATETAG_2 0x8004   // use private tags, because LEADTOOLS will reject attempts to write tags below 0x8000 
      L_UINT uIFDSize = 6 + TAG_COUNT * TAG_SIZE; 
      L_UINT16 *pIFD = (L_UINT16 *)malloc(uIFDSize); 
      if(!pIFD) 
         return ERROR_NO_MEMORY; 
      memset(pIFD, 0, uIFDSize); 
      // build the IFD: set the number of tags in the IFD 
      pIFD[0] = TAG_COUNT; 
      // and set dummy placeholders for each tag as follows: pIFD[1 + (TAG_SIZE / 2) * tag_index] = tag value 
      pIFD[1 + (TAG_SIZE / 2) * 0] = PRIVATETAG_1; 
      pIFD[1 + (TAG_SIZE / 2) * 1] = PRIVATETAG_2; 
      // write the tag as UNDEFINED 
      nRet = LFileSettings::SetTag(MY_SUBIFDTAG, TAG_UNDEFINED, uIFDSize, pIFD); 
      if(nRet != SUCCESS) 
         return nRet; 
      // write the SubIFD in the file 
      nRet = LeadFile.WriteTag(NULL); 
      if(nRet != SUCCESS) 
         return nRet; 
      // clear MY_TAG from the internal tag list. I don't need to write it anymore 
      nRet = LFileSettings::SetTag(MY_SUBIFDTAG, 0, 0, NULL); 
      if(nRet != SUCCESS) 
         return nRet; 
      // get the SubIFD offset. It should be > 0 now 
      uSubIFD = GetSubIFDOffset(&LeadFile); 
      if(uSubIFD == 0) 
         return FAILURE; 
   } 
   LBaseFile::GetDefaultSaveFileOption(&SaveFileOption, sizeof(SAVEFILEOPTION)); 
   SaveFileOption.Flags |= ESO_USEIFD; 
   SaveFileOption.IFD = (L_UINT)uSubIFD; 
   // write the private tags 
   // set private tags 1 and 2 
   L_UINT uValue = 5; 
   LFileSettings::SetTag(PRIVATETAG_1, TAG_LONG, 1, &uValue); 
   LFileSettings::SetTag(PRIVATETAG_2, TAG_ASCII, 10, "My String"); 
   // write the private tags into the SubIFD 
   nRet = LeadFile.WriteTag(&SaveFileOption); 
   if(nRet != SUCCESS) 
      return nRet; 
   LOADFILEOPTION LoadFileOption; 
   LBaseFile::GetDefaultLoadFileOption(&LoadFileOption, sizeof(LoadFileOption)); 
   LoadFileOption.Flags |= ESO_USEIFD; 
   LoadFileOption.IFD = SaveFileOption.IFD; 
   // read private tag 1 from SubIFD 
   L_UINT16 uType; 
   L_UINT uCount; 
   nRet = LeadFile.ReadTag(PRIVATETAG_1, &uType, &uCount, NULL, &LoadFileOption); 
   if(nRet == 4 && uType == TAG_LONG && uCount == 1) 
   { 
      LBuffer * pLeadBuffer = new LBuffer(sizeof(L_UINT)); 
      nRet = LeadFile.ReadTag(PRIVATETAG_1, &uType, &uCount, pLeadBuffer, &LoadFileOption); 
      L_UINT * pBuffer = (L_UINT *)pLeadBuffer->Lock(); 
      assert(*pBuffer == 5); 
      pLeadBuffer->Unlock(); 
      delete pLeadBuffer; 
   } 
   // read private tag 2 from SubIFD 
   nRet = LeadFile.ReadTag(PRIVATETAG_2, &uType, &uCount, NULL, &LoadFileOption); 
   if(nRet > 0 && uType == TAG_ASCII && uCount >= 9) 
   { 
      LBuffer * pLeadBuffer = new LBuffer(sizeof(char) * 10); 
      nRet = LeadFile.ReadTag(PRIVATETAG_2, &uType, &uCount, pLeadBuffer, &LoadFileOption); 
      delete pLeadBuffer; 
   } 
   return SUCCESS; 
}