// Read either "dog", "hound", or "hounddog". 
// If "dog" is found, return 1. 
// If "hound" is found, return 2. 
// If "hounddog" is found, return 3. 
// If none of these are found, return -1. 
int my_scan(streambuf* sb) 
{ 
      streammarker fence(sb); 
      char buffer[20]; 
      // Try reading "hounddog": 
      if (sb->sgetn(buffer, 8) == 8 
            && strncmp(buffer, "hounddog", 8) == 0) 
         return 3; 
      // No, no "hounddog": Back up to 'fence' 
      sb->seekmark(fence); // 
      // ... and try reading "dog": 
      if (sb->sgetn(buffer, 3) == 3 
            && strncmp(buffer, "dog", 3) == 0) 
         return 1; 
      // No, no "dog" either: Back up to 'fence' 
      sb->seekmark(fence); // 
      // ... and try reading "hound": 
      if (sb->sgetn(buffer, 5) == 5 
            && strncmp(buffer, "hound", 5) == 0) 
         return 2; 
      // No, no "hound" either: Back up and signal failure. 
      sb->seekmark(fence); // Backup to 'fence' 
      return -1; 
}

Create a streammarker associated with sbuf that remembers the current position of the get pointer.

int streammarker::delta (streammarker& mark2) 
Method

Return the difference between the get positions corresponding to *this and mark2 (which must point into the same streambuffer as this).

int streammarker::delta () 
Method

Return the position relative to the streambuffer’s current get position.

int streambuf::seekmark (streammarker& mark) 
Method

Move the get pointer to where it (logically) was when mark was constructed.