/*
 *              TTerminal::prevLines()
 *
 *              Rewritten on C++ by Ilfak Guilfanov
 *                      26.06.95
 *
 */

#define Uses_TTerminal
#include <tv.h>

#define DECPTR                          \
{                                       \
  if ( ptr <= buffer ) ptr += bufSize;  \
  ptr--;                                \
}

#define INCPTR                          \
{                                       \
  ptr++;                                \
  if ( ptr >= buffer+bufSize ) ptr = buffer; \
}

//------------------------------------------------------------------------
size_t TV_CDECL TTerminal::prevLines( size_t pos, int lines ) {
  char *ptr = buffer + pos;
  if ( lines != 0 ) {
    if ( buffer+queBack == ptr ) return queBack;
    DECPTR
    while ( 1 ) {
//loop:
      int counter;
      if ( ptr <= buffer+queBack )
        counter = ptr - buffer;
      else
        counter = ptr - (buffer+queBack);
      counter++;
      while ( 1 ) {
        if ( *ptr-- == '\n' ) {
          lines--;
          if ( lines == 0 ) goto ret;
          break;
        }
        counter--;
        if ( counter == 0 ) {
          if ( ptr-buffer+1 == queBack ) return queBack;
          ptr = buffer + bufSize;
          break;
        }
      }
    }
  }
ret:
  INCPTR
  INCPTR
  return ptr-buffer;
}