one of example read line for NSFileHandle

gistfile1.m

@interface NSFileHandle (fhreadline)
-(NSString*)readLine;
@end

@implementation NSFileHandle (fhreadline)

-(NSString*)readLine
{
  unsigned long long pos = [self offsetInFile];
    
  NSMutableData *r = [NSMutableData data];
  const char *buf = NULL;
  int p = 0;
  char ch = 0;
    
  for(int rlen = 32 ; rlen ; rlen *= 2)
  {
    NSData *d = [self readDataOfLength:rlen];
    if(!d) return nil;
    int dlen = d.length;
    if(!p && !dlen) return nil;
        
    [r appendData:d];
    if(dlen < rlen) [r appendBytes:"\r\n" length:2];
        
    buf = r.bytes;
    for(; p < r.length-1 ; p++)
    {
      ch = buf[p];
      if(ch == 0x0d || ch == 0x0a)
      {
        rlen = 0;
        break;
      }
    }
  }
    
  NSString *rs = [[NSString alloc] initWithData:[r subdataWithRange:NSMakeRange(0, p)] encoding:NSUTF8StringEncoding];
    
  p++;
  if(ch == 0x0d && buf && buf[p] == 0x0a) p++;	// LF skip (for CR+LF)
  [self seekToFileOffset:pos+p];                  // dont worry overseek
    
  return rs;
}