Modified tail.c - Original by @gesslar

tail.c

#include <driver/runtime_config.h>

// This function is expensive. It is also not compatible with
// old-style efun::tail() as 1) it acceptmp_size a second argument of
// the number of lines, and 2) it returns a string rather than
// printing out the resultmp_size. 
//
// Did some significant changes to how it reads the file data
// and allocates lines for the return data.  Based on my tests
// on a 120k file this reduced the execution time by over 99%.
// Jezu@Astaria 15 April 2021
varargs string tail(string file, int num_lines)
{
    string *lines, *tmp, chunk;
    int size, t1, t2, tmp_size, tmp_size2, lcut, bytes;
    string ret = "";
      
    seteuid( getuid( previous_object() ) );

    if( nullp( file ) ) 
      error("Missing arg 1 to tail()\n");
   
    num_lines = num_lines || 25;
    
    if( num_lines > 100 ) 
      num_lines = 100;

    size = file_size( file );
    if( size < 1 ) 
      return ret;

    bytes = 1000;
    if ( size < bytes )
      bytes = size;
    t1 = bytes;
    
    tmp_size = 0;
    tmp_size2 = 0;
    lines = allocate(num_lines);
    while ( tmp_size != num_lines )
    {
      chunk = read_bytes( file, size-t1, bytes);
      lcut = strsrch(chunk, 10);
      if ( lcut != -1 )
      {
        chunk = chunk[lcut..];
        t1 -= lcut;
      }
      tmp = explode(chunk, "\n");
      
      tmp_size = sizeof(tmp)+tmp_size;
      if ( tmp_size > num_lines )
      {
        tmp = tmp[<(num_lines-tmp_size2)..];
        tmp_size = num_lines;
      }

      lines[<tmp_size..<++tmp_size2] = tmp;
      
      if ( t1 == size )
        break;
        
      tmp_size2 = tmp_size;

      if ( size-t1 < bytes )
      {
        bytes = size-t1;
        t1 = size;
      }
      else
        t1 += bytes;
    }
    
    ret = implode(lines, "\n");
    if ( sizeof(ret) > __LARGEST_PRINTABLE_STRING__ )
      ret = ret[0..__LARGEST_PRINTABLE_STRING__];
      
    return ret;
}