Revision as of 16:22, 20 January 2024

The /bcopy command can be used to copy any amount of bytes from one variable starting at a specific position into a second variable at a specific position. This command supports copying of overlapping buffers.

If the number of bytes to copy is -1, all bytes available will be copied over to the destination variable. If the destination position is -1, the bytes will be appended.

Note: The first byte starts at the position/index 1, 0 is invalid and will produce an error. Note: Bytes between prior end of <&dest_binvar> and <dest_pos> are zero-filled with $chr(0)

Synopsis

/bcopy [-zc] <&dest_binvar> <dest_pos> <&src_binvar> <src_pos> <numBytes>

Switches

• -z - Bytes in the source which are copied are zero-filled with $chr(0) after the copy
• -c - Truncates the destination variable to remove bytes following the bytes copied. Where both N and M are positive, the new destination length is <des_pos> + <numBytes> -1

Parameters

• <dest_&binvar> - The destination binary variable. Source and destination can be the same variable.
• <dest_pos> - The position to which to copy the byte to (or -1 to append to destination).
• <&src_binvar> - The source binary variable.
• <src_pos> - The position from which to start copying bytes.
• <numBytes> - Number of bytes to copy beginning at <src_pos> (or -1 for everything beginning at <src_pos>).

Example

Alias Example {
  ; Create a binary variable 'example' and assign it some text
  bset -t &example 1 This is a cool test!
 
  ; Copy from '&example' all bytes from the 11th byte onward to a new variable
  ; Zero-fills the source variable's bytes which were copied to the destination
  bcopy -z &example2 1 &example 11 999
 
  ; Print out &example's content (up to the first null)
  echo -a $bvar(&example, 1-).text
  ; Print out &example's content as byte values including the nulls
  echo -a $bvar(&example, 1-)
 
  ; Print out &example2's content
  echo -a $bvar(&example2, 1-).text
}

The above example will output:

This is a
84 104 105 115 32 105 115 32 97 32 0 0 0 0 0 0 0 0 0 0
cool test!

;while these variables exist:
//bset &to 1 11 22 33 44 55 66 | bset &from 1 77 88 99 123
and &to contains "11 22 33 44 55 66" and &to contains "77 88 99 123"
each of the following commands are based on the above values and are not executed after any of the other following alternatives...
 
bcopy &to 2 &from 1 3
; copies 3 bytes at position 1 of &from to overwrite the 3 bytes at position 2 of &to. Length remains 6
11 77 88 99 55 66
 
bcopy -z &to 2 &from 1 3
; same alteration of &to, but all byte positions in &from which were copied are changed to 0x00's. &to is changed to the same 6 bytes as above, but now &from is altered to become "0 0 0 123"
 
bcopy -c &to 2 &from 1 3
; adding the -c switch causes any destination bytes following the copied bytes to be removed, shortening &to to length 4
11 77 88 99
bcopy -c &to 2 &from 1 0
; does not generate an error, but does not truncate the destination because 0 bytes were copied
11 22 33 44 55 66
 
bcopy &to 2 &from 1 99
; M is larger than bytes available beginning at position 1 of &from, so the 4 bytes are copied to destination positions 2-5 without affecting the destination's 6th byte.
11 77 88 99 0 66
 
bcopy &to -1 &from 1 -1
; Destination position -1 causes bytes to be appended. Using -1 as number of bytes to copy copies the entire &from string beginning at position 1.
11 22 33 44 55 66 77 88 99 123
 
bcopy -c &to 1 &to 2 999
; entirely within the &to variable, copies positions 2-6 to 1-5 and chops length past the last byte copied into. Without the -c switch, the length would still be 6 with the 66 repeated.
22 33 44 55 66
 
bcopy &to -1 &to 1 999
; appends the 6 bytes, doubling the length to 12
11 22 33 44 55 66 11 22 33 44 55 66
 
bcopy -c &to 2 &to 1 999
; places the old contents of positions 1-6 into positions 2-7. The bytes are not update after each byte, so does not cause 11 to be replicated in each position.
11 11 22 33 44 55 66
 
bcopy -c &to 3 &to 3 1
; truncates a variable to length 3

Binary variables can be longer than the length which can be displayed on a mIRC line. This alias creates a 7mb variable containing all $chr(1) bytes:

/fill_with_ones 7654321
 
fill_with_ones {
  if ($1 !isnum 1-) return
  bset &var 1 1
  while ($1 > $bvar(&var,0)) {
  bcopy &var -1 &var 1 $iif($calc($1 - $bvar(&var,0)) > $bvar(&var,0),$v2,$v1)
  echo -a current length: $bvar(&var,0)
  }
  echo -a variable length is $bvar(&var,0)
}

Compatibility

Added: mIRC v5.7
Added on: 02 Feb 2000
Note: Unless otherwise stated, this was the date of original functionality.
Further enhancements may have been made in later versions.

See also

• List of commands
• List of identifiers
• $bvar
• $bfind
• /bread
• /breplace
• /bset
• /btrunc
• /bunset
• /bwrite