CPU::Z80::Assembler::Opcode - Represents one assembly expression to be computed at link time

CPU-Z80-Assembler documentation Contained in the CPU-Z80-Assembler distribution.

Index

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NAME

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CPU::Z80::Assembler::Opcode - Represents one assembly expression to be computed at link time

SYNOPSIS

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  use CPU::Z80::Assembler::Opcode;
  $opcode = CPU::Z80::Assembler::Opcode->new(
					address => 0,
					line => $line,
					child => [byte, byte, ["type", $expr]]);
  $value = $opcode->evaluate;
  $bytes = $opcode->bytes($address, \%symbol_table);
  $size = $opcode->size;

DESCRIPTION

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This module defines the class that represents one assembly instruction to be added to the object code. The instruction can contain references to CPU::Z80::Assembler::Expr expressions that are computed at link time.

EXPORTS

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Nothing.

FUNCTIONS

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new

Creates a new object.

address

Address where this opcode is loaded, computed at link time.

child

The number of children is the number of bytes stored in the object code for this instruction.

Each child is either a scalar containing the byte value to be added to the object code, or a CPU::Z80::Assembler::Expr expression to be evaluated at link time. In case of a word expression, then a special undef value is used as a placeholder to keep the child list the correct size.

line

Get/set the line - text, file name and line number where the token was read.

evaluate

Called when opcode is referred to by a label, returns the opcode address.

bytes

  $bytes = $opcode->bytes($address, \%symbol_table);

Computes all the expressions in child and returns the bytes string with the result object code.

size

  $size = $opcode->size;

Return the number of bytes that this opcode will generate.

BUGS and FEEDBACK

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See CPU::Z80::Assembler.

SEE ALSO

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CPU::Z80::Assembler Asm::Preproc::Line

AUTHORS, COPYRIGHT and LICENCE

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CPU-Z80-Assembler documentation Contained in the CPU-Z80-Assembler distribution. 
# $Id: Opcode.pm,v 1.10 2010/11/21 16:37:05 Paulo Exp $

package CPU::Z80::Assembler::Opcode;

#------------------------------------------------------------------------------


#------------------------------------------------------------------------------

use strict;
use warnings;

our $VERSION = '2.13';

use Asm::Preproc::Line;

sub new { 
	my($class, %args) = @_;
	bless [
		$args{address}, 					# address where loaded
		$args{line} 	|| Asm::Preproc::Line->new(),
											# line where tokens found
		$args{child} 	|| [], 				# list of children of this node
											# each child is a byte value or an expression
											# to compute the byte(s)
	], $class;
}
sub address { defined($_[1]) ? $_[0][0] = $_[1] : $_[0][0] }
sub line 	{ defined($_[1]) ? $_[0][1] = $_[1] : $_[0][1] }
sub child	{ defined($_[1]) ? $_[0][2] = $_[1] : $_[0][2] }

#------------------------------------------------------------------------------


#------------------------------------------------------------------------------


#------------------------------------------------------------------------------

sub evaluate { my($self) = @_;
	return $self->address;
}

#------------------------------------------------------------------------------


#------------------------------------------------------------------------------

sub bytes { 
	my($self, $address, $symbol_table) = @_;
	
	my $bytes = "";
	for my $expr (@{$self->child}) {
		if (! defined($expr)) {
			# skip undefined values - used as placeholder for the second byte of a word
		}
		elsif (ref($expr)) {
			$bytes .= $expr->bytes($address, $symbol_table);
		}
		else {
			$bytes .= pack("C", $expr & 0xFF);
		}
	}
	return $bytes;
}

#------------------------------------------------------------------------------


#------------------------------------------------------------------------------

sub size { my($self) = @_;
	return scalar(@{$self->child});
}

#------------------------------------------------------------------------------


#------------------------------------------------------------------------------

1;