yagsdisasm/Input/Input_2MG.php

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2016-05-26 03:34:19 +00:00
<?php
/**
* Input_2MG - YAGSDisasm Input block device for .2MG image files
* from http://apple2.org.za/gswv/a2zine/Docs/DiskImage_2MG_Info.txt
*
*/
class Input_2MG
{
// have we been initialized yet?
private $is_initialized = false;
// source filename
private $source_filename;
// creator_id
private $creator_id;
// 2mg comment
private $comment = '';
// number of 512-byte blocks in image
private $total_blocks;
// header length
private $header_length;
// version number
private $version_number;
// image format
private $image_format;
// disk is locked?
private $is_locked=false;
// offset to image data
private $image_offset;
// DOS 3.3 Volume Number
private $volume_number;
// volume length in bytes
private $total_bytes;
// offset to comment
private $comment_offset;
// length of comment
private $comment_length;
// 2MG Creator data offset
private $creator_data_offset;
// 2MG Creator data length
private $creator_data_length;
// our file descriptor
private $fp;
public function __construct( $filename )
{
$fp = fopen( $filename, 'r' );
if( !$fp )
{
throw new Exception( 'Input_2MG: Unable to open source file '.$filename );
}
$this->source_filename = $filename;
// check for 2MG magic
$magic = fread( $fp, 4 );
if( $magic != '2IMG' )
{
throw new Exception( 'Input_2MG: source file not a 2MG file' );
}
// save creator id
$this->creator_id = fread( $fp, 4 );
// get header length (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$this->header_length = (ord( $byte2 )*256) + ord( $byte1 );
// get version number (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$this->version_number = (ord( $byte2 )*256) + ord( $byte1 );
// get image format (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$image_format_id = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
$known_format_ids = array(
0 => 'DOS 3.3',
1 => 'ProDOS',
2 => 'NIB',
);
$this->image_format = $known_format_ids[$image_format_id];
// flags / volume number (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
if( ord( $byte2 ) && 0x01 )
{
$this->volume_number = ord( $byte1 );
} else {
if( $image_format_id == 1 )
{
$this->volume_number = 254;
}
}
if( ord( $byte4 ) && 0x80 )
{
$this->is_locked = true;
} else {
$this->is_locked = false;
}
// block count (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->total_blocks = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// offset to image data (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->image_offset = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// bytes of disk data (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->total_bytes = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// offset to comment (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->comment_offset = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// comment length (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->comment_length = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// creator data offset (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->creator_data_offset = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// creator data length (little-endian)
$byte1 = fread( $fp, 1 );
$byte2 = fread( $fp, 1 );
$byte3 = fread( $fp, 1 );
$byte4 = fread( $fp, 1 );
$this->creator_data_length = (ord( $byte4 )*16777216) + (ord( $byte3 )*65536) + (ord( $byte2 )*256) + ord( $byte1 );
// reserved bytes
$reserved = fread( $fp, 8 );
// get Comment string if present
if( $this->comment_length > 0 )
{
fseek( $fp, $this->comment_offset, SEEK_SET );
$this->comment = fread( $fp, $this->comment_length );
}
$this->is_initialized = true;
$this->fp = $fp;
}
/**
* getBlocks( $starting_block, $num_blocks ) - Retrieve $num_blocks 512-byte blocks from the file, starting at $starting_block
* @param $starting_block int, $num_blocks int
* @return $data str
*/
public function getBlocks( $starting_block, $num_blocks )
{
fseek( $this->fp, $this->image_offset, SEEK_SET );
fseek( $this->fp, $starting_block*512, SEEK_CUR );
$data = '';
for( $blk=0;$blk<$num_blocks;$blk++ )
{
$data .= fread( $this->fp, 512 );
}
return $data;
}
/**
* printInfo() - Print some information about this 2MG image
*/
public function printInfo()
{
echo "Source Filename: ".$this->source_filename."\n";
echo " Creator ID: ".$this->creator_id."\n";
echo " Header Length: ".$this->header_length."\n";
echo " Version Number: ".$this->version_number."\n";
echo " Image Format: ".$this->image_format."\n";
if( $this->image_format == 'DOS 3.3' )
{
echo " Volume Number: ".$this->volume_number."\n";
}
echo " Is Locked? ";
if( $this->is_locked )
{
echo "Yes\n";
} else {
echo "No\n";
}
echo " Block Count: ".$this->total_blocks."\n";
echo " Total Bytes: ".$this->total_bytes."\n";
if( $this->comment != '' )
{
echo " Comment: ".$this->comment."\n";
}
}
}