Parsing SWF file header and tag Structure

Unit unit1;
Interface
Uses
Windows, messages, sysutils, variants, classes, graphics, controls, forms,
Dialogs, stdctrls, comctrls;
Type
Tform1 = Class (tform)
Edit1: tedit;
Button1: tbutton;
Opendialog1: topendialog;
Edit2: tedit;
Edit3: tedit;
Edit4: tedit;
Edit5: tedit;
Edit6: tedit;
Edit7: tedit;
Edit8: tedit;
Listview1: tlistview;
Button2: tbutton;
Edit9: tedit;
Procedure button1click (Sender: tobject );
Procedure button2click (Sender: tobject );
Private
{Private Declarations}
Public
{Public declarations}
End;
VaR
Form1: tform1;
Implementation
{$ R *. DFM}
Type tbuff = record
F: byte;
W: byte;
S: byte;
Version: byte;
File_length: Cardinal;
End;
VaR Buff: tbuff;
DT: array of byte;
Procedure tform1.button1click (Sender: tobject );
VaR
Filename: string;
Fileid: Cardinal;
Fileinfo: ofstruct;
Nbits: integer;
Vbitpos: integer;
Vbyte: integer;
Nbytesread: Cardinal;
Xmin, xmax, ymin, Ymax: longword;
ID, length, _ from, _ to: word;
_ Tlist: tlistitem;
Function getbitval: longword;
VaR vvsam: longword;
Begin
Vvsam: = dt [vbyte] * $1000000 + dt [vbyte + 1] * $10000 + dt [vbyte + 2] * $100 + dt [vbyte + 3]; // fetch number
Result: = longword (vvsam SHL vbitpos) SHR (32-nbits); // shift value
INC (vbitpos, nbits); // shift
INC (vbyte, vbitpos Div 8); // shift byte to new byte
Vbitpos: = vbitpos mod 8; // set a new bit
End;
Begin
If opendialog1.execute then
Filename: = opendialog1.filename;
Fileid: = openfile (pchar (filename), fileinfo, of_read );
Readfile (fileid, buff, 8, nbytesread, nil );
Setlength (DT, Buff. file_length );
Readfile (fileid, DT [0], Buff. file_length, nbytesread, nil); // eight bytes have been read into the buff, not included in DT
Setlength (DT, nbytesread );
Edit1.text: = 'f = '+ inttostr (buff. F );
Edit2.text: = 'W = '+ inttostr (buff. W );
Edit3.text: ='s = '+ inttostr (buff. s );
Edit4.text: = 'version = '+ inttostr (buff. version );
Edit5.text: = 'file _ length = '+ inttostr (buff. file_length );
Nbits: = byte (dt [0] SHR 3 );
Edit8.text: = 'nbits = '+ inttostr (nbits );
Vbyte: = 0;
Vbitpos: = 5;
Xmin: = getbitval;
Xmax: = getbitval Div 20;
Ymin: = getbitval;
Ymax: = getbitval Div 20;
Edit9.text: = ('xmin = '+ inttostr (xmin) +', '+
'Xmax = '+ inttostr (xmax) +', '+
'Ymin = '+ inttostr (ymin) +', '+
'Ymax = '+ inttostr (Ymax ));
If vbitpos> 0 then Inc (vbyte );
Edit6.text: = 'rate = '+ inttostr (dt [vbyte + 1]);
Edit7.text: = 'count = '+ inttostr (Word (@ dt [vbyte + 2]) ^ ));
// ------------------------------------------------------------------------- SWF File Header
_ From: = vbyte + 4;
While (_ from <= nBytesRead-1) Do begin
_ Tlist: = listview1.items. Add; // generate an object. Only objects that exist can be assigned a value.
ID: = word (@ dt [_ from]) ^ );
Length: = ID and $ 3f;
If length = $ 3f then length: = longword (@ dt [_ from + 2]) ^) + 4;
INC (length, 2 );
ID: = id shr 6;
_ To: = _ from + length;

_ Tlist. Caption: = inttostr (ID );
_ Tlist. subitems. Add (inttostr (length ));
_ Tlist. subitems. Add (inttostr (_ from ));
_ Tlist. subitems. Add (inttostr (_ ));
_ From: = _;
End;
// ------------------------------------------------------------------------ Tag = Length + tag header (2 or 6 );
End;