www.pudn.com > DriveRescuev1.8.zip > filedet.pas
// file detection unit
unit filedet;
interface
const
{ file data types }
data_unknown = 1;
data_stream = 2;
function IsFile(abuf: pointer; bufsize: longword; var fileext: string; var datatype: byte): boolean;
implementation
uses common, helpers, sysutils;
function IsFile(abuf: pointer; bufsize: longword; var fileext: string; var datatype: byte): boolean;
var
CRC: word;
procedure crc16_addbits(bitstring: longword; len: byte);
const
polynomial = $8005;
var
bitmask: longword;
begin
bitmask:=1 SHL (len-1);
repeat
if (NOT(crc AND $8000)) XOR (NOT(bitstring AND bitmask)) > 0 then
begin
crc:=crc SHL 1;
crc:=crc XOR polynomial;
end else crc:=crc SHL 1;
bitmask := bitmask SHR 1;
until (bitmask = 0);
end;
const
BitRates: array[0..5, 0..15] of word=
{ Version 2 and V2.5: L3,L2,L1 }
((0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,0),
(0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96,112,128,144,160,0),
(0, 32, 48, 56, 64, 80, 96,112,128,144,160,176,192,224,256,0),
{ Version 1: L3,L2,L1 }
(0, 32, 40, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,0),
(0, 32, 48, 56, 64, 80, 96,112,128,160,192,224,256,320,384,0),
(0, 32, 64, 96,128,160,192,224,256,288,320,352,384,416,448,0));
// Sampling rate frequency index (values are in Hz)
// for MPEG2.5, Reserved, MPEG2, MPEG1
SampleRates: array[0..3, 0..3] of word =
((11025, 12000, 8000, 0),
( 0, 0, 0, 0),
(22050, 24000, 16000, 0),
(44100, 48000, 32000, 0));
// MPEG Audio version IDs
MPEGIDVer25 = 0;
MPEGIDReserved = 1;
MPEGIDVer2 = 2;
MPEGIDVer1 = 3;
// Layer descriptions
LayerReserved = 0;
LayerIII = 1;
LayerII = 2;
LayerI = 3;
ChannelStereo = 0;
ChannelJointStereo = 1;
ChannelDual = 2;
ChannelSingle = 3;
var
buf: pbytearray;
bufpos: pbytearray;
maxbufpos: pbytearray;
i, j, row: integer;
framecount: integer;
hdr: longword;
MPEGAudioVer: byte;
Layer : byte;
ChannelMode : byte;
SampleRate : word;
Padding : byte;
BitRateIdx, SampleRateIdx: byte;
BitRate : word;
CRCProtected: boolean;
MPEG_CRC: word;
Emphasis : byte;
FrameLengthInBytes: word;
invalid: boolean;
s: shortstring;
recordno: word;
vers: byte;
recorddata: pbytearray;
label fin;
begin
result:=FALSE; datatype:=data_unknown;
try
longword(buf):=longword(abuf);
// -------------------- BINARY coded files ------------------------------------
// check for JPG...
{ SOI = Start Of Image = 'FFD8' This marker must be present in any JPG file *once* at the beginning of the file. (Any JPG file starts with the sequence FFD8.)
EOI = End Of Image = 'FFD9' Similar to EOI: any JPG file ends with FFD9. }
if (buf^[0] = $FF) AND (buf^[1]=$D8) then
begin
result:=TRUE; fileext:='JPG';
goto fin;
end;
// check for MS-WORD...
(* // Word's File-Information-Block (FIB) structure...
typedef struct _fib {
short magicNumber;
// Word 6.0: 0xA5DC
// Word 7.0 (95): 0xA5DC
// Word 8.0 (97): 0xA5EC
short version; // >= 101 for Word 6.0 and higher...
// Word 6.0: 101
// Word 7.0 (95): 104
// Word 8.0 (97): 105
} FIB, *LPFIB; *)
if (pword(@buf^[0])^ = $A5DC)
OR (pword(@buf^[0])^ = $A5DB)
OR (pword(@buf^[0])^ = $A5EC)
OR ((buf^[0] = $D0) AND (buf^[1]= $CF) AND (buf^[2]=$11) AND (buf^[3]=$E0)) then
begin
result:=TRUE; fileext:='DOC';
goto fin;
end;
// check for BIFF...
recordno:=pword(@buf^[0])^;
if (recordno AND $00FF) = $0009 then // BOF record (Beginning of file) ?
begin
vers:=recordno SHR 8;
if (vers = $04) OR (vers = $02) OR (vers = $00) OR (vers = $08) then // BIFF 3,4,5,7,8 ?
begin
result:=TRUE; fileext:='XLS'; // BIFF => XLS file
goto fin;
end;
end;
// check for BMP...
if (buf^[0] = $42) AND (buf^[1]= $4D) then // the header is "BM"
begin
result:=TRUE; fileext:='BMP';
goto fin;
end;
// check for GIF...
if (buf^[0] = $47) AND (buf^[1]= $49) AND (buf^[2]=$46) AND (buf^[3]=$38)
AND ((buf^[4]=$39) OR (buf^[4]=$37)) AND (buf^[4]=$61) then // the header is "GIF89a" or "GIF87a"
begin
result:=TRUE; fileext:='BMP';
goto fin;
end;
// check for TIFF...
if ((buf^[0] = $49) AND (buf^[1]= $49))
OR ((buf^[0]=$4D) AND (buf^[1]=$4D)) then // the header is "4949" or "4D4D"
begin
result:=TRUE; fileext:='TIF';
goto fin;
end;
// check for PNG...
// magic: 137 80 78 71 13 10 26 10
if (buf^[0] = 137) AND (buf^[1]= 80) AND (buf^[2]=78) AND (buf^[3]=71)
AND (buf^[4]=13) AND (buf^[5]=10) AND (buf^[6]=26) AND (buf^[7]=10) then
begin
result:=TRUE; fileext:='PNG';
goto fin;
end;
// check for RIFF...
if IsDataEqual(@buf^[0], 'RIFF') then // RIFF ID
begin
// RIFF file found...
// check for CDR...
if IsDataEqual(@buf^[8], 'CDR') then // the format is "CDR"
begin
result:=TRUE; fileext:='CDR';
goto fin;
end;
// check for WAVE...
if IsDataEqual(@buf^[8], 'WAVE') then // the format is "WAVE"
begin
result:=TRUE; fileext:='WAV';
goto fin;
end;
// check for AVI...
if IsDataEqual(@buf^[8], 'AVI ') then // the format is "AVI "
begin
result:=TRUE; fileext:='AVI';
goto fin;
end;
// else unknown RIFF...
result:=TRUE; fileext:='RIFF';
goto fin;
end;
// check for EXE...
if (buf^[0] = $4D) AND (buf^[1]= $5A) then // the header is "MZ"
begin
result:=TRUE; fileext:='EXE';
goto fin;
end;
// check for DBF...
if ((buf^[0] = $03) OR (buf^[0]= $83) OR (buf^[0]= $F5) OR (buf^[0]= $8B) OR (buf^[0]= $8E)) // dBase/FoxBase/FoxPro ?
AND (buf^[12] = 0) AND (buf^[13] = 0) // res=0 ?
AND (buf^[30] = 0) AND (buf^[31] = 0) then // res=0 ?
begin
result:=TRUE; fileext:='DBF';
goto fin;
end;
// check for HLP...
if plong(@buf^[0])^ = $00035f3f then // the magic is 0x00035f3f
begin
result:=TRUE; fileext:='HLP';
goto fin;
end;
// check for TAR...
if IsDataEqual(@buf^[257], 'ustar'+#0) then // the magic is "ustar"+0
begin
result:=TRUE; fileext:='TAR';
goto fin;
end;
// check for LZH...
if IsDataEqual(@buf^[2], '-lh') OR IsDataEqual(@buf^[2], '-lz') then // the magic is "-lh" or "-lz"
begin
result:=TRUE; fileext:='LZH';
goto fin;
end;
// check for ZIP...
if plong(@buf^[0])^ = $04034b50 then // the local file header is (0x04034b50)
begin
result:=TRUE; fileext:='ZIP';
goto fin;
end;
// check for ARJ...
if pword(@buf^[0])^ = $EA60 then // ARJ ID=EA60h
begin
result:=TRUE; fileext:='ARJ';
goto fin;
end;
// check for RAR...
// The marker block is actually considered as a fixed byte
// sequence: 0x52 0x61 0x72 0x21 0x1a 0x07 0x00
if (buf^[0] = $52) AND (buf^[1]= $61) AND (buf^[2]=$72) AND (buf^[3]=$21)
AND (buf^[4]=$1a) AND (buf^[5]=$07) AND (buf^[6]=$00) then
begin
result:=TRUE; fileext:='RAR';
goto fin;
end;
// check for PDF...
// The first line of a PDF file specifies the version number of the PDF specification to
// which the file adheres. The current version is 1.2; the first line of a 1.2-conforming
// PDF file should be %PDF-1.2. However, 1.0-conforming files and 1.1-
// conforming files are also 1.2-conforming files, so an application that understands
// PDF 1.2 also accepts a file that begins with either %PDF-1.1 or %PDF-1.0.
if (buf^[0] = $25) AND (buf^[1]= $50) AND (buf^[2]=$44) AND (buf^[3]=$46)
AND (buf^[4]=$2D) AND (buf^[5]=$31) AND (buf^[6]=$2E)
AND ((buf^[7]=$32) OR (buf^[7]=$31) OR (buf^[7]=$30)) then
begin
result:=TRUE; fileext:='PDF';
goto fin;
end;
// check for MIDI...
if IsDataEqual(@buf^[0], 'MThd') then // head chunk
begin
result:=TRUE; fileext:='MID';
goto fin;
end;
// check for QuickTime MOV...
if IsDataEqual(@buf^[4], 'moov') then // is basic atom type?
begin
result:=TRUE; fileext:='MOV';
goto fin;
end;
// -------------------- TEXT coded files ------------------------------------
// check for HTML...
i:=0;
while (i < bufsize-6) do
begin
if IsDataEqual(@buf^[i], '') then // HTML Tag found?
begin
result:=TRUE; fileext:='HTML';
goto fin;
end;
inc(i);
end;
longword(bufpos):=longword(buf);
maxbufpos:=pointer(longword(bufpos) + 32);
repeat
s:=GetNextTextLine(pointer(bufpos), pointer(maxbufpos));
// check for DXF...
// (find entries 0, SECTION, 2, HEADER)
if pos('0', s) <> 0 then
begin
s:=GetNextTextLine(pointer(bufpos), pointer(maxbufpos));
if s = 'SECTION' then
begin
s:=GetNextTextLine(pointer(bufpos), pointer(maxbufpos));
if pos('2', s) <> 0 then
begin
s:=GetNextTextLine(pointer(bufpos), pointer(maxbufpos));
if s = 'HEADER' then
begin
result:=TRUE; fileext:='DXF';
goto fin;
end;
end;
end;
end
// check for RTF...
else if pos('{\rtf', s) <> 0 then
begin
result:=TRUE; fileext:='RTF';
goto fin;
end;
until (s ='');
// check for MPEG...
{ Remember, this is not enough, frame sync can be easily (and very frequently) found in any binary file.
Also it is likely that MPEG file contains garbage on it's beginning which also may contain false sync.
Thus, you have to check two or more frames in a row to assure you are really dealing with MPEG audio file }
framecount:=0;
i:=0;
while i < bufsize-4 do
begin
if (buf^[i]=$FF) AND (buf^[i+1] AND $E0=$E0) then
begin
// sync found...
invalid:=TRUE;
hdr:=plong(@buf^[i])^;
MPEGAudioVer :=(buf^[i+1] SHR 3) AND 3;
if MPEGAudioVer <> MPEGIDReserved then
begin
Layer :=(buf^[i+1] SHR 1) AND 3;
if Layer <> LayerReserved then
begin
CRCProtected :=boolean((buf^[i+1]) AND 1);
BitRateIdx :=(buf^[i+2] SHR 4) AND $F;
if (BitRateIdx <> $F) AND (BitRateIdx <> 0) then
begin
case MPEGAudioVer of
MPEGIDVer25, MPEGIDVer2: row := 0;
MPEGIDVer1 : row := 3;
end;
BitRate:=BitRates[row + (Layer-1), BitRateIdx];
SampleRateIdx:=(buf^[i+2] SHR 2) AND 3;
if SampleRateIdx <> 3 then
begin
row:=MPEGAudioVer;
SampleRate:=SampleRates[row, SampleRateIdx];
Padding :=((buf^[i+2]) SHR 1) AND 1;
ChannelMode:=(buf^[i+3] SHR 6) AND 3;
Emphasis:=(buf^[i+3] AND 3);
if Emphasis <> 2 then
begin
// calculate frame lenth (length of compressed frame)...
if Layer = LayerI then
FrameLengthInBytes := (12 * BitRate*1000 div SampleRate + Padding) * 4
else if Layer IN [LayerII, LayerIII] then
FrameLengthInBytes := 144 * BitRate*1000 div SampleRate + Padding;
if FrameLengthInBytes >= 32 then
begin
if CRCProtected then
begin
MPEG_CRC:=pword(@buf^[i+4])^;
if MPEG_CRC <> 0 then
begin
// check CRC...
crc:=0;
for j:=i+4 to i+FrameLengthInBytes -1 do
begin
crc16_addbits(buf^[j], 8);
end;
if (CRC >= MPEG_CRC-8) AND (CRC <= MPEG_CRC+8) then invalid:=FALSE;
end else invalid:=FALSE;
end else invalid:=FALSE;
end;
end;
end;
end;
end;
end;
if invalid then
begin
inc(i);
framecount:=0; // reset frame count to zero
break;
end else
begin
// MP3 header is valid...
inc(i, FrameLengthInBytes);
inc(framecount);
end
end else inc(i);
end;
if (framecount >= bufsize DIV 512) then
begin
result:=TRUE; fileext:='MP3'; datatype:=data_stream;
goto fin;
end;
fin:
except
on E : Exception do
begin
result:=FALSE;
end;
end;
end;
end.