麻烦大家看一下这段代码！(50分)

microwave · 2001-08-26

为什么我用这段代码获取一个mp3文件的最后128字节，什么也得不到？'p' 始终为空！why??? procedure TForm1.Button1Click(Sender: TObject); var   FileHandle,filelength:integer;   P

char; begin         P:=Allocmem(130);         filehandle:=fileopen('01.mp3',fmOpenWrite or fmShareDenyNone);         if filehandle >0 then           begin             filelength:=fileseek(filehandle,0,2);             fileseek(filehandle,filelength-128,0);             fileread(filehandle,p,3);             fileclose(filehandle);             showmessage(p);                         freemem(p);           end         else           showmessage('error:'+pchar(getlasterror)); end;

probor · 2001-08-26

p:改为Pointer试试 检查filelength:=fileseek(filehandle,0,2);     fileseek(filehandle,filelength-128,0);的返回值

Kingron · 2001-08-26

你是要读取ID3信息吧？我有一个类，可以做到。 你的文件指针定位没有那么麻烦：直接用FileSeek(Fhandle,128,2)就可以了。 那个P必须改成p^就可以了。

microwave · 2001-08-26

To Kingron:    给我那个类可不可以？

Kingron · 2001-08-26

严黎斌 unit ID3Kernel; interface type   Tid3v1= record     Tag: array[0..2] of char;      //00..02 , ='TAG'     Title:array[0..$1d] of char;  //03..20     Artist:array[0..$1d] of char;  //21..3e     Album:array[0..$1d] of char;  //3f..5c     Year:array[0..3] of char;      //5d..60     Comment:array[0..$1c] of char; //61..7d     Track:byte;                    //7e     Genre:byte;                    //7f   end; function ReadID3v1(strFile:string;var pid3v1:Tid3v1):integer; function WriteID3v1(strFile:string;var pid3v1:Tid3v1):integer; function DeleteID3v1(strFile:string):integer; implementation function ReadID3v1(strFile:string;var pid3v1:Tid3v1):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;   i: integer; begin   result:=1;   if strFile='' then exit;   AssignFile(f1,strFile);   FileMode:=0;   Reset(f1);   if FileSize(f1)<=$80 then exit;   Seek(f1, FileSize(f1)-$80);   for i:=0 to $7f do Read(f1,bytAll);   if (bytAll[0]<>ord('T')) and (bytAll[1]<>ord('A'))     and (bytAll[2]<>ord('G')) then exit; // no 'TAG' found   Move(bytAll,pid3v1,$80);   CloseFile(f1);   result:=0; end; function WriteID3v1(strFile:string;var pid3v1:Tid3v1):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;   i: integer; begin   result:=1;   AssignFile(f1,strFile);   FileMode:=2;   Reset(f1);   if FileSize(f1)<=$80 then exit;   Seek(f1, FileSize(f1)-$80);   for i:=0 to $2 do Read(f1,bytAll); // test if 'TAG' exists   if (bytAll[0]=ord('T')) and (bytAll[1]=ord('A'))         and (bytAll[2]=ord('G'))     then Seek(f1,FileSize(f1)-$80)     else Seek(f1,FileSize(f1));   Move(pid3v1,bytAll,$80);   for i:=0 to $7f do Write(f1,bytAll);   CloseFile(f1);   result:=0; end; function DeleteID3v1(strFile:string):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;   i: integer; begin   Result:=1;   AssignFile(f1,strFile);   FileMode:=2;   Reset(f1);   if FileSize(f1)<=$80 then exit;   Seek(f1, FileSize(f1)-$80);   for i:=0 to $2 do Read(f1,bytAll); // test if 'TAG' exists   if (bytAll[0]=ord('T')) and (bytAll[1]=ord('A'))         and (bytAll[2]=ord('G'))     then begin       Seek(f1,FileSize(f1)-$80);       Truncate(f1)     end;   CloseFile(f1);   Result:=0; end; end.

microwave · 2001-08-27

谢谢您如此详细的回答，只是还有几点疑问，请看下面的注释： 严黎斌 //他是谁? unit ID3Kernel; interface type   Tid3v1= record     Tag: array[0..2] of char;      //00..02 , ='TAG'     Title:array[0..$1d] of char;  //03..20    $1d 是什么意思?     Artist:array[0..$1d] of char;  //21..3e   $1d是什么意思?     Album:array[0..$1d] of char;  //3f..5c     Year:array[0..3] of char;      //5d..60     Comment:array[0..$1c] of char; //61..7d   $1c是什么意思?     Track:byte;                    //7e           Genre:byte;                    //7f     这两个注释是什么意思?   end; function ReadID3v1(strFile:string;var pid3v1:Tid3v1):integer; function WriteID3v1(strFile:string;var pid3v1:Tid3v1):integer; function DeleteID3v1(strFile:string):integer; implementation function ReadID3v1(strFile:string;var pid3v1:Tid3v1):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;     //$7f 是什么意思?   i: integer; begin   result:=1;   if strFile='' then exit;   AssignFile(f1,strFile);   FileMode:=0;   Reset(f1);   if FileSize(f1)<=$80 then exit;      //$80 是什么意思?   Seek(f1, FileSize(f1)-$80);   for i:=0 to $7f do Read(f1,bytAll);   if (bytAll[0]<>ord('T')) and (bytAll[1]<>ord('A'))     and (bytAll[2]<>ord('G')) then exit; // no 'TAG' found   Move(bytAll,pid3v1,$80);   CloseFile(f1);   result:=0; end; function WriteID3v1(strFile:string;var pid3v1:Tid3v1):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;   i: integer; begin   result:=1;   AssignFile(f1,strFile);   FileMode:=2;   Reset(f1);   if FileSize(f1)<=$80 then exit;   Seek(f1, FileSize(f1)-$80);   for i:=0 to $2 do Read(f1,bytAll); // test if 'TAG' exists   if (bytAll[0]=ord('T')) and (bytAll[1]=ord('A'))         and (bytAll[2]=ord('G'))     then Seek(f1,FileSize(f1)-$80)     else Seek(f1,FileSize(f1));   Move(pid3v1,bytAll,$80);   for i:=0 to $7f do Write(f1,bytAll);   CloseFile(f1);   result:=0; end; function DeleteID3v1(strFile:string):integer; var   f1:file of byte;   bytAll: array [0..$7f] of byte;   i: integer; begin   Result:=1;   AssignFile(f1,strFile);   FileMode:=2;   Reset(f1);   if FileSize(f1)<=$80 then exit;   Seek(f1, FileSize(f1)-$80);   for i:=0 to $2 do Read(f1,bytAll); // test if 'TAG' exists   if (bytAll[0]=ord('T')) and (bytAll[1]=ord('A'))         and (bytAll[2]=ord('G'))     then begin       Seek(f1,FileSize(f1)-$80);       Truncate(f1)     end;   CloseFile(f1);   Result:=0; end; end.

Kingron · 2001-08-27

1：$表示十六进制的数，所以$1d=16+13=29。。。其他的类似。 2：严黎斌，是这个单元的作者，在CSDN有一个注册的账号。

pcexplorer · 2001-08-27

搞了半天$1d都不知道

microwave · 2001-08-27

To pcexplorer: 知识会有漏洞的嘛，我从未用十六进制表示过数当然不知道了。 To Kingron:  谢谢！

麻烦大家看一下这段代码！(50分)

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