id3 reader problem

[travism]

Ive never really used structs so here it goes... I created the id3 header structure

ID3_HEADER STRUCT
   tid     byte 3
   title   byte 30
   artist  byte 30
   album   byte 30
   year    byte 4 
   comment byte 30
   genre   byte 1
ID3_HEADER ENDS

then in .data I have

id3 ID3_HEADER <>

but when i try to reference it in my code "id3.title" or so on i get a "syntax error title"... Ive googled Ive searched I cant seem to get past this I know its something so easy.. Any input on what it could be?

[hutch--]

"title" is a reserve word in MASM. Change it to "title1" or similar.

[travism]

assembled perfectly now thank you! I feel like a retard now  :red

[hutch--]

I would not worry, we have all done it.  :bg

[ragdog]

Hi

; ########################################
        .386
        .model flat, stdcall
        option casemap :none

; ########################################

        include \masm32\include\windows.inc
        include \masm32\include\user32.inc
        include \masm32\include\kernel32.inc

        includelib \masm32\lib\user32.lib
        includelib \masm32\lib\kernel32.lib

; ########################################

    ID3Tag STRUCT
        szTitle     db 31 dup (?)
        szArtist    db 31 dup (?)
        szAlbum     db 31 dup (?)
        szYear      db 5 dup (?)
        szComment   db 29 dup (?)
    ID3Tag ENDS

; ########################################

    .data
        szTestMp3       db "test1.mp3", 0

; ########################################

    .data?
        szID3Tag        db 122 dup (?)
        hFile           dd ?
        nTmp            dd ?
        id3             ID3Tag <>

; ########################################

    .code

start:


    invoke CreateFile, addr szTestMp3, GENERIC_READ, \
                       FILE_SHARE_READ, 0, \
                       OPEN_EXISTING, 0, 0
    mov hFile, eax

    invoke SetFilePointer, eax, -125, 0, FILE_END

    invoke ReadFile, hFile, addr szID3Tag, 122, addr nTmp, 0

    invoke CloseHandle, hFile

    lea edi, szID3Tag
    lea esi, id3.szTitle
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 30
    jne @B

    lea esi, id3.szArtist
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 30
    jne @B

    lea esi, id3.szAlbum
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 30
    jne @B

    lea esi, id3.szYear
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 4
    jne @B

    lea esi, id3.szComment
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 28
    jne @B

    invoke MessageBox, 0, addr id3.szTitle, 0, 0
    invoke MessageBox, 0, addr id3.szArtist, 0, 0
    invoke MessageBox, 0, addr id3.szAlbum, 0, 0
    invoke MessageBox, 0, addr id3.szYear, 0, 0
    invoke MessageBox, 0, addr id3.szComment, 0, 0

    invoke ExitProcess, 0

end start

; ########################################

[travism]

Do you mind explaining why you did it this way:

lea edi, szID3Tag
    lea esi, id3.szTitle
    xor ecx, ecx
@@:
    mov al, byte ptr [edi]
    mov byte ptr [esi], al
    inc edi
    inc esi
    inc ecx
    cmp ecx, 30
    jne @B

and why you couldnt do something as simple as just printing the id3.title or whatever?

[hutch--]

Travis,

Look at the structure, it is a set of string addresses so there is no "simple" way to display it, you must write string data to each address and read the data as string data from that address.

[travism]

So in his example he is pretty much starting at the beginning of the data and counting each byte up till he gets to 30,29 or whatever the tag size is in the struct then prints it out? I think I get it now thanks :)

[hutch--]

No, the structure will do that for you, what you need to control with a structure like this is reading and writing to and from the structure. What you must also ensure is that the string data you write to it does not exceed the field length which is set in the byte count of eacyh structure member.

[travism]

AH! Thank you, I now understand structures alot more and using pointer registers better!  :bg

[hutch--]

Travis,

Note that the wordd "comment" is a masm reserve word as well. Tell us what you are trying to do with the structure and we may have a suggestion to help you out.

LATER : I deleted the example because it had an error in it.

[travism]

Well the reason I used a structure was because in C I was able to create a structure and then just:

memcpy(&id3header,ID3,128);

ID3 was my buffer of 128 bytes of data and &id3header was a pointer to my structure so it was able to I guess you could say fill it in, So i came to realize that I wasn't able to do it the same way in assembly. Which is ok I learned more :) but the method that ragdog worked out fine. I commented what he did maybe you could see if im understanding it right?

      lea edi,mp3Data             ;put offset of mp3data in edi
      lea esi,id3.id3tid             ;offset of our first field in esi
      xor ecx,ecx                   ;clear ecx (0) so we can count

@@:
      mov al, byte ptr [edi]      ;put the first/next value and size byte in al
      mov byte ptr [esi],al       ;now put it into our first field in esi
      inc edi                          ;increment to the next byte
      inc esi
      inc ecx
      cmp ecx, 3                  ;till it gets to 3 "TAG"
      jne @B

      push ecx                    ;test if its a mp3 file
      push offset id3.id3tid      ;id3.id3tid should = "TAG"
      push offset szTAG
      call szCmpi

Thanks everyone for all your help! Sorry for posting so much I just want to make sure I understand everything correctly :)

[hutch--]

Travis,

This is a more generic structure example for string data.

Code Select Expand


; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤
    include \masm32\include\masm32rt.inc
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

comment * -----------------------------------------------------
                        Build this  template with
                       "CONSOLE ASSEMBLE AND LINK"
        ----------------------------------------------------- *

    mystruct STRUCT
      item1 db 8  dup (?)
      item2 db 12 dup (?)
      item3 db 16 dup (?)
      item4 db 32 dup (?)
    mystruct ENDS

    .data
      mst mystruct <>

    .code

start:
   
; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

    call main
    inkey
    exit

; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

main proc

    fn szCopy,"16",ADDR mst.item1
    fn szCopy,"Long Name",ADDR mst.item2
    fn szCopy,"Title Text",ADDR mst.item3
    fn szCopy,"More Text",ADDR mst.item4

    print ADDR mst.item1,13,10
    print ADDR mst.item2,13,10
    print ADDR mst.item3,13,10
    print ADDR mst.item4,13,10

    ret

main endp

; ¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤¤

end start