Changeset 51 in xtideuniversalbios for trunk/Assembly_Library/Src/File

Timestamp:

Oct 11, 2010, 8:27:43 AM (14 years ago)

Author:

Tomi Tilli

google:author:

aitotat

Message:

Changes to Assembly Library:
File handle is now properly returned when opening file.
Added function for getting file size by using file handle.

File:

• trunk/Assembly_Library/Src/File/FileIO.asm (modified) (5 diffs)

trunk/Assembly_Library/Src/File/FileIO.asm

@@ -2 +2 @@
 ; Project name  :   Assembly Library
 ; Created date  :   1.9.2010
-; Last update   :   8.10.2010
+; Last update   :   10.10.2010
 ; Author        :   Tomi Tilli
 ; Description   :   Functions for file access.
@@ -28 +28 @@
     int     DOS_INTERRUPT_21h
     xchg    si, dx
+    mov     bx, ax      ; Copy file handle to BX
     ret
 
@@ -68 +69 @@
 ALIGN JUMP_ALIGN
 FileIO_ReadCXbytesToDSSIusingHandleFromBX:
-    xchg    dx, si              ; DS:DX now points to source buffer
+    xchg    dx, si              ; DS:DX now points to destination buffer
     mov     ah, READ_FROM_FILE_OR_DEVICE
     int     DOS_INTERRUPT_21h
@@ -102 +103 @@
 
 ;--------------------------------------------------------------------
+; FileIO_GetFileSizeToDXAXusingHandleFromBXandResetFilePosition:
+;   Parameters:
+;       BX:     File handle
+;   Returns:
+;       DX:AX:  Signed file size (if CF cleared)
+;       AX:     DOS error code (if CF set)
+;       CF:     Clear if successfull
+;               Set if error
+;   Corrupts registers:
+;       Nothing
+;--------------------------------------------------------------------
+ALIGN JUMP_ALIGN
+FileIO_GetFileSizeToDXAXusingHandleFromBXandResetFilePosition:
+    push    cx
+
+    ; Get file size to DX:AX
+    xor     cx, cx
+    xor     dx, dx
+    mov     al, SEEK_FROM.endOfFile
+    call    FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX
+    jc      SHORT .ReturnFileError
+    push    dx
+    push    ax
+
+    ; Reset file position
+    xor     dx, dx
+    mov     al, SEEK_FROM.startOfFile
+    call    FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX
+    pop     ax
+    pop     dx
+
+.ReturnFileError:
+    pop     cx
+    ret
+
+
+;--------------------------------------------------------------------
 ; FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
 ;   Parameters:
 ;       AL:     SEEK_FROM.(origin)
 ;       BX:     File handle
-;       DX:AX:  Seek offset (signed)
+;       CX:DX:  Signed offset to seek starting from AL
 ;   Returns:
-;       AX:     DOS error code if CF set
+;       DX:AX:  New file position in bytes from start of file (if CF cleared)
+;       AX:     DOS error code (if CF set)
 ;       CF:     Clear if successfull
 ;               Set if error
@@ -116 +155 @@
 ALIGN JUMP_ALIGN
 FileIO_SeekFromOriginInALtoOffsetInDXAXusingHandleFromBX:
-    push    dx
-    push    cx
-
-    mov     cx, dx              ; DOS wants high word in CX
-    xchg    dx, ax              ; DOS wants low word in DX
     mov     ah, SET_CURRENT_FILE_POSITION
     int     DOS_INTERRUPT_21h
-
-    pop     cx
-    pop     dx
     ret