Subroutine for Turbo Pascal’s:
File must already be associated with a filename using the Assign(File, Filename) prior.
SYS0364: MOV DX,fmInput
SYS0367: JMP 0371
Entry point for Reset(File).
SYS0369: MOV DX,fmOutput
SYS036C: JMP 0371
Entry point for Rewrite(File).
SYS036E: MOV DX,fmInOut
Entry point for typed and untyped files.
SYS0371: PUSH BP
SYS0372: MOV BP,SP
Upon entering this subroutine from any of the entrypoints: fmInput, fmInput, fmInput, and saving BP, the stack looks like this:
| Index | Contents |
|---|---|
| BP | Old BP value |
| BP+02 | Return Address (OFFSET) |
| SP+04 | Return Address (SEGMENT) |
| BP+06 | Pointer to File/Text Record Data (OFFSET) |
| BP+08 | Pointer to File/Text Record Data (SEGMENT) |
SYS0374: LES DI,[BP+06]
Loads the pointer to the File into ES:DI.
SYS0377: ES:
SYS0378: MOV AX,[DI:Mode]
Loads Mode int AX.
SYS037B: CMP AX,fmInput
SYS037E: JZ 0392
Checks if File was opened using Reset().
SYS0380: CMP AX,fmOutput
SYS0383: JZ 0392
Checks if File was opened using Rewrite().
SYS0385: CMP AX,fmClosed
SYS0388: JZ 039A
Check if File was closed.
SYS038A: MOV WORD PTR [InOutRes],0066
SYS0390: JMP 03B6
Exit with an error 66h/102: File not assigned.
SYS0392: PUSH DX
Save Mode in DX on to the stack.
SYS0393: PUSH ES
SYS0394: PUSH DI
SYS0395: PUSH CS
SYS0396: CALL 03BE
Call SYS:03BE Reset()/Rewrite() and pushing the pointer to File onto the stack.
SYS0399: POP DX
Recover Mode from the stack to in DX.
SYS039A: XOR AX,AX
Clears AX.
SYS039C: ES:
SYS039D: MOV [DI:Mode],DX
SYS03A0: ES:
SYS03A1: MOV [DI+08],AX
Resets buffer to the beginning.
SYS03A4: ES:
SYS03A5: MOV [DI+0A],AX
Resets the number of characters in the buffer to 0 (Empty).
SYS03A8: MOV BX,0010
SYS03AB: CALL 03FA
Open File with a call to its BX = 0010 OpenFunc() using SYS:03FA I/O Function Dispatcher.
SYS03AE: JZ 03B6
Return on succes.
SYS03B0: ES:
SYS03B1: MOV WORD PTR [DI:Mode],fmClosed
Mark the file as fmClosed on error.
SYS03B6: POP BP
SYS03B7: RETF 0004
Return and pop-off parameters from the stack.
See also: Text File Type, File Modes, SYS:03BA Reset/Rewrite Function (II), SYS:03FA I/O Function Dispatcher, or go back