ack/plat/msdos386/libsys/sys_isopen.s

#
! $Source$
! $State$
! $Revision$

#include "libsysasm.h"

! Say whether a given file descriptor number refers to a valid open file
! descriptor.

.define __sys_isopen
__sys_isopen:
	mov ebx, 4(esp)
	mov eax, 0x4400
	int 0x21
	sbb eax, eax
	inc eax
	ret
Cut-and-paste the msdos86 libsys so the msdos386 stuff now at least builds. 2022-08-07 20:10:08 +00:00			`#`
			`! $Source$`
			`! $State$`
			`! $Revision$`

plat/msdos386: refactor, firm up, and optimize - refactor code for transfer buffer reads/writes, real mode int 0x21 calls, and assembler segment declarations - define transfer buffer size in one place - beef up error checking for transfer buffer operations (prevent buffer overflows) - also optimize such operations to transfer dword by dword where feasible 2022-08-26 17:20:56 +00:00			`#include "libsysasm.h"`
Cut-and-paste the msdos86 libsys so the msdos386 stuff now at least builds. 2022-08-07 20:10:08 +00:00
			`! Say whether a given file descriptor number refers to a valid open file`
			`! descriptor.`

			`.define __sys_isopen`
			`__sys_isopen:`
plat/msdos386: fix some issues in libsys code - ensure es = ds = ss upon exit of each C runtime function - clear upper 16 bits of ebx before setting them to 0x0021, when invoking interrupt_ptr to simulate a RM int 0x21 - make _sys_exists use the transfer buffer (which it needs) - make _sys_rawread properly handle an end-of-file read (zero bytes read) - make argument to _sys_seterrno short --- after a failed int 0x21 call, only the lower 16 bits of eax hold the MS-DOs error code - _sys_rawlseek accepts only 3 longword arguments, not 4 (the offset is only 1 longword) - other minor fixes 2022-08-24 15:17:04 +00:00			`mov ebx, 4(esp)`
Most of read and write now works; filename-based operations partially work; but there's a nasty memory corruption somewhere which needs investigating. 2022-08-18 22:08:57 +00:00			`mov eax, 0x4400`
Cut-and-paste the msdos86 libsys so the msdos386 stuff now at least builds. 2022-08-07 20:10:08 +00:00			`int 0x21`
Most of read and write now works; filename-based operations partially work; but there's a nasty memory corruption somewhere which needs investigating. 2022-08-18 22:08:57 +00:00			`sbb eax, eax`
			`inc eax`
Cut-and-paste the msdos86 libsys so the msdos386 stuff now at least builds. 2022-08-07 20:10:08 +00:00			`ret`