ack/plat/msdos386/libsys/sys_rawwrite.s
tkchia cba54b205b 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 17:31:28 +00:00

49 lines
878 B
ArmAsm

#
! $Source$
! $State$
! $Revision$
#include "libsysasm.h"
! Write bytes to/to a file descriptor. These routines do not do any
! translation between CRLF and LF line endings.
!
! Note that, for MS-DOS, a raw "write" request of zero bytes will truncate
! (or extend) the file to the current file position.
.define __sys_rawwrite
__sys_rawwrite:
file_handle = 1*4
read_buffer = 2*4
amount_to_write = 3*4
mov eax, amount_to_write(esp)
mov ecx, TRANSFER_BUFFER_SIZE
cmp eax, ecx
jge 2f
mov ecx, eax
2:
! Copy ecx bytes into the transfer buffer.
mov eax, read_buffer(esp)
call .sys_cpyout
! Write from the transfer buffer to DOS.
xchg edx, eax
movb ah, 0x40
o16 mov bx, file_handle(esp)
call .sys_dpmidos
movzx eax, ax
jnc exit
push eax
call __sys_seterrno
pop ecx
exit:
ret
! vim: sw=4 ts=4 et