WebSVN – SvarDOS – Diff – /svarcom/trunk/rmod.asm


;
; rmod - resident module of the SvarCOM command interpreter
;
; Copyright (C) 2021 Mateusz Viste
; MIT license
;
; this is installed in memory by the transient part of SvarCOM. it has only
; two jobs: providing a resident buffer for command history, environment, etc
; and respawning COMMAND.COM whenever necessary.
 
CPU 8086
org 0x100
 
PSP_ENVSEG equ 0x2C
 
section .text    ; all goes into code segment
 
                 ; offset
SIG1 dw 0x1983   ;  +0
SIG2 dw 0x1985   ;  +2
SIG3 dw 0x2017   ;  +4
SIG4 dw 0x2019   ;  +6  this acts also as a guardval to detect stack overflows
 
; DOS int 21h functions that I use require at least 40 bytes of stack under
; DOS-C (FreeDOS) kernel, so here I reserve 64 bytes juste to be sure
STACKBUF db "XXX  SVARCOM RMOD BY MATEUSZ VISTE  XXXXXXXXXXXXXXXXXXXXXXXXXXXX"
STACKPTR dw 0
 
 
 
 
; offset of the COMSPEC variable in the environment block, 0 means "use
; boot drive". this value is patched by the transient part of COMMAND.COM
COMSPECPTR dw 0  ; +4Ah
 
; fallback COMSPEC string used if no COMPSEC is present in the environment
; drive. drive is patched by the transient part of COMMAND.COM
COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Ch
 
; exit code of last application
LEXCODE  db 0    ; +5Bh
 
; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:
;  offset  size  content
;     +0     2   segment of environment for child (0 = current)
;     +2     4   address of command line to place at PSP:0080
;     +6     4   address of an FCB to be placed at PSP:005c
;    +0Ah    4   address of an FCB to be placed at PSP:006c
EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0   ; +5Ch
 
; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ)  ; +6Ah
EXECPROG dd 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0
 
; offset within EXECPROG for out and in filenames in case stdin or stdout
; needs to be redirected (0xffff=no redirection)
REDIR_OUTFIL dw 0xffff    ; +EAh
REDIR_INFIL dw 0xffff     ; +ECh
REDIR_OUTAPPEND dw 0      ; +EEh
 
skipsig:         ; +F0h
 
; set up CS=DS=SS and point SP to my private stack buffer
mov ax, cs
mov ds, ax
mov es, ax
mov ss, ax
mov sp, STACKPTR
 
; revert stdin/stdout redirections (if any) to their initial state
call REVERT_REDIR_IF_ANY
 
; redirect stdout if required
call REDIR_OUTFILE_IF_REQUIRED
 
; should I executed command.com or a pre-set application?
or [EXECPROG], byte 0
jz EXEC_COMMAND_COM
 
; TODO: perhaps I should call the DOS SetPSP function here? But if I do, the
;       int 21h, ah=50h call freezes...
;mov ah, 0x50           ; DOS 2+ -- Set PSP
;mov bx, cs
;int 0x21
 
; exec an application preset (by SvarCOM) in the ExecParamRec
mov ax, 0x4B00         ; DOS 2+ - load & execute program
mov dx, EXECPROG       ; DS:DX  - ASCIZ program name (preset at PSP[already)
mov bx, EXEC_PARAM_REC ; ES:BX  - parameter block pointer
int 0x21
mov [cs:EXECPROG], byte 0 ; do not run app again (+DS might have been changed)
 
jmp short skipsig      ; enforce valid ds/ss/etc (can be lost after int 21,4b)
 
EXEC_COMMAND_COM:
 
; collect the exit code of previous application
mov ah, 0x4D
int 0x21
 
mov [LEXCODE], al
 
; zero out the exec param block (14 bytes)
mov al, 0              ; byte to write
mov cx, 14             ; how many times
mov di, EXEC_PARAM_REC ; ES:DI = destination
cld                    ; stosb must move forward
rep stosb              ; repeat cx times
 
; preset the default COMSPEC pointer to ES:DX (ES is already set to DS)
mov dx, COMSPECBOOT
 
; do I have a valid COMSPEC?
or [COMSPECPTR], word 0
jz USEDEFAULTCOMSPEC
; set ES:DX to actual COMSPEC (in env segment)
mov es, [PSP_ENVSEG]
mov dx, [COMSPECPTR]
USEDEFAULTCOMSPEC:
 
; prepare the exec param block
mov ax, [PSP_ENVSEG]
mov [EXEC_PARAM_REC], ax
mov [EXEC_PARAM_REC+2], word CMDTAIL
mov [EXEC_PARAM_REC+4], cs
 
; execute command.com
mov ax, 0x4B00         ; DOS 2+ - load & execute program
push es                ;
pop ds                 ;
;mov dx, COMSPEC       ; DS:DX  - ASCIZ program name (preset already)
push cs
pop es
mov bx, EXEC_PARAM_REC ; ES:BX  - parameter block pointer
int 0x21
 
; if all went well, jump back to start
jnc skipsig
 
; restore DS=CS
mov bx, cs
mov ds, bx
 
; update error string so it contains the error number
add al, '0'
mov [ERRLOAD + 4], al
 
; display error message
mov ah, 0x09
mov dx, ERRLOAD
int 0x21
 
; wait for keypress
mov ah, 0x08
int 0x21
 
; back to program start
jmp skipsig
 
; command.com tail arguments, in PSP format: length byte followed by args and
; terminated with \r) - a single 0x0A byte is passed so SvarCOM knows it is
; called as respawn (as opposed to being invoked as a normal application)
; this allows multiple copies of SvarCOM to stack upon each other.
CMDTAIL db 0x01, 0x0A, 0x0D
 
ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM", 13, 10, '$'
 
; variables used to revert stdin/stdout to their initial state
OLD_STDOUT dw 0xffff
OLD_STDIN  dw 0xffff
 
 
; ****************************************************************************
; *** ROUTINES ***************************************************************
; ****************************************************************************
 
; ----------------------------------------------------------------------------
; revert stdin/stdout redirections (if any) to their initial state
; all memory accesses are CS-prefixes because this code may be called at
; times when DS is out of whack.
REVERT_REDIR_IF_ANY:
; is stdout redirected?
mov bx, [OLD_STDOUT]
cmp bx, 0xffff
je STDOUT_DONE
; revert the stdout handle (dst in BX already)
mov cx, 1        ; src handle (1=stdout)
mov ah, 0x46     ; redirect a handle
int 0x21
; close the old handle (still in bx)
mov ah, 0x3e
int 0x21
mov [OLD_STDOUT], word 0xffff ; mark stdout as "not redirected"
STDOUT_DONE:
ret
; ----------------------------------------------------------------------------
 
 
; ----------------------------------------------------------------------------
; redirect stdout if REDIR_OUTFIL points to something
REDIR_OUTFILE_IF_REQUIRED:
mov si, [REDIR_OUTFIL]
cmp si, 0xffff
je NO_STDOUT_REDIR
add si, EXECPROG       ; si=output file
mov ax, 0x6c00         ; Extended Open/Create
mov bx, 1              ; access mode (0=read, 1=write, 2=r+w)
xor cx, cx             ; file attribs when(if) file is created (0=normal)
mov dx, [REDIR_OUTAPPEND] ; action if file exist (0x11=open, 0x12=truncate)
int 0x21               ; ax=handle on success (CF clear)
mov [REDIR_OUTFIL], word 0xffff
jc NO_STDOUT_REDIR     ; TODO: abort with an error message instead
 
; jump to end of file if flag was 0x11 (required for >> redirections)
cmp [REDIR_OUTAPPEND], word 0x11
jne SKIP_JMPEOF
mov bx, ax
mov ax, 0x4202         ; jump to position EOF - CX:DX in handle BX
xor cx, cx
xor dx, dx
int 0x21
mov ax, bx             ; put my handle back in ax, as expected by later code
SKIP_JMPEOF:
 
; duplicate current stdout so I can revert it later
push ax                ; save my file handle in stack
mov ah, 0x45           ; duplicate file handle BX
mov bx, 1              ; 1=stdout
int 0x21               ; ax=new (duplicated) file handle
mov [OLD_STDOUT], ax   ; save the old handle in memory
 
; redirect stdout to my file
pop bx                 ; dst handle
mov cx, 1              ; src handle (1=stdout)
mov ah, 0x46           ; "redirect a handle"
int 0x21
 
; close the original file handle, I no longer need it
mov ah, 0x3e           ; close a file handle (handle in BX)
int 0x21
NO_STDOUT_REDIR:
ret
; ----------------------------------------------------------------------------
 

Rev 520	Rev 529
1	`;`	1	`;`
2	`; rmod - resident module of the SvarCOM command interpreter`	2	`; rmod - resident module of the SvarCOM command interpreter`
3	`;`	3	`;`
4	`; Copyright (C) 2021 Mateusz Viste`	4	`; Copyright (C) 2021 Mateusz Viste`
5	`; MIT license`	5	`; MIT license`
6	`;`	6	`;`
7	`; this is installed in memory by the transient part of SvarCOM. it has only`	7	`; this is installed in memory by the transient part of SvarCOM. it has only`
8	`; two jobs: providing a resident buffer for command history, environment, etc`	8	`; two jobs: providing a resident buffer for command history, environment, etc`
9	`; and respawning COMMAND.COM whenever necessary.`	9	`; and respawning COMMAND.COM whenever necessary.`
10		10
11	`CPU 8086`	11	`CPU 8086`
12	`org 0x100`	12	`org 0x100`
13		13
14	`PSP_ENVSEG equ 0x2C`	14	`PSP_ENVSEG equ 0x2C`
15		15
16	`section .text ; all goes into code segment`	16	`section .text ; all goes into code segment`
17		17
18	`; offset`	18	`; offset`
19	`SIG1 dw 0x1983 ; +0`	19	`SIG1 dw 0x1983 ; +0`
20	`SIG2 dw 0x1985 ; +2`	20	`SIG2 dw 0x1985 ; +2`
21	`SIG3 dw 0x2017 ; +4`	21	`SIG3 dw 0x2017 ; +4`
22	`SIG4 dw 0x2019 ; +6 this acts also as a guardval to detect stack overflows`	22	`SIG4 dw 0x2019 ; +6 this acts also as a guardval to detect stack overflows`
23		23
24	`; DOS int 21h functions that I use require at least 40 bytes of stack under`	24	`; DOS int 21h functions that I use require at least 40 bytes of stack under`
25	`; DOS-C (FreeDOS) kernel, so here I reserve 64 bytes juste to be sure`	25	`; DOS-C (FreeDOS) kernel, so here I reserve 64 bytes juste to be sure`
26	`STACKBUF db "XXX SVARCOM RMOD BY MATEUSZ VISTE XXXXXXXXXXXXXXXXXXXXXXXXXXXX"`	26	`STACKBUF db "XXX SVARCOM RMOD BY MATEUSZ VISTE XXXXXXXXXXXXXXXXXXXXXXXXXXXX"`
27	`STACKPTR dw 0`	27	`STACKPTR dw 0`
28		28
29	`; exit code of last application`	-
30	`LEXCODE dw 0 ; +4Ah`	-
31		-
32	`; offset of the COMSPEC variable in the environment block, 0 means "use`	29	`; offset of the COMSPEC variable in the environment block, 0 means "use`
33	`; boot drive". this value is patched by the transient part of COMMAND.COM`	30	`; boot drive". this value is patched by the transient part of COMMAND.COM`
34	`COMSPECPTR dw 0 ; +4Ch`	31	`COMSPECPTR dw 0 ; +4Ah`
35		32
36	`; fallback COMSPEC string used if no COMPSEC is present in the environment`	33	`; fallback COMSPEC string used if no COMPSEC is present in the environment`
37	`; drive. drive is patched by the transient part of COMMAND.COM`	34	`; drive. drive is patched by the transient part of COMMAND.COM`
38	`COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Eh`	35	`COMSPECBOOT db "@:\COMMAND.COM", 0 ; +4Ch`
-		36
-		37	`; exit code of last application`
-		38	`LEXCODE db 0 ; +5Bh`
39		39
40	`; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:`	40	`; ExecParamRec used by INT 21h, AX=4b00 (load and execute program), 14 bytes:`
41	`; offset size content`	41	`; offset size content`
42	`; +0 2 segment of environment for child (0 = current)`	42	`; +0 2 segment of environment for child (0 = current)`
43	`; +2 4 address of command line to place at PSP:0080`	43	`; +2 4 address of command line to place at PSP:0080`
44	`; +6 4 address of an FCB to be placed at PSP:005c`	44	`; +6 4 address of an FCB to be placed at PSP:005c`
45	`; +0Ah 4 address of an FCB to be placed at PSP:006c`	45	`; +0Ah 4 address of an FCB to be placed at PSP:006c`
46	`EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +5Dh`	46	`EXEC_PARAM_REC db 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ; +5Ch`
47		47
48	`; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ) ; +6Bh`	48	`; Program to execute, preset by SvarCOM (128 bytes, ASCIIZ) ; +6Ah`
49	`EXECPROG dd 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0`	49	`EXECPROG dd 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0`
50		50
51	`; offset within EXECPROG for out and in filenames in case stdin or stdout`	51	`; offset within EXECPROG for out and in filenames in case stdin or stdout`
52	`; needs to be redirected (0xffff=no redirection)`	52	`; needs to be redirected (0xffff=no redirection)`
53	`REDIR_OUTFIL dw 0xffff ; +EBh`	53	`REDIR_OUTFIL dw 0xffff ; +EAh`
54	`REDIR_INFIL dw 0xffff ; +EDh`	54	`REDIR_INFIL dw 0xffff ; +ECh`
55	`REDIR_OUTAPPEND dw 0 ; +EFh`	55	`REDIR_OUTAPPEND dw 0 ; +EEh`
56		56
57	`skipsig: ; +F1h`	57	`skipsig: ; +F0h`
58		58
59	`; set up CS=DS=SS and point SP to my private stack buffer`	59	`; set up CS=DS=SS and point SP to my private stack buffer`
60	`mov ax, cs`	60	`mov ax, cs`
61	`mov ds, ax`	61	`mov ds, ax`
62	`mov es, ax`	62	`mov es, ax`
63	`mov ss, ax`	63	`mov ss, ax`
64	`mov sp, STACKPTR`	64	`mov sp, STACKPTR`
65		65
66	`; revert stdin/stdout redirections (if any) to their initial state`	66	`; revert stdin/stdout redirections (if any) to their initial state`
67	`call REVERT_REDIR_IF_ANY`	67	`call REVERT_REDIR_IF_ANY`
68		68
69	`; redirect stdout if required`	69	`; redirect stdout if required`
70	`call REDIR_OUTFILE_IF_REQUIRED`	70	`call REDIR_OUTFILE_IF_REQUIRED`
71		71
72	`; should I executed command.com or a pre-set application?`	72	`; should I executed command.com or a pre-set application?`
73	`or [EXECPROG], byte 0`	73	`or [EXECPROG], byte 0`
74	`jz EXEC_COMMAND_COM`	74	`jz EXEC_COMMAND_COM`
75		75
76	`; TODO: perhaps I should call the DOS SetPSP function here? But if I do, the`	76	`; TODO: perhaps I should call the DOS SetPSP function here? But if I do, the`
77	`; int 21h, ah=50h call freezes...`	77	`; int 21h, ah=50h call freezes...`
78	`;mov ah, 0x50 ; DOS 2+ -- Set PSP`	78	`;mov ah, 0x50 ; DOS 2+ -- Set PSP`
79	`;mov bx, cs`	79	`;mov bx, cs`
80	`;int 0x21`	80	`;int 0x21`
81		81
82	`; exec an application preset (by SvarCOM) in the ExecParamRec`	82	`; exec an application preset (by SvarCOM) in the ExecParamRec`
83	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`	83	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`
84	`mov dx, EXECPROG ; DS:DX - ASCIZ program name (preset at PSP[already)`	84	`mov dx, EXECPROG ; DS:DX - ASCIZ program name (preset at PSP[already)`
85	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`	85	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`
86	`int 0x21`	86	`int 0x21`
87	`mov [cs:EXECPROG], byte 0 ; do not run app again (+DS might have been changed)`	87	`mov [cs:EXECPROG], byte 0 ; do not run app again (+DS might have been changed)`
88		88
89	`jmp short skipsig ; enforce valid ds/ss/etc (can be lost after int 21,4b)`	89	`jmp short skipsig ; enforce valid ds/ss/etc (can be lost after int 21,4b)`
90		90
91	`EXEC_COMMAND_COM:`	91	`EXEC_COMMAND_COM:`
92		92
93	`; collect the exit code of previous application`	93	`; collect the exit code of previous application`
94	`mov ah, 0x4D`	94	`mov ah, 0x4D`
95	`int 0x21`	95	`int 0x21`
96	`xor ah, ah ; clear out termination status, I only want the exit code`	-
97	`mov [LEXCODE], ax`	96	`mov [LEXCODE], al`
98		97
99	`; zero out the exec param block (14 bytes)`	98	`; zero out the exec param block (14 bytes)`
100	`mov al, 0 ; byte to write`	99	`mov al, 0 ; byte to write`
101	`mov cx, 14 ; how many times`	100	`mov cx, 14 ; how many times`
102	`mov di, EXEC_PARAM_REC ; ES:DI = destination`	101	`mov di, EXEC_PARAM_REC ; ES:DI = destination`
103	`cld ; stosb must move forward`	102	`cld ; stosb must move forward`
104	`rep stosb ; repeat cx times`	103	`rep stosb ; repeat cx times`
105		104
106	`; preset the default COMSPEC pointer to ES:DX (ES is already set to DS)`	105	`; preset the default COMSPEC pointer to ES:DX (ES is already set to DS)`
107	`mov dx, COMSPECBOOT`	106	`mov dx, COMSPECBOOT`
108		107
109	`; do I have a valid COMSPEC?`	108	`; do I have a valid COMSPEC?`
110	`or [COMSPECPTR], word 0`	109	`or [COMSPECPTR], word 0`
111	`jz USEDEFAULTCOMSPEC`	110	`jz USEDEFAULTCOMSPEC`
112	`; set ES:DX to actual COMSPEC (in env segment)`	111	`; set ES:DX to actual COMSPEC (in env segment)`
113	`mov es, [PSP_ENVSEG]`	112	`mov es, [PSP_ENVSEG]`
114	`mov dx, [COMSPECPTR]`	113	`mov dx, [COMSPECPTR]`
115	`USEDEFAULTCOMSPEC:`	114	`USEDEFAULTCOMSPEC:`
116		115
117	`; prepare the exec param block`	116	`; prepare the exec param block`
118	`mov ax, [PSP_ENVSEG]`	117	`mov ax, [PSP_ENVSEG]`
119	`mov [EXEC_PARAM_REC], ax`	118	`mov [EXEC_PARAM_REC], ax`
120	`mov [EXEC_PARAM_REC+2], word CMDTAIL`	119	`mov [EXEC_PARAM_REC+2], word CMDTAIL`
121	`mov [EXEC_PARAM_REC+4], cs`	120	`mov [EXEC_PARAM_REC+4], cs`
122		121
123	`; execute command.com`	122	`; execute command.com`
124	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`	123	`mov ax, 0x4B00 ; DOS 2+ - load & execute program`
125	`push es ;`	124	`push es ;`
126	`pop ds ;`	125	`pop ds ;`
127	`;mov dx, COMSPEC ; DS:DX - ASCIZ program name (preset already)`	126	`;mov dx, COMSPEC ; DS:DX - ASCIZ program name (preset already)`
128	`push cs`	127	`push cs`
129	`pop es`	128	`pop es`
130	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`	129	`mov bx, EXEC_PARAM_REC ; ES:BX - parameter block pointer`
131	`int 0x21`	130	`int 0x21`
132		131
133	`; if all went well, jump back to start`	132	`; if all went well, jump back to start`
134	`jnc skipsig`	133	`jnc skipsig`
135		134
136	`; restore DS=CS`	135	`; restore DS=CS`
137	`mov bx, cs`	136	`mov bx, cs`
138	`mov ds, bx`	137	`mov ds, bx`
139		138
140	`; update error string so it contains the error number`	139	`; update error string so it contains the error number`
141	`add al, '0'`	140	`add al, '0'`
142	`mov [ERRLOAD + 4], al`	141	`mov [ERRLOAD + 4], al`
143		142
144	`; display error message`	143	`; display error message`
145	`mov ah, 0x09`	144	`mov ah, 0x09`
146	`mov dx, ERRLOAD`	145	`mov dx, ERRLOAD`
147	`int 0x21`	146	`int 0x21`
148		147
149	`; wait for keypress`	148	`; wait for keypress`
150	`mov ah, 0x08`	149	`mov ah, 0x08`
151	`int 0x21`	150	`int 0x21`
152		151
153	`; back to program start`	152	`; back to program start`
154	`jmp skipsig`	153	`jmp skipsig`
155		154
156	`; command.com tail arguments, in PSP format: length byte followed by args and`	155	`; command.com tail arguments, in PSP format: length byte followed by args and`
157	`; terminated with \r) - a single 0x0A byte is passed so SvarCOM knows it is`	156	`; terminated with \r) - a single 0x0A byte is passed so SvarCOM knows it is`
158	`; called as respawn (as opposed to being invoked as a normal application)`	157	`; called as respawn (as opposed to being invoked as a normal application)`
159	`; this allows multiple copies of SvarCOM to stack upon each other.`	158	`; this allows multiple copies of SvarCOM to stack upon each other.`
160	`CMDTAIL db 0x01, 0x0A, 0x0D`	159	`CMDTAIL db 0x01, 0x0A, 0x0D`
161		160
162	`ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM", 13, 10, '$'`	161	`ERRLOAD db "ERR x, FAILED TO LOAD COMMAND.COM", 13, 10, '$'`
163		162
164	`; variables used to revert stdin/stdout to their initial state`	163	`; variables used to revert stdin/stdout to their initial state`
165	`OLD_STDOUT dw 0xffff`	164	`OLD_STDOUT dw 0xffff`
166	`OLD_STDIN dw 0xffff`	165	`OLD_STDIN dw 0xffff`
167		166
168		167
169	`; ****************************************************************************`	168	`; ****************************************************************************`
170	`; * ROUTINES *************************************************************`	169	`; * ROUTINES *************************************************************`
171	`; ****************************************************************************`	170	`; ****************************************************************************`
172		171
173	`; ----------------------------------------------------------------------------`	172	`; ----------------------------------------------------------------------------`
174	`; revert stdin/stdout redirections (if any) to their initial state`	173	`; revert stdin/stdout redirections (if any) to their initial state`
175	`; all memory accesses are CS-prefixes because this code may be called at`	174	`; all memory accesses are CS-prefixes because this code may be called at`
176	`; times when DS is out of whack.`	175	`; times when DS is out of whack.`
177	`REVERT_REDIR_IF_ANY:`	176	`REVERT_REDIR_IF_ANY:`
178	`; is stdout redirected?`	177	`; is stdout redirected?`
179	`mov bx, [OLD_STDOUT]`	178	`mov bx, [OLD_STDOUT]`
180	`cmp bx, 0xffff`	179	`cmp bx, 0xffff`
181	`je STDOUT_DONE`	180	`je STDOUT_DONE`
182	`; revert the stdout handle (dst in BX already)`	181	`; revert the stdout handle (dst in BX already)`
183	`mov cx, 1 ; src handle (1=stdout)`	182	`mov cx, 1 ; src handle (1=stdout)`
184	`mov ah, 0x46 ; redirect a handle`	183	`mov ah, 0x46 ; redirect a handle`
185	`int 0x21`	184	`int 0x21`
186	`; close the old handle (still in bx)`	185	`; close the old handle (still in bx)`
187	`mov ah, 0x3e`	186	`mov ah, 0x3e`
188	`int 0x21`	187	`int 0x21`
189	`mov [OLD_STDOUT], word 0xffff ; mark stdout as "not redirected"`	188	`mov [OLD_STDOUT], word 0xffff ; mark stdout as "not redirected"`
190	`STDOUT_DONE:`	189	`STDOUT_DONE:`
191	`ret`	190	`ret`
192	`; ----------------------------------------------------------------------------`	191	`; ----------------------------------------------------------------------------`
193		192
194		193
195	`; ----------------------------------------------------------------------------`	194	`; ----------------------------------------------------------------------------`
196	`; redirect stdout if REDIR_OUTFIL points to something`	195	`; redirect stdout if REDIR_OUTFIL points to something`
197	`REDIR_OUTFILE_IF_REQUIRED:`	196	`REDIR_OUTFILE_IF_REQUIRED:`
198	`mov si, [REDIR_OUTFIL]`	197	`mov si, [REDIR_OUTFIL]`
199	`cmp si, 0xffff`	198	`cmp si, 0xffff`
200	`je NO_STDOUT_REDIR`	199	`je NO_STDOUT_REDIR`
201	`add si, EXECPROG ; si=output file`	200	`add si, EXECPROG ; si=output file`
202	`mov ax, 0x6c00 ; Extended Open/Create`	201	`mov ax, 0x6c00 ; Extended Open/Create`
203	`mov bx, 1 ; access mode (0=read, 1=write, 2=r+w)`	202	`mov bx, 1 ; access mode (0=read, 1=write, 2=r+w)`
204	`xor cx, cx ; file attribs when(if) file is created (0=normal)`	203	`xor cx, cx ; file attribs when(if) file is created (0=normal)`
205	`mov dx, [REDIR_OUTAPPEND] ; action if file exist (0x11=open, 0x12=truncate)`	204	`mov dx, [REDIR_OUTAPPEND] ; action if file exist (0x11=open, 0x12=truncate)`
206	`int 0x21 ; ax=handle on success (CF clear)`	205	`int 0x21 ; ax=handle on success (CF clear)`
207	`mov [REDIR_OUTFIL], word 0xffff`	206	`mov [REDIR_OUTFIL], word 0xffff`
208	`jc NO_STDOUT_REDIR ; TODO: abort with an error message instead`	207	`jc NO_STDOUT_REDIR ; TODO: abort with an error message instead`
209		208
210	`; jump to end of file if flag was 0x11 (required for >> redirections)`	209	`; jump to end of file if flag was 0x11 (required for >> redirections)`
211	`cmp [REDIR_OUTAPPEND], word 0x11`	210	`cmp [REDIR_OUTAPPEND], word 0x11`
212	`jne SKIP_JMPEOF`	211	`jne SKIP_JMPEOF`
213	`mov bx, ax`	212	`mov bx, ax`
214	`mov ax, 0x4202 ; jump to position EOF - CX:DX in handle BX`	213	`mov ax, 0x4202 ; jump to position EOF - CX:DX in handle BX`
215	`xor cx, cx`	214	`xor cx, cx`
216	`xor dx, dx`	215	`xor dx, dx`
217	`int 0x21`	216	`int 0x21`
218	`mov ax, bx ; put my handle back in ax, as expected by later code`	217	`mov ax, bx ; put my handle back in ax, as expected by later code`
219	`SKIP_JMPEOF:`	218	`SKIP_JMPEOF:`
220		219
221	`; duplicate current stdout so I can revert it later`	220	`; duplicate current stdout so I can revert it later`
222	`push ax ; save my file handle in stack`	221	`push ax ; save my file handle in stack`
223	`mov ah, 0x45 ; duplicate file handle BX`	222	`mov ah, 0x45 ; duplicate file handle BX`
224	`mov bx, 1 ; 1=stdout`	223	`mov bx, 1 ; 1=stdout`
225	`int 0x21 ; ax=new (duplicated) file handle`	224	`int 0x21 ; ax=new (duplicated) file handle`
226	`mov [OLD_STDOUT], ax ; save the old handle in memory`	225	`mov [OLD_STDOUT], ax ; save the old handle in memory`
227		226
228	`; redirect stdout to my file`	227	`; redirect stdout to my file`
229	`pop bx ; dst handle`	228	`pop bx ; dst handle`
230	`mov cx, 1 ; src handle (1=stdout)`	229	`mov cx, 1 ; src handle (1=stdout)`
231	`mov ah, 0x46 ; "redirect a handle"`	230	`mov ah, 0x46 ; "redirect a handle"`
232	`int 0x21`	231	`int 0x21`
233		232
234	`; close the original file handle, I no longer need it`	233	`; close the original file handle, I no longer need it`
235	`mov ah, 0x3e ; close a file handle (handle in BX)`	234	`mov ah, 0x3e ; close a file handle (handle in BX)`
236	`int 0x21`	235	`int 0x21`
237	`NO_STDOUT_REDIR:`	236	`NO_STDOUT_REDIR:`
238	`ret`	237	`ret`
239	`; ----------------------------------------------------------------------------`	238	`; ----------------------------------------------------------------------------`
240		239

Subversion Repositories SvarDOS

(root)/svarcom/trunk/rmod.asm @ 1141 – Rev 520 → 529