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1.1 root 1: ;
2: ; This is an example of an assembly language program using 286DOS calls.
3: ; It creates two threads, one which writes a message to the screen every
4: ; two seconds, the other every second. As an example of semaphore usage
5: ; the two threads request a semaphore before writing to the screen.
6: ;
1.1.1.2 ! root 7: ; Created by Microsoft Corp. 1986
1.1 root 8:
9: .286p ; Allow only protect mode instructions
10:
11: STACK_SIZE equ 400h ; Stack for each thread
12:
13: STACK segment word stack 'STACK'
14:
15: dw 2048 dup(?)
16:
17: STACK ends
18:
19: DSEG segment word public 'DATA'
20:
21: Selector dw ? ; selector returned from DOSALLOCSEG
22: sem dd 0 ; semaphore
23: thread1ID dw ? ; thread id
24:
25: ; message written from thread 0
26: ;
27: hello0 db "thread zero hello", 0dh, 0ah
28: HELLO0_SIZE equ ($ - hello0)
29:
30: ; message written from thread 1
31: ;
32: hello1 db "thread ONE hello", 0dh, 0ah
33: HELLO1_SIZE equ ($ - hello1)
34:
35: DSEG ends
36:
37: DGROUP GROUP DSEG
38: assume cs:CSEG, ds:DGROUP
39:
1.1.1.2 ! root 40: extrn DOSALLOCSEG :FAR ; MS OS/2 calls used
1.1 root 41: extrn DOSCREATETHREAD :FAR
42: extrn DOSEXIT :FAR
43: extrn DOSSEMCLEAR :FAR
44: extrn DOSSEMREQUEST :FAR
45: extrn DOSSLEEP :FAR
46: extrn DOSWRITE :FAR
47:
48: CSEG segment byte public 'CODE'
49:
50: ; allocate memory for the new thread's stack
51:
52: START:
53: push STACK_SIZE ; size requested
54: mov bx, SEG DGROUP
55: push bx ; push far address of selector
56: push offset DGROUP:[Selector]
57: push 0 ; not to be shared
58: call DOSALLOCSEG ; allocate stack
59: or ax, ax ; did an error occur?
60: jnz ErrorExit
61:
62: ; create the new thread
63:
64: push SEG CSEG ; push far call address for new thread
65: push offset CSEG:thread1
66: push bx ; far address of returned thread number
67: push offset DGROUP:[thread1ID]
68: push DGROUP:[Selector] ; far address of allocated stack
69: push STACK_SIZE
70: call DOSCREATETHREAD ; create a new thread
71: or ax, ax
72: jnz ErrorExit
73:
74: call far ptr thread0
75:
76: ErrorExit:
77: push 1 ; terminate all threads
78: push 1 ; return error code
79: call DOSEXIT ; exit program
80:
81: thread0 PROC FAR
82:
83: push bp ; set up local stack for access
84: mov bp, sp
85:
86: startThread0:
87: push bx ; far address of ram semaphore
88: push offset DGROUP:[sem]
89: mov ax, -1 ; no timeout, wait forever
90: cwd ; convert to long
91: push dx
92: push ax
93: call DOSSEMREQUEST ; request semaphore
94:
95: ; got semaphore, now write message to screen
96:
97: push 1 ; file handle for standard out
98: push bx ; far address of write buffer
99: push offset DGROUP:[hello0]
100: push HELLO0_SIZE ; size of write buffer
101: lea ax, [bp - 2] ; bytes written
102: push ss
103: push ax
104: call DOSWRITE ; write message
105:
106: push bx ; far ptr to semaphore
107: push offset DGROUP:[sem]
108: call DOSSEMCLEAR ; release semaphore
109:
110: push 0 ; give up processor
111: push 2000
112: call DOSSLEEP
113: jmp short startThread0 ; loop forever
114:
115: thread0 ENDP
116:
117:
118: ; This is where the new thread will execute.
119:
120: thread1 PROC FAR
121:
122: push bp ; set up local stack access
123: mov bp, sp
124:
125: startThread1:
126: push bx
127: push offset DGROUP:[sem] ; address of semaphore
128: mov ax, -1 ; wait forever
129: cwd ; convert to long
130: push dx
131: push ax
132: call DOSSEMREQUEST ; request semaphore
133:
134: ; got semaphore, now write message to screen
135:
136: push 1 ; file handle for standard out
137: push bx ; write buffer address
138: push offset DGROUP:[hello1]
139:
140: push HELLO1_SIZE ; write buffer size
141:
142: lea ax, [bp - 2] ; bytes written
143: push ss
144: push ax
145: call DOSWRITE ; write message
146:
147: push bx ; far ptr to semaphore
148: push offset DGROUP:[sem]
149: call DOSSEMCLEAR ; release semaphore
150:
151: push 0 ; give up processor
152: push 1000
153: call DOSSLEEP
154: jmp short startThread1 ; loop forever
155:
156: thread1 ENDP
157:
158: CSEG ends
159: end START
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