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page ,132
title setjmp - set and do long jump
;***
;setjmp.asm - set and do a long jump
;
; Copyright (c) 1985-1988, Microsoft Corporation. All rights reserved.
;
;Purpose:
; defines setjmp() and longjmp() - set and do a long jump.
; Stores machine state in a user-supplied buffer to set a jump
; and then retores that state to perform a long jump.
;
; format of the buffer 'env':
; -----------
; | ebp | env+0
; -----------
; | edi | env+4
; -----------
; | esi | env+8
; -----------
; | ebx | env+12
; -----------
; | esp | env+16 (8)
; -----------
; | retaddr | env+20
; -----------
;
; Calling longjmp(env,val); will generate a return of val to
; the last call of setjmp(env) by restoring sp, bp, pc, and
; other regs from buffer 'env' and doing a return. If val
; is 0, 1 is returned; else val is returned.
;
;Revision History:
; 10-19-83 RN initial version
; 08-08-88 JCR 386 version
; 10-24-88 JCR Cleaned up code for 386 only
;
;*******************************************************************************
.386p
.xlist
include ks386.inc
.list
OFFBP = 0
OFFBX = OFFBP + 4
OFFDI = OFFBX + 4
OFFSI = OFFDI + 4
OFFSP = OFFSI + 4
OFFRET = OFFSP + 4
_TEXT SEGMENT DWORD USE32 PUBLIC 'CODE'
ASSUME CS:FLAT, DS:FLAT, ES:FLAT, SS:NOTHING, FS:NOTHING, GS:NOTHING
page , 132
subttl "setjmp"
;***
;int setjmp(env) - save the current stack environment
;
;Purpose:
; Saves the current stack environment in env so that longjmp
; can jump back here at some later time.
;
;Entry:
; jmp_buf env - buffer to save stack environment in
;
;Exit:
; returns 0 after setting a jump point (saving environment)
; if returns as a result of longjmp call, returns value that
; that longjmp passed (1 if longjmp passed 0).
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************
public _setjmp
_setjmp proc
; remember where we are now, so we can
; come back later if we have to
mov eax,ebp ; save ebp
mov ebp,esp
mov edx,[ebp+4] ; edx=pointer to env
mov [edx+OFFBP],eax ; save ebp
mov [edx+OFFBX],ebx ; save ebx
mov [edx+OFFDI],edi ; save edi
mov [edx+OFFSI],esi ; save esi
mov [edx+OFFSP],esp ; save esp
mov ecx,[ebp]
mov [edx+OFFRET],ecx; save ret addr
mov ebp,eax ; restore ebp
xor eax,eax ; return 0
ret
_setjmp endp
page
;***
;longjmp(env, val) - Do a long jump
;
;Purpose:
; Restores the stack environment set by setjmp(), thereby transfering
; control to the point at which setjmp() was called. The specified
; value will be returned by the setjmp() call.
;
;Entry:
; jmp_buf env - buffer environment was previously stored in
; int val - value setjmp() returns (0 will be returned as 1)
;
;Exit:
; Routine does not exit - transfers control to place where
; setjmp() was called.
;
;Uses:
;
;Exceptions:
;
;*******************************************************************************
public _longjmp
_longjmp proc
mov ebp,esp
mov eax,[ebp+4+4]
; return value; get it before we lose bp
or eax,eax ; see if arg is 0; if so, return 1
jnz short not0 ; return value != 0, so return it
inc eax ; set ax to 1
not0:
mov edx,[ebp+4] ; ebx=pointer to env
mov ebx,[edx+OFFBX] ; restore ebx
mov edi,[edx+OFFDI] ; restore edi
mov esi,[edx+OFFSI] ; restore esi
mov esp,[edx+OFFSP] ; restore esp
mov ebp,esp ; ...to get into the old stack frame
mov ecx,[edx+OFFRET]; ret addr
mov [ebp],ecx ; restored
mov ebp,[edx+OFFBP]; restore ebp
; now everything is completely set up for a return to the old context
ret
_longjmp endp
_TEXT ends
end
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