| 1 | #
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| 2 |
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| 3 |
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| 4 | ; $Header: /cvsup/minix/src/lib/ack/libp/encaps.e,v 1.1 2005/10/10 15:27:46 beng Exp $
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| 5 | ; (c) copyright 1983 by the Vrije Universiteit, Amsterdam, The Netherlands.
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| 6 | ;
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| 7 | ; This product is part of the Amsterdam Compiler Kit.
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| 8 | ;
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| 9 | ; Permission to use, sell, duplicate or disclose this software must be
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| 10 | ; obtained in writing. Requests for such permissions may be sent to
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| 11 | ;
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| 12 | ; Dr. Andrew S. Tanenbaum
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| 13 | ; Wiskundig Seminarium
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| 14 | ; Vrije Universiteit
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| 15 | ; Postbox 7161
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| 16 | ; 1007 MC Amsterdam
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| 17 | ; The Netherlands
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| 18 | ;
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| 19 |
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| 20 | mes 2,_EM_WSIZE,_EM_PSIZE
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| 21 |
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| 22 | ; procedure encaps(procedure p; procedure(q(n:integer));
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| 23 | ; {call q if a trap occurs during the execution of p}
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| 24 | ; {if q returns, continue execution of p}
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| 25 |
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| 26 |
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| 27 | inp $handler
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| 28 |
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| 29 | #define PIISZ 2*_EM_PSIZE
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| 30 |
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| 31 | #define PARG 0
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| 32 | #define QARG PIISZ
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| 33 | #define E_ELB 0-_EM_PSIZE
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| 34 | #define E_EHA -2*_EM_PSIZE
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| 35 |
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| 36 | ; encaps is called with two parameters:
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| 37 | ; - procedure instance identifier of q (QARG)
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| 38 | ; - procedure instance identifier of p (PARG)
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| 39 | ; and two local variables:
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| 40 | ; - the lb of the previous encaps (E_ELB)
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| 41 | ; - the procedure identifier of the previous handler (E_EHA)
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| 42 | ;
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| 43 | ; One static variable:
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| 44 | ; - the lb of the currently active encaps (enc_lb)
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| 45 |
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| 46 | enc_lb
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| 47 | bss _EM_PSIZE,0,0
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| 48 |
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| 49 | exp $encaps
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| 50 | pro $encaps,PIISZ
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| 51 | ; save lb of previous encaps
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| 52 | lae enc_lb
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| 53 | loi _EM_PSIZE
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| 54 | lal E_ELB
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| 55 | sti _EM_PSIZE
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| 56 | ; set new lb
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| 57 | lxl 0
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| 58 | lae enc_lb
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| 59 | sti _EM_PSIZE
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| 60 | ; save old handler id while setting up the new handler
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| 61 | lpi $handler
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| 62 | sig
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| 63 | lal E_EHA
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| 64 | sti _EM_PSIZE
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| 65 | ; handler is ready, p can be called
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| 66 | ; p doesn't expect parameters except possibly the static link
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| 67 | ; always passing the link won't hurt
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| 68 | lal PARG
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| 69 | loi PIISZ
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| 70 | cai
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| 71 | asp _EM_PSIZE
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| 72 | ; reinstate old handler
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| 73 | lal E_ELB
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| 74 | loi _EM_PSIZE
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| 75 | lae enc_lb
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| 76 | sti _EM_PSIZE
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| 77 | lal E_EHA
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| 78 | loi _EM_PSIZE
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| 79 | sig
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| 80 | asp _EM_PSIZE
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| 81 | ret 0
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| 82 | end ?
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| 83 |
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| 84 | #define TRAP 0
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| 85 | #define H_ELB 0-_EM_PSIZE
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| 86 |
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| 87 | ; handler is called with one parameter:
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| 88 | ; - trap number (TRAP)
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| 89 | ; one local variable
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| 90 | ; - the current LB of the enclosing encaps (H_ELB)
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| 91 |
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| 92 |
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| 93 | pro $handler,_EM_PSIZE
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| 94 | ; save LB of nearest encaps
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| 95 | lae enc_lb
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| 96 | loi _EM_PSIZE
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| 97 | lal H_ELB
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| 98 | sti _EM_PSIZE
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| 99 | ; fetch setting for previous encaps via LB of nearest
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| 100 | lal H_ELB
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| 101 | loi _EM_PSIZE
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| 102 | adp E_ELB
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| 103 | loi _EM_PSIZE ; LB of previous encaps
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| 104 | lae enc_lb
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| 105 | sti _EM_PSIZE
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| 106 | lal H_ELB
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| 107 | loi _EM_PSIZE
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| 108 | adp E_EHA
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| 109 | loi _EM_PSIZE ; previous handler
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| 110 | sig
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| 111 | asp _EM_PSIZE
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| 112 | ; previous handler is re-instated, time to call Q
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| 113 | lol TRAP ; the one and only real parameter
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| 114 | lal H_ELB
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| 115 | loi _EM_PSIZE
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| 116 | lpb ; argument base of enclosing encaps
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| 117 | adp QARG
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| 118 | loi PIISZ
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| 119 | exg _EM_PSIZE
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| 120 | dup _EM_PSIZE ; The static link is now on top
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| 121 | zer _EM_PSIZE
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| 122 | cmp
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| 123 | zeq *1
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| 124 | ; non-zero LB
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| 125 | exg _EM_PSIZE
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| 126 | cai
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| 127 | asp _EM_WSIZE+_EM_PSIZE
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| 128 | bra *2
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| 129 | 1
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| 130 | ; zero LB
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| 131 | asp _EM_PSIZE
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| 132 | cai
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| 133 | asp _EM_WSIZE
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| 134 | 2
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| 135 | ; now reinstate handler for continued execution of p
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| 136 | lal H_ELB
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| 137 | loi _EM_PSIZE
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| 138 | lae enc_lb
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| 139 | sti _EM_PSIZE
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| 140 | lpi $handler
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| 141 | sig
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| 142 | asp _EM_PSIZE
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| 143 | rtt
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| 144 | end ?
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