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// ============================================================================

//        __

//   \\__/ o\    (C) 2012-2016  Robert Finch, Stratford

//    \  __ /    All rights reserved.

//     \/_//     robfinch<remove>@finitron.ca

//       ||

//

// LockSemaphore.c

//

// This source file is free software: you can redistribute it and/or modify 

// it under the terms of the GNU Lesser General Public License as published 

// by the Free Software Foundation, either version 3 of the License, or     

// (at your option) any later version.                                      

//                                                                          

// This source file is distributed in the hope that it will be useful,      

// but WITHOUT ANY WARRANTY; without even the implied warranty of           

// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            

// GNU General Public License for more details.                             

//                                                                          

// You should have received a copy of the GNU General Public License        

// along with this program.  If not, see <http://www.gnu.org/licenses/>.    

//                                                                          

// ============================================================================

//

pascal int LockSemaphore(int *sema, int retries)

{

    asm {

                ldi             r1,#1

                br              .0005

        lw      r1,32[bp]                ; r1 = pointer to semaphore

                lw      r2,40[bp]                ; r2 = #retries

.0001:

                tst             p0,r2                    ; timeout expired ?

p0.eq   mov             r1,r0                    ; if yes, return 0

p0.eq   br              .0005

        subui   r2,r2,#1                 ; decrement timeout

        lvwar   r3,[r1]                  ; load and reserve address

                tst             p0,r3

p0.lt   br      .0003            ; branch if free

        cmp     p0,r3,tr            ; test if already locked by this task

p0.eq   br              .0002

        ;chk     r3,r0,#256          ; check if locked by a valid task

.0003:

        swcr    tr,[r1]             ; try and lock it

p0.ne   br              .0001            ; lock failed, go try again

.0002:

        ldi     r1,#1

.0005:

    }

}