mirror of
https://github.com/gnif/LookingGlass.git
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70 lines
2.0 KiB
C
70 lines
2.0 KiB
C
/*
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Looking Glass - KVM FrameRelay (KVMFR) Client
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Copyright (C) 2017 Geoffrey McRae <geoff@hostfission.com>
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This program is free software; you can redistribute it and/or modify it under
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the terms of the GNU General Public License as published by the Free Software
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Foundation; either version 2 of the License, or (at your option) any later
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version.
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This program is distributed in the hope that it will be useful, but WITHOUT ANY
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WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
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PARTICULAR PURPOSE. See the GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along with
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this program; if not, write to the Free Software Foundation, Inc., 59 Temple
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Place, Suite 330, Boston, MA 02111-1307 USA
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*/
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#include "delay.h"
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#include <SDL2/SDL.h>
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#include "debug.h"
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static unsigned int delay_loop_count = 0;
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void delay()
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{
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unsigned char j;
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for(unsigned int i = 0; i < delay_loop_count; ++i)
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{
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j = 0;
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while(--j)
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asm("");
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}
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}
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void delay_calibrate()
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{
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// initialize the poll limit to a sane value
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for(int start = SDL_GetTicks(); SDL_GetTicks() - start < 10; ++delay_loop_count) {}
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DEBUG_INFO("Init : %u", delay_loop_count);
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// the following loop must produce 20 concurrent valid results to ensure a valid calculation
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int okCount = 0;
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while(okCount < 20)
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{
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// time the final loop and calculate the remaining time
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unsigned int ticks = SDL_GetTicks();
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delay();
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int remain = 10 - (SDL_GetTicks() - ticks);
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// if the remaining time is within 2ms, accept it (Linux is not a RTOS)
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if (remain > -2 && remain < 2)
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{
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++okCount;
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continue;
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}
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// the delay is out of spec, adjust the limit
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okCount = 0;
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DEBUG_INFO("Diff : %c%d ms", remain > 0 ? '-' : '+', abs(remain));
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delay_loop_count += ceil(((double)delay_loop_count / 10.0) * remain);
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}
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DEBUG_INFO("Final: %u", delay_loop_count);
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// scale the limit for a 1ms delay
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delay_loop_count = ceil((double)delay_loop_count / 10.0);
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} |