172 lines
4.2 KiB
D
172 lines
4.2 KiB
D
/+
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+ video/offsets.d
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+
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+ Copyright: 2007 Gerald Stocker
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+
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+ This file is part of Twoapple.
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+
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+ Twoapple is free software; you can redistribute it and/or modify
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+ it under the terms of the GNU General Public License as published by
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+ the Free Software Foundation; either version 2 of the License, or
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+ (at your option) any later version.
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+
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+ Twoapple is distributed in the hope that it will be useful,
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+ but WITHOUT ANY WARRANTY; without even the implied warranty of
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+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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+ GNU General Public License for more details.
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+
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+ You should have received a copy of the GNU General Public License
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+ along with Twoapple; if not, write to the Free Software
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+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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+/
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import video.base : Mode;
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static this()
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{
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hCounter = new HorizontalCounter();
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vCounter = new VerticalCounter();
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for (int scanLine = 0; scanLine < 192; ++scanLine)
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{
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firstDisplayedOffset[Mode.HIRES][scanLine] =
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screenOffset(&vCounter.states[scanLine], &hCounter.states[25],
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Mode.HIRES);
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firstDisplayedOffset[Mode.LORES][scanLine] =
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screenOffset(&vCounter.states[scanLine], &hCounter.states[25],
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Mode.LORES);
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firstDisplayedOffset[Mode.TEXT][scanLine] =
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screenOffset(&vCounter.states[scanLine], &hCounter.states[25],
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Mode.TEXT);
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}
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}
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ushort scanOffset(uint vidClock, Mode mode)
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{
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if (((vidClock % 65) == 25) && (vidClock / 65) < 192)
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return firstDisplayedOffset[mode][vidClock / 65];
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else
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return screenOffset(&vCounter.states[vidClock / 65],
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&hCounter.states[vidClock % 65], mode);
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}
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ushort scanOffset(uint line, uint col, Mode mode)
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{
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if ((col == 25) && (line < 192))
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return firstDisplayedOffset[mode][line];
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else
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return screenOffset(&vCounter.states[line], &hCounter.states[col],
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mode);
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}
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private:
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HorizontalCounter hCounter;
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VerticalCounter vCounter;
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ushort[192][3] firstDisplayedOffset;
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class HorizontalCounter
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{
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State[65] states;
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this()
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{
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uint counter = 0b0000000;
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int number = 0;
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while(counter <= 0b1111111)
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{
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states[number++] = new State(counter);
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if (counter == 0b0000000)
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counter = 0b1000000;
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else
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++counter;
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}
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}
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enum
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{
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HP = 0b1000000,
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H5 = 0b0100000,
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H4 = 0b0010000,
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H3 = 0b0001000,
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H2 = 0b0000100,
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H1 = 0b0000010,
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H0 = 0b0000001
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}
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class State
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{
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int a6_a5_a4_a3;
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int a2_a1_a0;
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this(int counter)
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{
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a6_a5_a4_a3 = counter & (H5 | H4 | H3);
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a2_a1_a0 = counter & (H2 | H1 | H0);
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}
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}
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}
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class VerticalCounter
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{
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State[] states;
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this()
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{
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uint counter = 0b011111010; // XXX PAL: 0b011001000
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states.length = 512 - counter;
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int scanline = 256;
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while (counter <= 0b111111111)
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{
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states[scanline++] = new State(counter++);
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if (counter == 0b100000000) scanline = 0;
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}
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}
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enum
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{
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V5 = 0b100000000,
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V4 = 0b010000000,
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V3 = 0b001000000,
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V2 = 0b000100000,
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V1 = 0b000010000,
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V0 = 0b000001000,
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VC = 0b000000100,
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VB = 0b000000010,
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VA = 0b000000001
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}
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class State
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{
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int a12_a11_a10;
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int a9_a8_a7;
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int a6_a5_a4_a3;
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this(int counter)
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{
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a12_a11_a10 = (counter & (VC | VB | VA)) << 10;
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a9_a8_a7 = (counter & (V2 | V1 | V0)) << 4;
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a6_a5_a4_a3 = ((counter & (V4 | V3)) >> 1) |
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((counter & (V4 | V3)) >> 3);
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}
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}
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}
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alias VerticalCounter.State vState;
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alias HorizontalCounter.State hState;
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ushort screenOffset(vState* vSt, hState* hSt, Mode mode)
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{
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ushort sum_a6_a5_a4_a3 =
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(vSt.a6_a5_a4_a3 + hSt.a6_a5_a4_a3 + 0b1101000) & 0b1111000;
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ushort offset = vSt.a9_a8_a7 | sum_a6_a5_a4_a3 | hSt.a2_a1_a0;
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if (mode == Mode.HIRES)
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{
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offset |= vSt.a12_a11_a10;
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}
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return offset;
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}
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