new cpu skeleton
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src/cpu6502.d
250
src/cpu6502.d
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@ -1,6 +1,9 @@
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module cpu6502;
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import std.array, std.format;
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enum Strict : bool
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{
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no, yes
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@ -12,8 +15,63 @@ enum Cumulative : bool
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}
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class Cpu(bool cumulative)
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template is6502(T)
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{
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enum is6502 = __traits(getMember, T, "_chip") == "6502";
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}
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template is65C02(T)
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{
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enum is65C02 = __traits(getMember, T, "_chip") == "65C02";
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}
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// The following versions are mutually exclusive.
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// OpDelegates: each opcode is a method of the Cpu class.
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version(OpDelegates)
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{
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enum versionCheck = 1;
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enum opArray = true;
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}
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// OpFunctions: each opcode is a free function with a Cpu argument.
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version(OpFunctions)
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{
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enum versionCheck = 2;
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enum opArray = true;
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}
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// OpSwitch: each opcode is inlined in a 256-case switch.
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version(OpSwitch)
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{
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enum versionCheck = 3;
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enum opArray = false;
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}
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// OpNestedSwitch: each opcode is inlined in a nested switch.
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// (The outer one switches on the high byte, with each case switching
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// on the low byte.)
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version(OpNestedSwitch)
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{
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enum versionCheck = 4;
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enum opArray = false;
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}
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// At least one of the previous versions must be specified.
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static if (!__traits(compiles, { bool b = opArray; })) enum opArray = 0;
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static assert (versionCheck);
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final class Cpu(string chip, bool strict, bool cumulative)
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{
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static assert(chip == "6502" || chip == "65C02" || chip == "65c02");
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enum _isCpu = true;
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enum _chip = (chip == "6502" ? "6502" : "65C02");
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enum _isStrict = strict;
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enum _isCumulative = cumulative;
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struct _Mem
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{
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// Reads a value from system memory.
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@ -41,5 +99,193 @@ class Cpu(bool cumulative)
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}
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_Clock clock;
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ubyte A, X, Y, S, P;
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ubyte A, X, Y, S;
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ushort PC;
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ubyte N, Z;
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bool V, D, I, C;
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static if (opArray) mixin(OpArrayDef());
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// TODO: other methods for stopping cpu
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bool keepRunning;
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this()
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{
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static if (opArray) mixin(OpArrayInit());
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}
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final void statusFromByte(ubyte p)
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{
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N = p;
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V = ((p & 0x40) != 0);
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D = ((p & 0x08) != 0);
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I = ((p & 0x04) != 0);
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Z = ((p & 0x02) ? 0 : 1);
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C = ((val & 0x01) != 0);
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}
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final ubyte statusToByte()
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{
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return (C ? 0x01 : 0) |
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((Z == 0) ? 0x02 : 0) |
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(I ? 0x04 : 0) |
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(D ? 0x08 : 0) |
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0x30 | // break and reserved both set
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(V ? 0x40 : 0) |
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(N & 0x80);
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}
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final void run(bool continuous)
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{
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keepRunning = continuous;
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// TODO debugging info?
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ubyte opcode;
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do {
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// XXX check signals
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// XXX figure out cumulative/final cycle stuff
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static if (cumulative) {}
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else
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clock.tick();
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opcode = memory.read(PC++);
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mixin(OpExecute(_chip));
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} while (keepRunning);
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}
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version(OpDelegates) mixin (OpBodies(_chip));
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}
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version(OpFunctions) mixin(OpBodies("6502"));
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version(OpFunctions) mixin(OpBodies("65C02"));
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string OpArrayDef()
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{
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version(OpDelegates)
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return q{void delegate()[256] opcodes;};
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else version(OpFunctions)
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return q{void function(typeof(this))[256] opcodes;};
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else
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return "";
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}
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string OpArrayInit()
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{
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static if (!opArray) return "";
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else
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{
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string ret;
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foreach (op; 0..256)
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{
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version(OpDelegates)
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ret ~= "opcodes[0x" ~ Hex2(op) ~ "] = &opcode_" ~ Hex2(op) ~
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";\n";
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version(OpFunctions)
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ret ~= "opcodes[0x" ~ Hex2(op) ~ "] = &opcode_" ~ Hex2(op) ~
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"!(typeof(this));\n";
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}
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return ret;
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}
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}
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string OpBodies(string chip)
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{
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static if (!opArray) return "";
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else
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{
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string ret;
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foreach (op; 0..256)
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{
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version(OpDelegates)
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ret ~= "final void opcode_" ~ Hex2(op) ~ "()\n{\n" ~
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OpBody(op, chip) ~ "}\n";
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version(OpFunctions)
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ret ~= "void opcode_" ~ Hex2(op) ~
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"(T)(T cpu) if (is" ~ chip ~ "!T)\n{\n" ~
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OpBody(op, chip) ~ "}\n";
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}
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return ret;
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}
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}
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string OpExecute(string chip)
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{
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version(OpDelegates)
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return q{opcodes[opcode]();};
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version(OpFunctions)
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return q{opcodes[opcode](this);};
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version(OpSwitch)
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return Switch256(chip);
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version(OpNestedSwitch)
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return Switch16x16(chip);
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}
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string Switch256(string chip)
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{
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string ret = "final switch (opcode)\n{\n";
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foreach (op; 0..256)
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ret ~= "case 0x" ~ Hex2(op) ~ ":\n" ~ OpBody(op, chip) ~ "break;\n\n";
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return ret ~ "}\n";
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}
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string Switch16x16(string chip)
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{
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string ret = "final switch (opcode & 0xF0)\n{\n";
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foreach (opHi; 0..16)
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{
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ret ~= "case 0x" ~ Hex1(opHi) ~ "0:\n" ~
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"final switch(opcode & 0x0F)\n{\n";
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foreach (opLo; 0..16)
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{
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int op = opLo | (opHi << 4);
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ret ~= "case 0x0" ~ Hex1(opLo) ~ ":\n" ~ OpBody(op, chip) ~
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"break;\n\n";
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}
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ret ~= "}\nbreak;\n";
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}
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return ret ~ "}\n";
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}
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string OpBody(int op, string chip)
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{
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return "";
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}
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// Custom hex printing.
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// (to!string(x, 16) uses uppercase, which makes "8" and "B" hard to
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// tell apart, and format("%0.2x", x) can't be used in CTFE.)
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enum HEX_DIGITS = "0123456789abcdef";
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string Hex1(int dec)
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{
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return HEX_DIGITS[dec..dec+1];
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}
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string Hex2(int dec)
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{
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int highNybble = (dec & 0xF0) >> 4;
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int lowNybble = dec & 0x0F;
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return HEX_DIGITS[highNybble..highNybble+1] ~
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HEX_DIGITS[lowNybble..lowNybble+1];
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}
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alias Cpu!("6502", false, false) T1;
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alias Cpu!("6502", false, true) T2;
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alias Cpu!("6502", true, false) T3;
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alias Cpu!("6502", true, true) T4;
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alias Cpu!("65C02", false, false) T5;
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alias Cpu!("65C02", false, true) T6;
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alias Cpu!("65C02", true, false) T7;
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alias Cpu!("65C02", true, true) T8;
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void main()
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{
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import std.stdio;
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writeln(Switch16x16("6502"));
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}
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