mirror of https://github.com/fadden/6502bench.git
356 lines
12 KiB
C#
356 lines
12 KiB
C#
/*
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* Copyright 2018 faddenSoft
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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using System;
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using System.Text;
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namespace Asm65 {
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/// <summary>
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/// Status flag holder. Each flag may be known to be zero, known to be one, or
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/// hold an indeterminate value (represented as a negative number).
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///
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/// For the 65802/65816, we also keep track of the E flag (emulation bit), even though
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/// that's not actually held in the P register.
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///
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/// Note this is a value type, not a reference type.
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///
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/// The default value is UNSPECIFIED for all bits.
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/// </summary>
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public struct StatusFlags {
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private TriState16 mState;
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/// <summary>
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/// Flag bits, from processor status register definition. The 'e' (emulation)
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/// flag from the 65816 is tacked onto the end.
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///
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/// The enumerated value matches the bit number in the P register.
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/// </summary>
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public enum FlagBits {
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C = 0,
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Z = 1,
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I = 2,
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D = 3,
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B = 4, // all CPUs except 65802/65816 in native mode
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X = 4, // 65802/65816 in native mode
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M = 5, // 65802/65816 in native mode (always 1 on other CPUs)
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V = 6,
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N = 7,
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E = 8 // not actually part of P-reg; accessible only through XCE
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}
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/// <summary>
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/// Default value (all flags UNSPECIFIED). A newly-created array of StatusFlags will
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/// all have this value.
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/// </summary>
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public static readonly StatusFlags DefaultValue =
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new StatusFlags { mState = new TriState16(0, 0) };
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/// <summary>
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/// All flags are INDETERMINATE.
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/// </summary>
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public static readonly StatusFlags AllIndeterminate =
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new StatusFlags() { mState = new TriState16(0x01ff, 0x01ff) };
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public int C {
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get {
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return mState.GetBit((int)FlagBits.C);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.C);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.C);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.C);
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} else {
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mState.SetIndeterminate((int)FlagBits.C);
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}
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}
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}
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public int Z {
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get {
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return mState.GetBit((int)FlagBits.Z);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.Z);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.Z);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.Z);
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} else {
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mState.SetIndeterminate((int)FlagBits.Z);
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}
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}
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}
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public int I {
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get {
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return mState.GetBit((int)FlagBits.I);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.I);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.I);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.I);
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} else {
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mState.SetIndeterminate((int)FlagBits.I);
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}
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}
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}
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public int D {
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get {
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return mState.GetBit((int)FlagBits.D);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.D);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.D);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.D);
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} else {
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mState.SetIndeterminate((int)FlagBits.D);
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}
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}
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}
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/// <summary>
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/// X (index register width) flag. For an unambiguous value, use IsShortX.
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/// </summary>
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public int X {
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get {
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return mState.GetBit((int)FlagBits.X);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.X);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.X);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.X);
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} else {
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mState.SetIndeterminate((int)FlagBits.X);
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}
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}
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}
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/// <summary>
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/// M (accumulator width) flag. For an unambiguous value, use IsShortM.
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/// </summary>
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public int M {
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get {
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return mState.GetBit((int)FlagBits.M);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.M);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.M);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.M);
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} else {
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mState.SetIndeterminate((int)FlagBits.M);
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}
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}
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}
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public int V {
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get {
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return mState.GetBit((int)FlagBits.V);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.V);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.V);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.V);
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} else {
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mState.SetIndeterminate((int)FlagBits.V);
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}
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}
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}
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public int N {
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get {
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return mState.GetBit((int)FlagBits.N);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.N);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.N);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.N);
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} else {
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mState.SetIndeterminate((int)FlagBits.N);
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}
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}
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}
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/// <summary>
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/// E (emulation) flag. For an unambiguous value, use IsEmulationMode.
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/// </summary>
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public int E {
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get {
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return mState.GetBit((int)FlagBits.E);
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}
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set {
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if (value == 0) {
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mState.SetZero((int)FlagBits.E);
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} else if (value == 1) {
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mState.SetOne((int)FlagBits.E);
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} else if (value == TriState16.UNSPECIFIED) {
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mState.SetUnspecified((int)FlagBits.E);
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} else {
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mState.SetIndeterminate((int)FlagBits.E);
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}
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}
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}
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public int GetBit(FlagBits index) {
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return mState.GetBit((int) index);
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}
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/// <summary>
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/// Returns true if the current processor status flags are configured for a short
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/// (8-bit) accumulator.
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/// </summary>
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/// <remarks>
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/// This is (mostly) where we decide how to treat ambiguous status flags. We favor
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/// short flags because, when we get it wrong, it tends to be easier to spot (e.g.
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/// LDA #$00xx becomes LDA+BRK). Mistakenly guessing "long" also tends to result in
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/// instructions with other instructions embedded in them, which can be confusing.
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/// </remarks>
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public bool IsShortM {
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get {
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// E==1 --> true (we're in emulation mode)
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// E==0 || E==? : native / assumed native
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// M==1 || M==? --> true (native mode, configured short or assumed short)
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// M==0 --> false (native mode, configured long)
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return (E == 1) || (M != 0);
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}
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}
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/// <summary>
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/// Returns true if the current processor status flags are configured for short
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/// (8-bit) X/Y registers.
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/// </summary>
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public bool IsShortX {
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get {
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// (same logic as ShortM)
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return (E == 1) || (X != 0);
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}
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}
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/// <summary>
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/// Returns true if the current processor status flags are configured for execution
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/// in native mode.
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/// </summary>
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public bool IsEmulationMode {
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get {
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// E==1 : emulation --> true
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// E==0 || E==? : native / assumed native --> false
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return E == 1;
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}
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}
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/// <summary>
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/// Access the value as a single integer. Used for serialization.
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/// </summary>
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public int AsInt {
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get {
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return mState.AsInt;
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}
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}
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/// <summary>
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/// Set the value from an integer. Used for serialization.
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/// </summary>
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public static StatusFlags FromInt(int value) {
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if ((value & ~0x01ff01ff) != 0) {
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throw new InvalidOperationException("Bad StatusFlags value " +
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value.ToString("x8"));
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}
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StatusFlags newFlags = new StatusFlags();
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newFlags.mState.AsInt = value;
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return newFlags;
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}
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/// <summary>
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/// Merge a set of status flags into this one.
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/// </summary>
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public void Merge(StatusFlags other) {
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mState.Merge(other.mState);
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}
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/// <summary>
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/// Applies flags, overwriting existing values. This will set one or more flags
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/// to 0, 1, or indeterminate. Unspecified (0/0) values have no effect.
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///
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/// This is useful when merging "overrides" in.
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/// </summary>
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public void Apply(StatusFlags overrides) {
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mState.Apply(overrides.mState);
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}
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/// <summary>
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/// Returns a string representation of the flags.
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/// </summary>
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/// <param name="showMXE">If set, include the 'E' flag, and show M/X.</param>
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public string ToString(bool showMXE) {
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StringBuilder sb = new StringBuilder(showMXE ? 10 : 8);
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sb.Append("-?nN"[N + 2]);
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sb.Append("-?vV"[V + 2]);
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sb.Append(showMXE ? "-?mM"[M + 2] : '-');
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sb.Append(showMXE ? "-?xX"[X + 2] : '-');
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sb.Append("-?dD"[D + 2]);
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sb.Append("-?iI"[I + 2]);
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sb.Append("-?zZ"[Z + 2]);
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sb.Append("-?cC"[C + 2]);
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if (showMXE) {
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sb.Append(' ');
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sb.Append("-?eE"[E + 2]);
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}
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return sb.ToString();
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}
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public static bool operator ==(StatusFlags a, StatusFlags b) {
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return a.mState == b.mState;
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}
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public static bool operator !=(StatusFlags a, StatusFlags b) {
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return !(a == b);
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}
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public override bool Equals(object obj) {
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return obj is StatusFlags && this == (StatusFlags)obj;
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}
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public override int GetHashCode() {
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return mState.GetHashCode();
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}
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public override string ToString() {
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return ToString(true);
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// + " [" + mState.ToString() + "]"
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}
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}
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}
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