feat(core/asm): add assembler pipeline orchestrator
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@@ -0,0 +1,265 @@
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using System;
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using System.Collections.Generic;
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using System.Globalization;
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using System.Text;
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namespace Chip8.Core.Assembly;
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public sealed class Assembler
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{
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const int layoutIterationLimit = 32;
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readonly ushort baseAddress;
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public Assembler(ushort baseAddress = Machine.programStart)
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{
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this.baseAddress = baseAddress;
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}
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public static byte[] assembleRom(string source, ushort baseAddress = Machine.programStart) =>
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new Assembler(baseAddress).assemble(source).rom;
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public AssemblyResult assemble(string source)
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{
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List<Token> tokens = new Lexer(source).tokenize();
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List<Token> expanded = new MacroExpander().expand(tokens);
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List<Statement> statements = new Parser(expanded).parse();
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Dictionary<string, int> symbols = resolveSymbols(statements);
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return emit(statements, symbols);
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}
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Dictionary<string, int> resolveSymbols(List<Statement> statements)
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{
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var symbols = new Dictionary<string, int>(StringComparer.Ordinal);
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for (int iteration = 0; iteration < layoutIterationLimit; iteration++)
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{
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var next = new Dictionary<string, int>(StringComparer.Ordinal);
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Func<Token, int> resolver = token => symbols.TryGetValue(token.text, out int value) ? value : 0;
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int address = baseAddress;
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foreach (Statement statement in statements)
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{
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address = layoutStatement(statement, next, resolver, address);
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}
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if (sameSymbols(symbols, next))
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{
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return next;
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}
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symbols = next;
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}
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throw new AsmException("symbol layout did not converge (possible circular reference)", new SourcePosition(0, 0));
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}
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int layoutStatement(Statement statement, Dictionary<string, int> symbols, Func<Token, int> resolver, int address)
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{
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switch (statement)
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{
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case LabelStatement label:
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define(symbols, label.name, address, label.position);
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return address;
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case ConstantStatement constant:
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define(symbols, constant.name, Expression.evaluate(constant.expression, resolver, constant.position), constant.position);
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return address;
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case OrgStatement org:
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return requireForward(Expression.evaluate(org.expression, resolver, org.position), org.position, address);
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case AlignStatement align:
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return alignTo(address, Expression.evaluate(align.expression, resolver, align.position), align.position);
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case DataStatement data:
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return address + data.items.Count * (data.word ? 2 : 1);
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case InstructionStatement instruction:
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return address + InstructionEncoder.measure(instruction, resolver);
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default:
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return address;
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}
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}
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AssemblyResult emit(List<Statement> statements, Dictionary<string, int> symbols)
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{
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Func<Token, int> resolver = token => symbols.TryGetValue(token.text, out int value)
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? value
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: throw new AsmException("undefined symbol '" + token.text + "'", token.position);
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var writes = new Dictionary<int, byte>();
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var listing = new StringBuilder();
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int address = baseAddress;
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int highest = baseAddress;
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foreach (Statement statement in statements)
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{
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switch (statement)
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{
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case LabelStatement label:
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listing.Append(labelLine(label.name, address));
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break;
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case ConstantStatement constant:
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listing.Append(constantLine(constant.name, symbols[constant.name]));
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break;
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case OrgStatement org:
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address = requireForward(Expression.evaluate(org.expression, resolver, org.position), org.position, address);
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break;
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case AlignStatement align:
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address = alignTo(address, Expression.evaluate(align.expression, resolver, align.position), align.position);
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break;
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case DataStatement data:
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address = emitData(data, resolver, writes, listing, address);
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break;
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case InstructionStatement instruction:
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address = emitInstruction(instruction, resolver, writes, listing, address);
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break;
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}
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highest = Math.Max(highest, address);
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}
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return new AssemblyResult(buildRom(writes, highest), baseAddress, symbols, listing.ToString());
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}
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int emitData(DataStatement data, Func<Token, int> resolver, Dictionary<int, byte> writes, StringBuilder listing, int address)
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{
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int start = address;
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var bytes = new List<byte>();
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foreach (IReadOnlyList<Token> item in data.items)
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{
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int value = Expression.evaluate(item, resolver, data.position);
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if (data.word)
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{
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if (value is < 0 or > 0xFFFF)
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{
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throw new AsmException("DW value 0x" + value.ToString("X") + " out of 16-bit range", data.position);
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}
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bytes.Add((byte)(value >> 8));
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bytes.Add((byte)(value & 0xFF));
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}
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else
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{
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if (value is < -128 or > 0xFF)
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{
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throw new AsmException("DB value 0x" + value.ToString("X") + " out of byte range", data.position);
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}
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bytes.Add((byte)(value & 0xFF));
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}
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}
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foreach (byte value in bytes)
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{
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writes[address++] = value;
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}
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listing.Append(bytesLine(start, bytes, data.word ? "DW" : "DB"));
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return address;
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}
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int emitInstruction(InstructionStatement instruction, Func<Token, int> resolver, Dictionary<int, byte> writes, StringBuilder listing, int address)
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{
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var bytes = new List<byte>();
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InstructionEncoder.emit(instruction, resolver, bytes);
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int start = address;
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foreach (byte value in bytes)
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{
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writes[address++] = value;
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}
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ushort opcode = (ushort)((bytes[0] << 8) | bytes[1]);
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ushort extra = bytes.Count == 4 ? (ushort)((bytes[2] << 8) | bytes[3]) : (ushort)0;
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listing.Append(instructionLine(start, bytes, Disassembler.describe(opcode, extra)));
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return address;
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}
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byte[] buildRom(Dictionary<int, byte> writes, int highest)
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{
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int length = Math.Max(0, highest - baseAddress);
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var rom = new byte[length];
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foreach (KeyValuePair<int, byte> write in writes)
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{
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rom[write.Key - baseAddress] = write.Value;
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}
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return rom;
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}
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static void define(Dictionary<string, int> symbols, string name, int value, SourcePosition position)
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{
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if (symbols.ContainsKey(name))
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{
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throw new AsmException("duplicate definition of '" + name + "'", position);
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}
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symbols[name] = value;
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}
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int requireForward(int target, SourcePosition position, int address)
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{
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if (target < baseAddress)
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{
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throw new AsmException("ORG 0x" + target.ToString("X") + " is below base 0x" + baseAddress.ToString("X"), position);
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}
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return target;
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}
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static int alignTo(int address, int boundary, SourcePosition position)
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{
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if (boundary <= 0)
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{
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throw new AsmException("ALIGN needs a positive boundary", position);
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}
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int remainder = address % boundary;
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return remainder == 0 ? address : address + (boundary - remainder);
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}
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static bool sameSymbols(Dictionary<string, int> left, Dictionary<string, int> right)
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{
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if (left.Count != right.Count)
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{
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return false;
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}
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foreach (KeyValuePair<string, int> entry in left)
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{
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if (!right.TryGetValue(entry.Key, out int value) || value != entry.Value)
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{
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return false;
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}
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}
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return true;
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}
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static string labelLine(string name, int address) =>
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" " + name + ": (= 0x" + address.ToString("X4", CultureInfo.InvariantCulture) + ")\n";
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static string constantLine(string name, int value) =>
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" " + name + " = 0x" + value.ToString("X", CultureInfo.InvariantCulture) + "\n";
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static string instructionLine(int address, List<byte> bytes, string text) =>
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addressColumn(address) + hexColumn(bytes).PadRight(12) + text + "\n";
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static string bytesLine(int address, List<byte> bytes, string keyword) =>
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addressColumn(address) + hexColumn(bytes).PadRight(12) + keyword + "\n";
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static string addressColumn(int address) =>
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"0x" + address.ToString("X4", CultureInfo.InvariantCulture) + ": ";
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static string hexColumn(List<byte> bytes)
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{
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var builder = new StringBuilder();
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foreach (byte value in bytes)
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{
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builder.Append(value.ToString("X2", CultureInfo.InvariantCulture)).Append(' ');
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}
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return builder.ToString().TrimEnd();
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}
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}
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@@ -0,0 +1,19 @@
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using System.Collections.Generic;
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namespace Chip8.Core.Assembly;
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public sealed class AssemblyResult
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{
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public AssemblyResult(byte[] rom, ushort baseAddress, IReadOnlyDictionary<string, int> symbols, string listing)
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{
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this.rom = rom;
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this.baseAddress = baseAddress;
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this.symbols = symbols;
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this.listing = listing;
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}
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public byte[] rom { get; }
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public ushort baseAddress { get; }
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public IReadOnlyDictionary<string, int> symbols { get; }
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public string listing { get; }
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}
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