166 lines
4.5 KiB
Zig
166 lines
4.5 KiB
Zig
const std = @import("std");
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const value = @import("value.zig");
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const Allocator = std.mem.Allocator;
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// hack. ugly hack. zig has compiler crash.
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const AllOpcodes = struct {
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pub Constant: u8 = 0,
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pub ConstantLong: u8 = 1,
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pub Return: u8 = 2,
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};
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pub const OpCode = AllOpcodes{};
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fn simpleInstruction(
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stdout: var,
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comptime name: []const u8,
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offset: usize,
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) !usize {
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try stdout.print("{}\n", name);
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return offset + 1;
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}
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fn constantInstruction(
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stdout: var,
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comptime name: []const u8,
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chunk: *Chunk,
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offset: usize,
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) !usize {
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// get the constant's index in constants slice
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var idx = chunk.code[offset + 1];
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try stdout.print("\t{}\t{} '", name, idx);
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try value.printValue(stdout, chunk.constants.values[idx]);
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try stdout.print("'\n");
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return offset + 2;
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}
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fn constantLongInstruction(
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stdout: var,
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comptime name: []const u8,
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chunk: *Chunk,
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offset: usize,
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) !usize {
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// get the constant's index in constants slice
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var v0: u8 = chunk.code[offset + 3];
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var v1: u8 = chunk.code[offset + 2];
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var v2: u8 = chunk.code[offset + 1];
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// TODO: this does not work. just decreased first term
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// to fix a compile error.
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// we should also move the actual printing into its own
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// function too since constantInstruction and
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// constantLongInstruction share code.
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var idx: u24 = (v2 << 4) | (v1 << 7) | v0;
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try stdout.print("\t{}\t{} '", name, idx);
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try value.printValue(stdout, chunk.constants.values[idx]);
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try stdout.print("'\n");
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return offset + 2;
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}
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pub const Chunk = struct {
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count: usize,
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lines: []usize,
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code: []u8,
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allocator: *Allocator,
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constants: value.ValueList,
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pub fn init(allocator: *Allocator) !Chunk {
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return Chunk{
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.count = 0,
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.allocator = allocator,
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.code = try allocator.alloc(u8, 0),
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.lines = try allocator.alloc(usize, 0),
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.constants = try value.ValueList.init(allocator),
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};
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}
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pub fn write(self: *Chunk, byte: u8, line: usize) !void {
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if (self.code.len < self.count + 1) {
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self.code = try self.allocator.realloc(
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self.code,
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self.count + 1,
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);
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self.lines = try self.allocator.realloc(
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self.lines,
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self.count + 1,
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);
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}
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self.code[self.count] = byte;
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self.lines[self.count] = line;
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self.count += 1;
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}
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pub fn addConstant(self: *Chunk, val: value.Value) !u8 {
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try self.constants.write(val);
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return self.constants.count - 1;
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}
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pub fn writeConstant(self: *Chunk, val: value.Value, line: usize) !void {
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try self.constants.write(val);
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var constant_idx = self.constants.count - 1;
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if (constant_idx < 256) {
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try self.write(OpCode.Constant, line);
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try self.write(@intCast(u8, constant_idx), line);
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} else {
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// TODO: convert the usize to u24, and from
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// u24, split it into three u8's.
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// also convert from u8 back to u24.
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// i know that we can do from two u8's to go to a u16
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// with (v1 << 7) | v0.
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try self.write(0, line);
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}
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}
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pub fn disassembleInstruction(
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self: *Chunk,
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stdout: var,
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index: usize,
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) !usize {
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try stdout.print("{} ", index);
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if (index > 0 and self.lines[index] == self.lines[index - 1]) {
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try stdout.print(" | ");
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} else {
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try stdout.print("{} ", self.lines[index]);
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}
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var instruction = self.code[index];
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if (instruction == OpCode.Return) {
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return try simpleInstruction(stdout, "OP_RETURN", index);
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} else if (instruction == OpCode.Constant) {
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return try constantInstruction(stdout, "OP_CONSTANT", self, index);
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} else if (instruction == OpCode.ConstantLong) {
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return try constantLongInstruction(
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stdout,
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"OP_CONSTANT_LONG",
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self,
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index,
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);
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} else {
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try stdout.print("Unknown opcode: {}\n", instruction);
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return index + 1;
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}
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}
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pub fn disassemble(self: *Chunk, stdout: var, name: []const u8) !void {
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try stdout.print("== {} ==\n", name);
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var i: usize = 0;
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while (i < self.count) {
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i = try self.disassembleInstruction(stdout, i);
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}
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}
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};
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