--- /dev/null
+# This file is for zig-specific build artifacts.
+# If you have OS-specific or editor-specific files to ignore,
+# such as *.swp or .DS_Store, put those in your global
+# ~/.gitignore and put this in your ~/.gitconfig:
+#
+# [core]
+# excludesfile = ~/.gitignore
+#
+# Cheers!
+# -andrewrk
+
+.zig-cache/
+zig-out/
+/release/
+/debug/
+/build/
+/build-*/
+/docgen_tmp/
+
+# Although this was renamed to .zig-cache, let's leave it here for a few
+# releases to make it less annoying to work with multiple branches.
+zig-cache/
+
--- /dev/null
+const std = @import("std");
+
+// Although this function looks imperative, it does not perform the build
+// directly and instead it mutates the build graph (`b`) that will be then
+// executed by an external runner. The functions in `std.Build` implement a DSL
+// for defining build steps and express dependencies between them, allowing the
+// build runner to parallelize the build automatically (and the cache system to
+// know when a step doesn't need to be re-run).
+pub fn build(b: *std.Build) void {
+ // Standard target options allow the person running `zig build` to choose
+ // what target to build for. Here we do not override the defaults, which
+ // means any target is allowed, and the default is native. Other options
+ // for restricting supported target set are available.
+ const target = b.standardTargetOptions(.{});
+ // Standard optimization options allow the person running `zig build` to select
+ // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not
+ // set a preferred release mode, allowing the user to decide how to optimize.
+ const optimize = b.standardOptimizeOption(.{});
+ // It's also possible to define more custom flags to toggle optional features
+ // of this build script using `b.option()`. All defined flags (including
+ // target and optimize options) will be listed when running `zig build --help`
+ // in this directory.
+
+ // This creates a module, which represents a collection of source files alongside
+ // some compilation options, such as optimization mode and linked system libraries.
+ // Zig modules are the preferred way of making Zig code available to consumers.
+ // addModule defines a module that we intend to make available for importing
+ // to our consumers. We must give it a name because a Zig package can expose
+ // multiple modules and consumers will need to be able to specify which
+ // module they want to access.
+ const mod = b.addModule("lc3-vm_zig", .{
+ // The root source file is the "entry point" of this module. Users of
+ // this module will only be able to access public declarations contained
+ // in this file, which means that if you have declarations that you
+ // intend to expose to consumers that were defined in other files part
+ // of this module, you will have to make sure to re-export them from
+ // the root file.
+ .root_source_file = b.path("src/root.zig"),
+ // Later on we'll use this module as the root module of a test executable
+ // which requires us to specify a target.
+ .target = target,
+ });
+
+ // Here we define an executable. An executable needs to have a root module
+ // which needs to expose a `main` function. While we could add a main function
+ // to the module defined above, it's sometimes preferable to split business
+ // business logic and the CLI into two separate modules.
+ //
+ // If your goal is to create a Zig library for others to use, consider if
+ // it might benefit from also exposing a CLI tool. A parser library for a
+ // data serialization format could also bundle a CLI syntax checker, for example.
+ //
+ // If instead your goal is to create an executable, consider if users might
+ // be interested in also being able to embed the core functionality of your
+ // program in their own executable in order to avoid the overhead involved in
+ // subprocessing your CLI tool.
+ //
+ // If neither case applies to you, feel free to delete the declaration you
+ // don't need and to put everything under a single module.
+ const exe = b.addExecutable(.{
+ .name = "lc3-vm_zig",
+ .root_module = b.createModule(.{
+ // b.createModule defines a new module just like b.addModule but,
+ // unlike b.addModule, it does not expose the module to consumers of
+ // this package, which is why in this case we don't have to give it a name.
+ .root_source_file = b.path("src/main.zig"),
+ // Target and optimization levels must be explicitly wired in when
+ // defining an executable or library (in the root module), and you
+ // can also hardcode a specific target for an executable or library
+ // definition if desireable (e.g. firmware for embedded devices).
+ .target = target,
+ .optimize = optimize,
+ // List of modules available for import in source files part of the
+ // root module.
+ .imports = &.{
+ // Here "lc3-vm_zig" is the name you will use in your source code to
+ // import this module (e.g. `@import("lc3-vm_zig")`). The name is
+ // repeated because you are allowed to rename your imports, which
+ // can be extremely useful in case of collisions (which can happen
+ // importing modules from different packages).
+ .{ .name = "lc3-vm_zig", .module = mod },
+ },
+ }),
+ });
+
+ // This declares intent for the executable to be installed into the
+ // install prefix when running `zig build` (i.e. when executing the default
+ // step). By default the install prefix is `zig-out/` but can be overridden
+ // by passing `--prefix` or `-p`.
+ b.installArtifact(exe);
+
+ // This creates a top level step. Top level steps have a name and can be
+ // invoked by name when running `zig build` (e.g. `zig build run`).
+ // This will evaluate the `run` step rather than the default step.
+ // For a top level step to actually do something, it must depend on other
+ // steps (e.g. a Run step, as we will see in a moment).
+ const run_step = b.step("run", "Run the app");
+
+ // This creates a RunArtifact step in the build graph. A RunArtifact step
+ // invokes an executable compiled by Zig. Steps will only be executed by the
+ // runner if invoked directly by the user (in the case of top level steps)
+ // or if another step depends on it, so it's up to you to define when and
+ // how this Run step will be executed. In our case we want to run it when
+ // the user runs `zig build run`, so we create a dependency link.
+ const run_cmd = b.addRunArtifact(exe);
+ run_step.dependOn(&run_cmd.step);
+
+ // By making the run step depend on the default step, it will be run from the
+ // installation directory rather than directly from within the cache directory.
+ run_cmd.step.dependOn(b.getInstallStep());
+
+ // This allows the user to pass arguments to the application in the build
+ // command itself, like this: `zig build run -- arg1 arg2 etc`
+ if (b.args) |args| {
+ run_cmd.addArgs(args);
+ }
+
+ // Creates an executable that will run `test` blocks from the provided module.
+ // Here `mod` needs to define a target, which is why earlier we made sure to
+ // set the releative field.
+ const mod_tests = b.addTest(.{
+ .root_module = mod,
+ });
+
+ // A run step that will run the test executable.
+ const run_mod_tests = b.addRunArtifact(mod_tests);
+
+ // Creates an executable that will run `test` blocks from the executable's
+ // root module. Note that test executables only test one module at a time,
+ // hence why we have to create two separate ones.
+ const exe_tests = b.addTest(.{
+ .root_module = exe.root_module,
+ });
+
+ // A run step that will run the second test executable.
+ const run_exe_tests = b.addRunArtifact(exe_tests);
+
+ // A top level step for running all tests. dependOn can be called multiple
+ // times and since the two run steps do not depend on one another, this will
+ // make the two of them run in parallel.
+ const test_step = b.step("test", "Run tests");
+ test_step.dependOn(&run_mod_tests.step);
+ test_step.dependOn(&run_exe_tests.step);
+
+ // Just like flags, top level steps are also listed in the `--help` menu.
+ //
+ // The Zig build system is entirely implemented in userland, which means
+ // that it cannot hook into private compiler APIs. All compilation work
+ // orchestrated by the build system will result in other Zig compiler
+ // subcommands being invoked with the right flags defined. You can observe
+ // these invocations when one fails (or you pass a flag to increase
+ // verbosity) to validate assumptions and diagnose problems.
+ //
+ // Lastly, the Zig build system is relatively simple and self-contained,
+ // and reading its source code will allow you to master it.
+}
--- /dev/null
+.{
+ // This is the default name used by packages depending on this one. For
+ // example, when a user runs `zig fetch --save <url>`, this field is used
+ // as the key in the `dependencies` table. Although the user can choose a
+ // different name, most users will stick with this provided value.
+ //
+ // It is redundant to include "zig" in this name because it is already
+ // within the Zig package namespace.
+ .name = .arithvm_zig,
+ // This is a [Semantic Version](https://semver.org/).
+ // In a future version of Zig it will be used for package deduplication.
+ .version = "0.0.0",
+ // Together with name, this represents a globally unique package
+ // identifier. This field is generated by the Zig toolchain when the
+ // package is first created, and then *never changes*. This allows
+ // unambiguous detection of one package being an updated version of
+ // another.
+ //
+ // When forking a Zig project, this id should be regenerated (delete the
+ // field and run `zig build`) if the upstream project is still maintained.
+ // Otherwise, the fork is *hostile*, attempting to take control over the
+ // original project's identity. Thus it is recommended to leave the comment
+ // on the following line intact, so that it shows up in code reviews that
+ // modify the field.
+ .fingerprint = 0x79da8ce1ed863de0, // Changing this has security and trust implications.
+ // Tracks the earliest Zig version that the package considers to be a
+ // supported use case.
+ .minimum_zig_version = "0.15.1",
+ // This field is optional.
+ // Each dependency must either provide a `url` and `hash`, or a `path`.
+ // `zig build --fetch` can be used to fetch all dependencies of a package, recursively.
+ // Once all dependencies are fetched, `zig build` no longer requires
+ // internet connectivity.
+ .dependencies = .{
+ // See `zig fetch --save <url>` for a command-line interface for adding dependencies.
+ //.example = .{
+ // // When updating this field to a new URL, be sure to delete the corresponding
+ // // `hash`, otherwise you are communicating that you expect to find the old hash at
+ // // the new URL. If the contents of a URL change this will result in a hash mismatch
+ // // which will prevent zig from using it.
+ // .url = "https://example.com/foo.tar.gz",
+ //
+ // // This is computed from the file contents of the directory of files that is
+ // // obtained after fetching `url` and applying the inclusion rules given by
+ // // `paths`.
+ // //
+ // // This field is the source of truth; packages do not come from a `url`; they
+ // // come from a `hash`. `url` is just one of many possible mirrors for how to
+ // // obtain a package matching this `hash`.
+ // //
+ // // Uses the [multihash](https://multiformats.io/multihash/) format.
+ // .hash = "...",
+ //
+ // // When this is provided, the package is found in a directory relative to the
+ // // build root. In this case the package's hash is irrelevant and therefore not
+ // // computed. This field and `url` are mutually exclusive.
+ // .path = "foo",
+ //
+ // // When this is set to `true`, a package is declared to be lazily
+ // // fetched. This makes the dependency only get fetched if it is
+ // // actually used.
+ // .lazy = false,
+ //},
+ },
+ // Specifies the set of files and directories that are included in this package.
+ // Only files and directories listed here are included in the `hash` that
+ // is computed for this package. Only files listed here will remain on disk
+ // when using the zig package manager. As a rule of thumb, one should list
+ // files required for compilation plus any license(s).
+ // Paths are relative to the build root. Use the empty string (`""`) to refer to
+ // the build root itself.
+ // A directory listed here means that all files within, recursively, are included.
+ .paths = .{
+ "build.zig",
+ "build.zig.zon",
+ "src",
+ // For example...
+ //"LICENSE",
+ //"README.md",
+ },
+}
--- /dev/null
+const std = @import("std");
+const lc3vm_zig = @import("lc3-vm_zig");
+
+pub fn main() !void {
+ var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+ defer arena.deinit();
+
+ var memory = &lc3vm_zig.memory;
+
+ memory[0x3000] = 0xF026; // 1111 0000 0010 0110 TRAP trp_in_u16 ;read an uint16_t from stdin and put it in R0
+ memory[0x3002] = 0x1220; // 0001 0010 0010 0000 ADD R1,R0,x0 ;add contents of R0 to R1
+ memory[0x3003] = 0xF026; // 1111 0000 0010 0110 TRAP trp_in_u16 ;read an uint16_t from stdin and put it in R0
+ memory[0x3004] = 0x1240; // 0001 0010 0010 0000 ADD R1,R1,R0 ;add contents of R0 to R1
+ memory[0x3006] = 0x1060; // 0001 0000 0110 0000 ADD R0,R1,x0 ;add contents of R1 to R0
+ memory[0x3007] = 0xF027; // 1111 0000 0010 0111 TRAP trp_out_u16;show the contents of R0 to stdout
+ memory[0x3008] = 0xF025; // 1111 0000 0010 0101 HALT ;halt
+
+ try lc3vm_zig.start(arena.allocator(), 0);
+}
+
--- /dev/null
+//! By convention, root.zig is the root source file when making a library.
+const std = @import("std");
+
+// Implementation of the Little Computer 3 following
+// https://www.andreinc.net/2021/12/01/writing-a-simple-vm-in-less-than-125-lines-of-c
+
+const pcStart: u16 = 0x3000;
+const u16Max: u32 = 65535;
+pub var memory: [u16Max + 1]u16 = .{0} ** (u16Max + 1);
+var running: bool = true;
+
+inline fn mr(address: u16) u16 { return memory[address]; }
+
+inline fn mw(address: u16, value: u16) void {
+ memory[address] = value;
+}
+
+const Register = enum(u16) {
+ R0 = 0,
+ R1 = 1,
+ R2 = 2,
+ R3 = 3,
+ R4 = 4,
+ R5 = 5,
+ R6 = 6,
+ R7 = 7,
+ RPC = 8,
+ RCND = 9,
+ RCNT = 10
+};
+
+var registers: [11]u16 = .{0} ** 11;
+
+// The instruction fits into u16:
+//
+// [ OP CODE ][ PARAM1 ][ PARAM2 ][ ][ PARAM3 ]
+// [ 4 bits ][ 12 bits ]
+
+const Opcode = enum {
+ br, // conditional
+ add, // addition
+ ld, // load RPC + offset
+ st, // store
+ jsr, // jump to subroutine
+ andop, // bitwise and
+ ldr, // load base + offset
+ str, // store base + offset
+ rti, // return from interrupt
+ not, // bitwise complement
+ ldi, // load indirect
+ sti, // store indirect
+ jmp, // jump/return to subroutine
+ unused, // unused opcode
+ lea, // load effective address
+ trap, // system trap/call
+
+ pub fn parse(instruction: u16) Opcode {
+ // shift 12 bits to the right to get first 4 bits
+ return @enumFromInt(instruction >> 12);
+ }
+};
+
+const TrapFunc = enum {
+ tgetc, tout, tputs, tin, tputsp, thalt, tinu16, toutu16,
+
+ pub fn parse(n: u16) TrapFunc {
+ return @enumFromInt(n);
+ }
+};
+
+const Flag = enum(u16) {
+ FP = (1 << 0),
+ FZ = (1 << 1),
+ FN = (1 << 2),
+};
+
+inline fn uf(r: u16) void {
+ if (registers[r] == 0) { registers[@intFromEnum(Register.RCND)] = @intFromEnum(Flag.FZ); }
+ else if ((registers[r] >> 15) == 1) { registers[@intFromEnum(Register.RCND)] = @intFromEnum(Flag.FN); }
+ else registers[@intFromEnum(Register.RCND)] = @intFromEnum(Flag.FP);
+}
+
+inline fn fcnd(instruction: u16) u16 { return (instruction >> 9) & 0x7; }
+inline fn dr(instruction: u16) u16 { return (instruction >> 9) & 0x7; }
+inline fn sr1(instruction: u16) u16 { return(instruction >> 6) & 0x7; }
+inline fn sr2(instruction: u16) u16 { return (instruction) & 0x7; }
+inline fn imm(instruction: u16) u16 { return (instruction) & 0x1F; }
+inline fn fimm(instruction: u16) u16 { return (instruction >> 5) & 1; }
+
+inline fn sext(n: u16, b: u32) u16 {
+ return if ((n >> (b - 1)) & 1 == 1) @truncate(@as(u32, n) | (0xFFFF << b)) else n;
+}
+
+// 0000 0000 0001 0110 <--- a in binary
+// 1111 1111 1111 0110 <--- sextimm(a) in binary
+inline fn sextimm(instruction: u16) u16 { return sext(imm(instruction), 5); }
+
+inline fn poff(instruction: u16) u16 { return sext(instruction & 0x3F, 6); }
+inline fn poff9(instruction: u16) u16 { return sext(instruction & 0x1FF, 9); }
+inline fn poff11(instruction: u16) u16 { return sext(instruction & 0x7FF, 11); }
+inline fn fl(instruction: u16) u16 { return (instruction >> 11) & 1; }
+inline fn br(instruction: u16) u16 { return (instruction >> 6) & 0x7; }
+inline fn trp(instruction: u16) u16 { return instruction & 0xFF; }
+
+pub fn evaluate(allocator: std.mem.Allocator, i: u16) !void {
+ switch (Opcode.parse(i)) {
+ inline .add => {
+ registers[dr(i)] = registers[sr1(i)] +
+ if (fimm(i) == 1)
+ sextimm(i)
+ else registers[sr2(i)];
+ uf(dr(i));
+ },
+ inline .andop => {
+ registers[dr(i)] = registers[sr1(i)] & (if (fimm(i) == 1) (sextimm(i)) else registers[sr2(i)]);
+ uf(dr(i));
+ },
+ inline .ld => {
+ registers[dr(i)] = mr(registers[@intFromEnum(Register.RPC)] + poff9(i));
+ uf(dr(i));
+ },
+ inline .ldi => {
+ registers[dr(i)] = mr(mr(registers[@intFromEnum(Register.RPC)] + poff9(i)));
+ uf(dr(i));
+ },
+ inline .ldr => {
+ registers[dr(i)] = mr(registers[sr1(i)] + poff(i));
+ uf(dr(i));
+ },
+ inline .lea => {
+ registers[dr(i)] = registers[@intFromEnum(Register.RPC)] + poff9(i);
+ uf(dr(i));
+ },
+ inline .not => {
+ registers[dr(i)] = ~ registers[sr1(i)];
+ uf(dr(i));
+ },
+ inline .st => {
+ mw(registers[@intFromEnum(Register.RPC)] + poff9(i), registers[dr(i)]);
+ },
+ inline .sti => {
+ mw(mr(registers[@intFromEnum(Register.RPC)] + poff9(i)), registers[dr(i)]);
+ },
+ inline .str => {
+ mw(registers[sr1(i)] + poff(i), registers[dr(i)]);
+ },
+ inline .jmp => {
+ registers[@intFromEnum(Register.RPC)] = registers[br(i)];
+ },
+ inline .jsr => {
+ registers[@intFromEnum(Register.R7)] = registers[@intFromEnum(Register.RPC)];
+ registers[@intFromEnum(Register.RPC)] = if (fl(i) == 1) (registers[@intFromEnum(Register.RPC)] + poff11(i)) else registers[br(i)];
+ },
+ inline .br => {
+ if (registers[@intFromEnum(Register.RCND)] & fcnd(i) == 1) {
+ registers[@intFromEnum(Register.RPC)] += poff9(i);
+ }
+ },
+ inline .unused, .rti => {
+ },
+ inline .trap => {
+ switch (TrapFunc.parse(trp(i) - 0x20)) {
+ inline .tgetc => {
+ const dest: []u8 = try allocator.alloc(u8, 1);
+ _ = try std.fs.File.stdin().read(dest);
+ registers[@intFromEnum(Register.R0)] = dest[0];
+ },
+ inline .tout => {
+ std.debug.print("{}", .{ registers[@intFromEnum(Register.R0)] });
+ },
+ inline .tputs => {
+ },
+ inline .tin => {
+ const buffer: []u8 = try allocator.alloc(u8, 1024);
+ defer allocator.free(buffer);
+
+ var stdin = std.fs.File.stdin().reader(buffer).interface;
+ const m = try stdin.takeInt(u8, .little);
+ registers[@intFromEnum(Register.R0)] = m;
+ },
+ inline .thalt => {
+ running = false;
+ },
+ inline .tinu16 => {
+ const buffer: []u8 = try allocator.alloc(u8, 1024);
+ defer allocator.free(buffer);
+
+ var line_buffer: []u8 = try allocator.alloc(u8, 1024);
+ defer allocator.free(line_buffer);
+ var writer: std.io.Writer = .fixed(line_buffer);
+
+ var stdin = std.fs.File.stdin().reader(buffer).interface;
+
+ const line_length = try stdin.streamDelimiterLimit(&writer, '\n', .unlimited);
+ const v: u16 = try std.fmt.parseInt(u16, line_buffer[0..line_length], 10);
+ registers[@intFromEnum(Register.R0)] = v;
+ },
+ inline .tputsp => {
+ },
+ inline .toutu16 => {
+ const buffer: []u8 = try allocator.alloc(u8, 1024);
+ defer allocator.free(buffer);
+
+ const v: u16 = registers[@intFromEnum(Register.R0)];
+ std.debug.print("{}\n", .{ v });
+ },
+ }
+ }
+ }
+}
+
+pub fn start(allocator: std.mem.Allocator, offset: u16) !void {
+ registers[@intFromEnum(Register.RPC)] = pcStart + offset;
+ while (running) {
+ const instruction = mr(registers[@intFromEnum(Register.RPC)]);
+ registers[@intFromEnum(Register.RPC)] += 1;
+
+ try evaluate(allocator, instruction);
+ }
+}
+
projects / lc3vm.zig.git / commitdiff