creating chunk interface (ch14)

.gitignore

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+zig-out
+.zig-cache

.justfile

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+build:
+    zig build
+
+run:
+    zig build run
+
+test:
+    zig build test

build.zig

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+const std = @import("std");
+
+// Although this function looks imperative, note that its job is to
+// declaratively construct a build graph that will be executed by an external
+// runner.
+pub fn build(b: *std.Build) void {
+    // Standard target options allows 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(.{});
+
+    const lib = b.addStaticLibrary(.{
+        .name = "zlox",
+        // In this case the main source file is merely a path, however, in more
+        // complicated build scripts, this could be a generated file.
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This declares intent for the library to be installed into the standard
+    // location when the user invokes the "install" step (the default step when
+    // running `zig build`).
+    b.installArtifact(lib);
+
+    const exe = b.addExecutable(.{
+        .name = "zlox",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    // This declares intent for the executable to be installed into the
+    // standard location when the user invokes the "install" step (the default
+    // step when running `zig build`).
+    b.installArtifact(exe);
+
+    // This *creates* a Run step in the build graph, to be executed when another
+    // step is evaluated that depends on it. The next line below will establish
+    // such a dependency.
+    const run_cmd = b.addRunArtifact(exe);
+
+    // By making the run step depend on the install step, it will be run from the
+    // installation directory rather than directly from within the cache directory.
+    // This is not necessary, however, if the application depends on other installed
+    // files, this ensures they will be present and in the expected location.
+    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);
+    }
+
+    // This creates a build step. It will be visible in the `zig build --help` menu,
+    // and can be selected like this: `zig build run`
+    // This will evaluate the `run` step rather than the default, which is "install".
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const lib_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/root.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_lib_unit_tests = b.addRunArtifact(lib_unit_tests);
+
+    const exe_unit_tests = b.addTest(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+
+    const run_exe_unit_tests = b.addRunArtifact(exe_unit_tests);
+
+    // Similar to creating the run step earlier, this exposes a `test` step to
+    // the `zig build --help` menu, providing a way for the user to request
+    // running the unit tests.
+    const test_step = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_lib_unit_tests.step);
+    test_step.dependOn(&run_exe_unit_tests.step);
+}

build.zig.zon

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+.{
+    // 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 = "zlox",
+
+    // 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",
+
+    // This field is optional.
+    // This is currently advisory only; Zig does not yet do anything
+    // with this value.
+    //.minimum_zig_version = "0.11.0",
+
+    // 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.
+        //    .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",
+    },
+}

src/main.zig

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+const std = @import("std");
+const debug = std.debug;
+const Allocator = std.mem.Allocator;
+
+const OpCode = enum(u8) { OP_RETURN };
+
+const Chunk = struct {
+    count: usize,
+    capacity: usize,
+    code: []u8,
+
+    pub fn new() Chunk {
+        return Chunk{
+            .count = 0,
+            .capacity = 0,
+            .code = &.{},
+        };
+    }
+
+    pub fn init(self: *Chunk, allocator: Allocator) !void {
+        self.deinit(allocator);
+
+        self.count = 0;
+        self.capacity = 0;
+        self.code = &.{};
+    }
+
+    pub fn write(self: *Chunk, allocator: Allocator, byte: u8) !void {
+        if (self.capacity < self.count + 1) {
+            const old_capacity = self.capacity;
+            self.capacity = grow_capacity(old_capacity);
+            self.code = try allocator.realloc(self.code, self.capacity);
+        }
+
+        self.code[self.count] = byte;
+        self.count += 1;
+    }
+
+    pub fn dump(self: Chunk) void {
+        debug.print("{any}\n", .{self});
+    }
+
+    pub fn dissassemble(self: Chunk, name: []const u8) void {
+        debug.print("== {s} ==\n", .{name});
+
+        for (0..self.count) |idx| {
+            const offset = self.dissassemble_instruction(idx);
+            _ = offset;
+        }
+    }
+
+    pub fn dissassemble_instruction(self: Chunk, offset: usize) usize {
+        debug.print("{x:0>4} ", .{offset});
+
+        const instruction = self.code[offset];
+
+        switch (instruction) {
+            @intFromEnum(OpCode.OP_RETURN) => return simple_instruction("OP_RETURN", offset),
+            else => {
+                debug.print("unknown opcode {d}\n", .{instruction});
+                return offset + 1;
+            },
+        }
+    }
+
+    pub fn deinit(self: *Chunk, allocator: Allocator) void {
+        if (self.capacity > 0) {
+            allocator.free(self.code);
+        }
+    }
+};
+
+pub fn simple_instruction(opcode_name: []const u8, offset: usize) usize {
+    debug.print("{s}\n", .{opcode_name});
+
+    return offset + 1;
+}
+
+pub fn grow_capacity(capacity: usize) usize {
+    if (capacity < 8) {
+        return 8;
+    }
+    return capacity * 2;
+}
+
+pub fn main() !void {
+    var gpa = std.heap.GeneralPurposeAllocator(.{ .safety = true }){};
+    defer _ = debug.assert(gpa.deinit() == .ok);
+    const allocator = gpa.allocator();
+
+    var chunk = Chunk.new();
+    try chunk.init(allocator);
+
+    try chunk.write(allocator, @intFromEnum(OpCode.OP_RETURN));
+    chunk.dissassemble("test chunk");
+
+    chunk.deinit(allocator);
+}

src/root.zig

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+const std = @import("std");
+const testing = std.testing;
+
+export fn add(a: i32, b: i32) i32 {
+    return a + b;
+}
+
+test "basic add functionality" {
+    try testing.expect(add(3, 7) == 10);
+}