benchmark: add codepoint width benchmark

src/benchmark/CodepointWidth.zig

@@ -0,0 +1,204 @@
+//! This benchmark tests the throughput of codepoint width calculation.
+//! This is a common operation in terminal character printing and the
+//! motivating factor to write this benchmark was discovering that our
+//! codepoint width function was 30% of the runtime of every character
+//! print.
+const CodepointWidth = @This();
+
+const std = @import("std");
+const assert = std.debug.assert;
+const Allocator = std.mem.Allocator;
+const Benchmark = @import("Benchmark.zig");
+const options = @import("options.zig");
+const UTF8Decoder = @import("../terminal/UTF8Decoder.zig");
+const simd = @import("../simd/main.zig");
+const table = @import("../unicode/main.zig").table;
+
+const log = std.log.scoped(.@"terminal-stream-bench");
+
+opts: Options,
+
+/// The file, opened in the setup function.
+data_f: ?std.fs.File = null,
+
+pub const Options = struct {
+    /// The type of codepoint width calculation to use.
+    mode: Mode = .noop,
+
+    /// The data to read as a filepath. If this is "-" then
+    /// we will read stdin. If this is unset, then we will
+    /// do nothing (benchmark is a noop). It'd be more unixy to
+    /// use stdin by default but I find that a hanging CLI command
+    /// with no interaction is a bit annoying.
+    data: ?[]const u8 = null,
+};
+
+pub const Mode = enum {
+    /// The baseline mode copies the data from the fd into a buffer. This
+    /// is used to show the minimal overhead of reading the fd into memory
+    /// and establishes a baseline for the other modes.
+    noop,
+
+    /// libc wcwidth
+    wcwidth,
+
+    /// Our SIMD implementation.
+    simd,
+
+    /// Test our lookup table implementation.
+    table,
+};
+
+/// Create a new terminal stream handler for the given arguments.
+pub fn create(
+    alloc: Allocator,
+    opts: Options,
+) !*CodepointWidth {
+    const ptr = try alloc.create(CodepointWidth);
+    errdefer alloc.destroy(ptr);
+    ptr.* = .{ .opts = opts };
+    return ptr;
+}
+
+pub fn destroy(self: *CodepointWidth, alloc: Allocator) void {
+    alloc.destroy(self);
+}
+
+pub fn benchmark(self: *CodepointWidth) Benchmark {
+    return .init(self, .{
+        .stepFn = switch (self.opts.mode) {
+            .noop => stepNoop,
+            .wcwidth => stepWcwidth,
+            .table => stepTable,
+            .simd => stepSimd,
+        },
+        .setupFn = setup,
+        .teardownFn = teardown,
+    });
+}
+
+fn setup(ptr: *anyopaque) Benchmark.Error!void {
+    const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
+
+    // Open our data file to prepare for reading. We can do more
+    // validation here eventually.
+    assert(self.data_f == null);
+    self.data_f = options.dataFile(self.opts.data) catch |err| {
+        log.warn("error opening data file err={}", .{err});
+        return error.BenchmarkFailed;
+    };
+}
+
+fn teardown(ptr: *anyopaque) void {
+    const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
+    if (self.data_f) |f| {
+        f.close();
+        self.data_f = null;
+    }
+}
+
+fn stepNoop(ptr: *anyopaque) Benchmark.Error!void {
+    _ = ptr;
+}
+
+extern "c" fn wcwidth(c: u32) c_int;
+
+fn stepWcwidth(ptr: *anyopaque) Benchmark.Error!void {
+    const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
+
+    const f = self.data_f orelse return;
+    var r = std.io.bufferedReader(f.reader());
+    var d: UTF8Decoder = .{};
+    var buf: [4096]u8 = undefined;
+    while (true) {
+        const n = r.read(&buf) catch |err| {
+            log.warn("error reading data file err={}", .{err});
+            return error.BenchmarkFailed;
+        };
+        if (n == 0) break; // EOF reached
+
+        for (buf[0..n]) |c| {
+            const cp_, const consumed = d.next(c);
+            assert(consumed);
+            if (cp_) |cp| {
+                const width = wcwidth(cp);
+
+                // Write the width to the buffer to avoid it being compiled
+                // away
+                buf[0] = @intCast(width);
+            }
+        }
+    }
+}
+
+fn stepTable(ptr: *anyopaque) Benchmark.Error!void {
+    const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
+
+    const f = self.data_f orelse return;
+    var r = std.io.bufferedReader(f.reader());
+    var d: UTF8Decoder = .{};
+    var buf: [4096]u8 = undefined;
+    while (true) {
+        const n = r.read(&buf) catch |err| {
+            log.warn("error reading data file err={}", .{err});
+            return error.BenchmarkFailed;
+        };
+        if (n == 0) break; // EOF reached
+
+        for (buf[0..n]) |c| {
+            const cp_, const consumed = d.next(c);
+            assert(consumed);
+            if (cp_) |cp| {
+                // This is the same trick we do in terminal.zig so we
+                // keep it here.
+                const width = if (cp <= 0xFF)
+                    1
+                else
+                    table.get(@intCast(cp)).width;
+
+                // Write the width to the buffer to avoid it being compiled
+                // away
+                buf[0] = @intCast(width);
+            }
+        }
+    }
+}
+
+fn stepSimd(ptr: *anyopaque) Benchmark.Error!void {
+    const self: *CodepointWidth = @ptrCast(@alignCast(ptr));
+
+    const f = self.data_f orelse return;
+    var r = std.io.bufferedReader(f.reader());
+    var d: UTF8Decoder = .{};
+    var buf: [4096]u8 = undefined;
+    while (true) {
+        const n = r.read(&buf) catch |err| {
+            log.warn("error reading data file err={}", .{err});
+            return error.BenchmarkFailed;
+        };
+        if (n == 0) break; // EOF reached
+
+        for (buf[0..n]) |c| {
+            const cp_, const consumed = d.next(c);
+            assert(consumed);
+            if (cp_) |cp| {
+                const width = simd.codepointWidth(cp);
+
+                // Write the width to the buffer to avoid it being compiled
+                // away
+                buf[0] = @intCast(width);
+            }
+        }
+    }
+}
+
+test CodepointWidth {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+
+    const impl: *CodepointWidth = try .create(alloc, .{});
+    defer impl.destroy(alloc);
+
+    const bench = impl.benchmark();
+    _ = try bench.run(.once);
+}

src/benchmark/TerminalStream.zig

@@ -18,6 +18,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const terminalpkg = @import("../terminal/main.zig");
 const Benchmark = @import("Benchmark.zig");
+const options = @import("options.zig");
 const Terminal = terminalpkg.Terminal;
 const Stream = terminalpkg.Stream(*Handler);
 
@@ -89,13 +90,11 @@ fn setup(ptr: *anyopaque) Benchmark.Error!void {
     // Open our data file to prepare for reading. We can do more
     // validation here eventually.
     assert(self.data_f == null);
-    if (self.opts.data) |path| {
-        self.data_f = std.fs.cwd().openFile(path, .{}) catch |err| {
+    self.data_f = options.dataFile(self.opts.data) catch |err| {
         log.warn("error opening data file err={}", .{err});
         return error.BenchmarkFailed;
     };
 }
-}
 
 fn teardown(ptr: *anyopaque) void {
     const self: *TerminalStream = @ptrCast(@alignCast(ptr));

src/benchmark/cli.zig

@@ -6,6 +6,7 @@ const cli = @import("../cli.zig");
 /// benchmarks.
 pub const Action = enum {
     @"terminal-stream",
+    @"codepoint-width",
 
     /// Returns the struct associated with the action. The struct
     /// should have a few decls:
@@ -18,6 +19,7 @@ pub const Action = enum {
     pub fn Struct(comptime action: Action) type {
         return switch (action) {
             .@"terminal-stream" => @import("TerminalStream.zig"),
+            .@"codepoint-width" => @import("CodepointWidth.zig"),
         };
     }
 };

src/benchmark/main.zig

@@ -2,6 +2,7 @@ pub const cli = @import("cli.zig");
 pub const Benchmark = @import("Benchmark.zig");
 pub const CApi = @import("CApi.zig");
 pub const TerminalStream = @import("TerminalStream.zig");
+pub const CodepointWidth = @import("CodepointWidth.zig");
 
 test {
     _ = @import("std").testing.refAllDecls(@This());

src/benchmark/options.zig

@@ -0,0 +1,20 @@
+//! This file contains helpers for CLI options.
+
+const std = @import("std");
+
+/// Returns the data file for the given path in a way that is consistent
+/// across our CLI. If the path is not set then no file is returned.
+/// If the path is "-", then we will return stdin. If the path is
+/// a file then we will open and return the handle.
+pub fn dataFile(path_: ?[]const u8) !?std.fs.File {
+    const path = path_ orelse return null;
+
+    // Stdin
+    if (std.mem.eql(u8, path, "-")) return std.io.getStdIn();
+
+    // Normal file
+    const file = try std.fs.cwd().openFile(path, .{});
+    errdefer file.close();
+
+    return file;
+}