chore: fix table

.gitignore

@@ -1,2 +1,2 @@
 zig-out/
-zig-cache/
+.zig-cache/

README.md

@@ -9,9 +9,11 @@ const std = @import("std");
 
  test "doc test" {
     const value: u8 = 0b10001011;
-    try std.testing.expectEqual(true, match("10001011", value));
+
+    try std.testing.expectEqual(true, match("1000_1011", value));
     try std.testing.expectEqual(false, match("11111011", value));
     try std.testing.expectEqual(true, match("1---1011", value));
+
     {
         const ret = extract("1000aaaa", value);
         try std.testing.expectEqual(@as(u4, 0b1011), ret.a);
@@ -34,10 +36,11 @@ test "doc test" {
 
  |  Token  |  Meaning  | Description
  | ------- | --------- | -----------
-| `0`     | Unset bit | In the equivalent position, the value's bit must be set.
+ | `0`     | Clear bit | In the equivalent position, the value's bit must be cleared.
  | `1`     | Set bit   | In the equivalent position, the value's bit must be set.
  | `a..=z` | Variable  | Given the 4-bit bit string, `"1aa0"`, the value `0b1010` would produce the variable `a` with the value `0b01`
  | `-`     | Ignored   | In the equivalent position, the value's bit does not matter.
+ | `_`     | Ignored*  | Underscores are completely ignored during parsing, use to make bit strings easier to read e.g. `1111_1111`
 
 ## Notes
 

build.zig

@@ -15,35 +15,53 @@ pub fn build(b: *std.Build) void {
     // set a preferred release mode, allowing the user to decide how to optimize.
     const optimize = b.standardOptimizeOption(.{});
 
-    _ = b.addModule("bit-string", .{ .source_file = .{ .path = "src/lib.zig" } });
-
-    const lib = b.addStaticLibrary(.{
-        .name = "bit-string",
+    // This creates a "module", which represents a collection of source files alongside
+    // some compilation options, such as optimization mode and linked system libraries.
+    // Every executable or library we compile will be based on one or more modules.
+    const lib_mod = b.createModule(.{
+        // `root_source_file` is the Zig "entry point" of the module. If a module
+        // only contains e.g. external object files, you can make this `null`.
         // 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 = .{ .path = "src/lib.zig" },
+        .root_source_file = b.path("src/lib.zig"),
         .target = target,
         .optimize = optimize,
     });
 
+    // Now, we will create a static library based on the module we created above.
+    // This creates a `std.Build.Step.Compile`, which is the build step responsible
+    // for actually invoking the compiler.
+    const lib = b.addLibrary(.{
+        .linkage = .static,
+        .name = "bit_string",
+        .root_module = lib_mod,
+    });
+
     // 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);
 
-    // Creates a step for unit testing. This only builds the test executable
-    // but does not run it.
-    const lib_tests = b.addTest(.{
-        .root_source_file = .{ .path = "src/test.zig" },
-        .target = target,
-        .optimize = optimize,
+    const docs = b.addInstallDirectory(.{
+        .install_dir = .prefix,
+        .install_subdir = "docs",
+        .source_dir = lib.getEmittedDocs(),
     });
 
-    const run_main_tests = b.addRunArtifact(lib_tests);
+    // Creates a step for unit testing. This only builds the test executable
+    // but does not run it.
+    const lib_unit_tests = b.addTest(.{
+        .root_module = lib_mod,
+    });
 
-    // This creates a build step. It will be visible in the `zig build --help` menu,
-    // and can be selected like this: `zig build test`
-    // This will evaluate the `test` step rather than the default, which is "install".
-    const test_step = b.step("test", "Run library tests");
-    test_step.dependOn(&run_main_tests.step);
+    const run_lib_unit_tests = b.addRunArtifact(lib_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);
+
+    const docs_step = b.step("docs", "Emit docs");
+    docs_step.dependOn(&docs.step);
 }

build.zig.zon

@@ -1,5 +1,86 @@
 .{
-    .name = "bit-string",
+    // 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 = .bit_string,
+
+    // This is a [Semantic Version](https://semver.org/).
+    // In a future version of Zig it will be used for package deduplication.
     .version = "0.1.0",
-    .dependencies = .{},
+
+    // 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 = 0x14a39efa6e959493, // 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 = "0.14.0",
+
+    // 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. 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",
+    },
 }

src/lib.zig

@@ -7,7 +7,7 @@
 //! test "doc test" {
 //!    const value: u8 = 0b10001011;
 //!
-//!     try std.testing.expectEqual(true, match("10001011", value));
+//!    try std.testing.expectEqual(true, match("1000_1011", value));
 //!    try std.testing.expectEqual(false, match("11111011", value));
 //!    try std.testing.expectEqual(true, match("1---1011", value));
 //!
@@ -29,12 +29,13 @@
 //! }
 //! ```
 //! ## Syntax
-//! |  Token  |  Meaning  | Description
-//! | ------- | --------- | -----------
-//! | `0`     | Unset bit | In the equivalent position, the value's bit must be set.
-//! | `1`     | Set bit   | In the equivalent position, the value's bit must be set.
-//! | `a..=z` | Variable  | Given the 4-bit bit string, `"1aa0"`, the value `0b1010` would produce the variable `a` with the value `0b01`
-//! | `-`     | Ignored   | In the equivalent position, the value's bit does not matter.
+//! |  Token  |  Meaning  | Description                                                                                                   |
+//! | :-----: | --------- | ------------------------------------------------------------------------------------------------------------- |
+//! | `0`     | Clear bit | In the equivalent position, the value's bit must be cleared.                                                  |
+//! | `1`     | Set bit   | In the equivalent position, the value's bit must be set.                                                      |
+//! | `a..=z` | Variable  | Given the 4-bit bit string, `"1aa0"`, the value `0b1010` would produce the variable `a` with the value `0b01` |
+//! | `-`     | Ignored   | In the equivalent position, the value's bit does not matter.                                                  |
+//! | `_`     | Ignored*  | Underscores are completely ignored during parsing, use to make bit strings easier to read e.g. `1111_1111`    |
 //!
 //! ## Notes
 //! - This library does the majority of it's work at `comptime`. Due to this, you cannot create strings to match against at runtime.
@@ -44,14 +45,6 @@ const std = @import("std");
 const Log2Int = std.math.Log2Int;
 
 /// Test to see if a value matches the provided bit-string
-///
-/// ### Example
-/// ```zig
-/// match("1100", @as(u4, 0b1100)) // true
-/// match("1100", @as(u4, 0b1110)) // false
-/// match("1--0", @as(u4, 0b1010)) // true
-/// match("1ab0", @as(u4, 0b1010)) // true
-/// ```
 pub fn match(comptime bit_string: []const u8, value: anytype) bool {
     @setEvalBranchQuota(std.math.maxInt(u32)); // FIXME: bad practice
 
@@ -59,16 +52,18 @@ pub fn match(comptime bit_string: []const u8, value: anytype) bool {
     comptime verify(ValT, bit_string);
 
     const masks: struct { ValT, ValT } = comptime blk: {
-        const bit_count = @typeInfo(ValT).Int.bits;
+        const bit_count = @typeInfo(ValT).int.bits;
 
         var set: ValT = 0;
         var clr: ValT = 0;
+        var offset = 0;
 
-        // FIXME: I linear search bit_string 4 separate times. Consider doing a single search and compromizing on memory + stateless API? (imagine a "regex compile"-like API)
+        // FIXME: I linear search like this 5 times across the entire lib. Consider structuring this like a regex lib (compiling a match)
         for (bit_string, 0..) |char, i| {
             switch (char) {
-                '0' => clr |= @as(ValT, 1) << @intCast(bit_count - 1 - i),
-                '1' => set |= @as(ValT, 1) << @intCast(bit_count - 1 - i),
+                '0' => clr |= @as(ValT, 1) << @intCast((bit_count - 1 - (i - offset))),
+                '1' => set |= @as(ValT, 1) << @intCast((bit_count - 1 - (i - offset))),
+                '_' => offset += 1,
                 'a'...'z', '-' => continue,
                 else => @compileError("'" ++ [_]u8{char} ++ "' was unexpected when parsing bitstring"),
             }
@@ -83,12 +78,14 @@ pub fn match(comptime bit_string: []const u8, value: anytype) bool {
     return (value & set_mask) == set_mask and (~value & clr_mask) == clr_mask;
 }
 
-test "match" {
+test match {
     // doc tests
-    try std.testing.expectEqual(true, match("1100", @as(u4, 0b1100))); // true
-    try std.testing.expectEqual(false, match("1100", @as(u4, 0b1110))); // false
-    try std.testing.expectEqual(true, match("1--0", @as(u4, 0b1010))); // true
-    try std.testing.expectEqual(true, match("1ab0", @as(u4, 0b1010))); // true
+    try std.testing.expectEqual(true, match("1100", @as(u4, 0b1100)));
+    try std.testing.expectEqual(false, match("1100", @as(u4, 0b1110)));
+
+    try std.testing.expectEqual(true, match("1--0", @as(u4, 0b1010)));
+    try std.testing.expectEqual(true, match("1ab0", @as(u4, 0b1010)));
+    try std.testing.expectEqual(true, match("11_00", @as(u4, 0b1100)));
 
     // other tests
     try std.testing.expectEqual(true, match("11111111", @as(u8, 0b11111111)));
@@ -98,18 +95,19 @@ test "match" {
     try std.testing.expectEqual(true, match("aaa---11", @as(u8, 0b01011111)));
     try std.testing.expectEqual(true, match("1a0b1c0d", @as(u8, 0b10011101)));
     try std.testing.expectEqual(false, match("aaa---11", @as(u8, 0b01011110)));
+
+    try std.testing.expectEqual(true, match("1111_1111", @as(u8, 0b11111111)));
+    try std.testing.expectEqual(true, match("________11111111", @as(u8, 0b11111111)));
+    try std.testing.expectEqual(true, match("11111111________", @as(u8, 0b11111111)));
+
+    try std.testing.expectEqual(true, match(
+        "11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111",
+        @as(u64, 0xFFFF_FFFF_FFFF_FFFF),
+    ));
 }
 
 /// Extracts the variables (defined in the bit string) from a value.
 ///
-/// ### Examples
-/// ```
-/// const ret = extract("aaaa", @as(u4, 0b1001)); // ret.a == 0b1001
-/// const ret = extract("abcd", @as(u4, 0b1001)); // ret.a == 0b1, ret.b == 0b0, ret.c == 0b0, ret.d == 0b1
-/// const ret = extract("a0ab", @as(u4, 0b1001)); // ret.a == 0b10, ret.b == 0b1
-/// const ret = extract("-a-a", @as(u4, 0b1001)); // ret.a == 0b01
-/// ```
-///
 /// Note: In Debug and ReleaseSafe builds, there's a runtime assert that
 /// ensures that the value matches against the bit string.
 pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_string) {
@@ -125,35 +123,33 @@ pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_str
 
     var ret: ReturnT = undefined;
 
-    inline for (@typeInfo(ReturnT).Struct.fields) |field| {
+    inline for (@typeInfo(ReturnT).@"struct".fields) |field| {
         @field(ret, field.name) = blk: {
             var masked_val: ValT = 0;
+            var offset: usize = 0; // FIXME(URGENT): this whole block should be happening at comptime...
 
             for (bit_string, 0..) |char, i| {
-                const rev = @typeInfo(ValT).Int.bits - 1 - i;
-                if (char == field.name[0]) masked_val |= @as(ValT, 1) << @intCast(rev); // no penalty
+                const rev = @typeInfo(ValT).int.bits - 1 - (i - offset);
+
+                switch (char) {
+                    '_' => offset += 1,
+                    else => if (char == field.name[0]) {
+                        masked_val |= @as(ValT, 1) << @intCast(rev); // no penalty
+                    },
+                }
             }
 
-            // TODO: decide at compile time if we're calling the 32-bit or 64-bit version of `PEXT`
+            const PextT = if (@typeInfo(ValT).int.bits > 32) u64 else u32;
+            const use_hw = bmi2 and !@inComptime();
 
-            // invariant: the bit count in the field we're writing to and the
-            // # of bits we happened to find in this linear search are identical
-            //
-            // we're confident in this because it's guaranteed to be the same bit_string,
-            // and it's the same linear search. If you're reading this double check that this is still the case lol
-            break :blk @truncate(if (bmi2 and !@inComptime()) pext.hardware(u32, value, masked_val) else pext.software(u32, value, masked_val));
+            break :blk @truncate(if (use_hw) pext.hw(PextT, value, masked_val) else pext.sw(PextT, value, masked_val));
         };
     }
 
     return ret;
 }
 
-pub fn matchExtract(comptime bit_string: []const u8, value: anytype) ?Bitfield(bit_string) {
-    if (!match(bit_string, value)) return null;
-    return extract(bit_string, value);
-}
-
-test "extract" {
+test extract {
     // doc tests
     {
         const ret = extract("aaaa", @as(u4, 0b1001));
@@ -175,6 +171,10 @@ test "extract" {
         const ret = extract("-a-a", @as(u4, 0b1001));
         try std.testing.expectEqual(@as(u2, 0b01), ret.a);
     }
+    {
+        const ret = extract("aa_aa", @as(u4, 0b1001));
+        try std.testing.expectEqual(@as(u4, 0b1001), ret.a);
+    }
 
     // other tests
     {
@@ -197,27 +197,41 @@ test "extract" {
         const ret = extract("--------", @as(u8, 0b00000000));
         const T = @TypeOf(ret);
 
-        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
+        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).@"struct".fields.len);
     }
     {
         const ret = extract("00000000", @as(u8, 0b00000000));
         const T = @TypeOf(ret);
 
-        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
+        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).@"struct".fields.len);
     }
     {
         const ret = extract("0-0-0-0-", @as(u8, 0b01010101));
         const T = @TypeOf(ret);
 
-        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
+        try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).@"struct".fields.len);
+    }
+
+    {
+        const ret = extract(
+            "11111111_ssssssss_11111111_dddddddd_11111111_vvvvvvvv_11111111_xxxxxxxx",
+            @as(u64, 0xFF55_FF77_FF33_FF00),
+        );
+
+        try std.testing.expectEqual(@as(u8, 0x55), ret.s);
+        try std.testing.expectEqual(@as(u8, 0x77), ret.d);
+        try std.testing.expectEqual(@as(u8, 0x33), ret.v);
+        try std.testing.expectEqual(@as(u8, 0x00), ret.x);
     }
 }
 
+pub fn matchExtract(comptime bit_string: []const u8, value: anytype) ?Bitfield(bit_string) {
+    if (!match(bit_string, value)) return null;
+    return extract(bit_string, value);
+}
+
 /// Parses a bit string and reifies a struct that will contain fields that correspond to the variables present in the bit string.
 ///
-///
-/// Note: If it weren't for the return type of `extract()`, this type would be a private implementation detail
-///
 /// TODO: I will probably rename this type
 pub fn Bitfield(comptime bit_string: []const u8) type {
     const StructField = std.builtin.Type.StructField;
@@ -252,18 +266,18 @@ pub fn Bitfield(comptime bit_string: []const u8) type {
                     things[pos].bits += 1;
                     things[pos].char = c;
                 },
-                '1', '0', '-' => continue,
-                else => @compileError("error when parsing bitset string"),
+                '1', '0', '-', '_' => continue,
+                else => @compileError("unexpected char '" ++ [_]u8{char} ++ "' when parsing bit string"),
             }
         }
 
         for (things, &tmp) |th, *field| {
-            const FieldInt = @Type(.{ .Int = .{ .signedness = .unsigned, .bits = th.bits } });
+            const FieldInt = @Type(.{ .int = .{ .signedness = .unsigned, .bits = th.bits } });
 
             field.* = .{
                 .name = &.{th.char.?},
                 .type = FieldInt,
-                .default_value = null,
+                .default_value_ptr = null,
                 .is_comptime = false,
                 .alignment = @alignOf(FieldInt),
             };
@@ -272,8 +286,8 @@ pub fn Bitfield(comptime bit_string: []const u8) type {
         break :blk tmp;
     };
 
-    return @Type(.{ .Struct = .{
-        .layout = .Auto,
+    return @Type(.{ .@"struct" = .{
+        .layout = .auto,
         .fields = &fields,
         .decls = &.{},
         .is_tuple = false,
@@ -283,17 +297,20 @@ pub fn Bitfield(comptime bit_string: []const u8) type {
 fn verify(comptime T: type, comptime bit_string: []const u8) void {
     const info = @typeInfo(T);
 
-    // FIXME: remove the need for this
-    if (info.Int.bits > 32) @compileError("TODO: 64-bit `PEXT` software implementation");
+    std.debug.assert(info != .comptime_int);
+    std.debug.assert(info.int.signedness == .unsigned);
+    std.debug.assert(info.int.bits <= 64); // x86 PEXT u32 and u64 operands only
 
-    std.debug.assert(info != .ComptimeInt);
-    std.debug.assert(info.Int.signedness == .unsigned);
-    std.debug.assert(info.Int.bits <= 64); // x86 PEXT u32 and u64 operands only
-    std.debug.assert(bit_string.len == info.Int.bits); // TODO: Support Underscores?
+    var underscore_count = 0;
+    for (bit_string) |c| {
+        if (c == '_') underscore_count += 1;
+    }
+
+    std.debug.assert((bit_string.len - underscore_count) == info.int.bits);
 }
 
 const pext = struct {
-    fn hardware(comptime T: type, value: T, mask: T) T {
+    fn hw(comptime T: type, value: T, mask: T) T {
         return switch (T) {
             u32 => asm ("pextl %[mask], %[value], %[ret]"
                 : [ret] "=r" (-> T),
@@ -309,72 +326,77 @@ const pext = struct {
         };
     }
 
-    // why we need this: https://github.com/ziglang/zig/issues/14995 (ideally compiler-rt implements this for us)
-    fn software(comptime T: type, value: T, mask: T) T {
+    inline fn sw(comptime T: type, value: T, mask: T) T {
+        // FIXME: will be replaced in the future by https://github.com/ziglang/zig/issues/14995 (hopefully?)
+
         return switch (T) {
-            u32 => {
-                // TODO: Looks (and is) like C code :pensive:
+            u32, u64 => {
                 // code source: https://stackoverflow.com/questions/41720249/detecting-matching-bits-in-c
+                // TODO: rewrite more in generic/idiomatic zig
+                const log2_bits = @typeInfo(Log2Int(T)).int.bits;
 
-                var _value: T = value;
-                var _mask: T = mask;
+                var val: T = value & mask; // immediately clear irrelevant bits
+                var msk: T = mask;
 
-                _value &= _mask;
-                var mk: T = ~_mask << 1;
-                var mp: T = undefined;
-                var mv: T = undefined;
-                var t: T = undefined;
+                var mk: T = ~msk << 1; // count 0s to the right
+
+                inline for (0..log2_bits) |i| {
+                    var mp: T = mk ^ (mk << 1);
+                    inline for (1..log2_bits) |j| {
+                        mp = mp ^ (mp << (1 << j)); // parallel suffix
+                    }
+
+                    const mv = (mp & msk); // bits to move
+                    msk = ((msk ^ mv) | (mv >> (1 << i))); // compress mask
+
+                    const t = (val & mv);
+                    val = ((val ^ t) | (t >> (1 << i))); // compress val
 
-                inline for (0..@typeInfo(u5).Int.bits) |i| {
-                    mp = mk ^ (mk << 1); // parallel suffix
-                    mp = mp ^ (mp << 2);
-                    mp = mp ^ (mp << 4);
-                    mp = mp ^ (mp << 8);
-                    mp = mp ^ (mp << 16);
-                    mv = (mp & _mask); // bits to move
-                    _mask = ((_mask ^ mv) | (mv >> (1 << i))); // compress _mask
-                    t = (_value & mv);
-                    _value = ((_value ^ t) | (t >> (1 << i))); // compress _value
                     mk &= ~mp;
                 }
 
-                return _value;
+                return val;
             },
-            u64 => @compileError("TODO: find/write branchless software impl of `PEXT` for 64-bit values"),
             else => @compileError("pext is sunsupported for " ++ @typeName(T) ++ "."),
         };
     }
 
-    test "pext" {
+    test pext {
         const builtin = @import("builtin");
 
+        try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.sw(u32, 0x12345678, 0xFF00FFF0));
+        try std.testing.expectEqual(@as(u64, 0x0001_2567), pext.sw(u64, 0x12345678, 0xFF00FFF0));
+
         switch (builtin.cpu.arch) {
             .x86_64 => if (std.Target.x86.featureSetHas(builtin.cpu.features, .bmi2)) {
-                try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.hardware(u32, 0x12345678, 0xFF00FFF0));
-                try std.testing.expectEqual(@as(u64, 0x0001_2567), pext.hardware(u64, 0x12345678, 0xFF00FFF0));
+                var rand_impl = std.Random.DefaultPrng.init(0xBAADF00D_DEADCAFE);
 
-                // random tests
-                // TODO: when implemented, test 64-bit fallback `PEXT` as well
-                var rand_impl = std.rand.DefaultPrng.init(0xBAADF00D_DEADCAFE);
                 for (0..100) |_| {
                     const value = rand_impl.random().int(u32);
                     const mask = rand_impl.random().int(u32);
 
-                    try std.testing.expectEqual(pext.hardware(u32, value, mask), pext.software(u32, value, mask));
+                    try std.testing.expectEqual(pext.hw(u32, value, mask), pext.sw(u32, value, mask));
+                }
+
+                for (0..100) |_| {
+                    const value = rand_impl.random().int(u64);
+                    const mask = rand_impl.random().int(u64);
+
+                    try std.testing.expectEqual(pext.hw(u64, value, mask), pext.sw(u64, value, mask));
                 }
             },
-            else => {},
+            else => return error.SkipZigTest,
         }
 
         // example values from: https://en.wikipedia.org/w/index.php?title=X86_Bit_manipulation_instruction_set&oldid=1170426748
-        try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.software(u32, 0x12345678, 0xFF00FFF0));
+        try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.sw(u32, 0x12345678, 0xFF00FFF0));
     }
 };
 
 test "doc test" {
     const value: u8 = 0b10001011;
 
-    try std.testing.expectEqual(true, match("10001011", value));
+    try std.testing.expectEqual(true, match("1000_1011", value));
     try std.testing.expectEqual(false, match("11111011", value));
     try std.testing.expectEqual(true, match("1---1011", value));