chore: clean up code + documentation
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54
src/lib.zig
54
src/lib.zig
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@ -45,16 +45,6 @@ const std = @import("std");
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const Log2Int = std.math.Log2Int;
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/// Test to see if a value matches the provided bit-string
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///
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/// ### Example
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/// ```zig
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/// match("1100", @as(u4, 0b1100)) // true
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/// match("1100", @as(u4, 0b1110)) // false
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///
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/// match("1--0", @as(u4, 0b1010)) // true
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/// match("1ab0", @as(u4, 0b1010)) // true
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/// match("11_00", @as(u4, 0b1100)) // true
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/// ```
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pub fn match(comptime bit_string: []const u8, value: anytype) bool {
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@setEvalBranchQuota(std.math.maxInt(u32)); // FIXME: bad practice
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@ -88,7 +78,7 @@ pub fn match(comptime bit_string: []const u8, value: anytype) bool {
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return (value & set_mask) == set_mask and (~value & clr_mask) == clr_mask;
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}
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test "match" {
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test match {
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// doc tests
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try std.testing.expectEqual(true, match("1100", @as(u4, 0b1100)));
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try std.testing.expectEqual(false, match("1100", @as(u4, 0b1110)));
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@ -113,15 +103,6 @@ test "match" {
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/// Extracts the variables (defined in the bit string) from a value.
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///
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/// ### Examples
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/// ```
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/// const ret = extract("aaaa", @as(u4, 0b1001)); // ret.a == 0b1001
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/// const ret = extract("abcd", @as(u4, 0b1001)); // ret.a == 0b1, ret.b == 0b0, ret.c == 0b0, ret.d == 0b1
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/// const ret = extract("a0ab", @as(u4, 0b1001)); // ret.a == 0b10, ret.b == 0b1
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/// const ret = extract("-a-a", @as(u4, 0b1001)); // ret.a == 0b01
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/// const ret = extract("aa_aa", @as(u4, 0b1001)); // ret.a == 0b1001
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/// ```
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///
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/// Note: In Debug and ReleaseSafe builds, there's a runtime assert that
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/// ensures that the value matches against the bit string.
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pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_string) {
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@ -161,19 +142,14 @@ pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_str
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//
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// we're confident in this because it's guaranteed to be the same bit_string,
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// and it's the same linear search. If you're reading this double check that this is still the case lol
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break :blk @truncate(if (bmi2 and !@inComptime()) pext.hardware(u32, value, masked_val) else pext.software(u32, value, masked_val));
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break :blk @truncate(if (bmi2 and !@inComptime()) pext.hw(u32, value, masked_val) else pext.sw(u32, value, masked_val));
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};
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}
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return ret;
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}
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pub fn matchExtract(comptime bit_string: []const u8, value: anytype) ?Bitfield(bit_string) {
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if (!match(bit_string, value)) return null;
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return extract(bit_string, value);
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}
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test "extract" {
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test extract {
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// doc tests
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{
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const ret = extract("aaaa", @as(u4, 0b1001));
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@ -237,11 +213,13 @@ test "extract" {
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}
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}
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pub fn matchExtract(comptime bit_string: []const u8, value: anytype) ?Bitfield(bit_string) {
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if (!match(bit_string, value)) return null;
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return extract(bit_string, value);
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}
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/// Parses a bit string and reifies a struct that will contain fields that correspond to the variables present in the bit string.
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///
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///
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/// Note: If it weren't for the return type of `extract()`, this type would be a private implementation detail
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///
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/// TODO: I will probably rename this type
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pub fn Bitfield(comptime bit_string: []const u8) type {
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const StructField = std.builtin.Type.StructField;
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@ -323,7 +301,7 @@ fn verify(comptime T: type, comptime bit_string: []const u8) void {
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}
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const pext = struct {
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fn hardware(comptime T: type, value: T, mask: T) T {
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fn hw(comptime T: type, value: T, mask: T) T {
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return switch (T) {
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u32 => asm ("pextl %[mask], %[value], %[ret]"
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: [ret] "=r" (-> T),
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@ -340,7 +318,7 @@ const pext = struct {
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}
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// why we need this: https://github.com/ziglang/zig/issues/14995 (ideally compiler-rt implements this for us)
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fn software(comptime T: type, value: T, mask: T) T {
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fn sw(comptime T: type, value: T, mask: T) T {
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return switch (T) {
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u32 => {
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// TODO: Looks (and is) like C code :pensive:
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@ -375,13 +353,13 @@ const pext = struct {
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};
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}
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test "pext" {
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test pext {
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const builtin = @import("builtin");
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switch (builtin.cpu.arch) {
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.x86_64 => if (std.Target.x86.featureSetHas(builtin.cpu.features, .bmi2)) {
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try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.hardware(u32, 0x12345678, 0xFF00FFF0));
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try std.testing.expectEqual(@as(u64, 0x0001_2567), pext.hardware(u64, 0x12345678, 0xFF00FFF0));
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try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.hw(u32, 0x12345678, 0xFF00FFF0));
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try std.testing.expectEqual(@as(u64, 0x0001_2567), pext.hw(u64, 0x12345678, 0xFF00FFF0));
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// random tests
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// TODO: when implemented, test 64-bit fallback `PEXT` as well
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@ -390,14 +368,14 @@ const pext = struct {
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const value = rand_impl.random().int(u32);
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const mask = rand_impl.random().int(u32);
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try std.testing.expectEqual(pext.hardware(u32, value, mask), pext.software(u32, value, mask));
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try std.testing.expectEqual(pext.hw(u32, value, mask), pext.sw(u32, value, mask));
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}
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},
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else => {},
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else => return error.SkipZigTest,
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}
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// example values from: https://en.wikipedia.org/w/index.php?title=X86_Bit_manipulation_instruction_set&oldid=1170426748
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try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.software(u32, 0x12345678, 0xFF00FFF0));
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try std.testing.expectEqual(@as(u32, 0x0001_2567), pext.sw(u32, 0x12345678, 0xFF00FFF0));
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}
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};
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