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feat: allow '_'s for legibility

This commit is contained in:
Rekai Nyangadzayi Musuka 2023-12-02 14:38:19 -06:00
parent e67d98de86
commit dbe6bd50cd
1 changed files with 63 additions and 33 deletions
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60
src/lib.zig
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@ -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));
//!
@ -31,10 +31,11 @@
//! ## Syntax
//! | 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
//! - This library does the majority of it's work at `comptime`. Due to this, you cannot create strings to match against at runtime.
@ -49,8 +50,10 @@ const Log2Int = std.math.Log2Int;
/// ```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
/// match("11_00", @as(u4, 0b1100)) // true
/// ```
pub fn match(comptime bit_string: []const u8, value: anytype) bool {
@setEvalBranchQuota(std.math.maxInt(u32)); // FIXME: bad practice
@ -63,12 +66,14 @@ pub fn match(comptime bit_string: []const u8, value: anytype) bool {
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 entie 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"),
}
@ -85,10 +90,12 @@ pub fn match(comptime bit_string: []const u8, value: anytype) bool {
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)));
@ -98,6 +105,10 @@ 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)));
}
/// Extracts the variables (defined in the bit string) from a value.
@ -108,6 +119,7 @@ test "match" {
/// 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
/// const ret = extract("aa_aa", @as(u4, 0b1001)); // ret.a == 0b1001
/// ```
///
/// Note: In Debug and ReleaseSafe builds, there's a runtime assert that
@ -128,13 +140,21 @@ pub fn extract(comptime bit_string: []const u8, value: anytype) Bitfield(bit_str
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`
// TODO: rewrite this invariant thing to account for underscores
// 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
@ -175,6 +195,10 @@ 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
{
@ -252,8 +276,8 @@ 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"),
}
}
@ -289,7 +313,13 @@ fn verify(comptime T: type, comptime bit_string: []const u8) void {
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 {
@ -374,7 +404,7 @@ const pext = struct {
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));