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fix: misuse of `@ctz` when finding index of bit string var in tmp buffer

This commit is contained in:
Rekai Nyangadzayi Musuka 2023-08-17 23:56:26 -05:00
parent de5474b6c3
commit e0ab786ef0
1 changed files with 25 additions and 2 deletions
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27
src/lib.zig
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@ -183,6 +183,29 @@ test "extract" {
try std.testing.expectEqual(@as(u4, 0b1110), ret.a);
try std.testing.expectEqual(@as(u4, 0b1011), ret.b);
}
{
const ret = extract("--------ddddrrrr", @as(u16, 0b0000_0010_1011_0110));
try std.testing.expectEqual(@as(u4, 0b1011), ret.d);
try std.testing.expectEqual(@as(u4, 0b0110), ret.r);
}
{
const ret = extract("--------", @as(u8, 0b00000000));
const T = @TypeOf(ret);
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);
}
{
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);
}
}
/// Parses a bit string and reifies a struct that will contain fields that correspond to the variables present in the bit string.
@ -213,13 +236,13 @@ pub fn Bitfield(comptime bit_string: []const u8) type {
var tmp: [field_len]StructField = undefined;
const Tmp = struct { bits: u8 = 0, char: ?u8 = null };
var things: [field_len]Tmp = [_]Tmp{.{}} ** field_len;
var things: [field_len]Tmp = [_]Tmp{.{}} ** field_len; // TODO: rename this lol
for (bit_string) |char| {
switch (char) {
'a'...'z' => |c| {
const bit_in_set = @as(u26, 1) << @intCast(c - 'a');
const pos = @ctz(alphabet_set & ~(bit_in_set - 1));
const pos = @popCount(alphabet_set & ~(bit_in_set - 1)) - 1; // TODO: investigate this off-by-one
things[pos].bits += 1;
things[pos].char = c;