fix: misuse of `@ctz` when finding index of bit string var in tmp buffer
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27
src/lib.zig
27
src/lib.zig
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@ -183,6 +183,29 @@ test "extract" {
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try std.testing.expectEqual(@as(u4, 0b1110), ret.a);
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try std.testing.expectEqual(@as(u4, 0b1011), ret.b);
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}
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{
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const ret = extract("--------ddddrrrr", @as(u16, 0b0000_0010_1011_0110));
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try std.testing.expectEqual(@as(u4, 0b1011), ret.d);
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try std.testing.expectEqual(@as(u4, 0b0110), ret.r);
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}
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{
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const ret = extract("--------", @as(u8, 0b00000000));
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const T = @TypeOf(ret);
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try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
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}
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{
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const ret = extract("00000000", @as(u8, 0b00000000));
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const T = @TypeOf(ret);
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try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
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}
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{
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const ret = extract("0-0-0-0-", @as(u8, 0b01010101));
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const T = @TypeOf(ret);
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try std.testing.expectEqual(@as(usize, 0), @typeInfo(T).Struct.fields.len);
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}
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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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@ -213,13 +236,13 @@ pub fn Bitfield(comptime bit_string: []const u8) type {
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var tmp: [field_len]StructField = undefined;
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const Tmp = struct { bits: u8 = 0, char: ?u8 = null };
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var things: [field_len]Tmp = [_]Tmp{.{}} ** field_len;
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var things: [field_len]Tmp = [_]Tmp{.{}} ** field_len; // TODO: rename this lol
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for (bit_string) |char| {
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switch (char) {
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'a'...'z' => |c| {
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const bit_in_set = @as(u26, 1) << @intCast(c - 'a');
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const pos = @ctz(alphabet_set & ~(bit_in_set - 1));
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const pos = @popCount(alphabet_set & ~(bit_in_set - 1)) - 1; // TODO: investigate this off-by-one
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things[pos].bits += 1;
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things[pos].char = c;
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