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Preprocessor: add support for UCN identifiers
Closes #823
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| //! Universal Character Name support | ||
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| const std = @import("std"); | ||
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| const Kind = enum { | ||
| /// Valid not escaped char | ||
| normal, | ||
| /// Not escaped, but not valid UTF-8 | ||
| invalid_utf_8, | ||
| /// Valid UCN char | ||
| ucn, | ||
| /// Incomplete UCN escape sequence | ||
| incomplete_ucn, | ||
| /// UCN escape sequence does not specify a unicode code point | ||
| invalid_codepoint, | ||
| /// UCN names a control character | ||
| control, | ||
| /// UCN names a basic character set character | ||
| not_allowed, | ||
| }; | ||
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| pub const DecodedUniversalChar = struct { | ||
| codepoint: u32, | ||
| consumed: usize, | ||
| buf: []const u8, | ||
| kind: Kind, | ||
| }; | ||
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| /// Decodes a C99-style universal character name (e.g., \uXXXX or \UXXXXXXXX) | ||
| /// into a unicode codepoint. Returns the decoded character and the number of | ||
| /// bytes consumed from the input string. | ||
| fn decodeUniversalChar(input: []const u8, output: []u8) DecodedUniversalChar { | ||
| std.debug.assert(input.len >= 2 and input[0] == '\\' and (input[1] == 'u' or input[1] == 'U')); | ||
| const is_long = input[1] == 'U'; | ||
| const required: usize = if (is_long) 10 else 6; | ||
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| if (input.len < required) { | ||
| return .{ | ||
| .codepoint = 0, | ||
| .consumed = input.len, | ||
| .buf = input, | ||
| .kind = .incomplete_ucn, | ||
| }; | ||
| } | ||
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| const hex_part = input[2..required]; | ||
| var codepoint: u32 = 0; | ||
| for (hex_part, 0..) |c, i| { | ||
| codepoint *= 16; | ||
| const value = switch (c) { | ||
| '0'...'9' => c - '0', | ||
| 'a'...'f' => 10 + (c - 'a'), | ||
| 'A'...'F' => 10 + (c - 'A'), | ||
| else => return .{ .codepoint = 0, .consumed = i, .buf = input[0..i], .kind = .incomplete_ucn }, | ||
| }; | ||
| codepoint += value; | ||
| } | ||
| if (codepoint > std.math.maxInt(u21)) { | ||
| return .{ .codepoint = 0, .consumed = required, .buf = input, .kind = .invalid_codepoint }; | ||
| } | ||
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| const len = std.unicode.utf8Encode(@as(u21, @intCast(codepoint)), output) catch { | ||
| return .{ .codepoint = codepoint, .consumed = required, .buf = input, .kind = .invalid_codepoint }; | ||
| }; | ||
| const kind: Kind = switch (codepoint) { | ||
| 0...0x1F, 0x7F...0x9F => .control, | ||
| 0x20...0x7E => .not_allowed, | ||
| else => .ucn, | ||
| }; | ||
| return .{ .codepoint = codepoint, .consumed = required, .buf = output[0..len], .kind = kind }; | ||
| } | ||
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| pub const CharIterator = struct { | ||
| str: []const u8, | ||
| i: usize, | ||
| buf: [10]u8, | ||
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| pub fn init(str: []const u8) CharIterator { | ||
| return .{ .str = str, .i = 0, .buf = undefined }; | ||
| } | ||
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| pub fn next(self: *@This()) ?DecodedUniversalChar { | ||
| if (self.i >= self.str.len) return null; | ||
| if (self.str[self.i] == '\\' and self.i + 1 < self.str.len and (self.str[self.i + 1] == 'u' or self.str[self.i + 1] == 'U')) { | ||
| const decoded = decodeUniversalChar(self.str[self.i..], self.buf[0..]); | ||
| self.i += decoded.consumed; | ||
| return decoded; | ||
| } else { | ||
| const len = std.unicode.utf8ByteSequenceLength(self.str[self.i]) catch { | ||
| defer self.i += 1; | ||
| return .{ .codepoint = self.str[self.i], .consumed = 1, .buf = self.str[self.i..][0..1], .kind = .invalid_utf_8 }; | ||
| }; | ||
| defer self.i += len; | ||
| return .{ .codepoint = 0, .consumed = len, .buf = self.str[self.i..][0..len], .kind = .normal }; | ||
| } | ||
| } | ||
| }; |
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