tiny.xkb.keymap.text.lexer

1const std = @import("std");23pub const Error = error{InvalidSyntax};45pub const Tag = enum {6    word,7    string,8    key_name,9    left_brace,10    right_brace,11    left_bracket,12    right_bracket,13    left_paren,14    right_paren,15    equal,16    semicolon,17    comma,18    plus,19    dot,20    bang,21    minus,22    end,23};2425pub const Token = struct {26    tag: Tag,27    text: []const u8,28};2930pub const Lexer = struct {31    input: []const u8,32    position: usize = 0,3334    pub fn next(self: *Lexer) Error!Token {35        try self.skipIgnored();36        if (self.position == self.input.len) return .{ .tag = .end, .text = "" };3738        const start = self.position;39        const byte = self.input[self.position];40        self.position += 1;41        return switch (byte) {42            '{' => self.punctuation(.left_brace, start),43            '}' => self.punctuation(.right_brace, start),44            '[' => self.punctuation(.left_bracket, start),45            ']' => self.punctuation(.right_bracket, start),46            '(' => self.punctuation(.left_paren, start),47            ')' => self.punctuation(.right_paren, start),48            '=' => self.punctuation(.equal, start),49            ';' => self.punctuation(.semicolon, start),50            ',' => self.punctuation(.comma, start),51            '+' => self.punctuation(.plus, start),52            '.' => self.punctuation(.dot, start),53            '!' => self.punctuation(.bang, start),54            '-' => self.punctuation(.minus, start),55            '"' => try self.quoted(start),56            '<' => try self.keyName(start),57            else => self.word(start),58        };59    }6061    fn punctuation(self: *const Lexer, tag: Tag, start: usize) Token {62        return .{ .tag = tag, .text = self.input[start .. start + 1] };63    }6465    fn quoted(self: *Lexer, start: usize) Error!Token {66        var escaped = false;67        while (self.position < self.input.len) : (self.position += 1) {68            const byte = self.input[self.position];69            if (escaped) {70                escaped = false;71                continue;72            }73            if (byte == '\\') {74                escaped = true;75                continue;76            }77            if (byte == '"') {78                const end = self.position;79                self.position += 1;80                return .{ .tag = .string, .text = self.input[start + 1 .. end] };81            }82            if (byte == 0) return error.InvalidSyntax;83        }84        return error.InvalidSyntax;85    }8687    fn keyName(self: *Lexer, start: usize) Error!Token {88        const end = std.mem.indexOfScalarPos(u8, self.input, self.position, '>') orelse89            return error.InvalidSyntax;90        if (end == self.position) return error.InvalidSyntax;91        self.position = end + 1;92        return .{ .tag = .key_name, .text = self.input[start + 1 .. end] };93    }9495    fn word(self: *Lexer, start: usize) Token {96        while (self.position < self.input.len and !delimiter(self.input[self.position])) {97            self.position += 1;98        }99        return .{ .tag = .word, .text = self.input[start..self.position] };100    }101102    fn skipIgnored(self: *Lexer) Error!void {103        while (self.position < self.input.len) {104            if (std.ascii.isWhitespace(self.input[self.position])) {105                self.position += 1;106                continue;107            }108            if (self.input[self.position] != '/' or self.position + 1 == self.input.len) return;109            switch (self.input[self.position + 1]) {110                '/' => {111                    self.position += 2;112                    while (self.position < self.input.len and self.input[self.position] != '\n') {113                        self.position += 1;114                    }115                },116                '*' => {117                    const end = std.mem.indexOfPos(118                        u8,119                        self.input,120                        self.position + 2,121                        "*/",122                    ) orelse return error.InvalidSyntax;123                    self.position = end + 2;124                },125                else => return,126            }127        }128    }129};130131fn delimiter(byte: u8) bool {132    return std.ascii.isWhitespace(byte) or switch (byte) {133        '{', '}', '[', ']', '(', ')', '=', ';', ',', '+', '.', '!', '-', '"', '<' => true,134        else => false,135    };136}137138test "lexer separates resolved XKB punctuation and comments" {139    var lexer = Lexer{ .input = "/* a */ key <AD01> { [ 0x61, NoSymbol ] }; // b" };140    const expected = [_]Tag{141        .word,142        .key_name,143        .left_brace,144        .left_bracket,145        .word,146        .comma,147        .word,148        .right_bracket,149        .right_brace,150        .semicolon,151        .end,152    };153    for (expected) |tag| try std.testing.expectEqual(tag, (try lexer.next()).tag);154}155156test "lexer rejects unterminated strings key names and comments" {157    var string = Lexer{ .input = "\"bad" };158    try std.testing.expectError(error.InvalidSyntax, string.next());159    var key_name = Lexer{ .input = "<BAD" };160    try std.testing.expectError(error.InvalidSyntax, key_name.next());161    var comment = Lexer{ .input = "/* bad" };162    try std.testing.expectError(error.InvalidSyntax, comment.next());163}

1pub const lexer = @import("lexer.zig");