101 lines
2.7 KiB
Zig
101 lines
2.7 KiB
Zig
const std = @import("std");
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const tokens = @import("token.zig");
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const Token = tokens.Token;
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const TokenType = tokens.TokenType;
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const Allocator = std.mem.Allocator;
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pub const TokenError = error{
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Unexpected,
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Unterminated,
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};
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pub const Scanner = struct {
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source: []const u8,
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start: usize = 0,
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current: usize = 0,
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line: usize = 1,
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allocator: *Allocator,
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pub fn init(allocator: *Allocator, data: []const u8) Scanner {
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return Scanner{
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.allocator = allocator,
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.source = data,
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};
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}
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fn isAtEnd(self: *Scanner) bool {
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return self.current >= self.source.len;
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}
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fn advance(self: *Scanner) u8 {
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self.current += 1;
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return self.source[self.current - 1];
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}
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fn makeToken(self: *Scanner, ttype: TokenType) Token {
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return Token{
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.ttype = ttype,
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.lexeme = self.source[self.start..self.current],
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.line = self.line,
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};
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}
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/// Check if the next character matches what is expected.
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fn match(self: *Scanner, expected: u8) bool {
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if (self.isAtEnd()) return false;
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if (self.source[self.current] != expected) return false;
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self.current += 1;
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return true;
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}
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/// Add a SimpleToken of type_match if the next character is
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/// `expected`. Adds a SimpleToken of type_nomatch when it is not.
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fn makeMatchToken(
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self: *Scanner,
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expected: u8,
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type_match: TokenType,
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type_nomatch: TokenType,
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) Token {
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if (self.match(expected)) {
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return self.makeToken(type_match);
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} else {
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return self.makeToken(type_nomatch);
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}
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}
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pub fn scanToken(self: *Scanner) !tokens.Token {
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self.start = self.current;
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if (self.isAtEnd()) return self.makeToken(TokenType.EOF);
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var c = self.advance();
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var token = switch (c) {
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'(' => self.makeToken(.LEFT_PAREN),
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')' => self.makeToken(.RIGHT_PAREN),
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'{' => self.makeToken(.LEFT_BRACE),
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'}' => self.makeToken(.RIGHT_BRACE),
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',' => self.makeToken(.COMMA),
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'.' => self.makeToken(.DOT),
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'-' => self.makeToken(.MINUS),
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'+' => self.makeToken(.PLUS),
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';' => self.makeToken(.SEMICOLON),
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'*' => self.makeToken(.STAR),
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'!' => self.makeMatchToken('=', .BANG_EQUAL, .BANG),
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'=' => self.makeMatchToken('=', .EQUAL_EQUAL, .EQUAL),
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'<' => self.makeMatchToken('=', .LESS_EQUAL, .LESS),
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'>' => self.makeMatchToken('=', .GREATER_EQUAL, .GREATER),
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else => return TokenError.Unexpected,
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};
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return token;
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}
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};
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