182 lines
5.0 KiB
Zig
182 lines
5.0 KiB
Zig
const std = @import("std");
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const token = @import("token.zig");
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const main = @import("main.zig");
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const TokenList = std.ArrayList(token.Token);
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pub const Scanner = struct {
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source: []u8,
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tokens: TokenList,
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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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pub fn init(allocator: *std.mem.Allocator, data: []u8) Scanner {
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return Scanner{
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.source = data,
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.tokens = TokenList.init(allocator),
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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 currentLexeme(self: *Scanner) []u8 {
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return self.source[self.start..self.current];
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}
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fn addSimpleToken(self: *Scanner, ttype: token.TokenType) !void {
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try self.addToken(token.Token{
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.Simple = token.SimpleToken.init(
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ttype,
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self.currentLexeme(),
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self.line,
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{},
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),
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});
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}
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fn addSliceToken(self: *Scanner, ttype: token.TokenType, slice: []u8) !void {
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try self.addToken(token.Token{
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.Slice = token.SliceToken.init(
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ttype,
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self.currentLexeme(),
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self.line,
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slice,
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),
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});
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}
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fn addToken(
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self: *Scanner,
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tok: token.Token,
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) !void {
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try self.tokens.append(tok);
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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 addMatchToken(
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self: *Scanner,
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expected: u8,
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type_match: token.TokenType,
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type_nomatch: token.TokenType,
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) !void {
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if (self.match(expected)) {
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try self.addSimpleToken(type_match);
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} else {
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try self.addSimpleToken(type_nomatch);
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}
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}
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fn peek(self: *Scanner) u8 {
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if (self.isAtEnd()) return 0;
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return self.source[self.current];
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}
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fn doString(self: *Scanner) !void {
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// consume entire string
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while (self.peek() != '"' and !self.isAtEnd()) {
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if (self.peek() == '\n') self.line += 1;
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_ = self.advance();
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}
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// unterminated string.
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if (self.isAtEnd()) {
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try main.doError(self.line, "Unterminated string.");
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return;
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}
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// the closing ".
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_ = self.advance();
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// trim the surrounding quotes.
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try self.addSliceToken(
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.STRING,
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self.source[self.start + 1 .. self.current - 1],
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);
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}
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/// Scan through our tokens and add them to the Scanner's token list.
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fn scanToken(self: *Scanner) !void {
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var c = self.advance();
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switch (c) {
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'(' => try self.addSimpleToken(.LEFT_PAREN),
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')' => try self.addSimpleToken(.RIGHT_PAREN),
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'{' => try self.addSimpleToken(.LEFT_BRACE),
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'}' => try self.addSimpleToken(.RIGHT_BRACE),
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',' => try self.addSimpleToken(.COMMA),
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'.' => try self.addSimpleToken(.DOT),
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'-' => try self.addSimpleToken(.MINUS),
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'+' => try self.addSimpleToken(.PLUS),
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';' => try self.addSimpleToken(.SEMICOLON),
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'*' => try self.addSimpleToken(.STAR),
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'!' => try self.addMatchToken('=', .BANG_EQUAL, .BANG),
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'=' => try self.addMatchToken('=', .EQUAL_EQUAL, .EQUAL),
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'<' => try self.addMatchToken('=', .LESS_EQUAL, .LESS),
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'>' => try self.addMatchToken('=', .GREATER_EQUAL, .GREATER),
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'/' => blk: {
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// consume comments
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if (self.match('/')) {
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while (self.peek() != '\n' and !self.isAtEnd()) {
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_ = self.advance();
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}
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} else {
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try self.addSimpleToken(.SLASH);
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}
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},
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' ', '\r', '\t' => blk: {},
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'\n' => blk: {
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self.line += 1;
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},
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'"' => try self.doString(),
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else => {
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try main.doError(self.line, "Unexpected character");
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},
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}
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}
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pub fn scanTokens(self: *Scanner) !TokenList {
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// while we aren't at the end, we're still consuming
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// tokens.
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while (!self.isAtEnd()) {
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self.start = self.current;
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try self.scanToken();
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}
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try self.addToken(token.Token{
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.Simple = token.SimpleToken.init(
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.EOF,
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"",
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self.line,
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{},
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),
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});
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return self.tokens;
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}
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};
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