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const std = @import("std");
pub fn Token(TokenKind: type) type {
return struct {
const Self = @This();
kind: TokenKind,
slice: []const u8,
pub fn start(comptime lexer: *const Lexer(TokenKind), kind: TokenKind) Self {
return .{
.kind = kind,
.slice = lexer.buffer,
};
}
pub inline fn stop(comptime self: Self, comptime lexer: *const Lexer(TokenKind)) Self {
comptime {
const length = self.slice.len - lexer.buffer.len;
return .{
.kind = self.kind,
.slice = self.slice[0..length],
};
}
}
pub fn format(self: *const Self, writer: *std.Io.Writer) !void {
try writer.print("Token{}(\"{s}\")", .{self.kind, self.slice});
}
};
}
pub fn Lexer(TokenKind: type) type {
return struct {
const Self = @This();
pub const Error = error{
UnexpectedToken,
EndOfBuffer,
};
buffer: []const u8,
last_buffer: []const u8,
tokens: []const Token(TokenKind) = &.{},
context: TokenKind.Context = .{},
pub fn init(buffer: []const u8) Self {
return .{
.buffer = buffer,
.last_buffer = buffer,
};
}
pub inline fn peekChar(self: *Self) ?u8 {
return self.peekCharAt(0);
}
pub inline fn peekCharAt(self: *Self, n: usize) ?u8 {
return if (n < self.buffer.len) self.buffer[n] else null;
}
pub fn peekSlice(self: *Self, length: usize) ?[]const u8 {
return self.peekSliceAt(length, 0);
}
pub fn peekSliceAt(self: *Self, length: usize, offset: usize) ?[]const u8 {
if (length + offset <= self.buffer.len) {
return self.buffer[offset .. offset + length];
}
return null;
}
pub fn consume(self: *Self) !u8 {
return (try self.consumeTo(1))[0];
}
pub fn consumeTo(self: *Self, n: usize) ![]const u8 {
if (n <= self.buffer.len) {
const slice = self.buffer[0..n];
self.buffer = self.buffer[n..];
return slice;
} else {
return Error.EndOfBuffer;
}
}
pub fn skip(self: *Self) !void {
return self.skipTo(1);
}
pub fn skipTo(self: *Self, n: usize) Error!void {
if (n <= self.buffer.len) {
self.buffer = self.buffer[n..];
} else {
return Error.EndOfBuffer;
}
}
pub fn skipUntil(self: *Self, literal: []const u8) Error!void {
if (std.mem.find(u8, self.buffer, literal)) |index| {
self.buffer = self.buffer[index + literal.len..];
} else {
return Error.EndOfBuffer;
}
}
pub fn skipToEnd(self: *Self) void {
self.buffer = self.buffer[self.buffer.len..];
}
pub fn start(self: *Self, kind: TokenKind) Token(TokenKind) {
return .start(self, kind);
}
pub fn revert(self: *Self) void {
self.buffer = self.last_buffer;
}
pub fn commit(self: *Self, tok: Token(TokenKind)) void {
self.tokens = self.tokens ++ [_]Token(TokenKind){tok.stop(self)};
self.last_buffer = self.buffer;
}
};
}
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