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|
const std = @import("std");
pub const Token = struct {
pub const Kind = enum { Literal, LParen, RParen, Class, Dot, Star, Plus, Question, Or };
pub const Value = union(Token.Kind) { Literal: u8, LParen, RParen, Class: RangeList, Dot, Star, Plus, Question, Or };
kind: Token.Kind,
value: ?Token.Value,
pos: usize,
pub fn format(self: *const Token, comptime fmt: []const u8, _: std.fmt.FormatOptions, writer: anytype) !void {
if (fmt.len != 0) { // must be {} or {any}
return std.invalidFmtError(fmt, self);
}
try writer.print("{{ kind: {s}", .{@tagName(self.kind)});
if (self.value) |val| {
switch (val) {
.Literal => |literal| try writer.print(", value: {c}", .{literal}),
.Class => |rl| try writer.print(", value: {}", .{rl}),
else => {},
}
}
try writer.print(" }}", .{});
}
};
pub const Lexer = struct {
start: usize,
cursor: usize,
regexp: []const u8,
allocator: *std.mem.Allocator,
pub const Error = error{ EndOfBuffer, InvalidCharacter, UnexpectedCharater };
pub fn init(regexp: []const u8, allocator: *std.mem.Allocator) Lexer {
return .{ .cursor = 0, .start = 0, .regexp = regexp, .allocator = allocator };
}
fn readChar(self: *Lexer) !u8 {
if (self.cursor >= self.regexp.len) {
return Error.EndOfBuffer;
}
return self.regexp[self.cursor];
}
pub fn advance(self: *Lexer) !Token {
self.start = self.cursor;
var c = try self.readChar();
const inferred_type: Token.Kind = switch (c) {
'(' => .LParen,
')' => .RParen,
'[' => .Class,
'.' => .Dot,
'*' => .Star,
'+' => .Plus,
'?' => .Question,
'|' => .Or,
else => .Literal,
};
switch (inferred_type) {
.Literal => {
if (c == '\\') {
self.cursor += 1;
c = try self.readChar(); // needs more verbose error handling
c = escapedChar(c);
}
self.cursor += 1;
return .{ .kind = inferred_type, .value = .{ .Literal = c }, .pos = self.start };
},
.Class => {
while (c != ']') { // needs more verbose error handling
c = try self.readChar();
self.cursor += 1;
}
return .{ .kind = inferred_type, .value = .{ .Class = try RangeList.init(self.regexp[self.start + 1 .. self.cursor - 1], self.allocator) }, .pos = self.start };
},
else => {
self.cursor += 1;
return .{ .kind = inferred_type, .pos = self.start, .value = null };
},
}
}
fn escapedChar(c: u8) u8 {
return switch (c) {
'n' => '\n', // placeholder for now
't' => '\t',
'r' => '\r',
else => c,
};
}
};
// could use something like a bst, but thinking about what regex classes people actually write makes me think that a list is more efficient
pub const RangeList = struct {
negated: bool,
head: ?*Node,
allocator: *std.mem.Allocator,
const Node = struct {
range: struct { min: u8, max: u8 },
next: ?*Node,
};
// need to do more error handling
pub fn init(str: []const u8, allocator: *std.mem.Allocator) !RangeList {
var rl = RangeList{
.negated = false,
.head = null,
.allocator = allocator,
};
var i: usize = 0;
if (str.len == 0) {
return rl;
}
if (str[0] == '^') {
rl.negated = true;
i += 1;
}
var p = rl.head;
while (i < str.len) : (i += 1) {
const node = try rl.allocator.create(Node);
const min = str[i];
var max = min;
i += 1;
if (i + 1 < str.len and str[i] == '-') {
i += 1;
max = str[i];
i += 1;
}
node.* = .{
.range = .{ .min = min, .max = max },
.next = null,
};
if (p) |tail| {
tail.next = node;
p = tail.next;
} else {
rl.head = node;
p = rl.head;
}
}
return rl;
}
pub fn deinit(self: *const RangeList) void {
var itr = self.head;
while (itr) |node| {
const prev = node;
itr = node.next;
self.allocator.destroy(prev);
}
}
pub fn format(self: *const RangeList, comptime fmt: []const u8, _: std.fmt.FormatOptions, writer: anytype) !void {
var itr = self.head;
if (fmt.len != 0) { // must be {} or {any}
return std.invalidFmtError(fmt, self);
}
if (self.negated) {
try writer.print("^", .{});
}
try writer.print("[", .{});
while (itr) |node| : (itr = node.next) {
if (node.range.min == node.range.max) {
try writer.print("{c}", .{node.range.min});
} else {
try writer.print("{c}-{c}", .{ node.range.min, node.range.max });
}
if (node.next) |_| {
try writer.print(", ", .{});
}
}
try writer.print("]", .{});
}
};
|
