zig/std/unicode.zig

301 lines
9.7 KiB
Zig

const std = @import("./index.zig");
const debug = std.debug;
/// Given the first byte of a UTF-8 codepoint,
/// returns a number 1-4 indicating the total length of the codepoint in bytes.
/// If this byte does not match the form of a UTF-8 start byte, returns Utf8InvalidStartByte.
pub fn utf8ByteSequenceLength(first_byte: u8) !u3 {
if (first_byte < 0b10000000) return u3(1);
if (first_byte & 0b11100000 == 0b11000000) return u3(2);
if (first_byte & 0b11110000 == 0b11100000) return u3(3);
if (first_byte & 0b11111000 == 0b11110000) return u3(4);
return error.Utf8InvalidStartByte;
}
/// Decodes the UTF-8 codepoint encoded in the given slice of bytes.
/// bytes.len must be equal to utf8ByteSequenceLength(bytes[0]) catch unreachable.
/// If you already know the length at comptime, you can call one of
/// utf8Decode2,utf8Decode3,utf8Decode4 directly instead of this function.
pub fn utf8Decode(bytes: []const u8) !u32 {
return switch (bytes.len) {
1 => u32(bytes[0]),
2 => utf8Decode2(bytes),
3 => utf8Decode3(bytes),
4 => utf8Decode4(bytes),
else => unreachable,
};
}
pub fn utf8Decode2(bytes: []const u8) !u32 {
debug.assert(bytes.len == 2);
debug.assert(bytes[0] & 0b11100000 == 0b11000000);
var value: u32 = bytes[0] & 0b00011111;
if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[1] & 0b00111111;
if (value < 0x80) return error.Utf8OverlongEncoding;
return value;
}
pub fn utf8Decode3(bytes: []const u8) !u32 {
debug.assert(bytes.len == 3);
debug.assert(bytes[0] & 0b11110000 == 0b11100000);
var value: u32 = bytes[0] & 0b00001111;
if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[1] & 0b00111111;
if (bytes[2] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[2] & 0b00111111;
if (value < 0x800) return error.Utf8OverlongEncoding;
if (0xd800 <= value and value <= 0xdfff) return error.Utf8EncodesSurrogateHalf;
return value;
}
pub fn utf8Decode4(bytes: []const u8) !u32 {
debug.assert(bytes.len == 4);
debug.assert(bytes[0] & 0b11111000 == 0b11110000);
var value: u32 = bytes[0] & 0b00000111;
if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[1] & 0b00111111;
if (bytes[2] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[2] & 0b00111111;
if (bytes[3] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
value <<= 6;
value |= bytes[3] & 0b00111111;
if (value < 0x10000) return error.Utf8OverlongEncoding;
if (value > 0x10FFFF) return error.Utf8CodepointTooLarge;
return value;
}
pub fn utf8ValidateSlice(s: []const u8) bool {
var i: usize = 0;
while (i < s.len) {
if (utf8ByteSequenceLength(s[i])) |cp_len| {
if (i + cp_len > s.len) {
return false;
}
if (utf8Decode(s[i..i+cp_len])) |_| {} else |_| { return false; }
i += cp_len;
} else |err| {
return false;
}
}
return true;
}
/// Utf8View iterates the code points of a utf-8 encoded string.
///
/// ```
/// var utf8 = (try std.unicode.Utf8View.init("hi there")).iterator();
/// while (utf8.nextCodepointSlice()) |codepoint| {
/// std.debug.warn("got codepoint {}\n", codepoint);
/// }
/// ```
pub const Utf8View = struct {
bytes: []const u8,
pub fn init(s: []const u8) !Utf8View {
if (!utf8ValidateSlice(s)) {
return error.InvalidUtf8;
}
return initUnchecked(s);
}
pub fn initUnchecked(s: []const u8) Utf8View {
return Utf8View {
.bytes = s,
};
}
pub fn initComptime(comptime s: []const u8) Utf8View {
if (comptime init(s)) |r| {
return r;
} else |err| switch (err) {
error.InvalidUtf8 => {
@compileError("invalid utf8");
unreachable;
}
}
}
pub fn iterator(s: &const Utf8View) Utf8Iterator {
return Utf8Iterator {
.bytes = s.bytes,
.i = 0,
};
}
};
const Utf8Iterator = struct {
bytes: []const u8,
i: usize,
pub fn nextCodepointSlice(it: &Utf8Iterator) ?[]const u8 {
if (it.i >= it.bytes.len) {
return null;
}
const cp_len = utf8ByteSequenceLength(it.bytes[it.i]) catch unreachable;
it.i += cp_len;
return it.bytes[it.i-cp_len..it.i];
}
pub fn nextCodepoint(it: &Utf8Iterator) ?u32 {
const slice = it.nextCodepointSlice() ?? return null;
const r = switch (slice.len) {
1 => u32(slice[0]),
2 => utf8Decode2(slice),
3 => utf8Decode3(slice),
4 => utf8Decode4(slice),
else => unreachable,
};
return r catch unreachable;
}
};
test "utf8 iterator on ascii" {
const s = Utf8View.initComptime("abc");
var it1 = s.iterator();
debug.assert(std.mem.eql(u8, "a", ??it1.nextCodepointSlice()));
debug.assert(std.mem.eql(u8, "b", ??it1.nextCodepointSlice()));
debug.assert(std.mem.eql(u8, "c", ??it1.nextCodepointSlice()));
debug.assert(it1.nextCodepointSlice() == null);
var it2 = s.iterator();
debug.assert(??it2.nextCodepoint() == 'a');
debug.assert(??it2.nextCodepoint() == 'b');
debug.assert(??it2.nextCodepoint() == 'c');
debug.assert(it2.nextCodepoint() == null);
}
test "utf8 view bad" {
// Compile-time error.
// const s3 = Utf8View.initComptime("\xfe\xf2");
const s = Utf8View.init("hel\xadlo");
if (s) |_| { unreachable; } else |err| { debug.assert(err == error.InvalidUtf8); }
}
test "utf8 view ok" {
const s = Utf8View.initComptime("東京市");
var it1 = s.iterator();
debug.assert(std.mem.eql(u8, "", ??it1.nextCodepointSlice()));
debug.assert(std.mem.eql(u8, "", ??it1.nextCodepointSlice()));
debug.assert(std.mem.eql(u8, "", ??it1.nextCodepointSlice()));
debug.assert(it1.nextCodepointSlice() == null);
var it2 = s.iterator();
debug.assert(??it2.nextCodepoint() == 0x6771);
debug.assert(??it2.nextCodepoint() == 0x4eac);
debug.assert(??it2.nextCodepoint() == 0x5e02);
debug.assert(it2.nextCodepoint() == null);
}
test "bad utf8 slice" {
debug.assert(utf8ValidateSlice("abc"));
debug.assert(!utf8ValidateSlice("abc\xc0"));
debug.assert(!utf8ValidateSlice("abc\xc0abc"));
debug.assert(utf8ValidateSlice("abc\xdf\xbf"));
}
test "valid utf8" {
testValid("\x00", 0x0);
testValid("\x20", 0x20);
testValid("\x7f", 0x7f);
testValid("\xc2\x80", 0x80);
testValid("\xdf\xbf", 0x7ff);
testValid("\xe0\xa0\x80", 0x800);
testValid("\xe1\x80\x80", 0x1000);
testValid("\xef\xbf\xbf", 0xffff);
testValid("\xf0\x90\x80\x80", 0x10000);
testValid("\xf1\x80\x80\x80", 0x40000);
testValid("\xf3\xbf\xbf\xbf", 0xfffff);
testValid("\xf4\x8f\xbf\xbf", 0x10ffff);
}
test "invalid utf8 continuation bytes" {
// unexpected continuation
testError("\x80", error.Utf8InvalidStartByte);
testError("\xbf", error.Utf8InvalidStartByte);
// too many leading 1's
testError("\xf8", error.Utf8InvalidStartByte);
testError("\xff", error.Utf8InvalidStartByte);
// expected continuation for 2 byte sequences
testError("\xc2", error.UnexpectedEof);
testError("\xc2\x00", error.Utf8ExpectedContinuation);
testError("\xc2\xc0", error.Utf8ExpectedContinuation);
// expected continuation for 3 byte sequences
testError("\xe0", error.UnexpectedEof);
testError("\xe0\x00", error.UnexpectedEof);
testError("\xe0\xc0", error.UnexpectedEof);
testError("\xe0\xa0", error.UnexpectedEof);
testError("\xe0\xa0\x00", error.Utf8ExpectedContinuation);
testError("\xe0\xa0\xc0", error.Utf8ExpectedContinuation);
// expected continuation for 4 byte sequences
testError("\xf0", error.UnexpectedEof);
testError("\xf0\x00", error.UnexpectedEof);
testError("\xf0\xc0", error.UnexpectedEof);
testError("\xf0\x90\x00", error.UnexpectedEof);
testError("\xf0\x90\xc0", error.UnexpectedEof);
testError("\xf0\x90\x80\x00", error.Utf8ExpectedContinuation);
testError("\xf0\x90\x80\xc0", error.Utf8ExpectedContinuation);
}
test "overlong utf8 codepoint" {
testError("\xc0\x80", error.Utf8OverlongEncoding);
testError("\xc1\xbf", error.Utf8OverlongEncoding);
testError("\xe0\x80\x80", error.Utf8OverlongEncoding);
testError("\xe0\x9f\xbf", error.Utf8OverlongEncoding);
testError("\xf0\x80\x80\x80", error.Utf8OverlongEncoding);
testError("\xf0\x8f\xbf\xbf", error.Utf8OverlongEncoding);
}
test "misc invalid utf8" {
// codepoint out of bounds
testError("\xf4\x90\x80\x80", error.Utf8CodepointTooLarge);
testError("\xf7\xbf\xbf\xbf", error.Utf8CodepointTooLarge);
// surrogate halves
testValid("\xed\x9f\xbf", 0xd7ff);
testError("\xed\xa0\x80", error.Utf8EncodesSurrogateHalf);
testError("\xed\xbf\xbf", error.Utf8EncodesSurrogateHalf);
testValid("\xee\x80\x80", 0xe000);
}
fn testError(bytes: []const u8, expected_err: error) void {
if (testDecode(bytes)) |_| {
unreachable;
} else |err| {
debug.assert(err == expected_err);
}
}
fn testValid(bytes: []const u8, expected_codepoint: u32) void {
debug.assert((testDecode(bytes) catch unreachable) == expected_codepoint);
}
fn testDecode(bytes: []const u8) !u32 {
const length = try utf8ByteSequenceLength(bytes[0]);
if (bytes.len < length) return error.UnexpectedEof;
debug.assert(bytes.len == length);
return utf8Decode(bytes);
}