Skip to content

Improve TextDecoder.decode #1042

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Sep 12, 2025
Merged

Improve TextDecoder.decode #1042

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
33 changes: 26 additions & 7 deletions src/browser/encoding/TextDecoder.zig
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,7 @@ const std = @import("std");
const log = @import("../../log.zig");

const Env = @import("../env.zig").Env;
const Page = @import("../page.zig").Page;

// https://encoding.spec.whatwg.org/#interface-textdecoder
const TextDecoder = @This();
Expand All @@ -37,6 +38,7 @@ const Options = struct {

fatal: bool,
ignore_bom: bool,
stream: std.ArrayList(u8),

pub fn constructor(label_: ?[]const u8, opts_: ?Options) !TextDecoder {
if (label_) |l| {
Expand All @@ -47,6 +49,7 @@ pub fn constructor(label_: ?[]const u8, opts_: ?Options) !TextDecoder {
}
const opts = opts_ orelse Options{};
return .{
.stream = .empty,
.fatal = opts.fatal,
.ignore_bom = opts.ignoreBOM,
};
Expand All @@ -64,18 +67,34 @@ pub fn get_fatal(self: *const TextDecoder) bool {
return self.fatal;
}

// TODO: Should accept an ArrayBuffer, TypedArray or DataView
// js.zig will currently only map a TypedArray to our []const u8.
pub fn _decode(self: *const TextDecoder, v: []const u8) ![]const u8 {
if (self.fatal and !std.unicode.utf8ValidateSlice(v)) {
const DecodeOptions = struct {
stream: bool = false,
};
pub fn _decode(self: *TextDecoder, input_: ?[]const u8, opts_: ?DecodeOptions, page: *Page) ![]const u8 {
var str = input_ orelse return "";
const opts: DecodeOptions = opts_ orelse .{};

if (self.stream.items.len > 0) {
try self.stream.appendSlice(page.arena, str);
str = self.stream.items;
}

if (self.fatal and !std.unicode.utf8ValidateSlice(str)) {
if (opts.stream) {
if (self.stream.items.len == 0) {
try self.stream.appendSlice(page.arena, str);
}
return "";
}
return error.InvalidUtf8;
}

if (self.ignore_bom == false and std.mem.startsWith(u8, v, &.{ 0xEF, 0xBB, 0xBF })) {
return v[3..];
self.stream.clearRetainingCapacity();
if (self.ignore_bom == false and std.mem.startsWith(u8, str, &.{ 0xEF, 0xBB, 0xBF })) {
return str[3..];
}

return v;
return str;
}

const testing = @import("../../testing.zig");
Expand Down
30 changes: 30 additions & 0 deletions src/tests/encoding/decoder.html
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -1,17 +1,47 @@
<!DOCTYPE html>
<meta charset="UTF-8">

<script src="../testing.js"></script>
<script id=decoder>
let d1 = new TextDecoder();
testing.expectEqual('utf-8', d1.encoding);
testing.expectEqual(false, d1.fatal);
testing.expectEqual(false, d1.ignoreBOM);

testing.expectEqual('', d1.decode());
testing.expectEqual('𠮷', d1.decode(new Uint8Array([240, 160, 174, 183])));
testing.expectEqual('𠮷', d1.decode(new Uint8Array([0xEF, 0xBB, 0xBF, 240, 160, 174, 183])));
testing.expectEqual('�2', d1.decode(new Uint8Array([249, 50])));

{
const buffer = new ArrayBuffer(4);
const ints = new Uint8Array(buffer)
ints[0] = 240;
ints[1] = 160;
ints[2] = 174;
ints[3] = 183;
testing.expectEqual('𠮷', d1.decode(buffer));
}

{
const buffer = new ArrayBuffer(4);
const dv = new DataView(buffer);
dv.setUint8(0, 240);
dv.setUint8(1, 160);
dv.setUint8(2, 174);
dv.setUint8(3, 183);
testing.expectEqual('𠮷', d1.decode(dv));
}

let d2 = new TextDecoder('utf8', {fatal: true})
testing.expectError('Error: InvalidUtf8', () => {
let data = new Uint8Array([240, 240, 160, 174, 183]);
d2.decode(data);
});
</script>

<script id=stream>
let d3 = new TextDecoder();
testing.expectEqual('', d2.decode(new Uint8Array([226, 153]), { stream: true }));
testing.expectEqual('♥', d2.decode(new Uint8Array([165]), { stream: true }));
</script>