diff --git a/lib/std/fmt.zig b/lib/std/fmt.zig index 81d7ce588d..b5b4998da6 100644 --- a/lib/std/fmt.zig +++ b/lib/std/fmt.zig @@ -76,6 +76,7 @@ fn peekIsAlign(comptime fmt: []const u8) bool { /// - `b`: output integer value in binary notation /// - `o`: output integer value in octal notation /// - `c`: output integer as an ASCII character. Integer type must have 8 bits at max. +/// - `u`: output integer as an UTF-8 sequence. Integer type must have 32 bits at max. /// - `*`: output the address of the value instead of the value itself. /// /// If a formatted user type contains a function of the type @@ -555,6 +556,12 @@ pub fn formatIntValue( } else { @compileError("Cannot escape character with more than 8 bits"); } + } else if (comptime std.mem.eql(u8, fmt, "u")) { + if (@TypeOf(int_value).bit_count <= 32) { + return formatUtf8Codepoint(@as(u32, int_value), options, context, Errors, output); + } else { + @compileError("Cannot print integer that is larger than 32 bits as an UTF-8 sequence"); + } } else if (comptime std.mem.eql(u8, fmt, "b")) { radix = 2; uppercase = false; @@ -641,6 +648,18 @@ pub fn formatAsciiChar( return writer.writeAll(@as(*const [1]u8, &c)); } +pub fn formatUtf8Codepoint( + c: u32, + options: FormatOptions, + context: anytype, + comptime Errors: type, + output: fn (@TypeOf(context), []const u8) Errors!void, +) Errors!void { + var buf: [4]u8 = undefined; + const len = std.unicode.utf8Encode(c, buf[0..]) catch unreachable; + return output(context, @as(*const [4]u8, &buf)[0..len]); +} + pub fn formatBuf( buf: []const u8, options: FormatOptions, @@ -1385,6 +1404,14 @@ test "int.specifier" { const value: u16 = 0o1234; try testFmt("u16: 0o1234\n", "u16: 0o{o}\n", .{value}); } + { + const value: u8 = 'a'; + try testFmt("UTF-8: a\n", "UTF-8: {u}\n", .{value}); + } + { + const value: u32 = 0x1F310; + try testFmt("UTF-8: 🌐\n", "UTF-8: {u}\n", .{value}); + } } test "int.padded" {