std: unicode codepoints are 21 bits

Author: daurnimator

lib/std/unicode.zig

@@ -6,7 +6,7 @@ const mem = std.mem;
 
 /// Returns how many bytes the UTF-8 representation would require
 /// for the given codepoint.
-pub fn utf8CodepointSequenceLength(c: u32) !u3 {
+pub fn utf8CodepointSequenceLength(c: u21) !u3 {
     if (c < 0x80) return @as(u3, 1);
     if (c < 0x800) return @as(u3, 2);
     if (c < 0x10000) return @as(u3, 3);
@@ -32,7 +32,7 @@ pub fn utf8ByteSequenceLength(first_byte: u8) !u3 {
 /// out: the out buffer to write to. Must have a len >= utf8CodepointSequenceLength(c).
 /// Errors: if c cannot be encoded in UTF-8.
 /// Returns: the number of bytes written to out.
-pub fn utf8Encode(c: u32, out: []u8) !u3 {
+pub fn utf8Encode(c: u21, out: []u8) !u3 {
     const length = try utf8CodepointSequenceLength(c);
     assert(out.len >= length);
     switch (length) {
@@ -68,9 +68,9 @@ const Utf8DecodeError = Utf8Decode2Error || Utf8Decode3Error || Utf8Decode4Error
 /// 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) Utf8DecodeError!u32 {
+pub fn utf8Decode(bytes: []const u8) Utf8DecodeError!u21 {
     return switch (bytes.len) {
-        1 => @as(u32, bytes[0]),
+        1 => @as(u21, bytes[0]),
         2 => utf8Decode2(bytes),
         3 => utf8Decode3(bytes),
         4 => utf8Decode4(bytes),
@@ -82,10 +82,10 @@ const Utf8Decode2Error = error{
     Utf8ExpectedContinuation,
     Utf8OverlongEncoding,
 };
-pub fn utf8Decode2(bytes: []const u8) Utf8Decode2Error!u32 {
+pub fn utf8Decode2(bytes: []const u8) Utf8Decode2Error!u21 {
     assert(bytes.len == 2);
     assert(bytes[0] & 0b11100000 == 0b11000000);
-    var value: u32 = bytes[0] & 0b00011111;
+    var value: u21 = bytes[0] & 0b00011111;
 
     if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
     value <<= 6;
@@ -101,10 +101,10 @@ const Utf8Decode3Error = error{
     Utf8OverlongEncoding,
     Utf8EncodesSurrogateHalf,
 };
-pub fn utf8Decode3(bytes: []const u8) Utf8Decode3Error!u32 {
+pub fn utf8Decode3(bytes: []const u8) Utf8Decode3Error!u21 {
     assert(bytes.len == 3);
     assert(bytes[0] & 0b11110000 == 0b11100000);
-    var value: u32 = bytes[0] & 0b00001111;
+    var value: u21 = bytes[0] & 0b00001111;
 
     if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
     value <<= 6;
@@ -125,10 +125,10 @@ const Utf8Decode4Error = error{
     Utf8OverlongEncoding,
     Utf8CodepointTooLarge,
 };
-pub fn utf8Decode4(bytes: []const u8) Utf8Decode4Error!u32 {
+pub fn utf8Decode4(bytes: []const u8) Utf8Decode4Error!u21 {
     assert(bytes.len == 4);
     assert(bytes[0] & 0b11111000 == 0b11110000);
-    var value: u32 = bytes[0] & 0b00000111;
+    var value: u21 = bytes[0] & 0b00000111;
 
     if (bytes[1] & 0b11000000 != 0b10000000) return error.Utf8ExpectedContinuation;
     value <<= 6;
@@ -224,11 +224,11 @@ pub const Utf8Iterator = struct {
         return it.bytes[it.i - cp_len .. it.i];
     }
 
-    pub fn nextCodepoint(it: *Utf8Iterator) ?u32 {
+    pub fn nextCodepoint(it: *Utf8Iterator) ?u21 {
         const slice = it.nextCodepointSlice() orelse return null;
 
         switch (slice.len) {
-            1 => return @as(u32, slice[0]),
+            1 => return @as(u21, slice[0]),
             2 => return utf8Decode2(slice) catch unreachable,
             3 => return utf8Decode3(slice) catch unreachable,
             4 => return utf8Decode4(slice) catch unreachable,
@@ -248,19 +248,19 @@ pub const Utf16LeIterator = struct {
         };
     }
 
-    pub fn nextCodepoint(it: *Utf16LeIterator) !?u32 {
+    pub fn nextCodepoint(it: *Utf16LeIterator) !?u21 {
         assert(it.i <= it.bytes.len);
         if (it.i == it.bytes.len) return null;
-        const c0: u32 = mem.readIntSliceLittle(u16, it.bytes[it.i .. it.i + 2]);
-        if (c0 & ~@as(u32, 0x03ff) == 0xd800) {
+        const c0: u21 = mem.readIntSliceLittle(u16, it.bytes[it.i .. it.i + 2]);
+        if (c0 & ~@as(u21, 0x03ff) == 0xd800) {
             // surrogate pair
             it.i += 2;
             if (it.i >= it.bytes.len) return error.DanglingSurrogateHalf;
-            const c1: u32 = mem.readIntSliceLittle(u16, it.bytes[it.i .. it.i + 2]);
-            if (c1 & ~@as(u32, 0x03ff) != 0xdc00) return error.ExpectedSecondSurrogateHalf;
+            const c1: u21 = mem.readIntSliceLittle(u16, it.bytes[it.i .. it.i + 2]);
+            if (c1 & ~@as(u21, 0x03ff) != 0xdc00) return error.ExpectedSecondSurrogateHalf;
             it.i += 2;
             return 0x10000 + (((c0 & 0x03ff) << 10) | (c1 & 0x03ff));
-        } else if (c0 & ~@as(u32, 0x03ff) == 0xdc00) {
+        } else if (c0 & ~@as(u21, 0x03ff) == 0xdc00) {
             return error.UnexpectedSecondSurrogateHalf;
         } else {
             it.i += 2;
@@ -304,10 +304,10 @@ fn testUtf8EncodeError() void {
     testErrorEncode(0xd800, array[0..], error.Utf8CannotEncodeSurrogateHalf);
     testErrorEncode(0xdfff, array[0..], error.Utf8CannotEncodeSurrogateHalf);
     testErrorEncode(0x110000, array[0..], error.CodepointTooLarge);
-    testErrorEncode(0xffffffff, array[0..], error.CodepointTooLarge);
+    testErrorEncode(0x1fffff, array[0..], error.CodepointTooLarge);
 }
 
-fn testErrorEncode(codePoint: u32, array: []u8, expectedErr: anyerror) void {
+fn testErrorEncode(codePoint: u21, array: []u8, expectedErr: anyerror) void {
     testing.expectError(expectedErr, utf8Encode(codePoint, array));
 }
 
@@ -455,11 +455,11 @@ fn testError(bytes: []const u8, expected_err: anyerror) void {
     testing.expectError(expected_err, testDecode(bytes));
 }
 
-fn testValid(bytes: []const u8, expected_codepoint: u32) void {
+fn testValid(bytes: []const u8, expected_codepoint: u21) void {
     testing.expect((testDecode(bytes) catch unreachable) == expected_codepoint);
 }
 
-fn testDecode(bytes: []const u8) !u32 {
+fn testDecode(bytes: []const u8) !u21 {
     const length = try utf8ByteSequenceLength(bytes[0]);
     if (bytes.len < length) return error.UnexpectedEof;
     testing.expect(bytes.len == length);