Example #1
0
        internal static void GetUtf16SurrogatePairFromAstralScalarValue(uint scalar, out char highSurrogate, out char lowSurrogate)
        {
            Debug.Assert(0x10000 <= scalar && scalar <= UNICODE_LAST_CODEPOINT);

            UnicodeDebug.AssertIsValidSupplementaryPlaneScalar(scalar);

            // This calculation comes from the Unicode specification, Table 3-5.

            highSurrogate = (char)((scalar + ((0xD800u - 0x40u) << 10)) >> 10);
            lowSurrogate  = (char)((scalar & 0x3FFu) + 0xDC00u);
        }
Example #2
0
        /// <summary>
        /// A copy of the logic in Rune.DecodeFromUtf8.
        /// </summary>
        public static OperationStatus DecodeScalarValueFromUtf8(ReadOnlySpan <byte> source, out uint result, out int bytesConsumed)
        {
            const char ReplacementChar = '\uFFFD';

            // This method follows the Unicode Standard's recommendation for detecting
            // the maximal subpart of an ill-formed subsequence. See The Unicode Standard,
            // Ch. 3.9 for more details. In summary, when reporting an invalid subsequence,
            // it tries to consume as many code units as possible as long as those code
            // units constitute the beginning of a longer well-formed subsequence per Table 3-7.

            int index = 0;

            // Try reading input[0].

            if ((uint)index >= (uint)source.Length)
            {
                goto NeedsMoreData;
            }

            uint tempValue = source[index];

            if (!UnicodeUtility.IsAsciiCodePoint(tempValue))
            {
                goto NotAscii;
            }

Finish:

            bytesConsumed = index + 1;
            Debug.Assert(1 <= bytesConsumed && bytesConsumed <= 4); // Valid subsequences are always length [1..4]
            result = tempValue;
            return(OperationStatus.Done);

NotAscii:

            // Per Table 3-7, the beginning of a multibyte sequence must be a code unit in
            // the range [C2..F4]. If it's outside of that range, it's either a standalone
            // continuation byte, or it's an overlong two-byte sequence, or it's an out-of-range
            // four-byte sequence.

            if (!UnicodeUtility.IsInRangeInclusive(tempValue, 0xC2, 0xF4))
            {
                goto FirstByteInvalid;
            }

            tempValue = (tempValue - 0xC2) << 6;

            // Try reading input[1].

            index++;
            if ((uint)index >= (uint)source.Length)
            {
                goto NeedsMoreData;
            }

            // Continuation bytes are of the form [10xxxxxx], which means that their two's
            // complement representation is in the range [-65..-128]. This allows us to
            // perform a single comparison to see if a byte is a continuation byte.

            int thisByteSignExtended = (sbyte)source[index];

            if (thisByteSignExtended >= -64)
            {
                goto Invalid;
            }

            tempValue += (uint)thisByteSignExtended;
            tempValue += 0x80;               // remove the continuation byte marker
            tempValue += (0xC2 - 0xC0) << 6; // remove the leading byte marker

            if (tempValue < 0x0800)
            {
                Debug.Assert(UnicodeUtility.IsInRangeInclusive(tempValue, 0x0080, 0x07FF));
                goto Finish; // this is a valid 2-byte sequence
            }

            // This appears to be a 3- or 4-byte sequence. Since per Table 3-7 we now have
            // enough information (from just two code units) to detect overlong or surrogate
            // sequences, we need to perform these checks now.

            if (!UnicodeUtility.IsInRangeInclusive(tempValue, ((0xE0 - 0xC0) << 6) + (0xA0 - 0x80), ((0xF4 - 0xC0) << 6) + (0x8F - 0x80)))
            {
                // The first two bytes were not in the range [[E0 A0]..[F4 8F]].
                // This is an overlong 3-byte sequence or an out-of-range 4-byte sequence.
                goto Invalid;
            }

            if (UnicodeUtility.IsInRangeInclusive(tempValue, ((0xED - 0xC0) << 6) + (0xA0 - 0x80), ((0xED - 0xC0) << 6) + (0xBF - 0x80)))
            {
                // This is a UTF-16 surrogate code point, which is invalid in UTF-8.
                goto Invalid;
            }

            if (UnicodeUtility.IsInRangeInclusive(tempValue, ((0xF0 - 0xC0) << 6) + (0x80 - 0x80), ((0xF0 - 0xC0) << 6) + (0x8F - 0x80)))
            {
                // This is an overlong 4-byte sequence.
                goto Invalid;
            }

            // The first two bytes were just fine. We don't need to perform any other checks
            // on the remaining bytes other than to see that they're valid continuation bytes.

            // Try reading input[2].

            index++;
            if ((uint)index >= (uint)source.Length)
            {
                goto NeedsMoreData;
            }

            thisByteSignExtended = (sbyte)source[index];
            if (thisByteSignExtended >= -64)
            {
                goto Invalid; // this byte is not a UTF-8 continuation byte
            }

            tempValue <<= 6;
            tempValue  += (uint)thisByteSignExtended;
            tempValue  += 0x80;                // remove the continuation byte marker
            tempValue  -= (0xE0 - 0xC0) << 12; // remove the leading byte marker

            if (tempValue <= 0xFFFF)
            {
                Debug.Assert(UnicodeUtility.IsInRangeInclusive(tempValue, 0x0800, 0xFFFF));
                goto Finish; // this is a valid 3-byte sequence
            }

            // Try reading input[3].

            index++;
            if ((uint)index >= (uint)source.Length)
            {
                goto NeedsMoreData;
            }

            thisByteSignExtended = (sbyte)source[index];
            if (thisByteSignExtended >= -64)
            {
                goto Invalid; // this byte is not a UTF-8 continuation byte
            }

            tempValue <<= 6;
            tempValue  += (uint)thisByteSignExtended;
            tempValue  += 0x80;                // remove the continuation byte marker
            tempValue  -= (0xF0 - 0xE0) << 18; // remove the leading byte marker

            UnicodeDebug.AssertIsValidSupplementaryPlaneScalar(tempValue);
            goto Finish; // this is a valid 4-byte sequence

FirstByteInvalid:

            index = 1; // Invalid subsequences are always at least length 1.

Invalid:

            Debug.Assert(1 <= index && index <= 3); // Invalid subsequences are always length 1..3
            bytesConsumed = index;
            result        = ReplacementChar;
            return(OperationStatus.InvalidData);

NeedsMoreData:

            Debug.Assert(0 <= index && index <= 3); // Incomplete subsequences are always length 0..3
            bytesConsumed = index;
            result        = ReplacementChar;
            return(OperationStatus.NeedMoreData);
        }