private static bool IsSecondCharTwoUtf8Bytes(uint value)
{
// Little-endian: Given [ BBBB #### ], return whether BBBB is in range [ 0080..07FF ].
// Big-endian: Given [ #### BBBB ], return whether BBBB is in range [ 0080..07FF ].
// TODO: I'd like to be able to write "(ushort)(value - 0x0080u) < 0x0780u" for the big-endian
// case, but the JIT doesn't currently emit 16-bit comparisons efficiently.
// Tracked as https://github.com/dotnet/runtime/issues/10337.
// Return statement is written this way to work around https://github.com/dotnet/runtime/issues/4207.
return((BitConverter.IsLittleEndian && UnicodeUtility.IsInRangeInclusive(value, 0x0080_0000u, 0x07FF_FFFFu)) ||
(!BitConverter.IsLittleEndian && ((value - 0x0080u) & 0xFFFFu) < 0x0780u));
}
public void EncodeUtf16_OperationStatus_AlphaNumericOnly(string input, int destBufferSize, string expectedOutput, int expectedCharsConsumed, OperationStatus expectedResult)
{
// Arrange
var encoder = new ConfigurableScalarTextEncoder(scalar => UnicodeUtility.IsInRangeInclusive((uint)scalar | 0x20, 'a', 'z')); // allow only [A-Za-z] unescaped
using BoundedMemory <char> boundedInput = BoundedMemory.AllocateFromExistingData <char>(input.AsSpan());
using BoundedMemory <char> boundedOutput = BoundedMemory.Allocate <char>(destBufferSize);
// Act
OperationStatus actualResult = encoder.Encode(boundedInput.Span, boundedOutput.Span, out int actualCharsConsumed, out int actualCharsWritten);
// Assert
Assert.Equal(expectedResult, actualResult);
Assert.Equal(expectedCharsConsumed, actualCharsConsumed);
Assert.Equal(expectedOutput, boundedOutput.Span.Slice(0, actualCharsWritten).ToString());
}
// Returns &inputBuffer[inputLength] if the input buffer is valid.
/// <summary>
/// Given an input buffer <paramref name="pInputBuffer"/> of byte length <paramref name="inputLength"/>,
/// returns a pointer to where the first invalid data appears in <paramref name="pInputBuffer"/>.
/// </summary>
/// <remarks>
/// Returns a pointer to the end of <paramref name="pInputBuffer"/> if the buffer is well-formed.
/// </remarks>
public static byte *GetPointerToFirstInvalidByte(byte *pInputBuffer, int inputLength, out int utf16CodeUnitCountAdjustment, out int scalarCountAdjustment)
{
Debug.Assert(inputLength >= 0, "Input length must not be negative.");
Debug.Assert(pInputBuffer != null || inputLength == 0, "Input length must be zero if input buffer pointer is null.");
// First, try to drain off as many ASCII bytes as we can from the beginning.
{
nuint numAsciiBytesCounted = ASCIIUtility.GetIndexOfFirstNonAsciiByte(pInputBuffer, (uint)inputLength);
pInputBuffer += numAsciiBytesCounted;
// Quick check - did we just end up consuming the entire input buffer?
// If so, short-circuit the remainder of the method.
inputLength -= (int)numAsciiBytesCounted;
if (inputLength == 0)
{
utf16CodeUnitCountAdjustment = 0;
scalarCountAdjustment = 0;
return(pInputBuffer);
}
}
#if DEBUG
// Keep these around for final validation at the end of the method.
byte *pOriginalInputBuffer = pInputBuffer;
int originalInputLength = inputLength;
#endif
// Enregistered locals that we'll eventually out to our caller.
int tempUtf16CodeUnitCountAdjustment = 0;
int tempScalarCountAdjustment = 0;
if (inputLength < sizeof(uint))
{
goto ProcessInputOfLessThanDWordSize;
}
byte *pFinalPosWhereCanReadDWordFromInputBuffer = pInputBuffer + (uint)inputLength - sizeof(uint);
// Begin the main loop.
#if DEBUG
byte *pLastBufferPosProcessed = null; // used for invariant checking in debug builds
#endif
while (pInputBuffer <= pFinalPosWhereCanReadDWordFromInputBuffer)
{
// Read 32 bits at a time. This is enough to hold any possible UTF8-encoded scalar.
uint thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
AfterReadDWord:
#if DEBUG
Debug.Assert(pLastBufferPosProcessed < pInputBuffer, "Algorithm should've made forward progress since last read.");
pLastBufferPosProcessed = pInputBuffer;
#endif
// First, check for the common case of all-ASCII bytes.
if (ASCIIUtility.AllBytesInUInt32AreAscii(thisDWord))
{
// We read an all-ASCII sequence.
pInputBuffer += sizeof(uint);
// If we saw a sequence of all ASCII, there's a good chance a significant amount of following data is also ASCII.
// Below is basically unrolled loops with poor man's vectorization.
// Below check is "can I read at least five DWORDs from the input stream?"
// n.b. Since we incremented pInputBuffer above the below subtraction may result in a negative value,
// hence using nint instead of nuint.
if ((nint)(void *)Unsafe.ByteOffset(ref *pInputBuffer, ref *pFinalPosWhereCanReadDWordFromInputBuffer) >= 4 * sizeof(uint))
{
// We want reads in the inner loop to be aligned. So let's perform a quick
// ASCII check of the next 32 bits (4 bytes) now, and if that succeeds bump
// the read pointer up to the next aligned address.
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
if (!ASCIIUtility.AllBytesInUInt32AreAscii(thisDWord))
{
goto AfterReadDWordSkipAllBytesAsciiCheck;
}
pInputBuffer = (byte *)((nuint)(pInputBuffer + 4) & ~(nuint)3);
// At this point, the input buffer offset points to an aligned DWORD. We also know that there's
// enough room to read at least four DWORDs from the buffer. (Heed the comment a few lines above:
// the original 'if' check confirmed that there were 5 DWORDs before the alignment check, and
// the alignment check consumes at most a single DWORD.)
byte *pInputBufferFinalPosAtWhichCanSafelyLoop = pFinalPosWhereCanReadDWordFromInputBuffer - 3 * sizeof(uint); // can safely read 4 DWORDs here
uint mask;
do
{
if (Sse2.IsSupported && Bmi1.IsSupported)
{
// pInputBuffer is 32-bit aligned but not necessary 128-bit aligned, so we're
// going to perform an unaligned load. We don't necessarily care about aligning
// this because we pessimistically assume we'll encounter non-ASCII data at some
// point in the not-too-distant future (otherwise we would've stayed entirely
// within the all-ASCII vectorized code at the entry to this method).
mask = (uint)Sse2.MoveMask(Sse2.LoadVector128((byte *)pInputBuffer));
if (mask != 0)
{
goto Sse2LoopTerminatedEarlyDueToNonAsciiData;
}
}
else
{
if (!ASCIIUtility.AllBytesInUInt32AreAscii(((uint *)pInputBuffer)[0] | ((uint *)pInputBuffer)[1]))
{
goto LoopTerminatedEarlyDueToNonAsciiDataInFirstPair;
}
if (!ASCIIUtility.AllBytesInUInt32AreAscii(((uint *)pInputBuffer)[2] | ((uint *)pInputBuffer)[3]))
{
goto LoopTerminatedEarlyDueToNonAsciiDataInSecondPair;
}
}
pInputBuffer += 4 * sizeof(uint); // consumed 4 DWORDs
} while (pInputBuffer <= pInputBufferFinalPosAtWhichCanSafelyLoop);
continue; // need to perform a bounds check because we might be running out of data
Sse2LoopTerminatedEarlyDueToNonAsciiData:
Debug.Assert(BitConverter.IsLittleEndian);
Debug.Assert(Sse2.IsSupported);
Debug.Assert(Bmi1.IsSupported);
// The 'mask' value will have a 0 bit for each ASCII byte we saw and a 1 bit
// for each non-ASCII byte we saw. We can count the number of ASCII bytes,
// bump our input counter by that amount, and resume processing from the
// "the first byte is no longer ASCII" portion of the main loop.
Debug.Assert(mask != 0);
pInputBuffer += Bmi1.TrailingZeroCount(mask);
if (pInputBuffer > pFinalPosWhereCanReadDWordFromInputBuffer)
{
goto ProcessRemainingBytesSlow;
}
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer); // no longer guaranteed to be aligned
goto BeforeProcessTwoByteSequence;
LoopTerminatedEarlyDueToNonAsciiDataInSecondPair:
pInputBuffer += 2 * sizeof(uint); // consumed 2 DWORDs
LoopTerminatedEarlyDueToNonAsciiDataInFirstPair:
// We know that there's *at least* two DWORDs of data remaining in the buffer.
// We also know that one of them (or both of them) contains non-ASCII data somewhere.
// Let's perform a quick check here to bypass the logic at the beginning of the main loop.
thisDWord = *(uint *)pInputBuffer; // still aligned here
if (ASCIIUtility.AllBytesInUInt32AreAscii(thisDWord))
{
pInputBuffer += sizeof(uint); // consumed 1 more DWORD
thisDWord = *(uint *)pInputBuffer; // still aligned here
}
goto AfterReadDWordSkipAllBytesAsciiCheck;
}
continue; // not enough data remaining to unroll loop - go back to beginning with bounds checks
}
AfterReadDWordSkipAllBytesAsciiCheck:
Debug.Assert(!ASCIIUtility.AllBytesInUInt32AreAscii(thisDWord)); // this should have been handled earlier
// Next, try stripping off ASCII bytes one at a time.
// We only handle up to three ASCII bytes here since we handled the four ASCII byte case above.
{
uint numLeadingAsciiBytes = ASCIIUtility.CountNumberOfLeadingAsciiBytesFromUInt32WithSomeNonAsciiData(thisDWord);
pInputBuffer += numLeadingAsciiBytes;
if (pFinalPosWhereCanReadDWordFromInputBuffer < pInputBuffer)
{
goto ProcessRemainingBytesSlow; // Input buffer doesn't contain enough data to read a DWORD
}
else
{
// The input buffer at the current offset contains a non-ASCII byte.
// Read an entire DWORD and fall through to multi-byte consumption logic.
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
}
}
BeforeProcessTwoByteSequence:
// At this point, we suspect we're working with a multi-byte code unit sequence,
// but we haven't yet validated it for well-formedness.
// The masks and comparands are derived from the Unicode Standard, Table 3-6.
// Additionally, we need to check for valid byte sequences per Table 3-7.
// Check the 2-byte case.
thisDWord -= (BitConverter.IsLittleEndian) ? 0x0000_80C0u : 0xC080_0000u;
if ((thisDWord & (BitConverter.IsLittleEndian ? 0x0000_C0E0u : 0xE0C0_0000u)) == 0)
{
// Per Table 3-7, valid sequences are:
// [ C2..DF ] [ 80..BF ]
//
// Due to our modification of 'thisDWord' above, this becomes:
// [ 02..1F ] [ 00..3F ]
//
// We've already checked that the leading byte was originally in the range [ C0..DF ]
// and that the trailing byte was originally in the range [ 80..BF ], so now we only need
// to check that the modified leading byte is >= [ 02 ].
if ((BitConverter.IsLittleEndian && (byte)thisDWord < 0x02u) ||
(!BitConverter.IsLittleEndian && thisDWord < 0x0200_0000u))
{
goto Error; // overlong form - leading byte was [ C0 ] or [ C1 ]
}
ProcessTwoByteSequenceSkipOverlongFormCheck:
// Optimization: If this is a two-byte-per-character language like Cyrillic or Hebrew,
// there's a good chance that if we see one two-byte run then there's another two-byte
// run immediately after. Let's check that now.
// On little-endian platforms, we can check for the two-byte UTF8 mask *and* validate that
// the value isn't overlong using a single comparison. On big-endian platforms, we'll need
// to validate the mask and validate that the sequence isn't overlong as two separate comparisons.
if ((BitConverter.IsLittleEndian && UInt32EndsWithValidUtf8TwoByteSequenceLittleEndian(thisDWord)) ||
(!BitConverter.IsLittleEndian && (UInt32EndsWithUtf8TwoByteMask(thisDWord) && !UInt32EndsWithOverlongUtf8TwoByteSequence(thisDWord))))
{
// We have two runs of two bytes each.
pInputBuffer += 4;
tempUtf16CodeUnitCountAdjustment -= 2; // 4 UTF-8 code units -> 2 UTF-16 code units (and 2 scalars)
if (pInputBuffer <= pFinalPosWhereCanReadDWordFromInputBuffer)
{
// Optimization: If we read a long run of two-byte sequences, the next sequence is probably
// also two bytes. Check for that first before going back to the beginning of the loop.
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
if (BitConverter.IsLittleEndian)
{
if (UInt32BeginsWithValidUtf8TwoByteSequenceLittleEndian(thisDWord))
{
// The next sequence is a valid two-byte sequence.
goto ProcessTwoByteSequenceSkipOverlongFormCheck;
}
}
else
{
if (UInt32BeginsWithUtf8TwoByteMask(thisDWord))
{
if (UInt32BeginsWithOverlongUtf8TwoByteSequence(thisDWord))
{
goto Error; // The next sequence purports to be a 2-byte sequence but is overlong.
}
goto ProcessTwoByteSequenceSkipOverlongFormCheck;
}
}
// If we reached this point, the next sequence is something other than a valid
// two-byte sequence, so go back to the beginning of the loop.
goto AfterReadDWord;
}
else
{
goto ProcessRemainingBytesSlow; // Running out of data - go down slow path
}
}
// The buffer contains a 2-byte sequence followed by 2 bytes that aren't a 2-byte sequence.
// Unlikely that a 3-byte sequence would follow a 2-byte sequence, so perhaps remaining
// bytes are ASCII?
tempUtf16CodeUnitCountAdjustment--; // 2-byte sequence + (some number of ASCII bytes) -> 1 UTF-16 code units (and 1 scalar) [+ trailing]
if (UInt32ThirdByteIsAscii(thisDWord))
{
if (UInt32FourthByteIsAscii(thisDWord))
{
pInputBuffer += 4;
}
else
{
pInputBuffer += 3;
// A two-byte sequence followed by an ASCII byte followed by a non-ASCII byte.
// Read in the next DWORD and jump directly to the start of the multi-byte processing block.
if (pInputBuffer <= pFinalPosWhereCanReadDWordFromInputBuffer)
{
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
goto BeforeProcessTwoByteSequence;
}
}
}
else
{
pInputBuffer += 2;
}
continue;
}
// Check the 3-byte case.
// We need to restore the C0 leading byte we stripped out earlier, then we can strip out the expected E0 byte.
thisDWord -= (BitConverter.IsLittleEndian) ? (0x0080_00E0u - 0x0000_00C0u) : (0xE000_8000u - 0xC000_0000u);
if ((thisDWord & (BitConverter.IsLittleEndian ? 0x00C0_C0F0u : 0xF0C0_C000u)) == 0)
{
ProcessThreeByteSequenceWithCheck:
// We assume the caller has confirmed that the bit pattern is representative of a three-byte
// sequence, but it may still be overlong or surrogate. We need to check for these possibilities.
//
// Per Table 3-7, valid sequences are:
// [ E0 ] [ A0..BF ] [ 80..BF ]
// [ E1..EC ] [ 80..BF ] [ 80..BF ]
// [ ED ] [ 80..9F ] [ 80..BF ]
// [ EE..EF ] [ 80..BF ] [ 80..BF ]
//
// Big-endian examples of using the above validation table:
// E0A0 = 1110 0000 1010 0000 => invalid (overlong ) patterns are 1110 0000 100# ####
// ED9F = 1110 1101 1001 1111 => invalid (surrogate) patterns are 1110 1101 101# ####
// If using the bitmask ......................................... 0000 1111 0010 0000 (=0F20),
// Then invalid (overlong) patterns match the comparand ......... 0000 0000 0000 0000 (=0000),
// And invalid (surrogate) patterns match the comparand ......... 0000 1101 0010 0000 (=0D20).
//
// It's ok if the caller has manipulated 'thisDWord' (e.g., by subtracting 0xE0 or 0x80)
// as long as they haven't touched the bits we're about to use in our mask checking below.
if (BitConverter.IsLittleEndian)
{
// The "overlong or surrogate" check can be implemented using a single jump, but there's
// some overhead to moving the bits into the correct locations in order to perform the
// correct comparison, and in practice the processor's branch prediction capability is
// good enough that we shouldn't bother. So we'll use two jumps instead.
// Can't extract this check into its own helper method because JITter produces suboptimal
// assembly, even with aggressive inlining.
// Code below becomes 5 instructions: test, jz, lea, test, jz
if (((thisDWord & 0x0000_200Fu) == 0) || (((thisDWord - 0x0000_200Du) & 0x0000_200Fu) == 0))
{
goto Error; // overlong or surrogate
}
}
else
{
if (((thisDWord & 0x0F20_0000u) == 0) || (((thisDWord - 0x0D20_0000u) & 0x0F20_0000u) == 0))
{
goto Error; // overlong or surrogate
}
}
ProcessSingleThreeByteSequenceSkipOverlongAndSurrogateChecks:
// Occasionally one-off ASCII characters like spaces, periods, or newlines will make their way
// in to the text. If this happens strip it off now before seeing if the next character
// consists of three code units.
// Branchless: consume a 3-byte UTF-8 sequence and optionally an extra ASCII byte hanging off the end
nint asciiAdjustment;
if (BitConverter.IsLittleEndian)
{
asciiAdjustment = (int)thisDWord >> 31; // smear most significant bit across entire value
}
else
{
asciiAdjustment = (nint)(sbyte)thisDWord >> 7; // smear most significant bit of least significant byte across entire value
}
// asciiAdjustment = 0 if fourth byte is ASCII; -1 otherwise
// Please *DO NOT* reorder the below two lines. It provides extra defense in depth in case this method
// is ever changed such that pInputBuffer becomes a 'ref byte' instead of a simple 'byte*'. It's valid
// to add 4 before backing up since we already checked previously that the input buffer contains at
// least a DWORD's worth of data, so we're not going to run past the end of the buffer where the GC can
// no longer track the reference. However, we can't back up before adding 4, since we might back up to
// before the start of the buffer, and the GC isn't guaranteed to be able to track this.
pInputBuffer += 4; // optimistically, assume consumed a 3-byte UTF-8 sequence plus an extra ASCII byte
pInputBuffer += asciiAdjustment; // back up if we didn't actually consume an ASCII byte
tempUtf16CodeUnitCountAdjustment -= 2; // 3 (or 4) UTF-8 bytes -> 1 (or 2) UTF-16 code unit (and 1 [or 2] scalar)
SuccessfullyProcessedThreeByteSequence:
if (IntPtr.Size >= 8 && BitConverter.IsLittleEndian)
{
// x64 little-endian optimization: A three-byte character could indicate CJK text,
// which makes it likely that the character following this one is also CJK.
// We'll try to process several three-byte sequences at a time.
// The check below is really "can we read 9 bytes from the input buffer?" since 'pFinalPos...' is already offset
// n.b. The subtraction below could result in a negative value (since we advanced pInputBuffer above), so
// use nint instead of nuint.
if ((nint)(pFinalPosWhereCanReadDWordFromInputBuffer - pInputBuffer) >= 5)
{
ulong thisQWord = Unsafe.ReadUnaligned <ulong>(pInputBuffer);
// Stage the next 32 bits into 'thisDWord' so that it's ready for us in case we need to jump backward
// to a previous location in the loop. This offers defense against reading main memory again (which may
// have been modified and could lead to a race condition).
thisDWord = (uint)thisQWord;
// Is this three 3-byte sequences in a row?
// thisQWord = [ 10yyyyyy 1110zzzz | 10xxxxxx 10yyyyyy 1110zzzz | 10xxxxxx 10yyyyyy 1110zzzz ] [ 10xxxxxx ]
// ---- CHAR 3 ---- --------- CHAR 2 --------- --------- CHAR 1 --------- -CHAR 3-
if ((thisQWord & 0xC0F0_C0C0_F0C0_C0F0ul) == 0x80E0_8080_E080_80E0ul && IsUtf8ContinuationByte(in pInputBuffer[8]))
{
// Saw a proper bitmask for three incoming 3-byte sequences, perform the
// overlong and surrogate sequence checking now.
// Check the first character.
// If the first character is overlong or a surrogate, fail immediately.
if ((((uint)thisQWord & 0x200Fu) == 0) || ((((uint)thisQWord - 0x200Du) & 0x200Fu) == 0))
{
goto Error;
}
// Check the second character.
// At this point, we now know the first three bytes represent a well-formed sequence.
// If there's an error beyond here, we'll jump back to the "process three known good bytes"
// logic.
thisQWord >>= 24;
if ((((uint)thisQWord & 0x200Fu) == 0) || ((((uint)thisQWord - 0x200Du) & 0x200Fu) == 0))
{
goto ProcessSingleThreeByteSequenceSkipOverlongAndSurrogateChecks;
}
// Check the third character (we already checked that it's followed by a continuation byte).
thisQWord >>= 24;
if ((((uint)thisQWord & 0x200Fu) == 0) || ((((uint)thisQWord - 0x200Du) & 0x200Fu) == 0))
{
goto ProcessSingleThreeByteSequenceSkipOverlongAndSurrogateChecks;
}
pInputBuffer += 9;
tempUtf16CodeUnitCountAdjustment -= 6; // 9 UTF-8 bytes -> 3 UTF-16 code units (and 3 scalars)
goto SuccessfullyProcessedThreeByteSequence;
}
// Is this two 3-byte sequences in a row?
// thisQWord = [ ######## ######## | 10xxxxxx 10yyyyyy 1110zzzz | 10xxxxxx 10yyyyyy 1110zzzz ]
// --------- CHAR 2 --------- --------- CHAR 1 ---------
if ((thisQWord & 0xC0C0_F0C0_C0F0ul) == 0x8080_E080_80E0ul)
{
// Saw a proper bitmask for two incoming 3-byte sequences, perform the
// overlong and surrogate sequence checking now.
// Check the first character.
// If the first character is overlong or a surrogate, fail immediately.
if ((((uint)thisQWord & 0x200Fu) == 0) || ((((uint)thisQWord - 0x200Du) & 0x200Fu) == 0))
{
goto Error;
}
// Check the second character.
// At this point, we now know the first three bytes represent a well-formed sequence.
// If there's an error beyond here, we'll jump back to the "process three known good bytes"
// logic.
thisQWord >>= 24;
if ((((uint)thisQWord & 0x200Fu) == 0) || ((((uint)thisQWord - 0x200Du) & 0x200Fu) == 0))
{
goto ProcessSingleThreeByteSequenceSkipOverlongAndSurrogateChecks;
}
pInputBuffer += 6;
tempUtf16CodeUnitCountAdjustment -= 4; // 6 UTF-8 bytes -> 2 UTF-16 code units (and 2 scalars)
// The next byte in the sequence didn't have a 3-byte marker, so it's probably
// an ASCII character. Jump back to the beginning of loop processing.
continue;
}
if (UInt32BeginsWithUtf8ThreeByteMask(thisDWord))
{
// A single three-byte sequence.
goto ProcessThreeByteSequenceWithCheck;
}
else
{
// Not a three-byte sequence; perhaps ASCII?
goto AfterReadDWord;
}
}
}
if (pInputBuffer <= pFinalPosWhereCanReadDWordFromInputBuffer)
{
thisDWord = Unsafe.ReadUnaligned <uint>(pInputBuffer);
// Optimization: A three-byte character could indicate CJK text, which makes it likely
// that the character following this one is also CJK. We'll check for a three-byte sequence
// marker now and jump directly to three-byte sequence processing if we see one, skipping
// all of the logic at the beginning of the loop.
if (UInt32BeginsWithUtf8ThreeByteMask(thisDWord))
{
goto ProcessThreeByteSequenceWithCheck; // Found another [not yet validated] three-byte sequence; process
}
else
{
goto AfterReadDWord; // Probably ASCII punctuation or whitespace; go back to start of loop
}
}
else
{
goto ProcessRemainingBytesSlow; // Running out of data
}
}
// Assume the 4-byte case, but we need to validate.
if (BitConverter.IsLittleEndian)
{
thisDWord &= 0xC0C0_FFFFu;
// After the above modifications earlier in this method, we expect 'thisDWord'
// to have the structure [ 10000000 00000000 00uuzzzz 00010uuu ]. We'll now
// perform two checks to confirm this. The first will verify the
// [ 10000000 00000000 00###### ######## ] structure by taking advantage of two's
// complement representation to perform a single *signed* integer check.
if ((int)thisDWord > unchecked ((int)0x8000_3FFF))
{
goto Error; // didn't have three trailing bytes
}
// Now we want to confirm that 0x01 <= uuuuu (otherwise this is an overlong encoding)
// and that uuuuu <= 0x10 (otherwise this is an out-of-range encoding).
thisDWord = BitOperations.RotateRight(thisDWord, 8);
// Now, thisDWord = [ 00010uuu 10000000 00000000 00uuzzzz ].
// The check is now a simple add / cmp / jcc combo.
if (!UnicodeUtility.IsInRangeInclusive(thisDWord, 0x1080_0010u, 0x1480_000Fu))
{
goto Error; // overlong or out-of-range
}
}
else
{
thisDWord -= 0x80u;
// After the above modifications earlier in this method, we expect 'thisDWord'
// to have the structure [ 00010uuu 00uuzzzz 00yyyyyy 00xxxxxx ]. We'll now
// perform two checks to confirm this. The first will verify the
// [ ######## 00###### 00###### 00###### ] structure.
if ((thisDWord & 0x00C0_C0C0u) != 0)
{
goto Error; // didn't have three trailing bytes
}
// Now we want to confirm that 0x01 <= uuuuu (otherwise this is an overlong encoding)
// and that uuuuu <= 0x10 (otherwise this is an out-of-range encoding).
// This is a simple range check. (We don't care about the low two bytes.)
if (!UnicodeUtility.IsInRangeInclusive(thisDWord, 0x1010_0000u, 0x140F_FFFFu))
{
goto Error; // overlong or out-of-range
}
}
// Validation of 4-byte case complete.
pInputBuffer += 4;
tempUtf16CodeUnitCountAdjustment -= 2; // 4 UTF-8 bytes -> 2 UTF-16 code units
tempScalarCountAdjustment--; // 2 UTF-16 code units -> 1 scalar
continue; // go back to beginning of loop for processing
}
goto ProcessRemainingBytesSlow;
ProcessInputOfLessThanDWordSize:
Debug.Assert(inputLength < 4);
nuint inputBufferRemainingBytes = (uint)inputLength;
goto ProcessSmallBufferCommon;
ProcessRemainingBytesSlow:
inputBufferRemainingBytes = (nuint)(void *)Unsafe.ByteOffset(ref *pInputBuffer, ref *pFinalPosWhereCanReadDWordFromInputBuffer) + 4;
ProcessSmallBufferCommon:
Debug.Assert(inputBufferRemainingBytes < 4);
while (inputBufferRemainingBytes > 0)
{
uint firstByte = pInputBuffer[0];
if ((byte)firstByte < 0x80u)
{
// 1-byte (ASCII) case
pInputBuffer++;
inputBufferRemainingBytes--;
continue;
}
else if (inputBufferRemainingBytes >= 2)
{
uint secondByte = pInputBuffer[1]; // typed as 32-bit since we perform arithmetic (not just comparisons) on this value
if ((byte)firstByte < 0xE0u)
{
// 2-byte case
if ((byte)firstByte >= 0xC2u && IsLowByteUtf8ContinuationByte(secondByte))
{
pInputBuffer += 2;
tempUtf16CodeUnitCountAdjustment--; // 2 UTF-8 bytes -> 1 UTF-16 code unit (and 1 scalar)
inputBufferRemainingBytes -= 2;
continue;
}
}
else if (inputBufferRemainingBytes >= 3)
{
if ((byte)firstByte < 0xF0u)
{
if ((byte)firstByte == 0xE0u)
{
if (!UnicodeUtility.IsInRangeInclusive(secondByte, 0xA0u, 0xBFu))
{
goto Error; // overlong encoding
}
}
else if ((byte)firstByte == 0xEDu)
{
if (!UnicodeUtility.IsInRangeInclusive(secondByte, 0x80u, 0x9Fu))
{
goto Error; // would be a UTF-16 surrogate code point
}
}
else
{
if (!IsLowByteUtf8ContinuationByte(secondByte))
{
goto Error; // first trailing byte doesn't have proper continuation marker
}
}
if (IsUtf8ContinuationByte(in pInputBuffer[2]))
{
pInputBuffer += 3;
tempUtf16CodeUnitCountAdjustment -= 2; // 3 UTF-8 bytes -> 2 UTF-16 code units (and 2 scalars)
inputBufferRemainingBytes -= 3;
continue;
}
}
}
}
// Error - no match.
goto Error;
}
// If we reached this point, we're out of data, and we saw no bad UTF8 sequence.
#if DEBUG
// Quick check that for the success case we're going to fulfill our contract of returning &inputBuffer[inputLength].
Debug.Assert(pOriginalInputBuffer + originalInputLength == pInputBuffer, "About to return an unexpected value.");
#endif
Error:
// Report back to our caller how far we got before seeing invalid data.
// (Also used for normal termination when falling out of the loop above.)
utf16CodeUnitCountAdjustment = tempUtf16CodeUnitCountAdjustment;
scalarCountAdjustment = tempScalarCountAdjustment;
return(pInputBuffer);
}
/// <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);
}