Changing Number.BigInteger and Number.NumberBuffer to directly use fi…

…xed-sized buffers (dotnet#20371)

* Moving Number.BigInteger to directly use a `fixed-sized buffer`

* Moving Number.NumberBuffer to directly use a `fixed-sized buffer`

src/System.Private.CoreLib/shared/System/Number.BigInteger.cs

@@ -130,7 +130,7 @@ internal unsafe ref struct BigInteger
  };
 
  private int _length;
- private BlocksBuffer _blocks;
+ private fixed uint _blocks[MaxBlockCount];
 
  public BigInteger(uint value)
  {
@@ -367,7 +367,7 @@ public static void Multiply(ref BigInteger lhs, ref BigInteger rhs, ref BigInteg
  Debug.Assert(unchecked((uint)(maxResultLength)) <= MaxBlockCount);
 
  // Zero out result internal blocks.
- Buffer.ZeroMemory((byte*)(result._blocks.GetPointer()), (maxResultLength * sizeof(uint)));
+ Buffer.ZeroMemory((byte*)(result.GetBlocksPointer()), (maxResultLength * sizeof(uint)));
 
  int smallIndex = 0;
  int resultStartIndex = 0;
@@ -559,7 +559,7 @@ public void ExtendBlocks(uint blockValue, uint blockCount)
  return;
  }
 
- Buffer.ZeroMemory((byte*)(_blocks.GetPointer() + _length), ((blockCount - 1) * sizeof(uint)));
+ Buffer.ZeroMemory((byte*)(GetBlocksPointer() + _length), ((blockCount - 1) * sizeof(uint)));
  _length += (int)(blockCount);
  _blocks[_length - 1] = blockValue;
  }
@@ -585,7 +585,7 @@ public void Multiply(ref BigInteger value)
  var result = new BigInteger(0);
  Multiply(ref this, ref value, ref result);
 
- Buffer.Memcpy((byte*)(_blocks.GetPointer()), (byte*)(result._blocks.GetPointer()), (result._length) * sizeof(uint));
+ Buffer.Memcpy((byte*)(GetBlocksPointer()), (byte*)(result.GetBlocksPointer()), (result._length) * sizeof(uint));
  _length = result._length;
  }
 
@@ -638,7 +638,7 @@ public void SetUInt64(ulong value)
  public void SetValue(ref BigInteger rhs)
  {
  int rhsLength = rhs._length;
- Buffer.Memcpy((byte*)(_blocks.GetPointer()), (byte*)(rhs._blocks.GetPointer()), (rhsLength * sizeof(uint)));
+ Buffer.Memcpy((byte*)(GetBlocksPointer()), (byte*)(rhs.GetBlocksPointer()), (rhsLength * sizeof(uint)));
  _length = rhsLength;
  }
 
@@ -678,7 +678,7 @@ public void ShiftLeft(uint shift)
  _length += (int)(blocksToShift);
 
  // Zero the remaining low blocks
- Buffer.ZeroMemory((byte*)(_blocks.GetPointer()), (blocksToShift * sizeof(uint)));
+ Buffer.ZeroMemory((byte*)(GetBlocksPointer()), (blocksToShift * sizeof(uint)));
  }
  else
  {
@@ -711,7 +711,7 @@ public void ShiftLeft(uint shift)
  _blocks[writeIndex - 1] = block << (int)(remainingBitsToShift);
 
  // Zero the remaining low blocks
- Buffer.ZeroMemory((byte*)(_blocks.GetPointer()), (blocksToShift * sizeof(uint)));
+ Buffer.ZeroMemory((byte*)(GetBlocksPointer()), (blocksToShift * sizeof(uint)));
 
  // Check if the terminating block has no set bits
  if (_blocks[_length - 1] == 0)
@@ -721,30 +721,10 @@ public void ShiftLeft(uint shift)
  }
  }
 
- [StructLayout(LayoutKind.Sequential, Pack = 1)]
- private struct BlocksBuffer
+ private uint* GetBlocksPointer()
  {
- private fixed uint _blocks[MaxBlockCount];
-
- public ref uint this[int index]
- {
- get
- {
- Debug.Assert(unchecked((uint)(index)) <= MaxBlockCount);
- return ref Unsafe.Add(ref GetPinnableReference(), index);
- }
- }
-
- public ref uint GetPinnableReference()
- {
- var pThis = Unsafe.AsPointer(ref this);
- return ref Unsafe.AsRef<uint>(pThis);
- }
-
- public uint* GetPointer()
- {
- return (uint*)(Unsafe.AsPointer(ref this));
- }
+ // This is safe to do since we are a ref struct
+ return (uint*)(Unsafe.AsPointer(ref _blocks[0]));
  }
  }
  }

src/System.Private.CoreLib/shared/System/Number.Dragon4.cs

@@ -204,7 +204,7 @@ private static unsafe void Dragon4(double value, int precision, ref NumberBuffer
  }
  else
  {
- char* pCurrentDigit = (number.digits + digitsNum);
+ char* pCurrentDigit = (number.GetDigitsPointer() + digitsNum);
 
  // Rounding up for 9 is special.
  if (currentDigit == 9)
@@ -213,7 +213,7 @@ private static unsafe void Dragon4(double value, int precision, ref NumberBuffer
  while (true)
  {
  // If we are at the first digit
- if (pCurrentDigit == number.digits)
+ if (pCurrentDigit == number.GetDigitsPointer())
  {
  // Output 1 at the next highest exponent
  *pCurrentDigit = '1';

src/System.Private.CoreLib/shared/System/Number.Formatting.cs

@@ -339,7 +339,7 @@ public static bool TryFormatDecimal(decimal value, ReadOnlySpan<char> format, Nu
 
  private static unsafe void DecimalToNumber(ref decimal d, ref NumberBuffer number)
  {
- char* buffer = number.digits;
+ char* buffer = number.GetDigitsPointer();
  number.precision = DecimalPrecision;
  number.sign = d.IsNegative;
  number.kind = NumberBufferKind.Decimal;
@@ -354,7 +354,7 @@ private static unsafe void DecimalToNumber(ref decimal d, ref NumberBuffer numbe
  int i = (int)((byte*)(buffer + DecimalPrecision) - (byte*)p) >> 1;
  number.scale = i - d.Scale;
 
- char* dst = number.digits;
+ char* dst = number.GetDigitsPointer();
  while (--i >= 0)
  {
  *dst++ = *p++;
@@ -947,14 +947,14 @@ private static unsafe void Int32ToNumber(int value, ref NumberBuffer number)
  value = -value;
  }
 
- char* buffer = number.digits;
+ char* buffer = number.GetDigitsPointer();
  char* p = UInt32ToDecChars(buffer + Int32Precision, (uint)value, 0);
  int i = (int)(buffer + Int32Precision - p);
 
  number.scale = i;
  number.kind = NumberBufferKind.Integer;
 
- char* dst = number.digits;
+ char* dst = number.GetDigitsPointer();
  while (--i >= 0)
  *dst++ = *p++;
  *dst = '\0';
@@ -1065,13 +1065,13 @@ private static unsafe void UInt32ToNumber(uint value, ref NumberBuffer number)
  number.precision = UInt32Precision;
  number.sign = false;
 
- char* buffer = number.digits;
+ char* buffer = number.GetDigitsPointer();
  char* p = UInt32ToDecChars(buffer + UInt32Precision, value, 0);
  int i = (int)(buffer + UInt32Precision - p);
  number.scale = i;
  number.kind = NumberBufferKind.Integer;
 
- char* dst = number.digits;
+ char* dst = number.GetDigitsPointer();
  while (--i >= 0)
  *dst++ = *p++;
  *dst = '\0';
@@ -1181,7 +1181,7 @@ private static unsafe void Int64ToNumber(long input, ref NumberBuffer number)
  value = (ulong)(-input);
  }
 
- char* buffer = number.digits;
+ char* buffer = number.GetDigitsPointer();
  char* p = buffer + Int64Precision;
  while (High32(value) != 0)
  p = UInt32ToDecChars(p, Int64DivMod1E9(ref value), 9);
@@ -1191,7 +1191,7 @@ private static unsafe void Int64ToNumber(long input, ref NumberBuffer number)
  number.scale = i;
  number.kind = NumberBufferKind.Integer;
 
- char* dst = number.digits;
+ char* dst = number.GetDigitsPointer();
  while (--i >= 0)
  *dst++ = *p++;
  *dst = '\0';
@@ -1322,7 +1322,7 @@ private static unsafe void UInt64ToNumber(ulong value, ref NumberBuffer number)
  number.precision = UInt64Precision;
  number.sign = false;
 
- char* buffer = number.digits;
+ char* buffer = number.GetDigitsPointer();
  char* p = buffer + UInt64Precision;
 
  while (High32(value) != 0)
@@ -1333,7 +1333,7 @@ private static unsafe void UInt64ToNumber(ulong value, ref NumberBuffer number)
  number.scale = i;
  number.kind = NumberBufferKind.Integer;
 
- char* dst = number.digits;
+ char* dst = number.GetDigitsPointer();
  while (--i >= 0)
  *dst++ = *p++;
  *dst = '\0';
@@ -1591,7 +1591,7 @@ internal static unsafe void NumberToStringFormat(ref ValueStringBuilder sb, ref
 
  int section;
  int src;
- char* dig = number.digits;
+ char* dig = number.GetDigitsPointer();
  char ch;
 
  section = FindSection(format, dig[0] == 0 ? 2 : number.sign ? 1 : 0);
@@ -1963,7 +1963,7 @@ private static void FormatCurrency(ref ValueStringBuilder sb, ref NumberBuffer n
  private static unsafe void FormatFixed(ref ValueStringBuilder sb, ref NumberBuffer number, int nMaxDigits, NumberFormatInfo info, int[] groupDigits, string sDecimal, string sGroup)
  {
  int digPos = number.scale;
- char* dig = number.digits;
+ char* dig = number.GetDigitsPointer();
 
  if (digPos > 0)
  {
@@ -2087,7 +2087,7 @@ private static void FormatNumber(ref ValueStringBuilder sb, ref NumberBuffer num
 
  private static unsafe void FormatScientific(ref ValueStringBuilder sb, ref NumberBuffer number, int nMaxDigits, NumberFormatInfo info, char expChar)
  {
- char* dig = number.digits;
+ char* dig = number.GetDigitsPointer();
 
  sb.Append((*dig != 0) ? *dig++ : '0');
 
@@ -2137,7 +2137,7 @@ private static unsafe void FormatGeneral(ref ValueStringBuilder sb, ref NumberBu
  }
  }
 
- char* dig = number.digits;
+ char* dig = number.GetDigitsPointer();
 
  if (digPos > 0)
  {
@@ -2197,7 +2197,7 @@ private static void FormatPercent(ref ValueStringBuilder sb, ref NumberBuffer nu
 
  private static unsafe void RoundNumber(ref NumberBuffer number, int pos)
  {
- char* dig = number.digits;
+ char* dig = number.GetDigitsPointer();
 
  int i = 0;
  while (i < pos && dig[i] != 0)

src/System.Private.CoreLib/shared/System/Number.Grisu3.cs

@@ -366,7 +366,7 @@ public static bool Run(double value, int precision, ref NumberBuffer number)
 
  // Step 4: Generate digits.
 
- bool isSuccess = DigitGen(ref D, precision, number.digits, out int length, out int kappa);
+ bool isSuccess = DigitGen(ref D, precision, number.GetDigitsPointer(), out int length, out int kappa);
 
  if (isSuccess)
  {

src/System.Private.CoreLib/shared/System/Number.NumberBuffer.cs

@@ -19,22 +19,20 @@ internal static partial class Number
  [StructLayout(LayoutKind.Sequential, Pack = 1)]
  internal unsafe ref struct NumberBuffer
  {
- public int precision; // 0
- public int scale; // 4
- private int _sign; // 8
- private NumberBufferKind _kind; // 12
- private char* _allDigits; // 16
- private DigitsAndNullTerminator _digits; // 20 or 24
-
- public bool sign { get => _sign != 0; set => _sign = value ? 1 : 0; }
- public char* digits => (char*)Unsafe.AsPointer(ref _digits);
- public NumberBufferKind kind { get => _kind; set => _kind = value; }
-
- [StructLayout(LayoutKind.Sequential, Size = (NumberMaxDigits + 1) * sizeof(char))]
- private struct DigitsAndNullTerminator { }
+ public int precision;
+ public int scale;
+ public bool sign;
+ public NumberBufferKind kind;
+ public fixed char digits[NumberMaxDigits + 1];
+
+ public char* GetDigitsPointer()
+ {
+ // This is safe to do since we are a ref struct
+ return (char*)(Unsafe.AsPointer(ref digits[0]));
+ }
  }
 
- internal enum NumberBufferKind
+ internal enum NumberBufferKind : byte
  {
  Unknown = 0,
  Integer = 1,

src/System.Private.CoreLib/shared/System/Number.NumberToDouble.cs

@@ -314,7 +314,7 @@ private static double NumberToDouble(ref NumberBuffer number)
  }
 #endif
 
- char* src = number.digits;
+ char* src = number.GetDigitsPointer();
  int total = GetLength(src);
  int remaining = total;
 

src/System.Private.CoreLib/shared/System/Number.Parsing.cs

@@ -59,7 +59,7 @@ private static unsafe bool NumberToInt32(ref NumberBuffer number, ref int value)
  {
  return false;
  }
- char* p = number.digits;
+ char* p = number.GetDigitsPointer();
  Debug.Assert(p != null);
  int n = 0;
  while (--i >= 0)
@@ -100,7 +100,7 @@ private static unsafe bool NumberToInt64(ref NumberBuffer number, ref long value
  {
  return false;
  }
- char* p = number.digits;
+ char* p = number.GetDigitsPointer();
  Debug.Assert(p != null);
  long n = 0;
  while (--i >= 0)
@@ -141,7 +141,7 @@ private static unsafe bool NumberToUInt32(ref NumberBuffer number, ref uint valu
  {
  return false;
  }
- char* p = number.digits;
+ char* p = number.GetDigitsPointer();
  Debug.Assert(p != null);
  uint n = 0;
  while (--i >= 0)
@@ -173,7 +173,7 @@ private static unsafe bool NumberToUInt64(ref NumberBuffer number, ref ulong val
  {
  return false;
  }
- char* p = number.digits;
+ char* p = number.GetDigitsPointer();
  Debug.Assert(p != null);
  ulong n = 0;
  while (--i >= 0)
@@ -1468,7 +1468,7 @@ internal static decimal ParseDecimal(ReadOnlySpan<char> value, NumberStyles styl
 
  private static unsafe bool NumberBufferToDecimal(ref NumberBuffer number, ref decimal value)
  {
- char* p = number.digits;
+ char* p = number.GetDigitsPointer();
  int e = number.scale;
  bool sign = number.sign;
  uint c = *p;