public static byte[] HexStringToByteArrayChecked(this string s)
{
s.ValidateNotNull(nameof(s));
foreach (char c in s)
{
if (!IsHex(c))
{
ThrowHelpers.ThrowArgumentException("Must provide a hex string.", nameof(s));
}
}
return(s.AsSpan().HexStringToByteArrayUnchecked());
bool IsHex(char c)
{
// at the time of writing, on both x86 and x64, the assembly for this method is 1
// byte smaller than the assembly for 3 range checks, it has 2 fewer conditional
// jumps, and the larger 0-9 case is tighter (early return instead of jump to end).
if ('0' <= c && c <= '9')
{
return(true);
}
c = unchecked ((char)(c & 0xFFDF));
return('A' <= c && c <= 'F');
}
}
// A version of the above that does slightly less work for IReadOnlyCollection<T> instances.
// Should JIT to something that gets optimized to something that's only marginally different
// than the other one, but it's still cheap and easy to do it this way.
public static void CopyTo <T>(this IReadOnlyCollection <T> collection, T[] array, int arrayIndex = 0)
{
collection.ValidateNotNull(nameof(collection));
array.ValidateNotNull(nameof(array));
arrayIndex.ValidateInRange(nameof(arrayIndex), 0, array.Length);
if (array.Length - arrayIndex < collection.Count)
{
ThrowHelpers.ThrowArgumentException("Not enough room", nameof(array));
}
foreach (T item in collection)
{
array[arrayIndex++] = item;
}
}
public static void CopyHexStringToByteArrayUnchecked(this ReadOnlySpan <char> s, Span <byte> b)
{
// this isn't really the kind of "check" that "checked / unchecked" was made for... that
// was more "throw if this string isn't *actually* a hex string".
if (s.Length != b.Length * 2)
{
ThrowHelpers.ThrowArgumentException("Hex string must have 2 chars for every desired output byte.");
}
unchecked
{
for (int i = 0; i < b.Length; ++i)
{
int hi = s[i * 2] - 65;
hi = hi + 10 + ((hi >> 31) & 7);
int lo = s[i * 2 + 1] - 65;
lo = lo + 10 + ((lo >> 31) & 7) & 0x0f;
b[i] = unchecked ((byte)(lo | hi << 4));
}
}
}
public static void CopyTo <T>(this IEnumerable <T> enumerable, T[] array, int arrayIndex = 0)
{
enumerable.ValidateNotNull(nameof(enumerable));
array.ValidateNotNull(nameof(array));
arrayIndex.ValidateInRange(nameof(arrayIndex), 0, array.Length);
bool prevalidate = enumerable.TryGetCount(out var count);
if (prevalidate && array.Length - arrayIndex < count)
{
ThrowHelpers.ThrowArgumentException("Not enough room", nameof(array));
}
foreach (T item in enumerable)
{
if (!prevalidate && arrayIndex == array.Length)
{
ThrowHelpers.ThrowArgumentException("Not enough room", nameof(array));
}
array[arrayIndex++] = item;
}
}