/// <summary>
/// Managed wrapper around the raw match API.
/// <para>From the RE2 docs for the underlying function:
/// Don't ask for more match information than you will use:
/// runs much faster with nsubmatch == 1 than nsubmatch > 1, and
/// runs even faster if nsubmatch == 0.
/// Doesn't make sense to use nsubmatch > 1 + NumberOfCapturingGroups(),
/// but will be handled correctly.
/// </para>
/// </summary>
/// <param name="hayBytes">The string to match the pattern against</param>
/// <param name="startByteIndex">The byte offset to start at</param>
/// <param name="numCaptures">The number of match groups to return</param>
/// <returns>An array of byte ranges for the captures</returns>
private unsafe ByteRange[] RawMatch(
ReadOnlySpan <byte> hayBytes, int startByteIndex, int numCaptures)
{
var captures = new Re2Ffi.cre2_string_t[numCaptures];
fixed(byte *pinnedHayBytes = hayBytes)
{
// TODO: Support anchor as a parameter
var matchResult = Re2Ffi.cre2_match(
RawHandle,
pinnedHayBytes, hayBytes.Length,
startByteIndex, hayBytes.Length,
Re2Ffi.cre2_anchor_t.CRE2_UNANCHORED,
captures, captures.Length);
if (matchResult != 1)
{
return(Array.Empty <ByteRange>());
}
// Convert the captured strings to array indices while we still
// have the haystack pinned. We can't have the haystack move
// between the `_match` and the conversion to byte ranges
// otherwise the pointer arithmetic we do will be invalidated.
return(StringsToRanges(captures, new IntPtr(pinnedHayBytes)));
}
}
/// <summary>
/// Checks if the pattern matches somewhere in the given
/// <paramref name="haystack" />.
/// </summary>
/// <param name="haystack">The text to find the pattern in</param>
/// <returns>True if the pattern matches, false otherwise.</returns>
public unsafe bool IsMatch(ReadOnlySpan <byte> haystack)
{
var captures = Array.Empty <Re2Ffi.cre2_string_t>();
fixed(byte *hayBytesPtr = haystack)
{
// TODO: Support anchor as a parameter
var matchResult = Re2Ffi.cre2_match(
RawHandle,
hayBytesPtr, haystack.Length,
0, haystack.Length,
Re2Ffi.cre2_anchor_t.CRE2_UNANCHORED,
captures, 0);
return(matchResult == 1);
}
}