Here is my implementation of BMH algorithm (it works like a charm):
public static Int64 IndexOf(this Byte[] value, Byte[] pattern)
{
    if (value == null)
        throw new ArgumentNullException("value");
    if (pattern == null)
        throw new ArgumentNullException("pattern");
    Int64 valueLength = value.LongLength;
    Int64 patternLength = pattern.LongLength;
    if ((valueLength == 0) || (patternLength == 0) || (patternLength > valueLength))
        return -1;
    Int64[] badCharacters = new Int64[256];
    for (Int64 i = 0; i < 256; ++i)
        badCharacters[i] = patternLength;
    Int64 lastPatternByte = patternLength - 1;
    for (Int64 i = 0; i < lastPatternByte; ++i)
        badCharacters[pattern[i]] = lastPatternByte - i;
    // Beginning
    Int64 index = 0;
    while (index <= (valueLength - patternLength))
    {
        for (Int64 i = lastPatternByte; value[(index + i)] == pattern[i]; --i)
        {
            if (i == 0)
                return index;
        }
        index += badCharacters[value[(index + lastPatternByte)]];
    }
    return -1;
}
I tried to modify it in order to return all the matches instead of only the first index, but I'm getting IndexOutOfRangeException everywhere D:
Obviously I'm missing something important or I didn't properly understood how it works. What am I doing wrong?
public static List<Int64> IndexesOf(this Byte[] value, Byte[] pattern)
{
    if (value == null)
        throw new ArgumentNullException("value");
    if (pattern == null)
        throw new ArgumentNullException("pattern");
    Int64 valueLength = value.LongLength;
    Int64 patternLength = pattern.LongLength;
    if ((valueLength == 0) || (patternLength == 0) || (patternLength > valueLength))
        return (new List<Int64>());
    Int64[] badCharacters = new Int64[256];
    for (Int64 i = 0; i < 256; ++i)
        badCharacters[i] = patternLength;
    Int64 lastPatternByte = patternLength - 1;
    for (Int64 i = 0; i < lastPatternByte; ++i)
        badCharacters[pattern[i]] = lastPatternByte - i;
    // Beginning
    Int64 index = 0;
    List<Int64> indexes = new List<Int64>();
    while (index <= (valueLength - patternLength))
    {
        for (Int64 i = lastPatternByte; value[(index + i)] == pattern[i]; --i)
        {
            if (i == 0)
                indexes.Add(index);
        }
        index += badCharacters[value[(index + lastPatternByte)]];
    }
    return indexes;
}
                Change
if (i == 0)
    indexes.Add(index);
to
if (i == 0)
{
    indexes.Add(index);
    break;
}
                        If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With