Base class for precomputed factories that create MultiSearchProcessors.
The purpose of MultiSearchProcessor is to perform efficient simultaneous search for multiple needles in the haystack, while scanning every byte of the input sequentially, only once. While it can also be used to search for just a single needle, using a SearchProcessorFactory would be more efficient for doing that.
See the documentation of AbstractSearchProcessorFactory for a comprehensive description of common usage. In addition to the functionality provided by SearchProcessor, MultiSearchProcessor adds a method to get the index of the needle found at the current position of the MultiSearchProcessor - MultiSearchProcessor#getFoundNeedleId()

     MultiSearchProcessorFactory factory = MultiSearchProcessorFactory.newAhoCorasicSearchProcessorFactory(
         "AB".getBytes(CharsetUtil.UTF_8), "BC".getBytes(CharsetUtil.UTF_8), "CD".getBytes(CharsetUtil.UTF_8));
     MultiSearchProcessor processor = factory.newSearchProcessor();

     int idx1 = haystack.forEachByte(processor);
     // idx1 is 1 (index of the last character of the occurrence of "AB" in the haystack)
     // processor.getFoundNeedleId() is 0 (index of "AB" in needles[])

     int continueFrom1 = idx1 + 1;
     // continue the search starting from the next character

     int idx2 = haystack.forEachByte(continueFrom1, haystack.readableBytes() - continueFrom1, processor);
     // idx2 is 2 (index of the last character of the occurrence of "BC" in the haystack)
     // processor.getFoundNeedleId() is 1 (index of "BC" in needles[])

     int continueFrom2 = idx2 + 1;

     int idx3 = haystack.forEachByte(continueFrom2, haystack.readableBytes() - continueFrom2, processor);
     // idx3 is 3 (index of the last character of the occurrence of "CD" in the haystack)
     // processor.getFoundNeedleId() is 2 (index of "CD" in needles[])

     int continueFrom3 = idx3 + 1;

     int idx4 = haystack.forEachByte(continueFrom3, haystack.readableBytes() - continueFrom3, processor);
     // idx4 is -1 (no more occurrences of any of the needles)

     // This search session is complete, processor should be discarded.
     // To search for the same needles again, reuse the same AbstractMultiSearchProcessorFactory
     // to get a new MultiSearchProcessor.