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Solr plugin to add support for highlighting directly from various OCR formats (hOCR/ALTO/MiniOCR) without having to store the OCR documents in the index.

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package de.digitalcollections.solrocr.util;

/** Some utility functions to work with character buffers */
public class CharBufUtils {
  /**
   * Find the offset of the needle in the haystack.
   *
   * FIXME: Is there really no stdlib method for this?
   *
   * @param haystack target buffer to find characters in
   * @param fromIndex offset to start looking for in the haystack buffer
   * @param toIndex length of target buffer, everything beyond this offset is ignored
   * @param needle sequence of chars to look for in the haystack buffer
   * @return the starting offset of {@code needle} in the {@code haystack} or -1 if not found
   */
  public static int indexOf(char[] haystack, int fromIndex, int toIndex, char[] needle) {
    int needleIdx = 0;
    while (needleIdx < needle.length && fromIndex < toIndex) {
      if (haystack[fromIndex] == needle[needleIdx]) {
        needleIdx++;
      } else {
        needleIdx = 0;
      }
      fromIndex++;
    }

    if (needleIdx == needle.length) {
      return fromIndex - needle.length;
    }
    return -1;
  }
}