Check in the pristine copy of ICU 4.6...

icu46/source/i18n/unicode/bms.h

+/*
+ * Copyright (C) 1996-2010, International Business Machines Corporation and Others.
+ * All rights reserved.
+ */
+
+/**
+ * \file 
+ * \brief C API: Boyer-Moore StringSearch prototype.
+ * \internal
+ */
+
+#ifndef _BMS_H
+#define _BMS_H
+
+#include "unicode/utypes.h"
+
+#if !UCONFIG_NO_COLLATION && !UCONFIG_NO_BREAK_ITERATION
+
+#include "unicode/ucol.h"
+
+/**
+ * A <code>UCD</code> object holds the Collator-specific data needed to
+ * compute the length of the shortest string that can
+ * generate a partcular list of CEs.
+ *
+ * <code>UCD</code> objects are quite expensive to compute. Because
+ * of this, they are cached. When you call <code>ucd_open</code> it
+ * returns a reference counted cached object. When you call <code>ucd_close</code>
+ * the reference count on the object is decremented but the object is not deleted.
+ *
+ * If you do not need to reuse any unreferenced objects in the cache, you can call
+ * <code>ucd_flushCCache</code>. If you no longer need any <code>UCD</code>
+ * objects, you can call <code>ucd_freeCache</code>
+ */
+typedef void UCD;
+
+/**
+ * Open a <code>UCD</code> object.
+ *
+ * @param coll - the collator
+ * @param status - will be set if any errors occur. 
+ *
+ * @return the <code>UCD</code> object. You must call
+ *         <code>ucd_close</code> when you are done using the object.
+ *
+ * Note: if on return status is set to an error, the only safe
+ * thing to do with the returned object is to call <code>ucd_close</code>.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI UCD * U_EXPORT2
+ucd_open(UCollator *coll, UErrorCode *status);
+
+/**
+ * Release a <code>UCD</code> object.
+ *
+ * @param ucd - the object
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI void U_EXPORT2
+ucd_close(UCD *ucd);
+
+/**
+ * Get the <code>UCollator</code> object used to create a <code>UCD</code> object.
+ * The <code>UCollator</code> object returned may not be the exact
+ * object that was used to create this object, but it will have the
+ * same behavior.
+ *
+ * @param ucd - the <code>UCD</code> object
+ *
+ * @return the <code>UCollator</code> used to create the given
+ *         <code>UCD</code> object.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI UCollator * U_EXPORT2
+ucd_getCollator(UCD *ucd);
+
+/**
+ * <code>UCD</code> objects are expensive to compute, and so
+ * may be cached. This routine will free the cached objects and delete
+ * the cache.
+ *
+ * WARNING: Don't call this until you are have called <code>close</code>
+ * for each <code>UCD</code> object that you have used. also,
+ * DO NOT call this if another thread may be calling <code>ucd_flushCache</code>
+ * at the same time.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI void U_EXPORT2
+ucd_freeCache();
+
+/**
+ * <code>UCD</code> objects are expensive to compute, and so
+ * may be cached. This routine will remove any unused <code>UCD</code>
+ * objects from the cache.
+ *
+ * @internal 4.0.1 technology preview
+ */
+U_CAPI void U_EXPORT2
+ucd_flushCache();
+
+/**
+ * BMS
+ *
+ * This object holds the information needed to do a Collation sensitive Boyer-Moore search. It encapulates
+ * the pattern, the "bad character" and "good suffix" tables, the Collator-based data needed to compute them,
+ * and a reference to the text being searched.
+ *
+ * To do a search, you first need to get a <code>UCD</code> object by calling <code>ucd_open</code>.
+ * Then you construct a <code>BMS</code> object from the <code>UCD</code> object, the pattern
+ * string and the target string. Then you call the <code>search</code> method. Here's a code sample:
+ *
+ * <pre>
+ * void boyerMooreExample(UCollator *collator, UChar *pattern, int32_t patternLen, UChar *target, int32_t targetLength)
+ * {
+ *     UErrorCode status = U_ZERO_ERROR;
+ *     int32_t offset = 0, start = -1, end = -1;
+ *     UCD *ucd = NULL);
+ *     BMS *bms = NULL;
+ *
+ *     ucd = ucd_open(collator, &status);
+ *     if (U_FAILURE(status)) {
+ *         // could not create a UCD object
+ *         return;
+ *     }
+ *
+ *     BMS *bms = bms_open(ucd, pattern, patternLength, target, targetlength, &status);
+ *     if (U_FAILURE(status)) {
+ *         // could not create a BMS object
+ *         ucd_close(ucd);
+ *         return;
+ *     }
+ *
+ *
+ *     // Find all matches
+ *     while (bms_search(bms, offset, &start, &end)) {
+ *         // process the match between start and end
+ *         ...
+ *
+ *         // advance past the match
+ *         offset = end; 
+ *     }
+ *
+ *     // at this point, if offset == 0, there were no matches
+ *     if (offset == 0) {
+ *         // handle the case of no matches
+ *     }
+ *
+ *     bms_close(bms);
+ *     ucd_close(ucd);
+ *
+ *     // UCD objects are cached, so the call to
+ *     // ucd_close doesn't delete the object.
+ *     // Call this if you don't need the object any more.
+ *     ucd_flushCache();
+ * }
+ * </pre>
+ *
+ * NOTE: This is a technology preview. The final version of this API may not bear any resenblence to this API.
+ *
+ * Knows linitations:
+ *   1) Backwards searching has not been implemented.
+ *
+ *   2) For Han and Hangul characters, this code ignores any Collation tailorings. In general,
+ *      this isn't a problem, but in Korean locals, at strength 1, Hangul characters are tailored
+ *      to be equal to Han characters with the same pronounciation. Because this code ignroes
+ *      tailorings, searching for a Hangul character will not find a Han character and visa-versa.
+ *
+ *   3) In some cases, searching for a pattern that needs to be normalized and ends
+ *      in a discontiguous contraction may fail. The only known cases of this are with
+ *      the Tibetan script. For example searching for the pattern
+ *      "\u0F7F\u0F80\u0F81\u0F82\u0F83\u0F84\u0F85" will fail. (This case is artificial. We've
+ *      been unable to find a pratical, real-world example of this failure.)  
+ *
+ * NOTE: This is a technology preview. The final version of this API may not bear any resenblence to this API.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+struct BMS;
+typedef struct BMS BMS; /**< @see BMS */
+
+/**
+ * Construct a <code>MBS</code> object.
+ *
+ * @param ucd - A <code>UCD</code> object holding the Collator-sensitive data
+ * @param pattern - the string for which to search
+ * @param patternLength - the length of the string for which to search
+ * @param target - the string in which to search
+ * @param targetLength - the length of the string in which to search
+ * @param status - will be set if any errors occur. 
+ *
+ * @return the <code>BMS</code> object.
+ *
+ * Note: if on return status is set to an error, the only safe
+ * thing to do with the returned object is to call
+ * <code>bms_close</code>.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI BMS * U_EXPORT2
+bms_open(UCD *ucd,
+         const UChar *pattern, int32_t patternLength,
+         const UChar *target,  int32_t targetLength,
+         UErrorCode  *status);
+
+/**
+ * Close a <code>BMS</code> object and release all the
+ * storage associated with it.
+ *
+ * @param bms - the <code>BMS</code> object to close.
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI void U_EXPORT2
+bms_close(BMS *bms);
+
+/**
+ * Test the pattern to see if it generates any CEs.
+ *
+ * @param bms - the <code>BMS</code> object
+ * @return <code>TRUE</code> if the pattern string did not generate any CEs
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI UBool U_EXPORT2
+bms_empty(BMS *bms);
+
+/**
+ * Get the <code>UCD</code> object used to create
+ * a given <code>BMS</code> object.
+ *
+ * @param bms - the <code>BMS</code> object
+ *
+ * @return - the <code>UCD</code> object used to create
+ *           the given <code>BMS</code> object.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI UCD * U_EXPORT2
+bms_getData(BMS *bms);
+
+/**
+ * Search for the pattern string in the target string.
+ *
+ * @param bms - the <code>BMS</code> object
+ * @param offset - the offset in the target string at which to begin the search
+ * @param start - will be set to the starting offset of the match, or -1 if there's no match
+ * @param end - will be set to the ending offset of the match, or -1 if there's no match
+ *
+ * @return <code>TRUE</code> if the match succeeds, <code>FALSE</code> otherwise.
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI UBool U_EXPORT2
+bms_search(BMS *bms, int32_t offset, int32_t *start, int32_t *end);
+
+/**
+ * Set the target string for the match.
+ *
+ * @param bms - the <code>BMS</code> object
+ * @param target - the new target string
+ * @param targetLength - the length of the new target string
+ * @param status - will be set if any errors occur. 
+ *
+ * @internal ICU 4.0.1 technology preview
+ */
+U_CAPI void U_EXPORT2
+bms_setTargetString(BMS *bms, const UChar *target, int32_t targetLength, UErrorCode *status);
+
+#endif
+
+#endif /* _BMS_H */