99 lines
3.2 KiB
C++
99 lines
3.2 KiB
C++
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// © 2020 and later: Unicode, Inc. and others.
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// License & terms of use: http://www.unicode.org/copyright.html
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// uniquecharstr.h
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// created: 2020sep01 Frank Yung-Fong Tang
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#ifndef __UNIQUECHARSTR_H__
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#define __UNIQUECHARSTR_H__
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#include "charstr.h"
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#include "uassert.h"
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#include "uhash.h"
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U_NAMESPACE_BEGIN
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/**
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* Stores NUL-terminated strings with duplicate elimination.
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* Checks for unique UTF-16 string pointers and converts to invariant characters.
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*
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* Intended to be stack-allocated. Add strings, get a unique number for each,
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* freeze the object, get a char * pointer for each string,
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* call orphanCharStrings() to capture the string storage, and let this object go out of scope.
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*/
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class UniqueCharStrings {
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public:
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UniqueCharStrings(UErrorCode &errorCode) : strings(nullptr) {
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// Note: We hash on string contents but store stable char16_t * pointers.
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// If the strings are stored in resource bundles which should be built with
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// duplicate elimination, then we should be able to hash on just the pointer values.
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uhash_init(&map, uhash_hashUChars, uhash_compareUChars, uhash_compareLong, &errorCode);
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if (U_FAILURE(errorCode)) { return; }
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strings = new CharString();
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if (strings == nullptr) {
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errorCode = U_MEMORY_ALLOCATION_ERROR;
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}
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}
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~UniqueCharStrings() {
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uhash_close(&map);
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delete strings;
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}
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/** Returns/orphans the CharString that contains all strings. */
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CharString *orphanCharStrings() {
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CharString *result = strings;
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strings = nullptr;
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return result;
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}
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/**
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* Adds a string and returns a unique number for it.
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* The string's buffer contents must not change, nor move around in memory,
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* while this UniqueCharStrings is in use.
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* The string contents must be NUL-terminated exactly at s.length().
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*
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* Best used with read-only-alias UnicodeString objects that point to
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* stable storage, such as strings returned by resource bundle functions.
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*/
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int32_t add(const UnicodeString &s, UErrorCode &errorCode) {
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if (U_FAILURE(errorCode)) { return 0; }
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if (isFrozen) {
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errorCode = U_NO_WRITE_PERMISSION;
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return 0;
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}
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// The string points into the resource bundle.
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const char16_t *p = s.getBuffer();
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int32_t oldIndex = uhash_geti(&map, p);
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if (oldIndex != 0) { // found duplicate
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return oldIndex;
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}
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// Explicit NUL terminator for the previous string.
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// The strings object is also terminated with one implicit NUL.
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strings->append(0, errorCode);
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int32_t newIndex = strings->length();
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strings->appendInvariantChars(s, errorCode);
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uhash_puti(&map, const_cast<char16_t *>(p), newIndex, &errorCode);
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return newIndex;
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}
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void freeze() { isFrozen = true; }
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/**
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* Returns a string pointer for its unique number, if this object is frozen.
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* Otherwise nullptr.
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*/
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const char *get(int32_t i) const {
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U_ASSERT(isFrozen);
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return isFrozen && i > 0 ? strings->data() + i : nullptr;
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}
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private:
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UHashtable map;
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CharString *strings;
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bool isFrozen = false;
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};
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U_NAMESPACE_END
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#endif // __UNIQUECHARSTR_H__
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