452 lines
15 KiB
C
452 lines
15 KiB
C
/*
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******************************************************************************
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* Copyright (C) 1997-2001, International Business Machines
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* Corporation and others. All Rights Reserved.
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******************************************************************************
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* Date Name Description
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* 03/22/00 aliu Adapted from original C++ ICU Hashtable.
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******************************************************************************
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*/
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#ifndef UHASH_H
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#define UHASH_H
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#include "unicode/utypes.h"
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/**
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* UHashtable stores key-value pairs and does moderately fast lookup
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* based on keys. It provides a good tradeoff between access time and
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* storage space. As elements are added to it, it grows to accomodate
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* them. By default, the table never shrinks, even if all elements
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* are removed from it.
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*
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* Keys and values are stored as void* pointers. These void* pointers
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* may be actual pointers to strings, objects, or any other structure
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* in memory, or they may simply be integral values cast to void*.
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* UHashtable doesn't care and manipulates them via user-supplied
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* functions. These functions hash keys, compare keys, delete keys,
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* and delete values. Some function pointers are optional (may be
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* NULL); others must be supplied. Several prebuilt functions exist
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* to handle common key types.
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*
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* UHashtable ownership of keys and values is flexible, and controlled
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* by whether or not the key deleter and value deleter functions are
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* set. If a void* key is actually a pointer to a deletable object,
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* then UHashtable can be made to delete that object by setting the
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* key deleter function pointer to a non-NULL value. If this is done,
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* then keys passed to uhash_put() are owned by the hashtable and will
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* be deleted by it at some point, either as keys are replaced, or
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* when uhash_close() is finally called. The same is true of values
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* and the value deleter function pointer. Keys passed to methods
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* other than uhash_put() are never owned by the hashtable.
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*
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* NULL values are not allowed. uhash_get() returns NULL to indicate
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* a key that is not in the table, and having a NULL value in the
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* table would generate an ambiguous result. If a key and a NULL
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* value is passed to uhash_put(), this has the effect of doing a
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* uhash_remove() on that key. This keeps uhash_get(), uhash_count(),
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* and uhash_nextElement() consistent with one another.
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*
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* To see everything in a hashtable, use uhash_nextElement() to
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* iterate through its contents. Each call to this function returns a
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* UHashElement pointer. A hash element contains a key, value, and
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* hashcode. During iteration an element may be deleted by calling
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* uhash_removeElement(); iteration may safely continue thereafter.
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* The uhash_remove() function may also be safely called in
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* mid-iteration. However, if uhash_put() is called during iteration
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* then the iteration will be out of sync. Under no circumstances
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* should the UHashElement returned by uhash_nextElement be modified
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* directly.
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*
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* By default, the hashtable grows when necessary, but never shrinks,
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* even if all items are removed. For most applications this is
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* optimal. However, in a highly dynamic usage where memory is at a
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* premium, the table can be set to both grow and shrink by calling
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* uhash_setResizePolicy() with the policy U_GROW_AND_SHRINK. In a
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* situation where memory is critical and the client wants a table
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* that does not grow at all, the constant U_FIXED can be used.
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*/
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/********************************************************************
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* Data Structures
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********************************************************************/
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U_CDECL_BEGIN
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/**
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* A hashing function.
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* @param key A key stored in a hashtable
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* @return A NON-NEGATIVE hash code for parm.
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*/
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typedef int32_t (* U_CALLCONV UHashFunction)(const void* key);
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/**
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* A key comparison function.
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* @param key1 A key stored in a hashtable
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* @param key2 A key stored in a hashtable
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* @return TRUE if the two keys are equal.
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*/
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typedef UBool (* U_CALLCONV UKeyComparator)(const void* key1,
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const void* key2);
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/**
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* A function called by <TT>uhash_remove</TT>,
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* <TT>uhash_close</TT>, or <TT>uhash_put</TT> to delete
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* an existing key or value.
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* @param obj A key or value stored in a hashtable
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*/
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typedef void (* U_CALLCONV UObjectDeleter)(void* obj);
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/**
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* This is a single hash element. These should pack nicely
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* into exactly 24 bytes. If this is not true, then split
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* the elements array into 3 separate arrays for the hash,
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* key, and value.
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*/
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struct UHashElement {
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int32_t hashcode;
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void* key;
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void* value;
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};
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typedef struct UHashElement UHashElement;
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/**
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* This specifies whether or not, and how, the hastable resizes itself.
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* See uhash_setResizePolicy().
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*/
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enum UHashResizePolicy {
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U_GROW, /* Grow on demand, do not shrink */
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U_GROW_AND_SHRINK, /* Grow and shrink on demand */
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U_FIXED /* Never change size */
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};
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/**
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* The UHashtable struct. Clients should treat this as an opaque data
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* type and manipulate it only through the uhash_... API.
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*/
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struct UHashtable {
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/* Main key-value pair storage array */
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UHashElement *elements;
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/* Size parameters */
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int32_t count; /* The number of key-value pairs in this table.
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* 0 <= count <= length. In practice we
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* never let count == length (see code). */
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int32_t length; /* The physical size of the arrays hashes, keys
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* and values. Must be prime. */
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int32_t primeIndex; /* Index into our prime table for length.
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* length == PRIMES[primeIndex] */
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/* Rehashing thresholds */
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int32_t highWaterMark; /* If count > highWaterMark, rehash */
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int32_t lowWaterMark; /* If count < lowWaterMark, rehash */
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float highWaterRatio; /* 0..1; high water as a fraction of length */
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float lowWaterRatio; /* 0..1; low water as a fraction of length */
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/* Function pointers */
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UHashFunction keyHasher; /* Computes hash from key.
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* Never null. */
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UKeyComparator keyComparator; /* Compares keys for equality.
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* Never null. */
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UObjectDeleter keyDeleter; /* Deletes keys when required.
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* If NULL won't do anything */
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UObjectDeleter valueDeleter; /* Deletes values when required.
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* If NULL won't do anything */
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};
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typedef struct UHashtable UHashtable;
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U_CDECL_END
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/********************************************************************
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* API
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********************************************************************/
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/**
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* Initialize a new UHashtable.
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* @param keyHash A pointer to the key hashing function. Must not be
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* NULL.
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* @param keyComp A pointer to the function that compares keys. Must
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* not be NULL.
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* @param status A pointer to an UErrorCode to receive any errors.
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* @return A pointer to a UHashtable, or 0 if an error occurred.
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* @see uhash_openSize
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*/
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U_CAPI UHashtable*
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uhash_open(UHashFunction keyHash,
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UKeyComparator keyComp,
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UErrorCode *status);
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/**
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* Initialize a new UHashtable with a given initial size.
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* @param keyHash A pointer to the key hashing function. Must not be
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* NULL.
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* @param keyComp A pointer to the function that compares keys. Must
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* not be NULL.
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* @param size The initial capacity of this hash table.
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* @param status A pointer to an UErrorCode to receive any errors.
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* @return A pointer to a UHashtable, or 0 if an error occurred.
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* @see uhash_open
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*/
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U_CAPI UHashtable*
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uhash_openSize(UHashFunction keyHash,
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UKeyComparator keyComp,
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int32_t size,
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UErrorCode *status);
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/**
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* Close a UHashtable, releasing the memory used.
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* @param hash The UHashtable to close.
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*/
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U_CAPI void
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uhash_close(UHashtable *hash);
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/**
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* Set the function used to hash keys.
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* @param fn the function to be used hash keys; must not be NULL
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* @return the previous key hasher; non-NULL
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*/
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U_CAPI UHashFunction
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uhash_setKeyHasher(UHashtable *hash, UHashFunction fn);
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/**
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* Set the function used to compare keys. The default comparison is a
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* void* pointer comparison.
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* @param fn the function to be used compare keys; must not be NULL
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* @return the previous key comparator; non-NULL
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*/
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U_CAPI UKeyComparator
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uhash_setKeyComparator(UHashtable *hash, UKeyComparator fn);
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/**
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* Set the function used to delete keys. If this function pointer is
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* NULL, this hashtable does not delete keys. If it is non-NULL, this
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* hashtable does delete keys. This function should be set once
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* before any elements are added to the hashtable and should not be
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* changed thereafter.
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* @param fn the function to be used delete keys, or NULL
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* @return the previous key deleter; may be NULL
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*/
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U_CAPI UObjectDeleter
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uhash_setKeyDeleter(UHashtable *hash, UObjectDeleter fn);
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/**
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* Set the function used to delete values. If this function pointer
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* is NULL, this hashtable does not delete values. If it is non-NULL,
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* this hashtable does delete values. This function should be set
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* once before any elements are added to the hashtable and should not
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* be changed thereafter.
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* @param fn the function to be used delete values, or NULL
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* @return the previous value deleter; may be NULL
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*/
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U_CAPI UObjectDeleter
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uhash_setValueDeleter(UHashtable *hash, UObjectDeleter fn);
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/**
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* Specify whether or not, and how, the hastable resizes itself.
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* By default, tables grow but do not shrink (policy U_GROW).
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* See enum UHashResizePolicy.
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*/
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U_CAPI void
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uhash_setResizePolicy(UHashtable *hash, enum UHashResizePolicy policy);
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/**
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* Get the number of key-value pairs stored in a UHashtable.
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* @param hash The UHashtable to query.
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* @return The number of key-value pairs stored in hash.
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*/
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U_CAPI int32_t
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uhash_count(const UHashtable *hash);
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/**
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* Put an item in a UHashtable. If the keyDeleter is non-NULL, then
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* the hashtable owns 'key' after this call. If the valueDeleter is
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* non-NULL, then the hashtable owns 'value' after this call.
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* Storing a NULL value is the same as calling uhash_remove().
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* @param hash The target UHashtable.
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* @param key The key to store.
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* @param value The value to store, may be NULL (see above).
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* @param status A pointer to an UErrorCode to receive any errors.
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* @return The previous value, or NULL if none.
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* @see uhash_get
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*/
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U_CAPI void*
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uhash_put(UHashtable *hash,
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void *key,
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void *value,
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UErrorCode *status);
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/**
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* Get an item from a UHashtable.
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* @param hash The target UHashtable.
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* @param key The hash code of the desired value.
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* @return The requested item, or 0 if not found.
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*/
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U_CAPI void*
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uhash_get(const UHashtable *hash,
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const void *key);
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/**
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* Remove an item from a UHashtable.
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* @param hash The target UHashtable.
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* @param key The hash code of the value to be removed.
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* @return The item removed, or 0 if not found.
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*/
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U_CAPI void*
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uhash_remove(UHashtable *hash,
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const void *key);
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/**
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* Remove all items from a UHashtable.
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* @param hash The target UHashtable.
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*/
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U_CAPI void
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uhash_removeAll(UHashtable *hash);
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/**
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* Iterate through the elements of a UHashtable. The caller must not
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* modify the returned object. However, uhash_removeElement() may be
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* called during iteration to remove an element from the table.
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* Iteration may safely be resumed afterwards. If uhash_put() is
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* called during iteration the iteration will then be out of sync and
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* should be restarted.
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* @param hash The target UHashtable.
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* @param pos This should be set to -1 initially, and left untouched
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* thereafter.
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* @return a hash element, or NULL if no further key-value pairs
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* exist in the table.
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*/
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U_CAPI const UHashElement*
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uhash_nextElement(const UHashtable *hash,
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int32_t *pos);
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/**
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* Remove an element, returned by uhash_nextElement(), from the table.
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* Iteration may be safely continued afterwards.
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* @param hash The hashtable
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* @param e The element, returned by uhash_nextElement(), to remove.
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* Must not be NULL. Must not be an empty or deleted element (as long
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* as this was returned by uhash_nextElement() it will not be empty or
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* deleted). Note: Although this parameter is const, it will be
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* modified.
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* @return the value that was removed.
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*/
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U_CAPI void*
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uhash_removeElement(UHashtable *hash, const UHashElement* e);
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/********************************************************************
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* UChar* and char* Support Functions
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********************************************************************/
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/**
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* Generate a hash code for a null-terminated UChar* string. If the
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* string is not null-terminated do not use this function. Use
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* together with uhash_compareUChars.
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* @param key The string (const UChar*) to hash.
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* @return A hash code for the key.
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*/
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U_CAPI int32_t
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uhash_hashUChars(const void *key);
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/**
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* Generate a hash code for a null-terminated char* string. If the
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* string is not null-terminated do not use this function. Use
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* together with uhash_compareChars.
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* @param key The string (const char*) to hash.
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* @return A hash code for the key.
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*/
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U_CAPI int32_t
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uhash_hashChars(const void *key);
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/* Used by UnicodeString to compute its hashcode - Not public API. */
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U_CAPI int32_t
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uhash_hashUCharsN(const UChar *key, int32_t length);
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/**
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* Generate a case-insensitive hash code for a null-terminated char*
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* string. If the string is not null-terminated do not use this
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* function. Use together with uhash_compareIChars.
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* @param key The string (const char*) to hash.
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* @return A hash code for the key.
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*/
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U_CAPI int32_t
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uhash_hashIChars(const void *key);
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/**
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* Comparator for null-terminated UChar* strings. Use together with
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* uhash_hashUChars.
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*/
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U_CAPI UBool
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uhash_compareUChars(const void *key1, const void *key2);
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/**
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* Comparator for null-terminated char* strings. Use together with
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* uhash_hashChars.
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*/
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U_CAPI UBool
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uhash_compareChars(const void *key1, const void *key2);
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/**
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* Case-insensitive comparator for null-terminated char* strings. Use
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* together with uhash_hashIChars.
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*/
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U_CAPI UBool
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uhash_compareIChars(const void *key1, const void *key2);
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/********************************************************************
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* UnicodeString Support Functions
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********************************************************************/
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/**
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* Hash function for UnicodeString* keys.
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*/
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U_CAPI int32_t
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uhash_hashUnicodeString(const void *key);
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/**
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* Comparator function for UnicodeString* keys.
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*/
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U_CAPI UBool
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uhash_compareUnicodeString(const void *key1, const void *key2);
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/**
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* Deleter function for UnicodeString* keys or values.
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*/
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U_CAPI void
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uhash_deleteUnicodeString(void *obj);
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/********************************************************************
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* int32_t Support Functions
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********************************************************************/
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/**
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* Hash function for 32-bit integer keys.
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*/
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U_CAPI int32_t
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uhash_hashLong(const void *key);
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/**
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* Comparator function for 32-bit integer keys.
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*/
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U_CAPI UBool
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uhash_compareLong(const void *key1, const void *key2);
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/********************************************************************
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* Other Support Functions
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********************************************************************/
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/**
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* Deleter for any key or value allocated using uprv_malloc. Calls
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* uprv_free.
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*/
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U_CAPI void
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uhash_freeBlock(void *obj);
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#endif
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