/* ihash.h - Integer keyed hash table interface. Copyright (C) 1995, 2003, 2004, 2014, 2015 Free Software Foundation, Inc. Written by Miles Bader . Revised by Marcus Brinkmann . This file is part of the GNU Hurd. The GNU Hurd is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2, or (at your option) any later version. The GNU Hurd is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with the GNU Hurd; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. */ #ifndef _HURD_IHASH_H #define _HURD_IHASH_H 1 #include #include #include #include #include /* The type of the values corresponding to the keys. Must be a pointer type. The values (hurd_ihash_value_t) 0 and (hurd_ihash_value_t) ~0 are reserved for the implementation. */ typedef void *hurd_ihash_value_t; /* When an value entry in the hash table is _HURD_IHASH_EMPTY or _HURD_IHASH_DELETED, then the location is available, and none of the other members of the item are valid at that index. The difference is that searches continue though _HURD_IHASH_DELETED, but stop at _HURD_IHASH_EMPTY. */ #define _HURD_IHASH_EMPTY ((hurd_ihash_value_t) 0) #define _HURD_IHASH_DELETED ((hurd_ihash_value_t) -1) /* Test if VALUE is valid. */ static inline int hurd_ihash_value_valid (hurd_ihash_value_t value) { return value != _HURD_IHASH_EMPTY && value != _HURD_IHASH_DELETED; } /* The type of integer we want to use for the keys. */ typedef uintptr_t hurd_ihash_key_t; /* The type of a location pointer, which is a pointer to the hash value stored in the hash table. */ typedef hurd_ihash_value_t *hurd_ihash_locp_t; /* We support non-integer keys using the generalized key interface. To use it, supply a pair of functions matching the following specification, and use pointers to the key instead of the key itself in all calls to libihash. */ /* The type of a function computing a hash for the given key. */ typedef hurd_ihash_key_t (*hurd_ihash_fct_hash_t) (const void *); /* The type of a function comparing two given keys. Return true if both keys are equal. */ typedef int (*hurd_ihash_fct_cmp_t) (const void *, const void *); /* The type of the cleanup function, which is called for every value removed from the hash table. */ typedef void (*hurd_ihash_cleanup_t) (hurd_ihash_value_t value, void *arg); struct _hurd_ihash_item { /* The value of this hash item. Must be the first element of the struct for the HURD_IHASH_ITERATE macro. */ hurd_ihash_value_t value; /* The integer key of this hash item. */ hurd_ihash_key_t key; }; typedef struct _hurd_ihash_item *_hurd_ihash_item_t; struct hurd_ihash { /* The number of hashed elements. */ size_t nr_items; /* An array of (key, value) pairs. */ _hurd_ihash_item_t items; /* The length of the array ITEMS. */ size_t size; /* The offset of the location pointer from the hash value. */ intptr_t locp_offset; /* The maximum load factor in binary percent. */ unsigned int max_load; /* When freeing or overwriting an element, this function is called with the value as the first argument, and CLEANUP_DATA as the second argument. This does not happen if CLEANUP is NULL. */ hurd_ihash_cleanup_t cleanup; void *cleanup_data; /* User-supplied functions for the generalized key interface. */ hurd_ihash_fct_hash_t fct_hash; hurd_ihash_fct_cmp_t fct_cmp; }; typedef struct hurd_ihash *hurd_ihash_t; /* Construction and destruction of hash tables. */ /* The size of the initial allocation in number of items. This must be a power of two. */ #define HURD_IHASH_MIN_SIZE 32 /* The default value for the maximum load factor in binary percent. 96b% is equivalent to 75%, 128b% to 100%. */ #define HURD_IHASH_MAX_LOAD_DEFAULT 96 /* The LOCP_OFFS to use if no location pointer is available. */ #define HURD_IHASH_NO_LOCP INTPTR_MIN /* The static initializer for a struct hurd_ihash. */ #define HURD_IHASH_INITIALIZER(locp_offs) \ { .nr_items = 0, .size = 0, .cleanup = (hurd_ihash_cleanup_t) 0, \ .max_load = HURD_IHASH_MAX_LOAD_DEFAULT, \ .locp_offset = (locp_offs)} #define HURD_IHASH_INITIALIZER_GKI(locp_offs, f_clean, f_clean_data, \ f_hash, f_compare) \ { .nr_items = 0, .size = 0, \ .cleanup = (f_clean), \ .cleanup_data = (f_clean_data), \ .max_load = HURD_IHASH_MAX_LOAD_DEFAULT, \ .locp_offset = (locp_offs), \ .fct_hash = (f_hash), \ .fct_cmp = (f_compare)} \ /* Initialize the hash table at address HT. If LOCP_OFFSET is not HURD_IHASH_NO_LOCP, then this is an offset (in bytes) from the address of a hash value where a location pointer can be found. The location pointer must be of type hurd_ihash_locp_t and can be used for fast removal with hurd_ihash_locp_remove(). */ void hurd_ihash_init (hurd_ihash_t ht, intptr_t locp_offs); /* Destroy the hash table at address HT. This first removes all elements which are still in the hash table, and calling the cleanup function for them (if any). */ void hurd_ihash_destroy (hurd_ihash_t ht); /* Create a hash table, initialize it and return it in HT. If LOCP_OFFSET is not HURD_IHASH_NO_LOCP, then this is an offset (in bytes) from the address of a hash value where a location pointer can be found. The location pointer must be of type hurd_ihash_locp_t and can be used for fast removal with hurd_ihash_locp_remove(). If a memory allocation error occurs, ENOMEM is returned, otherwise 0. */ error_t hurd_ihash_create (hurd_ihash_t *ht, intptr_t locp_offs); /* Destroy the hash table HT and release the memory allocated for it by hurd_ihash_create(). */ void hurd_ihash_free (hurd_ihash_t ht); /* Configuration of the hash table. */ /* Set the cleanup function for the hash table HT to CLEANUP. The second argument to CLEANUP will be CLEANUP_DATA on every invocation. */ void hurd_ihash_set_cleanup (hurd_ihash_t ht, hurd_ihash_cleanup_t cleanup, void *cleanup_data); /* Use the generalized key interface. Must be called before any item is inserted into the table. */ void hurd_ihash_set_gki (hurd_ihash_t ht, hurd_ihash_fct_hash_t fct_hash, hurd_ihash_fct_cmp_t fct_cmp); /* Set the maximum load factor in binary percent to MAX_LOAD, which should be between 64 and 128. The default is HURD_IHASH_MAX_LOAD_DEFAULT. New elements are only added to the hash table while the number of hashed elements is that much binary percent of the total size of the hash table. If more elements are added, the hash table is first expanded and reorganized. A MAX_LOAD of 128 will always fill the whole table before enlarging it, but note that this will increase the cost of operations significantly when the table is almost full. If the value is set to a smaller value than the current load factor, the next reorganization will happen when a new item is added to the hash table. */ void hurd_ihash_set_max_load (hurd_ihash_t ht, unsigned int max_load); /* Get the current load factor of HT in binary percent, where 128b% corresponds to 100%. The reason we do this is that it is so efficient to compute: As the size is always a power of two, and 128 is also, the quotient of both is also a power of two. Therefore, we can use bit shifts to scale the number of items. load = nr_items * 128 / size = nr_items * 2^{log2 (128) - log2 (size)} = nr_items >> (log2 (size) - log2 (128)) -- if size >= 128 = nr_items << (log2 (128) - log2 (size)) -- otherwise If you want to convert this to percent, just divide by 1.28. */ static inline unsigned int hurd_ihash_get_load (hurd_ihash_t ht) { int d = __builtin_ctzl (ht->size) - 7; return d >= 0 ? ht->nr_items >> d : ht->nr_items << -d; } /* Add ITEM to the hash table HT under the key KEY. If there already is an item under this key, call the cleanup function (if any) for it before overriding the value. If a memory allocation error occurs, ENOMEM is returned, otherwise 0. */ error_t hurd_ihash_add (hurd_ihash_t ht, hurd_ihash_key_t key, hurd_ihash_value_t item); /* Add VALUE to the hash table HT under the key KEY at LOCP. If there already is an item under this key, call the cleanup function (if any) for it before overriding the value. This function is faster than hurd_ihash_add. If LOCP is NULL, fall back to hurd_ihash_add. Otherwise, LOCP must be valid and may either be obtained from hurd_ihash_locp_find, or from an item that is currently in the hash table. If an item is replaced, KEY must match the key of the previous item. If a memory allocation error occurs, ENOMEM is returned, otherwise 0. */ error_t hurd_ihash_locp_add (hurd_ihash_t ht, hurd_ihash_locp_t locp, hurd_ihash_key_t key, hurd_ihash_value_t value); /* Find and return the item in the hash table HT with key KEY, or NULL if it doesn't exist. */ hurd_ihash_value_t hurd_ihash_find (hurd_ihash_t ht, hurd_ihash_key_t key); /* Find and return the item in the hash table HT with key KEY, or NULL if it doesn't exist. If it is not found, this function may still return a location in SLOT. If the lookup is successful, the returned location can be used with hurd_ihash_locp_add to update the item, and with hurd_ihash_locp_remove to remove it. If the lookup is not successful, the returned location can be used with hurd_ihash_locp_add to add the item. Note that returned location is only valid until the next insertion or deletion. */ hurd_ihash_value_t hurd_ihash_locp_find (hurd_ihash_t ht, hurd_ihash_key_t key, hurd_ihash_locp_t *slot); /* Iterate over all elements in the hash table. You use this macro with a block, for example like this: error_t err; HURD_IHASH_ITERATE (ht, value) { err = foo (value); if (err) break; } if (err) cleanup_and_return (); Or even like this: HURD_IHASH_ITERATE (ht, value) foo (value); The block will be run for every element in the hash table HT. The value of the current element is available in the variable VALUE (which is declared for you and local to the block). */ /* The implementation of this macro is peculiar. We want the macro to execute a block following its invocation, so we can only prepend code. This excludes creating an outer block. However, we must define two variables: The hash value variable VALUE, and the loop variable. We can define variables inside the for-loop initializer (C99), but we can only use one basic type to do that. We can not use two for-loops, because we want a break statement inside the iterator block to terminate the operation. So we must have both variables of the same basic type, but we can make one (or both) of them a pointer type. The pointer to the value can be used as the loop variable. This is also the first element of the hash item, so we can cast the pointer freely between these two types. The pointer is only dereferenced after the loop condition is checked (but of course the value the pointer pointed to must not have an influence on the condition result, so the comma operator is used to make sure this subexpression is always true). */ #define HURD_IHASH_ITERATE(ht, val) \ for (hurd_ihash_value_t val, \ *_hurd_ihash_valuep = (ht)->size ? &(ht)->items[0].value : 0; \ (ht)->size \ && (size_t) ((_hurd_ihash_item_t) _hurd_ihash_valuep \ - &(ht)->items[0]) \ < (ht)->size \ && (val = *_hurd_ihash_valuep, 1); \ _hurd_ihash_valuep = (hurd_ihash_value_t *) \ (((_hurd_ihash_item_t) _hurd_ihash_valuep) + 1)) \ if (val != _HURD_IHASH_EMPTY && val != _HURD_IHASH_DELETED) /* Iterate over all elements in the hash table making both the key and the value available. You use this macro with a block, for example like this: HURD_IHASH_ITERATE_ITEMS (ht, item) foo (item->key, item->value); The block will be run for every element in the hash table HT. The key and value of the current element is available as ITEM->key and ITEM->value. */ #define HURD_IHASH_ITERATE_ITEMS(ht, item) \ for (_hurd_ihash_item_t item = (ht)->size? &(ht)->items[0]: 0; \ (ht)->size && item - &(ht)->items[0] < (ht)->size; \ item++) \ if (item->value != _HURD_IHASH_EMPTY && \ item->value != _HURD_IHASH_DELETED) /* Remove the entry with the key KEY from the hash table HT. If such an entry was found and removed, 1 is returned, otherwise 0. */ int hurd_ihash_remove (hurd_ihash_t ht, hurd_ihash_key_t key); /* Remove the entry pointed to by the location pointer LOCP from the hash table HT. LOCP is the location pointer of which the address was provided to hurd_ihash_add(). This call is faster than hurd_ihash_remove(). */ void hurd_ihash_locp_remove (hurd_ihash_t ht, hurd_ihash_locp_t locp); #endif /* _HURD_IHASH_H */