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#pragma once
#include <stddef.h>
/// Type for hash number (hash calculation result).
typedef size_t hash_T;
/// Hashtable item.
///
/// Each item has a NUL terminated string key.
/// A key can appear only once in the table.
///
/// A hash number is computed from the key for quick lookup. When the hashes
/// of two different keys point to the same entry an algorithm is used to
/// iterate over other entries in the table until the right one is found.
/// To make the iteration work removed keys are different from entries where a
/// key was never present.
///
/// Note that this does not contain a pointer to the key and another pointer to
/// the value. Instead, it is assumed that the key is contained within the
/// value, so that you can get a pointer to the value subtracting an offset from
/// the pointer to the key.
/// This reduces the size of this item by 1/3.
typedef struct {
/// Cached hash number for hi_key.
hash_T hi_hash;
/// Item key.
///
/// Possible values mean the following:
/// NULL : Item was never used.
/// HI_KEY_REMOVED : Item was removed.
/// (Any other pointer value) : Item is currently being used.
char *hi_key;
} hashitem_T;
enum {
/// Initial size for a hashtable.
/// Our items are relatively small and growing is expensive, thus start with 16.
/// Must be a power of 2.
/// This allows for storing 10 items (2/3 of 16) before a resize is needed.
HT_INIT_SIZE = 16,
};
/// An array-based hashtable.
///
/// Keys are NUL terminated strings. They cannot be repeated within a table.
/// Values are of any type.
///
/// The hashtable grows to accommodate more entries when needed.
typedef struct {
hash_T ht_mask; ///< mask used for hash value
///< (nr of items in array is "ht_mask" + 1)
size_t ht_used; ///< number of items used
size_t ht_filled; ///< number of items used or removed
int ht_changed; ///< incremented when adding or removing an item
int ht_locked; ///< counter for hash_lock()
hashitem_T *ht_array; ///< points to the array, allocated when it's
///< not "ht_smallarray"
hashitem_T ht_smallarray[HT_INIT_SIZE]; ///< initial array
} hashtab_T;
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