json-c: linkhash.h File Reference

json-c 0.19

Data Structures | Macros | Typedefs | Functions
linkhash.h File Reference

Internal methods for working with json_type_object objects. Although this is exposed by the json_object_get_object() function and within the json_object_iter type, it is not recommended for direct use. More...

## Data Structures
struct | lh_entry
struct | lh_table

## Macros
#define | LH_PRIME 0x9e370001UL
#define | LH_LOAD_FACTOR 0.66
#define | LH_EMPTY (void *)-1
#define | LH_FREED (void *)-2
#define | JSON_C_STR_HASH_DFLT 0
#define | JSON_C_STR_HASH_PERLLIKE 1
#define | lh_foreach(table, entry) for (entry = lh_table_head(table); entry; entry = lh_entry_next(entry))
#define | lh_foreach_safe(table, entry, tmp) for (entry = lh_table_head(table); entry && ((tmp = lh_entry_next(entry)) || 1); entry = tmp)

## Typedefs
typedef void() | lh_entry_free_fn(struct lh_entry *e)
typedef unsigned long() | lh_hash_fn(const void *k)
typedef int() | lh_equal_fn(const void *k1, const void *k2)
typedef struct lh_table | lh_table

## Functions
int | json_global_set_string_hash (const int h)
struct lh_table * | lh_table_new (int size, lh_entry_free_fn *free_fn, lh_hash_fn *hash_fn, lh_equal_fn *equal_fn)
struct lh_table * | lh_kchar_table_new (int size, lh_entry_free_fn *free_fn)
struct lh_table * | lh_kptr_table_new (int size, lh_entry_free_fn *free_fn)
void | lh_table_free (struct lh_table *t)
int | lh_table_insert (struct lh_table *t, const void *k, const void *v)
int | lh_table_insert_w_hash (struct lh_table *t, const void *k, const void *v, const unsigned long h, const unsigned opts)
struct lh_entry * | lh_table_lookup_entry (struct lh_table *t, const void *k)
struct lh_entry * | lh_table_lookup_entry_w_hash (struct lh_table *t, const void *k, const unsigned long h)
json_bool | lh_table_lookup_ex (struct lh_table *t, const void *k, void **v)
int | lh_table_delete_entry (struct lh_table *t, struct lh_entry *e)
int | lh_table_delete_entry_to_tail (struct lh_table *t, struct lh_entry *e)
int | lh_table_delete (struct lh_table *t, const void *k)
int | lh_table_length (struct lh_table *t)
int | lh_table_resize (struct lh_table *t, int new_size)
static struct lh_entry * | lh_table_head (const lh_table *t)
static unsigned long | lh_get_hash (const struct lh_table *t, const void *k)
static void * | lh_entry_k (const struct lh_entry *e)
static int | lh_entry_k_is_constant (const struct lh_entry *e)
static void * | lh_entry_v (const struct lh_entry *e)
static void | lh_entry_set_val (struct lh_entry *e, void *newval)
static struct lh_entry * | lh_entry_next (const struct lh_entry *e)
static struct lh_entry * | lh_entry_prev (const struct lh_entry *e)

## Detailed Description

Internal methods for working with json_type_object objects. Although this is exposed by the json_object_get_object() function and within the json_object_iter type, it is not recommended for direct use.

## Macro Definition Documentation

## ◆ JSON_C_STR_HASH_DFLT

#define JSON_C_STR_HASH_DFLT 0

default string hash function

## ◆ JSON_C_STR_HASH_PERLLIKE

#define JSON_C_STR_HASH_PERLLIKE 1

perl-like string hash function

## ◆ LH_EMPTY

#define LH_EMPTY (void *)-1

sentinel pointer value for empty slots

## ◆ lh_foreach

#define lh_foreach | ( |  | table,
|  |  | entry
| ) |  | for (entry = lh_table_head(table); entry; entry = lh_entry_next(entry))

Convenience list iterator.

## ◆ lh_foreach_safe

#define lh_foreach_safe | ( |  | table,
|  |  | entry,
|  |  | tmp
| ) |  | for (entry = lh_table_head(table); entry && ((tmp = lh_entry_next(entry)) || 1); entry = tmp)

lh_foreach_safe allows calling of deletion routine while iterating.

Parameters

  table | a struct lh_table * to iterate over
  entry | a struct lh_entry * variable to hold each element
  tmp | a struct lh_entry * variable to hold a temporary pointer to the next element

## ◆ LH_FREED

#define LH_FREED (void *)-2

sentinel pointer value for freed slots

## ◆ LH_LOAD_FACTOR

#define LH_LOAD_FACTOR 0.66

The fraction of filled hash buckets until an insert will cause the table to be resized. This can range from just above 0 up to 1.0.

## ◆ LH_PRIME

#define LH_PRIME 0x9e370001UL

golden prime used in hash functions

## Typedef Documentation

## ◆ lh_entry_free_fn

typedef void() lh_entry_free_fn(struct lh_entry *e)

callback function prototypes

## ◆ lh_equal_fn

typedef int() lh_equal_fn(const void *k1, const void *k2)

callback function prototypes

## ◆ lh_hash_fn

typedef unsigned long() lh_hash_fn(const void *k)

callback function prototypes

## ◆ lh_table

typedef struct lh_table lh_table

## Function Documentation

## ◆ json_global_set_string_hash()

int json_global_set_string_hash | ( | const int | h | ) |

This function sets the hash function to be used for strings. Must be one of the JSON_C_STR_HASH_* values.

Returns
  0 - ok, -1 if parameter was invalid

## ◆ lh_entry_k()

static void * lh_entry_k | ( | const struct lh_entry * | e | ) |
| inlinestatic

Return a non-const version of lh_entry.k.

lh_entry.k is const to indicate and help ensure that linkhash itself doesn't modify it, but callers are allowed to do what they want with it.

See also
  lh_entry_k_is_constant()

References lh_entry::k.

## ◆ lh_entry_k_is_constant()

static int lh_entry_k_is_constant | ( | const struct lh_entry * | e | ) |
| inlinestatic

Returns 1 if the key for the given entry is constant, and thus does not need to be freed when the lh_entry is freed.

See also
  lh_table_insert_w_hash()

References lh_entry::k_is_constant.

## ◆ lh_entry_next()

static struct lh_entry * lh_entry_next | ( | const struct lh_entry * | e | ) |
| inlinestatic

Return the next element, or NULL if there is no next element.

See also
  lh_table_head()
  lh_entry_prev()

References lh_entry::next.

## ◆ lh_entry_prev()

static struct lh_entry * lh_entry_prev | ( | const struct lh_entry * | e | ) |
| inlinestatic

Return the previous element, or NULL if there is no previous element.

See also
  lh_table_head()
  lh_entry_next()

References lh_entry::prev.

## ◆ lh_entry_set_val()

static void lh_entry_set_val | ( | struct lh_entry * | e,
|  | void * | newval
| ) |  |
| inlinestatic

Change the value for an entry. The caller is responsible for freeing the previous value.

References lh_entry::v.

## ◆ lh_entry_v()

static void * lh_entry_v | ( | const struct lh_entry * | e | ) |
| inlinestatic

Return a non-const version of lh_entry.v.

v is const to indicate and help ensure that linkhash itself doesn't modify it, but callers are allowed to do what they want with it.

References lh_entry::v.

## ◆ lh_get_hash()

static unsigned long lh_get_hash | ( | const struct lh_table * | t,
|  | const void * | k
| ) |  |
| inlinestatic

Calculate the hash of a key for a given table.

This is an extension to support functions that need to calculate the hash several times and allows them to do it just once and then pass in the hash to all utility functions. Depending on use case, this can be a considerable performance improvement.

Parameters

  t | the table (used to obtain hash function)
  k | a pointer to the key to lookup

Returns
  the key's hash

References lh_table::hash_fn, and lh_entry::k.

## ◆ lh_kchar_table_new()

struct lh_table * lh_kchar_table_new | ( | int | size,
|  | lh_entry_free_fn * | free_fn
| ) |  |
| extern

Convenience function to create a new linkhash table with char keys.

Parameters

  size | initial table size.
  free_fn | callback function used to free memory for entries.

Returns
  On success, a pointer to the new linkhash table is returned. On error, a null pointer is returned.

## ◆ lh_kptr_table_new()

struct lh_table * lh_kptr_table_new | ( | int | size,
|  | lh_entry_free_fn * | free_fn
| ) |  |
| extern

Convenience function to create a new linkhash table with ptr keys.

Parameters

  size | initial table size.
  free_fn | callback function used to free memory for entries.

Returns
  On success, a pointer to the new linkhash table is returned. On error, a null pointer is returned.

## ◆ lh_table_delete()

int lh_table_delete | ( | struct lh_table * | t,
|  | const void * | k
| ) |  |
| extern

Delete a record from the table.

If a callback free function is provided then it is called for the for the item being deleted.

Parameters

  t | the table to delete from.
  k | a pointer to the key to delete.

Returns
  0 if the item was deleted.
  -1 if it was not found.

## ◆ lh_table_delete_entry()

int lh_table_delete_entry | ( | struct lh_table * | t,
|  | struct lh_entry * | e
| ) |  |
| extern

Delete a record from the table.

If a callback free function is provided then it is called for the for the item being deleted.

Parameters

  t | the table to delete from.
  e | a pointer to the entry to delete.

Returns
  0 if the item was deleted.
  -1 if it was not found.

## ◆ lh_table_delete_entry_to_tail()

int lh_table_delete_entry_to_tail | ( | struct lh_table * | t,
|  | struct lh_entry * | e
| ) |  |
| extern

Delete all entries from the specified one to the tail of the list. Same as calling lh_table_delete_entry() on each of them.

Parameters

  t | the table to delete from.
  e | a pointer to the first entry to delete.

Returns
  0 if the item was deleted.
  -1 if it was not found.

## ◆ lh_table_free()

void lh_table_free | ( | struct lh_table * | t | ) |
| extern

Free a linkhash table.

If a lh_entry_free_fn callback free function was provided then it is called for all entries in the table.

Parameters

  t | table to free.

## ◆ lh_table_head()

static struct lh_entry * lh_table_head | ( | const lh_table * | t | ) |
| inlinestatic

Return the first entry in the lh_table.

See also
  lh_entry_next()

References lh_table::head.

## ◆ lh_table_insert()

int lh_table_insert | ( | struct lh_table * | t,
|  | const void * | k,
|  | const void * | v
| ) |  |
| extern

Insert a record into the table.

Parameters

  t | the table to insert into.
  k | a pointer to the key to insert.
  v | a pointer to the value to insert.

Returns
  On success, `0` is returned. On error, a negative value is returned.

## ◆ lh_table_insert_w_hash()

int lh_table_insert_w_hash | ( | struct lh_table * | t,
|  | const void * | k,
|  | const void * | v,
|  | const unsigned long | h,
|  | const unsigned | opts
| ) |  |
| extern

Insert a record into the table using a precalculated key hash.

The hash h, which should be calculated with lh_get_hash() on k, is provided by the caller, to allow for optimization when multiple operations with the same key are known to be needed.

Parameters

  t | the table to insert into.
  k | a pointer to the key to insert.
  v | a pointer to the value to insert.
  h | hash value of the key to insert
  opts | if set to JSON_C_OBJECT_ADD_CONSTANT_KEY, sets lh_entry.k_is_constant so t's free function knows to avoid freeing the key.

## ◆ lh_table_length()

int lh_table_length | ( | struct lh_table * | t | ) |
| extern

Return the number of entries in the table.

## ◆ lh_table_lookup_entry()

struct lh_entry * lh_table_lookup_entry | ( | struct lh_table * | t,
|  | const void * | k
| ) |  |
| extern

Lookup a record in the table.

Parameters

  t | the table to lookup
  k | a pointer to the key to lookup

Returns
  a pointer to the record structure of the value or NULL if it does not exist.

## ◆ lh_table_lookup_entry_w_hash()

struct lh_entry * lh_table_lookup_entry_w_hash | ( | struct lh_table * | t,
|  | const void * | k,
|  | const unsigned long | h
| ) |  |
| extern

Lookup a record in the table using a precalculated key hash.

The hash h, which should be calculated with lh_get_hash() on k, is provided by the caller, to allow for optimization when multiple operations with the same key are known to be needed.

Parameters

  t | the table to lookup
  k | a pointer to the key to lookup
  h | hash value of the key to lookup

Returns
  a pointer to the record structure of the value or NULL if it does not exist.

## ◆ lh_table_lookup_ex()

json_bool lh_table_lookup_ex | ( | struct lh_table * | t,
|  | const void * | k,
|  | void ** | v
| ) |  |
| extern

Lookup a record in the table.

Parameters

  t | the table to lookup
  k | a pointer to the key to lookup
  v | a pointer to a where to store the found value (set to NULL if it doesn't exist).

Returns
  whether or not the key was found

## ◆ lh_table_new()

struct lh_table * lh_table_new | ( | int | size,
|  | lh_entry_free_fn * | free_fn,
|  | lh_hash_fn * | hash_fn,
|  | lh_equal_fn * | equal_fn
| ) |  |
| extern

Create a new linkhash table.

Parameters

  size | initial table size. The table is automatically resized although this incurs a performance penalty.
  free_fn | callback function used to free memory for entries when lh_table_free or lh_table_delete is called. If NULL is provided, then memory for keys and values must be freed by the caller.
  hash_fn | function used to hash keys. 2 standard ones are defined: lh_ptr_hash and lh_char_hash for hashing pointer values and C strings respectively.
  equal_fn | comparison function to compare keys. 2 standard ones defined: lh_ptr_hash and lh_char_hash for comparing pointer values and C strings respectively.

Returns
  On success, a pointer to the new linkhash table is returned. On error, a null pointer is returned.

## ◆ lh_table_resize()

int lh_table_resize | ( | struct lh_table * | t,
|  | int | new_size
| ) |  |

Resizes the specified table.

Parameters

  t | Pointer to table to resize.
  new_size | New table size. Must be positive.

Returns
  On success, `0` is returned. On error, a negative value is returned.