/*

 * Generic implementation of hash-based key value mappings.

 */

#include "git-compat-util.h"

#include "hashmap.h"

#define FNV32_BASE ((unsigned int) 0x811c9dc5)

#define FNV32_PRIME ((unsigned int) 0x01000193)

unsigned int strhash(const char *str)

{

  unsigned int c, hash = FNV32_BASE;

  while ((c = (unsigned char) *str++))

    hash = (hash * FNV32_PRIME) ^ c;

  return hash;

}

unsigned int strihash(const char *str)

{

  unsigned int c, hash = FNV32_BASE;

  while ((c = (unsigned char) *str++)) {

    if (c >= 'a' && c <= 'z')

      c -= 'a' - 'A';

    hash = (hash * FNV32_PRIME) ^ c;

  }

  return hash;

}

unsigned int memhash(const void *buf, size_t len)

{

  unsigned int hash = FNV32_BASE;

  unsigned char *ucbuf = (unsigned char *) buf;

  while (len--) {

    unsigned int c = *ucbuf++;

    hash = (hash * FNV32_PRIME) ^ c;

  }

  return hash;

}

unsigned int memihash(const void *buf, size_t len)

{

  unsigned int hash = FNV32_BASE;

  unsigned char *ucbuf = (unsigned char *) buf;

  while (len--) {

    unsigned int c = *ucbuf++;

    if (c >= 'a' && c <= 'z')

      c -= 'a' - 'A';

    hash = (hash * FNV32_PRIME) ^ c;

  }

  return hash;

}

/*

 * Incorporate another chunk of data into a memihash

 * computation.

 */

unsigned int memihash_cont(unsigned int hash_seed, const void *buf, size_t len)

{

  unsigned int hash = hash_seed;

  unsigned char *ucbuf = (unsigned char *) buf;

  while (len--) {

    unsigned int c = *ucbuf++;

    if (c >= 'a' && c <= 'z')

      c -= 'a' - 'A';

    hash = (hash * FNV32_PRIME) ^ c;

  }

  return hash;

}

#define HASHMAP_INITIAL_SIZE 64

/* grow / shrink by 2^2 */

#define HASHMAP_RESIZE_BITS 2

/* load factor in percent */

#define HASHMAP_LOAD_FACTOR 80

static void alloc_table(struct hashmap *map, unsigned int size)

{

  map->tablesize = size;

  CALLOC_ARRAY(map->table, size);

  /* calculate resize thresholds for new size */

  map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);

  if (size <= HASHMAP_INITIAL_SIZE)

    map->shrink_at = 0;

  else

    /*

     * The shrink-threshold must be slightly smaller than

     * (grow-threshold / resize-factor) to prevent erratic resizing,

     * thus we divide by (resize-factor + 1).

     */

    map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);

}

static inline int entry_equals(const struct hashmap *map,

             const struct hashmap_entry *e1,

             const struct hashmap_entry *e2,

             const void *keydata)

{

  return (e1 == e2) ||

         (e1->hash == e2->hash &&

    !map->cmpfn(map->cmpfn_data, e1, e2, keydata));

}

static inline unsigned int bucket(const struct hashmap *map,

          const struct hashmap_entry *key)

{

  return key->hash & (map->tablesize - 1);

}

int hashmap_bucket(const struct hashmap *map, unsigned int hash)

{

  return hash & (map->tablesize - 1);

}

static void rehash(struct hashmap *map, unsigned int newsize)

{

  /* map->table MUST NOT be NULL when this function is called */

  unsigned int i, oldsize = map->tablesize;

  struct hashmap_entry **oldtable = map->table;

  alloc_table(map, newsize);

  for (i = 0; i < oldsize; i++) {

    struct hashmap_entry *e = oldtable[i];

    while (e) {

      struct hashmap_entry *next = e->next;

      unsigned int b = bucket(map, e);

      e->next = map->table[b];

      map->table[b] = e;

      e = next;

    }

  }

  free(oldtable);

}

static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,

    const struct hashmap_entry *key, const void *keydata)

{

  /* map->table MUST NOT be NULL when this function is called */

  struct hashmap_entry **e = &map->table[bucket(map, key)];

  while (*e && !entry_equals(map, *e, key, keydata))

    e = &(*e)->next;

  return e;

}

static int always_equal(const void *cmp_data UNUSED,

      const struct hashmap_entry *entry1 UNUSED,

      const struct hashmap_entry *entry2 UNUSED,

      const void *keydata UNUSED)

{

  return 0;

}

void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,

      const void *cmpfn_data, size_t initial_size)

{

  unsigned int size = HASHMAP_INITIAL_SIZE;

  memset(map, 0, sizeof(*map));

  map->cmpfn = equals_function ? equals_function : always_equal;

  map->cmpfn_data = cmpfn_data;

  /* calculate initial table size and allocate the table */

  initial_size = (unsigned int) ((uint64_t) initial_size * 100

      / HASHMAP_LOAD_FACTOR);

  while (initial_size > size)

    size <<= HASHMAP_RESIZE_BITS;

  alloc_table(map, size);

  /*

   * Keep track of the number of items in the map and

   * allow the map to automatically grow as necessary.

   */

  map->do_count_items = 1;

}

static void free_individual_entries(struct hashmap *map, ssize_t entry_offset)

{

  struct hashmap_iter iter;

  struct hashmap_entry *e;

  hashmap_iter_init(map, &iter);

  while ((e = hashmap_iter_next(&iter)))

    /*

     * like container_of, but using caller-calculated

     * offset (caller being hashmap_clear_and_free)

     */

    free((char *)e - entry_offset);

}

void hashmap_partial_clear_(struct hashmap *map, ssize_t entry_offset)

{

  if (!map || !map->table)

    return;

  if (entry_offset >= 0)  /* called by hashmap_clear_entries */

    free_individual_entries(map, entry_offset);

  memset(map->table, 0, map->tablesize * sizeof(struct hashmap_entry *));

  map->shrink_at = 0;

  map->private_size = 0;

}

void hashmap_clear_(struct hashmap *map, ssize_t entry_offset)

{

  if (!map || !map->table)

    return;

  if (entry_offset >= 0)  /* called by hashmap_clear_and_free */

    free_individual_entries(map, entry_offset);

  free(map->table);

  memset(map, 0, sizeof(*map));

}

struct hashmap_entry *hashmap_get(const struct hashmap *map,

        const struct hashmap_entry *key,

        const void *keydata)

{

  if (!map->table)

    return NULL;

  return *find_entry_ptr(map, key, keydata);

}

struct hashmap_entry *hashmap_get_next(const struct hashmap *map,

               const struct hashmap_entry *entry)

{

  struct hashmap_entry *e = entry->next;

  for (; e; e = e->next)

    if (entry_equals(map, entry, e, NULL))

      return e;

  return NULL;

}

void hashmap_add(struct hashmap *map, struct hashmap_entry *entry)

{

  unsigned int b;

  if (!map->table)

    alloc_table(map, HASHMAP_INITIAL_SIZE);

  b = bucket(map, entry);

  /* add entry */

  entry->next = map->table[b];

  map->table[b] = entry;

  /* fix size and rehash if appropriate */

  if (map->do_count_items) {

    map->private_size++;

    if (map->private_size > map->grow_at)

      rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);

  }

}

struct hashmap_entry *hashmap_remove(struct hashmap *map,

             const struct hashmap_entry *key,

             const void *keydata)

{

  struct hashmap_entry *old;

  struct hashmap_entry **e;

  if (!map->table)

    return NULL;

  e = find_entry_ptr(map, key, keydata);

  if (!*e)

    return NULL;

  /* remove existing entry */

  old = *e;

  *e = old->next;

  old->next = NULL;

  /* fix size and rehash if appropriate */

  if (map->do_count_items) {

    map->private_size--;

    if (map->private_size < map->shrink_at)

      rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);

  }

  return old;

}

struct hashmap_entry *hashmap_put(struct hashmap *map,

          struct hashmap_entry *entry)

{

  struct hashmap_entry *old = hashmap_remove(map, entry, NULL);

  hashmap_add(map, entry);

  return old;

}

void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)

{

  iter->map = map;

  iter->tablepos = 0;

  iter->next = NULL;

}

struct hashmap_entry *hashmap_iter_next(struct hashmap_iter *iter)

{

  struct hashmap_entry *current = iter->next;

  for (;;) {

    if (current) {

      iter->next = current->next;

      return current;

    }

    if (iter->tablepos >= iter->map->tablesize)

      return NULL;

    current = iter->map->table[iter->tablepos++];

  }

}

struct pool_entry {

  struct hashmap_entry ent;

  size_t len;

  unsigned char data[FLEX_ARRAY];

};

static int pool_entry_cmp(const void *cmp_data UNUSED,

        const struct hashmap_entry *eptr,

        const struct hashmap_entry *entry_or_key,

        const void *keydata)

{

  const struct pool_entry *e1, *e2;

  e1 = container_of(eptr, const struct pool_entry, ent);

  e2 = container_of(entry_or_key, const struct pool_entry, ent);

  return e1->data != keydata &&

         (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));

}

const void *memintern(const void *data, size_t len)

{

  static struct hashmap map;

  struct pool_entry key, *e;

  /* initialize string pool hashmap */

  if (!map.tablesize)

    hashmap_init(&map, pool_entry_cmp, NULL, 0);

  /* lookup interned string in pool */

  hashmap_entry_init(&key.ent, memhash(data, len));

  key.len = len;

  e = hashmap_get_entry(&map, &key, ent, data);

  if (!e) {

    /* not found: create it */

    FLEX_ALLOC_MEM(e, data, data, len);

    hashmap_entry_init(&e->ent, key.ent.hash);

    e->len = len;

    hashmap_add(&map, &e->ent);

  }

  return e->data;

}