/*

 * SHL - Dynamic hash-table

 *

 * Written-by: Rusty Russell <rusty@rustcorp.com.au>

 * Adjusted-by: David Herrmann <dh.herrmann@gmail.com>

 * Licensed under LGPLv2+ - see LICENSE_htable file for details

 */

/*

 * Please see ccan/htable/_info at:

 *   https://github.com/rustyrussell/ccan/tree/master/ccan/htable

 * for information on the hashtable algorithm. This file copies the code inline

 * and is released under the same conditions.

 *

 * At the end of the file you can find some helpers to use this htable to store

 * objects with "unsigned long" or "char*" keys.

 */

#include <assert.h>

#include <errno.h>

#include <limits.h>

#include <stdbool.h>

#include <stdint.h>

#include <stdlib.h>

#include <string.h>

#include "shl-htable.h"

#define COLD __attribute__((cold))

struct htable {

  /* KEEP IN SYNC WITH "struct shl_htable_int" */

  size_t (*rehash)(const void *elem, void *priv);

  void *priv;

  unsigned int bits;

  size_t elems, deleted, max, max_with_deleted;

  /* These are the bits which are the same in all pointers. */

  uintptr_t common_mask, common_bits;

  uintptr_t perfect_bit;

  uintptr_t *table;

};

#define HTABLE_INITIALIZER(name, rehash, priv)        \

  { rehash, priv, 0, 0, 0, 0, 0, -1, 0, 0, &name.perfect_bit }

struct htable_iter {

  size_t off;

};

/*

 * INLINE COPY OF ccan/htable.c

 */

/* We use 0x1 as deleted marker. */

#define HTABLE_DELETED (0x1)

/* We clear out the bits which are always the same, and put metadata there. */

static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,

             uintptr_t e)

{

  return e & ht->common_mask;

}

static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)

{

  return (void *)((e & ~ht->common_mask) | ht->common_bits);

}

static inline uintptr_t make_hval(const struct htable *ht,

          const void *p, uintptr_t bits)

{

  return ((uintptr_t)p & ~ht->common_mask) | bits;

}

static inline bool entry_is_valid(uintptr_t e)

{

  return e > HTABLE_DELETED;

}

static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,

            size_t hash)

{

  /* Shuffling the extra bits (as specified in mask) down the

   * end is quite expensive.  But the lower bits are redundant, so

   * we fold the value first. */

  return (hash ^ (hash >> ht->bits))

    & ht->common_mask & ~ht->perfect_bit;

}

static void htable_init(struct htable *ht,

      size_t (*rehash)(const void *elem, void *priv),

      void *priv)

{

  struct htable empty = HTABLE_INITIALIZER(empty, NULL, NULL);

  *ht = empty;

  ht->rehash = rehash;

  ht->priv = priv;

  ht->table = &ht->perfect_bit;

}

static void htable_clear(struct htable *ht,

       void (*free_cb) (void *entry, void *ctx),

       void *ctx)

{

  size_t i;

  if (ht->table != &ht->perfect_bit) {

    if (free_cb) {

      for (i = 0; i < (size_t)1 << ht->bits; ++i) {

        if (entry_is_valid(ht->table[i]))

          free_cb(get_raw_ptr(ht, ht->table[i]),

            ctx);

      }

    }

    free((void *)ht->table);

  }

  htable_init(ht, ht->rehash, ht->priv);

}

static void htable_visit(struct htable *ht,

       void (*visit_cb) (void *elem, void *ctx),

       void *ctx)

{

  size_t i;

  if (visit_cb && ht->table != &ht->perfect_bit) {

    for (i = 0; i < (size_t)1 << ht->bits; ++i) {

      if (entry_is_valid(ht->table[i]))

        visit_cb(get_raw_ptr(ht, ht->table[i]), ctx);

    }

  }

}

static size_t hash_bucket(const struct htable *ht, size_t h)

{

  return h & ((1 << ht->bits)-1);

}

static void *htable_val(const struct htable *ht,

      struct htable_iter *i, size_t hash, uintptr_t perfect)

{

  uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect;

  while (ht->table[i->off]) {

    if (ht->table[i->off] != HTABLE_DELETED) {

      if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)

        return get_raw_ptr(ht, ht->table[i->off]);

    }

    i->off = (i->off + 1) & ((1 << ht->bits)-1);

    h2 &= ~perfect;

  }

  return NULL;

}

static void *htable_firstval(const struct htable *ht,

           struct htable_iter *i, size_t hash)

{

  i->off = hash_bucket(ht, hash);

  return htable_val(ht, i, hash, ht->perfect_bit);

}

static void *htable_nextval(const struct htable *ht,

          struct htable_iter *i, size_t hash)

{

  i->off = (i->off + 1) & ((1 << ht->bits)-1);

  return htable_val(ht, i, hash, 0);

}

/* This does not expand the hash table, that's up to caller. */

static void ht_add(struct htable *ht, const void *new, size_t h)

{

  size_t i;

  uintptr_t perfect = ht->perfect_bit;

  i = hash_bucket(ht, h);

  while (entry_is_valid(ht->table[i])) {

    perfect = 0;

    i = (i + 1) & ((1 << ht->bits)-1);

  }

  ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);

}

static COLD bool double_table(struct htable *ht)

{

  unsigned int i;

  size_t oldnum = (size_t)1 << ht->bits;

  uintptr_t *oldtable, e;

  oldtable = ht->table;

  ht->table = calloc(1 << (ht->bits+1), sizeof(size_t));

  if (!ht->table) {

    ht->table = oldtable;

    return false;

  }

  ht->bits++;

  ht->max = ((size_t)3 << ht->bits) / 4;

  ht->max_with_deleted = ((size_t)9 << ht->bits) / 10;

  /* If we lost our "perfect bit", get it back now. */

  if (!ht->perfect_bit && ht->common_mask) {

    for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) {

      if (ht->common_mask & ((size_t)1 << i)) {

        ht->perfect_bit = (size_t)1 << i;

        break;

      }

    }

  }

  if (oldtable != &ht->perfect_bit) {

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

      if (entry_is_valid(e = oldtable[i])) {

        void *p = get_raw_ptr(ht, e);

        ht_add(ht, p, ht->rehash(p, ht->priv));

      }

    }

    free(oldtable);

  }

  ht->deleted = 0;

  return true;

}

static COLD void rehash_table(struct htable *ht)

{

  size_t start, i;

  uintptr_t e;

  /* Beware wrap cases: we need to start from first empty bucket. */

  for (start = 0; ht->table[start]; start++);

  for (i = 0; i < (size_t)1 << ht->bits; i++) {

    size_t h = (i + start) & ((1 << ht->bits)-1);

    e = ht->table[h];

    if (!e)

      continue;

    if (e == HTABLE_DELETED)

      ht->table[h] = 0;

    else if (!(e & ht->perfect_bit)) {

      void *p = get_raw_ptr(ht, e);

      ht->table[h] = 0;

      ht_add(ht, p, ht->rehash(p, ht->priv));

    }

  }

  ht->deleted = 0;

}

/* We stole some bits, now we need to put them back... */

static COLD void update_common(struct htable *ht, const void *p)

{

  unsigned int i;

  uintptr_t maskdiff, bitsdiff;

  if (ht->elems == 0) {

    /* Always reveal one bit of the pointer in the bucket,

     * so it's not zero or HTABLE_DELETED (1), even if

     * hash happens to be 0.  Assumes (void *)1 is not a

     * valid pointer. */

    for (i = sizeof(uintptr_t)*CHAR_BIT - 1; i > 0; i--) {

      if ((uintptr_t)p & ((uintptr_t)1 << i))

        break;

    }

    ht->common_mask = ~((uintptr_t)1 << i);

    ht->common_bits = ((uintptr_t)p & ht->common_mask);

    ht->perfect_bit = 1;

    return;

  }

  /* Find bits which are unequal to old common set. */

  maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);

  /* These are the bits which go there in existing entries. */

  bitsdiff = ht->common_bits & maskdiff;

  for (i = 0; i < (size_t)1 << ht->bits; i++) {

    if (!entry_is_valid(ht->table[i]))

      continue;

    /* Clear the bits no longer in the mask, set them as

     * expected. */

    ht->table[i] &= ~maskdiff;

    ht->table[i] |= bitsdiff;

  }

  /* Take away those bits from our mask, bits and perfect bit. */

  ht->common_mask &= ~maskdiff;

  ht->common_bits &= ~maskdiff;

  ht->perfect_bit &= ~maskdiff;

}

static bool htable_add(struct htable *ht, size_t hash, const void *p)

{

  if (ht->elems+1 > ht->max && !double_table(ht))

    return false;

  if (ht->elems+1 + ht->deleted > ht->max_with_deleted)

    rehash_table(ht);

  assert(p);

  if (((uintptr_t)p & ht->common_mask) != ht->common_bits)

    update_common(ht, p);

  ht_add(ht, p, hash);

  ht->elems++;

  return true;

}

static void htable_delval(struct htable *ht, struct htable_iter *i)

{

  assert(i->off < (size_t)1 << ht->bits);

  assert(entry_is_valid(ht->table[i->off]));

  ht->elems--;

  ht->table[i->off] = HTABLE_DELETED;

  ht->deleted++;

}

/*

 * Wrapper code to make it easier to use this hash-table as map.

 */

void shl_htable_init(struct shl_htable *htable,

         bool (*compare) (const void *a, const void *b),

         size_t (*rehash)(const void *elem, void *priv),

         void *priv)

{

  struct htable *ht = (void*)&htable->htable;

  htable->compare = compare;

  htable_init(ht, rehash, priv);

}

void shl_htable_clear(struct shl_htable *htable,

          void (*free_cb) (void *elem, void *ctx),

          void *ctx)

{

  struct htable *ht = (void*)&htable->htable;

  htable_clear(ht, free_cb, ctx);

}

void shl_htable_visit(struct shl_htable *htable,

          void (*visit_cb) (void *elem, void *ctx),

          void *ctx)

{

  struct htable *ht = (void*)&htable->htable;

  htable_visit(ht, visit_cb, ctx);

}

bool shl_htable_lookup(struct shl_htable *htable, const void *obj, size_t hash,

           void **out)

{

  struct htable *ht = (void*)&htable->htable;

  struct htable_iter i;

  void *c;

  for (c = htable_firstval(ht, &i, hash);

       c;

       c = htable_nextval(ht, &i, hash)) {

    if (htable->compare(obj, c)) {

      if (out)

        *out = c;

      return true;

    }

  }

  return false;

}

int shl_htable_insert(struct shl_htable *htable, const void *obj, size_t hash)

{

  struct htable *ht = (void*)&htable->htable;

  bool b;

  b = htable_add(ht, hash, (void*)obj);

  return b ? 0 : -ENOMEM;

}

bool shl_htable_remove(struct shl_htable *htable, const void *obj, size_t hash,

           void **out)

{

  struct htable *ht = (void*)&htable->htable;

  struct htable_iter i;

  void *c;

  for (c = htable_firstval(ht, &i, hash);

       c;

       c = htable_nextval(ht, &i, hash)) {

    if (htable->compare(obj, c)) {

      if (out)

        *out = c;

      htable_delval(ht, &i);

      return true;

    }

  }

  return false;

}

/*

 * Helpers

 */

bool shl_htable_compare_ulong(const void *a, const void *b)

{

  return *(const unsigned long*)a == *(const unsigned long*)b;

}

size_t shl_htable_rehash_ulong(const void *elem, void *priv)

{

  return (size_t)*(const unsigned long*)elem;

}

bool shl_htable_compare_str(const void *a, const void *b)

{

  return !strcmp(*(char**)a, *(char**)b);

}

/* DJB's hash function */

size_t shl_htable_rehash_str(const void *elem, void *priv)

{

  const char *str = *(char**)elem;

  size_t hash = 5381;

  for ( ; *str; ++str)

    hash = (hash << 5) + hash + (size_t)*str;

  return hash;

}