/*

 * nghttp2 - HTTP/2 C Library

 *

 * Copyright (c) 2017 ngtcp2 contributors

 * Copyright (c) 2012 nghttp2 contributors

 *

 * Permission is hereby granted, free of charge, to any person obtaining

 * a copy of this software and associated documentation files (the

 * "Software"), to deal in the Software without restriction, including

 * without limitation the rights to use, copy, modify, merge, publish,

 * distribute, sublicense, and/or sell copies of the Software, and to

 * permit persons to whom the Software is furnished to do so, subject to

 * the following conditions:

 *

 * The above copyright notice and this permission notice shall be

 * included in all copies or substantial portions of the Software.

 *

 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,

 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF

 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND

 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE

 * LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION

 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION

 * WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

 */

#include "nghttp2_map.h"

#include <string.h>

#include <assert.h>

#include <stdio.h>

#include "nghttp2_helper.h"

#define NGHTTP2_INITIAL_HASHBITS 4

void nghttp2_map_init(nghttp2_map *map, uint64_t seed, nghttp2_mem *mem) {

  *map = (nghttp2_map){

    .mem = mem,

    .seed = seed,

  };

}

void nghttp2_map_free(nghttp2_map *map) {

  if (!map) {

    return;

  }

  nghttp2_mem_free(map->mem, map->keys);

}

int nghttp2_map_each(const nghttp2_map *map, int (*func)(void *data, void *ptr),

                     void *ptr) {

  int rv;

  size_t i;

  size_t tablelen;

  if (map->size == 0) {

    return 0;

  }

  tablelen = (size_t)1 << map->hashbits;

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

    if (map->psl[i] == 0) {

      continue;

    }

    rv = func(map->data[i], ptr);

    if (rv != 0) {

      return rv;

    }

  }

  return 0;

}

/* Hasher from

   https://github.com/rust-lang/rustc-hash/blob/dc5c33f1283de2da64d8d7a06401d91aded03ad4/src/lib.rs

   to maximize the output's sensitivity to all input bits. */

#define NGHTTP2_MAP_HASHER 0xF1357AEA2E62A9C5ULL

/* 64-bit Fibonacci hashing constant, Golden Ratio constant, to get

   the high bits with the good distribution. */

#define NGHTTP2_MAP_FIBO 0x9E3779B97F4A7C15ULL

static size_t map_index(const nghttp2_map *map, nghttp2_map_key_type key32) {

  uint64_t key = (uint64_t)key32;

  key += map->seed;

  key *= NGHTTP2_MAP_HASHER;

  return (size_t)((key * NGHTTP2_MAP_FIBO) >> (64 - map->hashbits));

}

#ifndef WIN32

void nghttp2_map_print_distance(const nghttp2_map *map) {

  size_t i;

  size_t idx;

  size_t tablelen;

  if (map->size == 0) {

    return;

  }

  tablelen = (size_t)1 << map->hashbits;

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

    if (map->psl[i] == 0) {

      fprintf(stderr, "@%zu <EMPTY>\n", i);

      continue;

    }

    idx = map_index(map, map->keys[i]);

    fprintf(stderr, "@%zu key=%d base=%zu distance=%u\n", i, map->keys[i], idx,

            map->psl[i] - 1);

  }

}

#endif /* !defined(WIN32) */

static void map_set_entry(nghttp2_map *map, size_t idx,

                          nghttp2_map_key_type key, void *data, size_t psl) {

  map->keys[idx] = key;

  map->data[idx] = data;

  map->psl[idx] = (uint8_t)psl;

}

#define NGHTTP2_SWAP(TYPE, A, B)                                               \

  do {                                                                         \

    TYPE t = (TYPE) * (A);                                                     \

                                                                               \

    *(A) = *(B);                                                               \

    *(B) = t;                                                                  \

  } while (0)

/*

 * map_insert inserts |key| and |data| to |map|, and returns the index

 * where the pair is stored if it succeeds.  Otherwise, it returns one

 * of the following negative error codes:

 *

 * NGHTTP2_ERR_INVALID_ARGUMENT

 *     The another data associated to |key| is already present.

 */

static nghttp2_ssize map_insert(nghttp2_map *map, nghttp2_map_key_type key,

                                void *data) {

  size_t idx = map_index(map, key);

  size_t mask = ((size_t)1 << map->hashbits) - 1;

  size_t psl = 1;

  size_t kpsl;

  for (;;) {

    kpsl = map->psl[idx];

    if (kpsl == 0) {

      map_set_entry(map, idx, key, data, psl);

      ++map->size;

      return (nghttp2_ssize)idx;

    }

    if (psl > kpsl) {

      NGHTTP2_SWAP(nghttp2_map_key_type, &key, &map->keys[idx]);

      NGHTTP2_SWAP(void *, &data, &map->data[idx]);

      NGHTTP2_SWAP(uint8_t, &psl, &map->psl[idx]);

    } else if (map->keys[idx] == key) {

      /* This check ensures that no duplicate keys are inserted.  But

         it is just a waste after first swap or if this function is

         called from map_resize.  That said, there is no difference

         with or without this conditional in performance wise. */

      return NGHTTP2_ERR_INVALID_ARGUMENT;

    }

    ++psl;

    idx = (idx + 1) & mask;

  }

}

/* NGHTTP2_MAP_MAX_HASHBITS is the maximum number of bits used for

   hash table.  The theoretical limit of the maximum number of keys

   that can be stored is 1 << NGHTTP2_MAP_MAX_HASHBITS. */

#define NGHTTP2_MAP_MAX_HASHBITS (sizeof(size_t) * 8 - 1)

static int map_resize(nghttp2_map *map, size_t new_hashbits) {

  size_t i;

  size_t tablelen;

  nghttp2_ssize idx;

  nghttp2_map new_map = {

    .mem = map->mem,

    .seed = map->seed,

    .hashbits = new_hashbits,

  };

  void *buf;

  (void)idx;

  if (new_hashbits > NGHTTP2_MAP_MAX_HASHBITS) {

    return NGHTTP2_ERR_NOMEM;

  }

  tablelen = (size_t)1 << new_hashbits;

  buf = nghttp2_mem_calloc(map->mem, tablelen,

                           sizeof(nghttp2_map_key_type) + sizeof(void *) +

                             sizeof(uint8_t));

  if (buf == NULL) {

    return NGHTTP2_ERR_NOMEM;

  }

  new_map.keys = buf;

  new_map.data =

    (void *)((uint8_t *)new_map.keys + tablelen * sizeof(nghttp2_map_key_type));

  new_map.psl = (uint8_t *)new_map.data + tablelen * sizeof(void *);

  if (map->size) {

    tablelen = (size_t)1 << map->hashbits;

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

      if (map->psl[i] == 0) {

        continue;

      }

      idx = map_insert(&new_map, map->keys[i], map->data[i]);

      /* map_insert must not fail because all keys are unique during

         resize. */

      assert(idx >= 0);

    }

  }

  nghttp2_mem_free(map->mem, map->keys);

  map->keys = new_map.keys;

  map->data = new_map.data;

  map->psl = new_map.psl;

  map->hashbits = new_hashbits;

  return 0;

}

/* NGHTTP2_MAX_PSL_RESIZE_THRESH is the maximum psl threshold.  If

   reached, resize the table. */

#define NGHTTP2_MAX_PSL_RESIZE_THRESH 128

int nghttp2_map_insert(nghttp2_map *map, nghttp2_map_key_type key, void *data) {

  int rv;

  size_t tablelen;

  nghttp2_ssize idx;

  assert(data);

  /* tablelen is incorrect if map->hashbits == 0 which leads to

     tablelen = 1, but it is only used to check the load factor, and

     it works in this special case. */

  tablelen = (size_t)1 << map->hashbits;

  /* Load factor is 7 / 8.  Because tablelen is power of 2, (tablelen

     - (tablelen >> 3)) computes tablelen * 7 / 8. */

  if (map->size + 1 >= (tablelen - (tablelen >> 3))) {

    rv = map_resize(map, map->hashbits ? map->hashbits + 1

                                       : NGHTTP2_INITIAL_HASHBITS);

    if (rv != 0) {

      return rv;

    }

    idx = map_insert(map, key, data);

    if (idx < 0) {

      return (int)idx;

    }

    return 0;

  }

  idx = map_insert(map, key, data);

  if (idx < 0) {

    return (int)idx;

  }

  /* Resize if psl reaches really large value which is almost

     improbable, but just in case. */

  if (map->psl[idx] - 1 < NGHTTP2_MAX_PSL_RESIZE_THRESH) {

    return 0;

  }

  return map_resize(map, map->hashbits + 1);

}

void *nghttp2_map_find(const nghttp2_map *map, nghttp2_map_key_type key) {

  size_t idx;

  size_t psl = 1;

  size_t mask;

  if (map->size == 0) {

    return NULL;

  }

  idx = map_index(map, key);

  mask = ((size_t)1 << map->hashbits) - 1;

  for (;;) {

    if (psl > map->psl[idx]) {

      return NULL;

    }

    if (map->keys[idx] == key) {

      return map->data[idx];

    }

    ++psl;

    idx = (idx + 1) & mask;

  }

}

int nghttp2_map_remove(nghttp2_map *map, nghttp2_map_key_type key) {

  size_t idx;

  size_t dest;

  size_t psl = 1, kpsl;

  size_t mask;

  if (map->size == 0) {

    return NGHTTP2_ERR_INVALID_ARGUMENT;

  }

  idx = map_index(map, key);

  mask = ((size_t)1 << map->hashbits) - 1;

  for (;;) {

    if (psl > map->psl[idx]) {

      return NGHTTP2_ERR_INVALID_ARGUMENT;

    }

    if (map->keys[idx] == key) {

      dest = idx;

      idx = (idx + 1) & mask;

      for (;;) {

        kpsl = map->psl[idx];

        if (kpsl <= 1) {

          map->psl[dest] = 0;

          break;

        }

        map_set_entry(map, dest, map->keys[idx], map->data[idx], kpsl - 1);

        dest = idx;

        idx = (idx + 1) & mask;

      }

      --map->size;

      return 0;

    }

    ++psl;

    idx = (idx + 1) & mask;

  }

}

void nghttp2_map_clear(nghttp2_map *map) {

  if (map->size == 0) {

    return;

  }

  memset(map->psl, 0, sizeof(*map->psl) * ((size_t)1 << map->hashbits));

  map->size = 0;

}

size_t nghttp2_map_size(const nghttp2_map *map) { return map->size; }