/*	$NetBSD: cdbw.c,v 1.7 2021/01/07 14:41:50 joerg Exp $	*/
/*-
 * Copyright (c) 2009, 2010, 2015 The NetBSD Foundation, Inc.
 * All rights reserved.
 *
 * This code is derived from software contributed to The NetBSD Foundation
 * by Joerg Sonnenberger and Alexander Nasonov.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
#include <sys/endian.h>
#include <sys/queue.h>
#include <sys/bitops.h>
#include <cdbw.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

struct key_hash {
  SLIST_ENTRY(key_hash) link;
  uint32_t hashes[3];
  uint32_t idx;
  void *key;
  size_t keylen;
};

SLIST_HEAD(key_hash_head, key_hash);

struct cdbw {
  size_t data_counter;
  size_t data_allocated;
  size_t data_size;
  size_t *data_len;
  void **data_ptr;

  size_t hash_size;
  struct key_hash_head *hash;
  size_t key_counter;
};

/* Max. data counter that allows the index size to be 32bit. */
static const uint32_t max_data_counter = 0xccccccccU;

struct cdbw *cdbw_open(void) {
  struct cdbw *cdbw;
  size_t i;

  cdbw = calloc(sizeof(*cdbw), 1);
  if (cdbw == NULL)
    return NULL;

  cdbw->hash_size = 1024;
  cdbw->hash = calloc(cdbw->hash_size, sizeof(*cdbw->hash));
  if (cdbw->hash == NULL) {
    free(cdbw);
    return NULL;
  }

  for (i = 0; i < cdbw->hash_size; ++i)
    SLIST_INIT(cdbw->hash + i);

  return cdbw;
}

int cdbw_put(struct cdbw *cdbw, const void *key, size_t keylen,
             const void *data, size_t datalen) {
  uint32_t idx;
  int rv;

  rv = cdbw_put_data(cdbw, data, datalen, &idx);
  if (rv)
    return rv;
  rv = cdbw_put_key(cdbw, key, keylen, idx);
  if (rv) {
    --cdbw->data_counter;
    free(cdbw->data_ptr[cdbw->data_counter]);
    cdbw->data_size -= datalen;
    return rv;
  }
  return 0;
}

int cdbw_put_data(struct cdbw *cdbw, const void *data, size_t datalen,
                  uint32_t *idx) {

  if (cdbw->data_counter == max_data_counter)
    return -1;

  if (cdbw->data_size + datalen < cdbw->data_size ||
      cdbw->data_size + datalen > 0xffffffffU)
    return -1; /* Overflow */

  if (cdbw->data_allocated == cdbw->data_counter) {
    void **new_data_ptr;
    size_t *new_data_len;
    size_t new_allocated;

    if (cdbw->data_allocated == 0)
      new_allocated = 256;
    else
      new_allocated = cdbw->data_allocated * 2;

    new_data_ptr =
      realloc(cdbw->data_ptr, sizeof(*cdbw->data_ptr) * new_allocated);
    if (new_data_ptr == NULL)
      return -1;
    cdbw->data_ptr = new_data_ptr;

    new_data_len =
      realloc(cdbw->data_len, sizeof(*cdbw->data_len) * new_allocated);
    if (new_data_len == NULL)
      return -1;
    cdbw->data_len = new_data_len;

    cdbw->data_allocated = new_allocated;
  }

  cdbw->data_ptr[cdbw->data_counter] = malloc(datalen);
  if (cdbw->data_ptr[cdbw->data_counter] == NULL)
    return -1;
  memcpy(cdbw->data_ptr[cdbw->data_counter], data, datalen);
  cdbw->data_len[cdbw->data_counter] = datalen;
  cdbw->data_size += datalen;
  *idx = cdbw->data_counter++;
  return 0;
}

int cdbw_put_key(struct cdbw *cdbw, const void *key, size_t keylen,
                 uint32_t idx) {
  uint32_t hashes[3];
  struct key_hash_head *head, *head2, *new_head;
  struct key_hash *key_hash;
  size_t new_hash_size, i;

  if (idx >= cdbw->data_counter || cdbw->key_counter == max_data_counter)
    return -1;

  mi_vector_hash(key, keylen, 0, hashes);

  head = cdbw->hash + (hashes[0] & (cdbw->hash_size - 1));
  SLIST_FOREACH(key_hash, head, link) {
    if (key_hash->keylen != keylen)
      continue;
    if (key_hash->hashes[0] != hashes[0])
      continue;
    if (key_hash->hashes[1] != hashes[1])
      continue;
    if (key_hash->hashes[2] != hashes[2])
      continue;
    if (memcmp(key, key_hash->key, keylen))
      continue;
    return -1;
  }
  key_hash = malloc(sizeof(*key_hash));
  if (key_hash == NULL)
    return -1;
  key_hash->key = malloc(keylen);
  if (key_hash->key == NULL) {
    free(key_hash);
    return -1;
  }
  memcpy(key_hash->key, key, keylen);
  key_hash->hashes[0] = hashes[0];
  key_hash->hashes[1] = hashes[1];
  key_hash->hashes[2] = hashes[2];
  key_hash->keylen = keylen;
  key_hash->idx = idx;
  SLIST_INSERT_HEAD(head, key_hash, link);
  ++cdbw->key_counter;

  if (cdbw->key_counter <= cdbw->hash_size)
    return 0;

  /* Try to resize the hash table, but ignore errors. */
  new_hash_size = cdbw->hash_size * 2;
  new_head = calloc(sizeof(*new_head), new_hash_size);
  if (new_head == NULL)
    return 0;

  head = &cdbw->hash[hashes[0] & (cdbw->hash_size - 1)];
  for (i = 0; i < new_hash_size; ++i)
    SLIST_INIT(new_head + i);

  for (i = 0; i < cdbw->hash_size; ++i) {
    head = cdbw->hash + i;

    while ((key_hash = SLIST_FIRST(head)) != NULL) {
      SLIST_REMOVE_HEAD(head, link);
      head2 = new_head + (key_hash->hashes[0] & (new_hash_size - 1));
      SLIST_INSERT_HEAD(head2, key_hash, link);
    }
  }
  free(cdbw->hash);
  cdbw->hash_size = new_hash_size;
  cdbw->hash = new_head;

  return 0;
}

void cdbw_close(struct cdbw *cdbw) {
  struct key_hash_head *head;
  struct key_hash *key_hash;
  size_t i;

  for (i = 0; i < cdbw->hash_size; ++i) {
    head = cdbw->hash + i;
    while ((key_hash = SLIST_FIRST(head)) != NULL) {
      SLIST_REMOVE_HEAD(head, link);
      free(key_hash->key);
      free(key_hash);
    }
  }

  for (i = 0; i < cdbw->data_counter; ++i)
    free(cdbw->data_ptr[i]);
  free(cdbw->data_ptr);
  free(cdbw->data_len);
  free(cdbw->hash);
  free(cdbw);
}

uint32_t cdbw_stable_seeder(void) {
  return 0;
}

uint32_t cdbw_random_seeder(void) {
  return (uint32_t)random();
}

/*
 * For each vertex in the 3-graph, the incidence lists needs to be kept.
 * Avoid storing the full list by just XORing the indices of the still
 * incident edges and remember the number of such edges as that's all
 * the peeling computation needs. This is inspired by:
 *   Cache-Oblivious Peeling of Random Hypergraphs by Djamal Belazzougui,
 *   Paolo Boldi, Giuseppe Ottaviano, Rossano Venturini, and Sebastiano
 *   Vigna. https://arxiv.org/abs/1312.0526
 *
 * Unlike in the paper, we don't care about external storage and have
 * the edge list at hand all the time. As such, no ordering is necessary
 * and the vertices of the edge don't have to be copied.
 *
 * The core observation of the paper above is that for a degree of one,
 * the incident edge can be obtained directly.
 */
struct vertex {
  uint32_t degree;
  uint32_t edges;
};

struct edge {
  uint32_t vertices[3];
  uint32_t idx;
};

struct state {
  uint32_t data_entries;
  uint32_t entries;
  uint32_t keys;
  uint32_t seed;

  uint32_t *g;
  char *visited;

  struct vertex *vertices;
  struct edge *edges;
  uint32_t output_index;
  uint32_t *output_order;
};

/*
 * Add (delta == 1) or remove (delta == -1) the edge e
 * from the incidence lists.
 */
static inline void change_edge(struct state *state, int delta, uint32_t e) {
  int i;
  struct vertex *v;
  struct edge *e_ = &state->edges[e];

  for (i = 0; i < 3; ++i) {
    v = &state->vertices[e_->vertices[i]];
    v->edges ^= e;
    v->degree += delta;
  }
}

static inline void remove_vertex(struct state *state, uint32_t v) {
  struct vertex *v_ = &state->vertices[v];
  uint32_t e;

  if (v_->degree == 1) {
    e = v_->edges;
    state->output_order[--state->output_index] = e;
    change_edge(state, -1, e);
  }
}

static int build_graph(struct cdbw *cdbw, struct state *state) {
  struct key_hash_head *head;
  struct key_hash *key_hash;
  struct edge *e;
  uint32_t entries_m;
  uint8_t entries_s1, entries_s2;
  uint32_t hashes[3];
  size_t i;
  int j;

  memset(state->vertices, 0, sizeof(*state->vertices) * state->entries);

  e = state->edges;
  fast_divide32_prepare(state->entries, &entries_m, &entries_s1, &entries_s2);

  for (i = 0; i < cdbw->hash_size; ++i) {
    head = &cdbw->hash[i];
    SLIST_FOREACH(key_hash, head, link) {
      mi_vector_hash(key_hash->key, key_hash->keylen, state->seed, hashes);

      for (j = 0; j < 3; ++j) {
        e->vertices[j] = fast_remainder32(hashes[j], state->entries, entries_m,
                                          entries_s1, entries_s2);
      }

      if (e->vertices[0] == e->vertices[1])
        return -1;
      if (e->vertices[0] == e->vertices[2])
        return -1;
      if (e->vertices[1] == e->vertices[2])
        return -1;
      e->idx = key_hash->idx;
      ++e;
    }
  }

  /*
   * Do the edge processing separately as there is a good chance
   * the degraded edge case above will happen; this avoid
   *unnecessary  work.
   */
  for (i = 0; i < state->keys; ++i)
    change_edge(state, 1, i);

  state->output_index = state->keys;
  for (i = 0; i < state->entries; ++i)
    remove_vertex(state, i);

  i = state->keys;
  while (i > 0 && i > state->output_index) {
    --i;
    e = state->edges + state->output_order[i];
    for (j = 0; j < 3; ++j)
      remove_vertex(state, e->vertices[j]);
  }

  return state->output_index == 0 ? 0 : -1;
}

static void assign_nodes(struct state *state) {
  struct edge *e;
  size_t i;

  uint32_t v0, v1, v2, entries_m;
  uint8_t entries_s1, entries_s2;

  fast_divide32_prepare(state->data_entries, &entries_m, &entries_s1,
                        &entries_s2);

  for (i = 0; i < state->keys; ++i) {
    e = state->edges + state->output_order[i];
    if (!state->visited[e->vertices[0]]) {
      v0 = e->vertices[0];
      v1 = e->vertices[1];
      v2 = e->vertices[2];
    } else if (!state->visited[e->vertices[1]]) {
      v0 = e->vertices[1];
      v1 = e->vertices[0];
      v2 = e->vertices[2];
    } else {
      v0 = e->vertices[2];
      v1 = e->vertices[0];
      v2 = e->vertices[1];
    }
    state->g[v0] = fast_remainder32(
      (2 * state->data_entries + e->idx - state->g[v1] - state->g[v2]),
      state->data_entries, entries_m, entries_s1, entries_s2);
    state->visited[v0] = 1;
    state->visited[v1] = 1;
    state->visited[v2] = 1;
  }
}

static size_t compute_size(uint32_t size) {
  if (size < 0x100)
    return 1;
  else if (size < 0x10000)
    return 2;
  else
    return 4;
}

#define COND_FLUSH_BUFFER(n)                                                   \
  do {                                                                         \
    if (__predict_false(cur_pos + (n) >= sizeof(buf))) {                       \
      ret = write(fd, buf, cur_pos);                                           \
      if (ret == -1 || (size_t)ret != cur_pos)                                 \
        return -1;                                                             \
      cur_pos = 0;                                                             \
    }                                                                          \
  } while (/* CONSTCOND */ 0)

static int print_hash(struct cdbw *cdbw, struct state *state, int fd,
                      const char *descr) {
  uint32_t data_size;
  uint8_t buf[90000];
  size_t i, size, size2, cur_pos;
  ssize_t ret;

  memcpy(buf, "NBCDB\n\0", 7);
  buf[7] = 1;
  strncpy((char *)buf + 8, descr, 16);
  le32enc(buf + 24, cdbw->data_size);
  le32enc(buf + 28, cdbw->data_counter);
  le32enc(buf + 32, state->entries);
  le32enc(buf + 36, state->seed);
  cur_pos = 40;

  size = compute_size(state->entries);
  for (i = 0; i < state->entries; ++i) {
    COND_FLUSH_BUFFER(4);
    le32enc(buf + cur_pos, state->g[i]);
    cur_pos += size;
  }
  size2 = compute_size(cdbw->data_size);
  size = size * state->entries % size2;
  if (size != 0) {
    size = size2 - size;
    COND_FLUSH_BUFFER(4);
    le32enc(buf + cur_pos, 0);
    cur_pos += size;
  }
  for (data_size = 0, i = 0; i < cdbw->data_counter; ++i) {
    COND_FLUSH_BUFFER(4);
    le32enc(buf + cur_pos, data_size);
    cur_pos += size2;
    data_size += cdbw->data_len[i];
  }
  COND_FLUSH_BUFFER(4);
  le32enc(buf + cur_pos, data_size);
  cur_pos += size2;

  for (i = 0; i < cdbw->data_counter; ++i) {
    COND_FLUSH_BUFFER(cdbw->data_len[i]);
    if (cdbw->data_len[i] < sizeof(buf)) {
      memcpy(buf + cur_pos, cdbw->data_ptr[i], cdbw->data_len[i]);
      cur_pos += cdbw->data_len[i];
    } else {
      ret = write(fd, cdbw->data_ptr[i], cdbw->data_len[i]);
      if (ret == -1 || (size_t)ret != cdbw->data_len[i])
        return -1;
    }
  }
  if (cur_pos != 0) {
    ret = write(fd, buf, cur_pos);
    if (ret == -1 || (size_t)ret != cur_pos)
      return -1;
  }
  return 0;
}

int cdbw_output(struct cdbw *cdbw, int fd, const char descr[16],
                uint32_t (*seedgen)(void)) {
  struct state state;
  int rv;

  if (cdbw->data_counter == 0 || cdbw->key_counter == 0) {
    state.entries = 0;
    state.seed = 0;
    print_hash(cdbw, &state, fd, descr);
    return 0;
  }

  if (seedgen == NULL)
    seedgen = cdbw_random_seeder;

  rv = 0;

  state.keys = cdbw->key_counter;
  state.data_entries = cdbw->data_counter;
  state.entries = state.keys + (state.keys + 3) / 4;
  if (state.entries < 10)
    state.entries = 10;

#define NALLOC(var, n) var = calloc(sizeof(*var), n)
  NALLOC(state.g, state.entries);
  NALLOC(state.visited, state.entries);
  NALLOC(state.vertices, state.entries);
  NALLOC(state.edges, state.keys);
  NALLOC(state.output_order, state.keys);
#undef NALLOC

  if (state.g == NULL || state.visited == NULL || state.edges == NULL ||
      state.vertices == NULL || state.output_order == NULL) {
    rv = -1;
    goto release;
  }

  state.seed = 0;
  do {
    if (seedgen == cdbw_stable_seeder)
      ++state.seed;
    else
      state.seed = (*seedgen)();
  } while (build_graph(cdbw, &state));

  assign_nodes(&state);
  rv = print_hash(cdbw, &state, fd, descr);

release:
  free(state.g);
  free(state.visited);
  free(state.vertices);
  free(state.edges);
  free(state.output_order);

  return rv;
}
