text: // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file. See the AUTHORS file for names of contributors.
  
  #include "leveldb/c.h"
  
  #include <stdlib.h>
  #include <unistd.h>
  #include "leveldb/cache.h"
  #include "leveldb/comparator.h"
  #include "leveldb/db.h"
  #include "leveldb/env.h"
  #include "leveldb/filter_policy.h"
  #include "leveldb/iterator.h"
  #include "leveldb/options.h"
  #include "leveldb/status.h"
  #include "leveldb/write_batch.h"
  
  using leveldb::Cache;
  using leveldb::Comparator;
  using leveldb::CompressionType;
  using leveldb::DB;
  using leveldb::Env;
  using leveldb::FileLock;
  using leveldb::FilterPolicy;
  using leveldb::Iterator;
  using leveldb::kMajorVersion;
  using leveldb::kMinorVersion;
  using leveldb::Logger;
  using leveldb::NewBloomFilterPolicy;
  using leveldb::NewLRUCache;
  using leveldb::Options;
  using leveldb::RandomAccessFile;
  using leveldb::Range;
  using leveldb::ReadOptions;
  using leveldb::SequentialFile;
  using leveldb::Slice;
  using leveldb::Snapshot;
  using leveldb::Status;
  using leveldb::WritableFile;
  using leveldb::WriteBatch;
  using leveldb::WriteOptions;
  
  extern "C" {
  
  struct leveldb_t              { DB*               rep; };
  struct leveldb_iterator_t     { Iterator*         rep; };
  struct leveldb_writebatch_t   { WriteBatch        rep; };
  struct leveldb_snapshot_t     { const Snapshot*   rep; };
  struct leveldb_readoptions_t  { ReadOptions       rep; };
  struct leveldb_writeoptions_t { WriteOptions      rep; };
  struct leveldb_options_t      { Options           rep; };
  struct leveldb_cache_t        { Cache*            rep; };
  struct leveldb_seqfile_t      { SequentialFile*   rep; };
  struct leveldb_randomfile_t   { RandomAccessFile* rep; };
  struct leveldb_writablefile_t { WritableFile*     rep; };
  struct leveldb_logger_t       { Logger*           rep; };
  struct leveldb_filelock_t     { FileLock*         rep; };
  
  struct leveldb_comparator_t : public Comparator {
    void* state_;
    void (*destructor_)(void*);
    int (*compare_)(
        void*,
        const char* a, size_t alen,
        const char* b, size_t blen);
    const char* (*name_)(void*);
  
    virtual ~leveldb_comparator_t() {
      (*destructor_)(state_);
    }
  
    virtual int Compare(const Slice& a, const Slice& b) const {
      return (*compare_)(state_, a.data(), a.size(), b.data(), b.size());
    }
  
    virtual const char* Name() const {
      return (*name_)(state_);
    }
  
    // No-ops since the C binding does not support key shortening methods.
    virtual void FindShortestSeparator(std::string*, const Slice&) const { }
    virtual void FindShortSuccessor(std::string* key) const { }
  };
  
  struct leveldb_filterpolicy_t : public FilterPolicy {
    void* state_;
    void (*destructor_)(void*);
    const char* (*name_)(void*);
    char* (*create_)(
        void*,
        const char* const* key_array, const size_t* key_length_array,
        int num_keys,
        size_t* filter_length);
    unsigned char (*key_match_)(
        void*,
        const char* key, size_t length,
        const char* filter, size_t filter_length);
  
    virtual ~leveldb_filterpolicy_t() {
      (*destructor_)(state_);
    }
  
    virtual const char* Name() const {
      return (*name_)(state_);
    }
  
    virtual void CreateFilter(const Slice* keys, int n, std::string* dst) const {
      std::vector<const char*> key_pointers(n);
      std::vector<size_t> key_sizes(n);
      for (int i = 0; i < n; i++) {
        key_pointers[i] = keys[i].data();
        key_sizes[i] = keys[i].size();
      }
      size_t len;
      char* filter = (*create_)(state_, &key_pointers[0], &key_sizes[0], n, &len);
      dst->append(filter, len);
      free(filter);
    }
  
    virtual bool KeyMayMatch(const Slice& key, const Slice& filter) const {
      return (*key_match_)(state_, key.data(), key.size(),
                           filter.data(), filter.size());
    }
  };
  
  struct leveldb_env_t {
    Env* rep;
    bool is_default;
  };
  
  static bool SaveError(char** errptr, const Status& s) {
    assert(errptr != NULL);
    if (s.ok()) {
      return false;
    } else if (*errptr == NULL) {
      *errptr = strdup(s.ToString().c_str());
    } else {
      // TODO(sanjay): Merge with existing error?
      free(*errptr);
      *errptr = strdup(s.ToString().c_str());
    }
    return true;
  }
  
  static char* CopyString(const std::string& str) {
    char* result = reinterpret_cast<char*>(malloc(sizeof(char) * str.size()));
    memcpy(result, str.data(), sizeof(char) * str.size());
    return result;
  }
  
  leveldb_t* leveldb_open(
      const leveldb_options_t* options,
      const char* name,
      char** errptr) {
    DB* db;
    if (SaveError(errptr, DB::Open(options->rep, std::string(name), &db))) {
      return NULL;
    }
    leveldb_t* result = new leveldb_t;
    result->rep = db;
    return result;
  }
  
  void leveldb_close(leveldb_t* db) {
    delete db->rep;
    delete db;
  }
  
  void leveldb_put(
      leveldb_t* db,
      const leveldb_writeoptions_t* options,
      const char* key, size_t keylen,
      const char* val, size_t vallen,
      char** errptr) {
    SaveError(errptr,
              db->rep->Put(options->rep, Slice(key, keylen), Slice(val, vallen)));
  }
  
  void leveldb_delete(
      leveldb_t* db,
      const leveldb_writeoptions_t* options,
      const char* key, size_t keylen,
      char** errptr) {
    SaveError(errptr, db->rep->Delete(options->rep, Slice(key, keylen)));
  }
  
  
  void leveldb_write(
      leveldb_t* db,
      const leveldb_writeoptions_t* options,
      leveldb_writebatch_t* batch,
      char** errptr) {
    SaveError(errptr, db->rep->Write(options->rep, &batch->rep));
  }
  
  char* leveldb_get(
      leveldb_t* db,
      const leveldb_readoptions_t* options,
      const char* key, size_t keylen,
      size_t* vallen,
      char** errptr) {
    char* result = NULL;
    std::string tmp;
    Status s = db->rep->Get(options->rep, Slice(key, keylen), &tmp);
    if (s.ok()) {
      *vallen = tmp.size();
      result = CopyString(tmp);
    } else {
      *vallen = 0;
      if (!s.IsNotFound()) {
        SaveError(errptr, s);
      }
    }
    return result;
  }
  
  leveldb_iterator_t* leveldb_create_iterator(
      leveldb_t* db,
      const leveldb_readoptions_t* options) {
    leveldb_iterator_t* result = new leveldb_iterator_t;
    result->rep = db->rep->NewIterator(options->rep);
    return result;
  }
  
  const leveldb_snapshot_t* leveldb_create_snapshot(
      leveldb_t* db) {
    leveldb_snapshot_t* result = new leveldb_snapshot_t;
    result->rep = db->rep->GetSnapshot();
    return result;
  }
  
  void leveldb_release_snapshot(
      leveldb_t* db,
      const leveldb_snapshot_t* snapshot) {
    db->rep->ReleaseSnapshot(snapshot->rep);
    delete snapshot;
  }
  
  char* leveldb_property_value(
      leveldb_t* db,
      const char* propname) {
    std::string tmp;
    if (db->rep->GetProperty(Slice(propname), &tmp)) {
      // We use strdup() since we expect human readable output.
      return strdup(tmp.c_str());
    } else {
      return NULL;
    }
  }
  
  void leveldb_approximate_sizes(
      leveldb_t* db,
      int num_ranges,
      const char* const* range_start_key, const size_t* range_start_key_len,
      const char* const* range_limit_key, const size_t* range_limit_key_len,
      uint64_t* sizes) {
    Range* ranges = new Range[num_ranges];
    for (int i = 0; i < num_ranges; i++) {
      ranges[i].start = Slice(range_start_key[i], range_start_key_len[i]);
      ranges[i].limit = Slice(range_limit_key[i], range_limit_key_len[i]);
    }
    db->rep->GetApproximateSizes(ranges, num_ranges, sizes);
    delete[] ranges;
  }
  
  void leveldb_compact_range(
      leveldb_t* db,
      const char* start_key, size_t start_key_len,
      const char* limit_key, size_t limit_key_len) {
    Slice a, b;
    db->rep->CompactRange(
        // Pass NULL Slice if corresponding "const char*" is NULL
        (start_key ? (a = Slice(start_key, start_key_len), &a) : NULL),
        (limit_key ? (b = Slice(limit_key, limit_key_len), &b) : NULL));
  }
  
  void leveldb_destroy_db(
      const leveldb_options_t* options,
      const char* name,
      char** errptr) {
    SaveError(errptr, DestroyDB(name, options->rep));
  }
  
  void leveldb_repair_db(
      const leveldb_options_t* options,
      const char* name,
      char** errptr) {
    SaveError(errptr, RepairDB(name, options->rep));
  }
  
  void leveldb_iter_destroy(leveldb_iterator_t* iter) {
    delete iter->rep;
    delete iter;
  }
  
  unsigned char leveldb_iter_valid(const leveldb_iterator_t* iter) {
    return iter->rep->Valid();
  }
  
  void leveldb_iter_seek_to_first(leveldb_iterator_t* iter) {
    iter->rep->SeekToFirst();
  }
  
  void leveldb_iter_seek_to_last(leveldb_iterator_t* iter) {
    iter->rep->SeekToLast();
  }
  
  void leveldb_iter_seek(leveldb_iterator_t* iter, const char* k, size_t klen) {
    iter->rep->Seek(Slice(k, klen));
  }
  
  void leveldb_iter_next(leveldb_iterator_t* iter) {
    iter->rep->Next();
  }
  
  void leveldb_iter_prev(leveldb_iterator_t* iter) {
    iter->rep->Prev();
  }
  
  const char* leveldb_iter_key(const leveldb_iterator_t* iter, size_t* klen) {
    Slice s = iter->rep->key();
    *klen = s.size();
    return s.data();
  }
  
  const char* leveldb_iter_value(const leveldb_iterator_t* iter, size_t* vlen) {
    Slice s = iter->rep->value();
    *vlen = s.size();
    return s.data();
  }
  
  void leveldb_iter_get_error(const leveldb_iterator_t* iter, char** errptr) {
    SaveError(errptr, iter->rep->status());
  }
  
  leveldb_writebatch_t* leveldb_writebatch_create() {
    return new leveldb_writebatch_t;
  }
  
  void leveldb_writebatch_destroy(leveldb_writebatch_t* b) {
    delete b;
  }
  
  void leveldb_writebatch_clear(leveldb_writebatch_t* b) {
    b->rep.Clear();
  }
  
  void leveldb_writebatch_put(
      leveldb_writebatch_t* b,
      const char* key, size_t klen,
      const char* val, size_t vlen) {
    b->rep.Put(Slice(key, klen), Slice(val, vlen));
  }
  
  void leveldb_writebatch_delete(
      leveldb_writebatch_t* b,
      const char* key, size_t klen) {
    b->rep.Delete(Slice(key, klen));
  }
  
  void leveldb_writebatch_iterate(
      leveldb_writebatch_t* b,
      void* state,
      void (*put)(void*, const char* k, size_t klen, const char* v, size_t vlen),
      void (*deleted)(void*, const char* k, size_t klen)) {
    class H : public WriteBatch::Handler {
     public:
      void* state_;
      void (*put_)(void*, const char* k, size_t klen, const char* v, size_t vlen);
      void (*deleted_)(void*, const char* k, size_t klen);
      virtual void Put(const Slice& key, const Slice& value) {
        (*put_)(state_, key.data(), key.size(), value.data(), value.size());
      }
      virtual void Delete(const Slice& key) {
        (*deleted_)(state_, key.data(), key.size());
      }
    };
    H handler;
    handler.state_ = state;
    handler.put_ = put;
    handler.deleted_ = deleted;
    b->rep.Iterate(&handler);
  }
  
  leveldb_options_t* leveldb_options_create() {
    return new leveldb_options_t;
  }
  
  void leveldb_options_destroy(leveldb_options_t* options) {
    delete options;
  }
  
  void leveldb_options_set_comparator(
      leveldb_options_t* opt,
      leveldb_comparator_t* cmp) {
    opt->rep.comparator = cmp;
  }
  
  void leveldb_options_set_filter_policy(
      leveldb_options_t* opt,
      leveldb_filterpolicy_t* policy) {
    opt->rep.filter_policy = policy;
  }
  
  void leveldb_options_set_create_if_missing(
      leveldb_options_t* opt, unsigned char v) {
    opt->rep.create_if_missing = v;
  }
  
  void leveldb_options_set_error_if_exists(
      leveldb_options_t* opt, unsigned char v) {
    opt->rep.error_if_exists = v;
  }
  
  void leveldb_options_set_paranoid_checks(
      leveldb_options_t* opt, unsigned char v) {
    opt->rep.paranoid_checks = v;
  }
  
  void leveldb_options_set_env(leveldb_options_t* opt, leveldb_env_t* env) {
    opt->rep.env = (env ? env->rep : NULL);
  }
  
  void leveldb_options_set_info_log(leveldb_options_t* opt, leveldb_logger_t* l) {
    opt->rep.info_log = (l ? l->rep : NULL);
  }
  
  void leveldb_options_set_write_buffer_size(leveldb_options_t* opt, size_t s) {
    opt->rep.write_buffer_size = s;
  }
  
  void leveldb_options_set_max_open_files(leveldb_options_t* opt, int n) {
    opt->rep.max_open_files = n;
  }
  
  void leveldb_options_set_cache(leveldb_options_t* opt, leveldb_cache_t* c) {
    opt->rep.block_cache = c->rep;
  }
  
  void leveldb_options_set_block_size(leveldb_options_t* opt, size_t s) {
    opt->rep.block_size = s;
  }
  
  void leveldb_options_set_block_restart_interval(leveldb_options_t* opt, int n) {
    opt->rep.block_restart_interval = n;
  }
  
  void leveldb_options_set_max_file_size(leveldb_options_t* opt, size_t s) {
    opt->rep.max_file_size = s;
  }
  
  void leveldb_options_set_compression(leveldb_options_t* opt, int t) {
    opt->rep.compression = static_cast<CompressionType>(t);
  }
  
  leveldb_comparator_t* leveldb_comparator_create(
      void* state,
      void (*destructor)(void*),
      int (*compare)(
          void*,
          const char* a, size_t alen,
          const char* b, size_t blen),
      const char* (*name)(void*)) {
    leveldb_comparator_t* result = new leveldb_comparator_t;
    result->state_ = state;
    result->destructor_ = destructor;
    result->compare_ = compare;
    result->name_ = name;
    return result;
  }
  
  void leveldb_comparator_destroy(leveldb_comparator_t* cmp) {
    delete cmp;
  }
  
  leveldb_filterpolicy_t* leveldb_filterpolicy_create(
      void* state,
      void (*destructor)(void*),
      char* (*create_filter)(
          void*,
          const char* const* key_array, const size_t* key_length_array,
          int num_keys,
          size_t* filter_length),
      unsigned char (*key_may_match)(
          void*,
          const char* key, size_t length,
          const char* filter, size_t filter_length),
      const char* (*name)(void*)) {
    leveldb_filterpolicy_t* result = new leveldb_filterpolicy_t;
    result->state_ = state;
    result->destructor_ = destructor;
    result->create_ = create_filter;
    result->key_match_ = key_may_match;
    result->name_ = name;
    return result;
  }
  
  void leveldb_filterpolicy_destroy(leveldb_filterpolicy_t* filter) {
    delete filter;
  }
  
  leveldb_filterpolicy_t* leveldb_filterpolicy_create_bloom(int bits_per_key) {
    // Make a leveldb_filterpolicy_t, but override all of its methods so
    // they delegate to a NewBloomFilterPolicy() instead of user
    // supplied C functions.
    struct Wrapper : public leveldb_filterpolicy_t {
      const FilterPolicy* rep_;
      ~Wrapper() { delete rep_; }
      const char* Name() const { return rep_->Name(); }
      void CreateFilter(const Slice* keys, int n, std::string* dst) const {
        return rep_->CreateFilter(keys, n, dst);
      }
      bool KeyMayMatch(const Slice& key, const Slice& filter) const {
        return rep_->KeyMayMatch(key, filter);
      }
      static void DoNothing(void*) { }
    };
    Wrapper* wrapper = new Wrapper;
    wrapper->rep_ = NewBloomFilterPolicy(bits_per_key);
    wrapper->state_ = NULL;
    wrapper->destructor_ = &Wrapper::DoNothing;
    return wrapper;
  }
  
  leveldb_readoptions_t* leveldb_readoptions_create() {
    return new leveldb_readoptions_t;
  }
  
  void leveldb_readoptions_destroy(leveldb_readoptions_t* opt) {
    delete opt;
  }
  
  void leveldb_readoptions_set_verify_checksums(
      leveldb_readoptions_t* opt,
      unsigned char v) {
    opt->rep.verify_checksums = v;
  }
  
  void leveldb_readoptions_set_fill_cache(
      leveldb_readoptions_t* opt, unsigned char v) {
    opt->rep.fill_cache = v;
  }
  
  void leveldb_readoptions_set_snapshot(
      leveldb_readoptions_t* opt,
      const leveldb_snapshot_t* snap) {
    opt->rep.snapshot = (snap ? snap->rep : NULL);
  }
  
  leveldb_writeoptions_t* leveldb_writeoptions_create() {
    return new leveldb_writeoptions_t;
  }
  
  void leveldb_writeoptions_destroy(leveldb_writeoptions_t* opt) {
    delete opt;
  }
  
  void leveldb_writeoptions_set_sync(
      leveldb_writeoptions_t* opt, unsigned char v) {
    opt->rep.sync = v;
  }
  
  leveldb_cache_t* leveldb_cache_create_lru(size_t capacity) {
    leveldb_cache_t* c = new leveldb_cache_t;
    c->rep = NewLRUCache(capacity);
    return c;
  }
  
  void leveldb_cache_destroy(leveldb_cache_t* cache) {
    delete cache->rep;
    delete cache;
  }
  
  leveldb_env_t* leveldb_create_default_env() {
    leveldb_env_t* result = new leveldb_env_t;
    result->rep = Env::Default();
    result->is_default = true;
    return result;
  }
  
  void leveldb_env_destroy(leveldb_env_t* env) {
    if (!env->is_default) delete env->rep;
    delete env;
  }
  
  void leveldb_free(void* ptr) {
    free(ptr);
  }
  
  int leveldb_major_version() {
    return kMajorVersion;
  }
  
  int leveldb_minor_version() {
    return kMinorVersion;
  }
  
  }  // end extern "C"
  