Inline defaults in options.

This CL moves default values for
leveldb::{Options,ReadOptions,WriteOptions} from constructors to member
declarations, and removes now-redundant comments stating the defaults.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=239271242

db/fault_injection_test.cc

@@ -469,7 +469,6 @@ class FaultInjectionTest {
 
   void DeleteAllData() {
     Iterator* iter = db_->NewIterator(ReadOptions());
-    WriteOptions options;
     for (iter->SeekToFirst(); iter->Valid(); iter->Next()) {
       ASSERT_OK(db_->Delete(WriteOptions(), iter->key()));
     }

include/leveldb/options.h

@@ -42,20 +42,17 @@ struct LEVELDB_EXPORT Options {
   const Comparator* comparator;
 
   // If true, the database will be created if it is missing.
-  // Default: false
-  bool create_if_missing;
+  bool create_if_missing = false;
 
   // If true, an error is raised if the database already exists.
-  // Default: false
-  bool error_if_exists;
+  bool error_if_exists = false;
 
   // If true, the implementation will do aggressive checking of the
   // data it is processing and will stop early if it detects any
   // errors.  This may have unforeseen ramifications: for example, a
   // corruption of one DB entry may cause a large number of entries to
   // become unreadable or for the entire DB to become unopenable.
-  // Default: false
-  bool paranoid_checks;
+  bool paranoid_checks = false;
 
   // Use the specified object to interact with the environment,
   // e.g. to read/write files, schedule background work, etc.
@@ -65,8 +62,7 @@ struct LEVELDB_EXPORT Options {
   // Any internal progress/error information generated by the db will
   // be written to info_log if it is non-null, or to a file stored
   // in the same directory as the DB contents if info_log is null.
-  // Default: nullptr
-  Logger* info_log;
+  Logger* info_log = nullptr;
 
   // -------------------
   // Parameters that affect performance
@@ -79,39 +75,30 @@ struct LEVELDB_EXPORT Options {
   // so you may wish to adjust this parameter to control memory usage.
   // Also, a larger write buffer will result in a longer recovery time
   // the next time the database is opened.
-  //
-  // Default: 4MB
-  size_t write_buffer_size;
+  size_t write_buffer_size = 4 * 1024 * 1024;
 
   // Number of open files that can be used by the DB.  You may need to
   // increase this if your database has a large working set (budget
   // one open file per 2MB of working set).
-  //
-  // Default: 1000
-  int max_open_files;
+  int max_open_files = 1000;
 
   // Control over blocks (user data is stored in a set of blocks, and
   // a block is the unit of reading from disk).
 
   // If non-null, use the specified cache for blocks.
   // If null, leveldb will automatically create and use an 8MB internal cache.
-  // Default: nullptr
-  Cache* block_cache;
+  Cache* block_cache = nullptr;
 
   // Approximate size of user data packed per block.  Note that the
   // block size specified here corresponds to uncompressed data.  The
   // actual size of the unit read from disk may be smaller if
   // compression is enabled.  This parameter can be changed dynamically.
-  //
-  // Default: 4K
-  size_t block_size;
+  size_t block_size = 4 * 1024;
 
   // Number of keys between restart points for delta encoding of keys.
   // This parameter can be changed dynamically.  Most clients should
   // leave this parameter alone.
-  //
-  // Default: 16
-  int block_restart_interval;
+  int block_restart_interval = 16;
 
   // Leveldb will write up to this amount of bytes to a file before
   // switching to a new one.
@@ -121,9 +108,7 @@ struct LEVELDB_EXPORT Options {
   // compactions and hence longer latency/performance hiccups.
   // Another reason to increase this parameter might be when you are
   // initially populating a large database.
-  //
-  // Default: 2MB
-  size_t max_file_size;
+  size_t max_file_size = 2 * 1024 * 1024;
 
   // Compress blocks using the specified compression algorithm.  This
   // parameter can be changed dynamically.
@@ -139,20 +124,18 @@ struct LEVELDB_EXPORT Options {
   // worth switching to kNoCompression.  Even if the input data is
   // incompressible, the kSnappyCompression implementation will
   // efficiently detect that and will switch to uncompressed mode.
-  CompressionType compression;
+  CompressionType compression = kSnappyCompression;
 
   // EXPERIMENTAL: If true, append to existing MANIFEST and log files
   // when a database is opened.  This can significantly speed up open.
   //
   // Default: currently false, but may become true later.
-  bool reuse_logs;
+  bool reuse_logs = false;
 
   // If non-null, use the specified filter policy to reduce disk reads.
   // Many applications will benefit from passing the result of
   // NewBloomFilterPolicy() here.
-  //
-  // Default: nullptr
-  const FilterPolicy* filter_policy;
+  const FilterPolicy* filter_policy = nullptr;
 
   // Create an Options object with default values for all fields.
   Options();
@@ -162,26 +145,19 @@ struct LEVELDB_EXPORT Options {
 struct LEVELDB_EXPORT ReadOptions {
   // If true, all data read from underlying storage will be
   // verified against corresponding checksums.
-  // Default: false
-  bool verify_checksums;
+  bool verify_checksums = false;
 
   // Should the data read for this iteration be cached in memory?
   // Callers may wish to set this field to false for bulk scans.
-  // Default: true
-  bool fill_cache;
+  bool fill_cache = true;
 
   // If "snapshot" is non-null, read as of the supplied snapshot
   // (which must belong to the DB that is being read and which must
   // not have been released).  If "snapshot" is null, use an implicit
   // snapshot of the state at the beginning of this read operation.
-  // Default: nullptr
-  const Snapshot* snapshot;
-
-  ReadOptions()
-      : verify_checksums(false),
-        fill_cache(true),
-        snapshot(nullptr) {
-  }
+  const Snapshot* snapshot = nullptr;
+
+  ReadOptions() = default;
 };
 
 // Options that control write operations
@@ -200,13 +176,9 @@ struct LEVELDB_EXPORT WriteOptions {
   // crash semantics as the "write()" system call.  A DB write
   // with sync==true has similar crash semantics to a "write()"
   // system call followed by "fsync()".
-  //
-  // Default: false
-  bool sync;
+  bool sync = false;
 
-  WriteOptions()
-      : sync(false) {
-  }
+  WriteOptions() = default;
 };
 
 }  // namespace leveldb

util/options.cc

@@ -11,20 +11,7 @@ namespace leveldb {
 
 Options::Options()
     : comparator(BytewiseComparator()),
-      create_if_missing(false),
-      error_if_exists(false),
-      paranoid_checks(false),
-      env(Env::Default()),
-      info_log(nullptr),
-      write_buffer_size(4<<20),
-      max_open_files(1000),
-      block_cache(nullptr),
-      block_size(4096),
-      block_restart_interval(16),
-      max_file_size(2<<20),
-      compression(kSnappyCompression),
-      reuse_logs(false),
-      filter_policy(nullptr) {
+      env(Env::Default()) {
 }
 
 }  // namespace leveldb