DB#initialize(readonly)

API.md

@@ -1,12 +1,12 @@
 # Supported API
-## Implemented 8% (22/259)
-### Database (2 / 24)
+## Implemented 8% (23/259)
+### Database (3 / 24)
 
 |Command                                              |impl|test|note|
 |-----------------------------------------------------|:--:|:--:|----|
 |`rocksdb_open`                                       |  ✓ |  ✓ |    |
 |`rocksdb_close`                                      |  ✓ |  ✓ |    |
-|`rocksdb_open_for_read_only`                         |    |    |    |
+|`rocksdb_open_for_read_only`                         |  ✓ |  ✓ |    |
 |`rocksdb_backup_engine_open`                         |    |    |    |
 |`rocksdb_backup_engine_create_new_backup`            |    |    |    |
 |`rocksdb_restore_options_create`                     |    |    |    |

README.md

@@ -39,6 +39,14 @@ db.get!("foo")     # raise RocksDB::NotFound.new("foo")
 db.close
 ```
 
+### readonly mode
+
+```crystal
+db = RocksDB::DB.new("tmp/db1", readonly: true)
+# or RocksDB::DB.read("tmp/db1")
+db.put("foo", "1")  # raise RocksDB::Error("Not supported operation in read only mode.")
+```
+
 ### Iterations
 
 ```shell
@@ -94,6 +102,7 @@ db.get("\u{0}")   # => "\t"
 
 #### 0.4.0
 
+- [x] readonly mode
 - [ ] Iterations for Binary
 
 ## Testing

doc/api/impl

@@ -12,6 +12,7 @@ rocksdb_iter_seek_to_last
 rocksdb_iter_valid
 rocksdb_iter_value
 rocksdb_open
+rocksdb_open_for_read_only
 rocksdb_options_create
 rocksdb_options_destroy
 rocksdb_put

doc/api/test

@@ -15,4 +15,5 @@ rocksdb_iter_seek_to_last
 rocksdb_iter_valid
 rocksdb_iter_value
 rocksdb_open
+rocksdb_open_for_read_only
 rocksdb_put

spec/readonly_spec.cr

@@ -0,0 +1,60 @@
+require "./spec_helper"
+
+describe RocksDB::DB do
+  path = "tmp/db_readonly"
+  invalid_path = "tmp/xxx"
+
+  it "(setup)" do
+    db = RocksDB::DB.new(path)
+    db.put("key", "1")
+    db.close
+  end
+
+  describe ".new(readonly: true)" do
+    it "can read data" do
+      db = RocksDB::DB.new(path, readonly: true)
+      db.get("key").should eq("1")
+      db.keys.should eq(["key"])
+      db.close
+    end
+
+    it "can't write data" do
+      db = RocksDB::DB.new(path, readonly: true)
+      expect_raises(RocksDB::Error, /Not supported operation in read only mode/) do
+        db.put("key", "10")
+      end
+      db.close
+    end
+
+    it "can't open when file not found" do
+      expect_raises(RocksDB::Error, /No such file or directory/) do
+        RocksDB::DB.new(invalid_path, readonly: true)
+      end
+    end
+  end
+
+  describe "read" do
+    it "can read data" do
+      db = RocksDB::DB.read(path)
+      db.get("key").should eq("1")
+      db.keys.should eq(["key"])
+      db.close
+    end
+
+    it "can't write data" do
+      db = RocksDB::DB.read(path)
+      expect_raises(RocksDB::Error, /Not supported operation in read only mode/) do
+        db.put("key", "10")
+      end
+      db.close
+    end
+
+    it "can't open when file not found" do
+      expect_raises(RocksDB::Error, /No such file or directory/) do
+        RocksDB::DB.read(invalid_path)
+      end
+    end
+  end
+
+  it "#rocksdb_open_for_read_only" do; end
+end

src/rocksdb/api.cr

@@ -13,7 +13,7 @@ end
 private  macro try(name)
   def {{name.id}}(*args)
     LibRocksDB.{{name.id}}(*args, @err).tap {
-      raise "ERR: {{name}} #{String.new(@err.value)}" if !@err.value.null?
+      raise RocksDB::Error.new("ERR: {{name}} #{String.new(@err.value)}") if !@err.value.null?
     }
   end
 end
@@ -22,6 +22,7 @@ module RocksDB::Api
   ### Basic
 
   try rocksdb_open
+  try rocksdb_open_for_read_only
   api rocksdb_close
   try rocksdb_get
   try rocksdb_put

src/rocksdb/db.cr

@@ -11,7 +11,11 @@ class RocksDB::DB
   getter! read_options
   getter! write_options
 
-  def initialize(@path : String, options : Options? = nil, read_options : ReadOptions? = nil, write_options : WriteOptions? = nil)
+  def self.read(path : String, options : Options? = nil, read_options : ReadOptions? = nil, error_if_log_file_exist : Bool = false)
+    new(path, options: options, read_options: read_options, readonly: true, error_if_log_file_exist: error_if_log_file_exist)
+  end
+
+  def initialize(@path : String, options : Options? = nil, read_options : ReadOptions? = nil, write_options : WriteOptions? = nil, readonly : Bool = false, error_if_log_file_exist : Bool = false)
     @closables = [] of Closable
 
     @options       = options       || mark_closable(Options.new.set_create_if_missing(1))
@@ -20,7 +24,12 @@ class RocksDB::DB
 
     @len = Pointer(UInt64).malloc(1_u64)
     @err = Pointer(Pointer(UInt8)).malloc(1_u64)
-    @raw = rocksdb_open(@options.raw, @path)
+    if readonly
+      flag = error_if_log_file_exist ? 1_u8 : 0_u8
+      @raw = rocksdb_open_for_read_only(@options.raw, @path, flag)
+    else
+      @raw = rocksdb_open(@options.raw, @path)
+    end
     @opened = true
   end