Add basic Kotlin support (#5409)

* [Kotlin] Add kotlin generate code for tests and add kotlin test to TestAll.sh * [Kotlin] Add Kotlin generator This change adds support for generating Kotlin classes. The approach of this generator is to keep it as close as possible to the java generator for now, in order to keep the change simple. It uses the already implemented java runtime, so we don't support cross-platform nor js Kotlin yet. Kotlin tests are just a copy of the java tests. * Add optional ident support for CodeWriter Identation is important for some languages and different projects have different ways of ident code, e.g. tabs vs spaces, so we are adding optional support on CodeWriter for identation. * [Kotlin] Add Documentation for Kotlin * [Kotlin] Modify generated code to use experimental Unsigned types.
2026-06-02 20:15:34 +00:00 · 2019-07-22 20:05:15 -03:00
parent a752d1b88c
commit de9aa0cdee
54 changed files with 4995 additions and 64 deletions
--- a/docs/source/Tutorial.md
+++ b/docs/source/Tutorial.md
@@ -23,6 +23,7 @@ Please select your desired language for our quest:
 <form>
  <input type="radio" name="language" value="cpp" checked="checked">C++</input>
  <input type="radio" name="language" value="java">Java</input>
+  <input type="radio" name="language" value="kotlin">Kotlin</input>
  <input type="radio" name="language" value="csharp">C#</input>
  <input type="radio" name="language" value="go">Go</input>
  <input type="radio" name="language" value="python">Python</input>
@@ -115,6 +116,9 @@ For your chosen language, please cross-reference with:
 <div class="language-java">
 [SampleBinary.java](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.java)
 </div>
+<div class="language-kotlin">
+[SampleBinary.kt](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.kt)
+</div>
 <div class="language-csharp">
 [SampleBinary.cs](https://github.com/google/flatbuffers/blob/master/samples/SampleBinary.cs)
 </div>
@@ -284,6 +288,12 @@ Please be aware of the difference between `flatc` and `flatcc` tools.
  ./../flatc --java monster.fbs
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.sh}
+  cd flatbuffers/samples
+  ./../flatc --kotlin monster.fbs
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.sh}
  cd flatbuffers/samples
@@ -382,6 +392,13 @@ The first step is to import/include the library, generated files, etc.
  import com.google.flatbuffers.FlatBufferBuilder;
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kotlin}
+  import MyGame.Sample.* //The `flatc` generated files. (Monster, Vec3, etc.)
+
+  import com.google.flatbuffers.FlatBufferBuilder
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  using FlatBuffers;
@@ -525,6 +542,13 @@ which will grow automatically if needed:
  FlatBufferBuilder builder = new FlatBufferBuilder(1024);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // Create a `FlatBufferBuilder`, which will be used to create our
+  // monsters' FlatBuffers.
+  val builder = FlatBufferBuilder(1024)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // Create a `FlatBufferBuilder`, which will be used to create our
@@ -633,6 +657,19 @@ our `orc` Monster, lets create some `Weapon`s: a `Sword` and an `Axe`.
  int axe = Weapon.createWeapon(builder, weaponTwoName, weaponTwoDamage);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val weaponOneName = builder.createString("Sword")
+  val weaponOneDamage: Short = 3;
+
+  val weaponTwoName = builder.createString("Axe")
+  val weaponTwoDamage: Short = 5;
+
+  // Use the `createWeapon()` helper function to create the weapons, since we set every field.
+  val sword = Weapon.createWeapon(builder, weaponOneName, weaponOneDamage)
+  val axe = Weapon.createWeapon(builder, weaponTwoName, weaponTwoDamage)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  var weaponOneName = builder.CreateString("Sword");
@@ -875,6 +912,17 @@ traversal. This is generally easy to do on any tree structures.
  int inv = Monster.createInventoryVector(builder, treasure);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // Serialize a name for our monster, called "Orc".
+  val name = builder.createString("Orc")
+
+  // Create a `vector` representing the inventory of the Orc. Each number
+  // could correspond to an item that can be claimed after he is slain.
+  val treasure = byteArrayOf(0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
+  val inv = Monster.createInventoryVector(builder, treasure)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // Serialize a name for our monster, called "Orc".
@@ -1060,6 +1108,16 @@ offsets.
  int weapons = Monster.createWeaponsVector(builder, weaps);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // Place the two weapons into an array, and pass it to the `createWeaponsVector()` method to
+  // create a FlatBuffer vector.
+  val weaps = intArrayOf(sword, axe)
+
+  // Pass the `weaps` array into the `createWeaponsVector()` method to create a FlatBuffer vector.
+  val weapons = Monster.createWeaponsVector(builder, weaps)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  var weaps = new Offset<Weapon>[2];
@@ -1180,6 +1238,14 @@ for the `path` field above:
  int path = fbb.endVector();
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  Monster.startPathVector(fbb, 2)
+  Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f)
+  Vec3.createVec3(builder, 4.0f, 5.0f, 6.0f)
+  val path = fbb.endVector()
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  Monster.StartPathVector(fbb, 2);
@@ -1318,6 +1384,22 @@ can serialize the monster itself:
  int orc = Monster.endMonster(builder);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // Create our monster using `startMonster()` and `endMonster()`.
+  Monster.startMonster(builder)
+  Monster.addPos(builder, Vec3.createVec3(builder, 1.0f, 2.0f, 3.0f))
+  Monster.addName(builder, name)
+  Monster.addColor(builder, Color.Red)
+  Monster.addHp(builder, 300.toShort())
+  Monster.addInventory(builder, inv)
+  Monster.addWeapons(builder, weapons)
+  Monster.addEquippedType(builder, Equipment.Weapon)
+  Monster.addEquipped(builder, axe)
+  Monster.addPath(builder, path)
+  val orc = Monster.endMonster(builder)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // Create our monster using `StartMonster()` and `EndMonster()`.
@@ -1627,6 +1709,12 @@ Here is a repetition these lines, to help highlight them more clearly:
    Monster.addEquipped(axe); // Union data
  ~~~
 </div>
+<div class="language-kotlin">
+  ~~~{.kt}
+    Monster.addEquippedType(builder, Equipment.Weapon) // Union type
+    Monster.addEquipped(axe) // Union data
+  ~~~
+</div>
 <div class="language-csharp">
  ~~~{.cs}
    Monster.AddEquippedType(builder, Equipment.Weapon); // Union type
@@ -1722,6 +1810,12 @@ appropriate `finish` method.
  builder.finish(orc); // You could also call `Monster.finishMonsterBuffer(builder, orc);`.
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // Call `finish()` to instruct the builder that this monster is complete.
+  builder.finish(orc) // You could also call `Monster.finishMonsterBuffer(builder, orc);`.
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // Call `Finish()` to instruct the builder that this monster is complete.
@@ -1814,6 +1908,17 @@ like so:
  byte[] buf = builder.sizedByteArray();
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  // This must be called after `finish()`.
+  val buf = builder.dataBuffer()
+  // The data in this ByteBuffer does NOT start at 0, but at buf.position().
+  // The number of bytes is buf.remaining().
+
+  // Alternatively this copies the above data out of the ByteBuffer for you:
+  val buf = builder.sizedByteArray()
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // This must be called after `Finish()`.
@@ -1936,6 +2041,13 @@ before:
  import com.google.flatbuffers.FlatBufferBuilder;
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  import MyGame.Sample.* //The `flatc` generated files. (Monster, Vec3, etc.)
+
+  import com.google.flatbuffers.FlatBufferBuilder
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  using FlatBuffers;
@@ -2084,6 +2196,15 @@ won't work**
  Monster monster = Monster.getRootAsMonster(buf);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val bytes = /* the data you just read */
+  val buf = java.nio.ByteBuffer.wrap(bytes)
+
+  // Get an accessor to the root object inside the buffer.
+  Monster monster = Monster.getRootAsMonster(buf)
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  byte[] bytes = /* the data you just read */
@@ -2208,6 +2329,13 @@ accessors for all non-`deprecated` fields. For example:
  String name = monster.name();
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val hp = monster.hp
+  val mana = monster.mana
+  val name = monster.name
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  // For C#, unlike most other languages support by FlatBuffers, most values (except for
@@ -2313,6 +2441,14 @@ To access sub-objects, in the case of our `pos`, which is a `Vec3`:
  float z = pos.z();
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val pos = monster.pos!!
+  val x = pos.x
+  val y = pos.y
+  val z = pos.z
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  var pos = monster.Pos.Value;
@@ -2429,6 +2565,12 @@ FlatBuffers `vector`.
  byte thirdItem = monster.inventory(2);
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kotlin}
+  val invLength = monster.inventoryLength
+  val thirdItem = monster.inventory(2)!!
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  int invLength = monster.InventoryLength;
@@ -2520,6 +2662,13 @@ except your need to handle the result as a FlatBuffer `table`:
  short secondWeaponDamage = monster.weapons(1).damage();
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val weaponsLength = monster.weaponsLength
+  val secondWeaponName = monster.weapons(1)!!.name
+  val secondWeaponDamage = monster.weapons(1)!!.damage
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  int weaponsLength = monster.WeaponsLength;
@@ -2640,6 +2789,19 @@ We can access the type to dynamically cast the data as needed (since the
  }
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val unionType = monster.EquippedType
+
+  if (unionType == Equipment.Weapon) {
+    val weapon = monster.equipped(Weapon()) as Weapon // Requires explicit cast
+                                                            // to `Weapon`.
+
+    val weaponName = weapon.name   // "Axe"
+    val weaponDamage = weapon.damage // 5
+  }
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  var unionType = monster.EquippedType;
@@ -2816,6 +2978,14 @@ mutators like so:
  monster.mutateInventory(0, 1);   // Set vector element.
 ~~~
 </div>
+<div class="language-kotlin">
+~~~{.kt}
+  val monster = Monster.getRootAsMonster(buf)
+  monster.mutateHp(10)            // Set table field.
+  monster.pos!!.mutateZ(4)        // Set struct field.
+  monster.mutateInventory(0, 1)   // Set vector element.
+~~~
+</div>
 <div class="language-csharp">
 ~~~{.cs}
  var monster = Monster.GetRootAsMonster(buf);
@@ -2903,9 +3073,9 @@ See the individual language documents for support.

 If you are working with C, C++, or Lobster, you can parse JSON at runtime.
 If your language does not support JSON at the moment, `flatc` may provide an
-alternative. Using `flatc` is often the preferred method, as it doesn't require you to 
-add any new code to your program. It is also efficient, since you can ship with 
-the binary data. The drawback is that it requires an extra step for your 
+alternative. Using `flatc` is often the preferred method, as it doesn't require you to
+add any new code to your program. It is also efficient, since you can ship with
+the binary data. The drawback is that it requires an extra step for your
 users/developers to perform (although it may be able to be automated
 as part of your compilation).

@@ -2979,13 +3149,13 @@ Converting from a FlatBuffer binary representation to JSON is supported as well:
 ./../flatc --json --raw-binary monster.fbs -- monsterdata.bin
 ~~~
 This will convert `monsterdata.bin` back to its original JSON representation.
-You need to pass the corresponding FlatBuffers schema so that flatc knows how to 
-interpret the binary buffer. Since `monster.fbs` does not specify an explicit 
-`file_identifier` for binary buffers, `flatc` needs to be forced into reading 
+You need to pass the corresponding FlatBuffers schema so that flatc knows how to
+interpret the binary buffer. Since `monster.fbs` does not specify an explicit
+`file_identifier` for binary buffers, `flatc` needs to be forced into reading
 the `.bin` file using the `--raw-binary` option.

-The FlatBuffer binary representation does not explicitly encode default values, 
-therefore they are not present in the resulting JSON unless you specify 
+The FlatBuffer binary representation does not explicitly encode default values,
+therefore they are not present in the resulting JSON unless you specify
 `--defaults-json`.

 If you intend to process the JSON with other tools, you may consider switching
@@ -2993,7 +3163,7 @@ on `--strict-json` so that identifiers are quoted properly.

 *Note: The resulting JSON file is not necessarily identical with the original JSON.
 If the binary representation contains floating point numbers, floats and doubles
-are rounded to 6 and 12 digits, respectively, in order to represent them as 
+are rounded to 6 and 12 digits, respectively, in order to represent them as
 decimals in the JSON document. *

 ## Advanced Features for Each Language
@@ -3009,6 +3179,9 @@ For your chosen language, see:
 <div class="language-java">
 [Use in Java/C#](@ref flatbuffers_guide_use_java_c-sharp)
 </div>
+<div class="language-kotlin">
+[Use in Kotlin](@ref flatbuffers_guide_use_kotlin)
+</div>
 <div class="language-csharp">
 [Use in Java/C#](@ref flatbuffers_guide_use_java_c-sharp)
 </div>