Add README.md for src/ directory.

#codehealth

PiperOrigin-RevId: 691395061

src/README.md

@@ -0,0 +1,123 @@
+# src/
+
+Directory of the source code.
+
+## Overview of components and directories
+
+```
++------------+            +------------+            +------------+
+| Server     | <--------> | Client     | <--------> | UI         |
++------------+  Protocol  +------------+  Protocol  +------------+
+| Session    |            | Platform   |
++------------+            +------------+
+| Converter  |
++------------+
+| Dictionary |
++------------+
+```
+
+Note: Platform is used for various components for platform specific
+requirements.
+
+### Platform
+
+*   [android/](android/)
+    *   Android specific implementation.
+    *   Note: Mozc does not contain the client UI implementation for Android.
+*   [unix/](unix/)
+    *   Linux specific implementation.
+*   [win32/](win32/)
+    *   Windows specific implementation.
+*   [mac/](mac/)
+    *   macOS specific implementation.
+*   [ios/](ios/)
+    *   iOS specific implementation.
+    *   Note: Mozc does not officially support iOS build.
+
+### Build
+
+*   [build_tools/](build_tools/)
+    *   Utilities used for build (e.g. code generation).
+*   [bazel/](bazel/)
+    *   Build rules and tools for Bazel build.
+*   [gyp/](gyp/)
+    *   Build rules and tools for GYP.
+*   [protobuf/](protobuf/)
+    *   Build rules and tools of GYP for Protocol Buffers.
+
+### Base
+
+*   [base/](base/)
+    *   Fundamental libraries for generic purposes.
+*   [data/](data/)
+    *   Directory and subdirectories of data files.
+*   [third_party/](third_party/)
+    *   Third party libraries (e.g. Abseil).
+*   [testing/](testing/)
+    *   Libraries for testing.
+*   [usage_stats/](usage_stats/)
+    *   Libraries for usage statistics.
+    *   Note: Mozc does not use usage statistics.
+
+### Protocol
+
+*   [protocol/](protocol/)
+    *   Protocol definitions of function API (e.g. API between client and
+        server).
+*   [config/](config/)
+    *   Libraries to manage user configurations.
+*   [request/](request/)
+    *   Libraries of request used for text conversion.
+
+### Client / Server
+
+*   [client/](client/)
+    *   Libraries of client code.
+    *   Note: The main function of the client is in each platform directory.
+*   [server/](server/)
+    *   Libraries of server code.
+    *   The main function is in this directory.
+*   [ipc/](ipc/)
+    *   Libraries of IPC to communicate between client, server and other
+        processes.
+
+### Session
+
+*   [session/](session/)
+    *   Libraries of state management between user interactions and text
+        conversion.
+*   [composer/](composer/)
+    *   Libraries of text composing (e.g. Romaji-Hiragana conversion).
+*   [transliteration/](transliteration/)
+    *   Libraries of script type transliteration (e.g. half-width Katakana,
+        full-width Ascii).
+
+### Converter
+
+*   [engine/](engine/)
+    *   Libraries to manage converter libraries.
+*   [data_manager/](data_manager/)
+    *   Libraries to manage converter data.
+*   [converter/](converter/)
+    *   Libraries of text conversion (e.g. Hiragana to Kanji exact match
+        conversion).
+*   [rewriter/](rewriter/)
+    *   Libraries for additional conversions (e.g. date input, symbol input, zip
+        code input).
+*   [prediction/](prediction/)
+    *   Libraries of text prediction (e.g. Hiragana to Kanji prefix match
+        conversion).
+
+### Dictionary
+
+*   [dictionary/](dictionary/)
+    *   Libraries of dictionary lookup (e.g. Hiragana key to possible words).
+*   [storage/](storage/)
+    *   Libraries of dictionary data storage (e.g. LOUDS, etc.).
+
+### UI
+
+*   [renderer/](renderer/)
+    *   UI application of candidate words.
+*   [gui/](gui/)
+    *   GUI applications for configurations.