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src Directory Reference

## Directories

| benchmark
| plugin
| tools

## Files

| BinaryDict.hpp
| CmdLineOutput.hpp
| Common.hpp
| Config.hpp
| ConfigBasedConverter.hpp
| ConfigTestBase.hpp
| Conversion.hpp
| ConversionChain.hpp
| ConversionInspection.hpp
| Converter.hpp
| DartsDict.hpp
| Dict.hpp
| DictConverter.hpp
| DictEntry.hpp
| DictGroup.hpp
| DictGroupTestBase.hpp
| Exception.hpp
| Export.hpp
| Lexicon.hpp
| MarisaDict.hpp
| MaxMatchSegmentation.hpp
| opencc.h
| Optional.hpp
| PhraseExtract.hpp
| PipelineConverter.hpp
| PluginSegmentation.hpp
| PrefixMatch.hpp
| ResourceProvider.hpp
| Segmentation.hpp
| Segments.hpp
| SerializableDict.hpp
| SerializedValues.hpp
| SimpleConverter.hpp
| SingleStageConverter.hpp
| TestUtils.hpp
| TestUtilsUTF8.hpp
| TextDict.hpp
| TextDictTestBase.hpp
| UTF8StringSlice.hpp
| UTF8Util.hpp
| WinUtil.hpp

## Detailed Description

# OpenCC Source Layout

This directory contains the C++ core library, the public C API, command-line tools, and native extension entry points. The code is organized around a simple conversion pipeline:

1. Load a JSON configuration.
2. Load segmenters and dictionaries referenced by that configuration.
3. Segment input text.
4. Apply one or more dictionary-based conversion stages.
5. Return converted text or inspection data.

The data files that drive this pipeline live outside this directory:

- data/config/*.json: conversion schemes.
- data/dictionary/*.txt: source dictionaries.
- generated .ocd2 files: marisa-trie dictionary binaries.

# Main Pipeline

## Configuration

- Config.hpp, Config.cpp
  - Finds and parses JSON configuration files.
  - Builds segmenters, dictionaries, dictionary groups, conversions, and converters.
  - Resolves dictionary/resource files through ResourceProvider.
  - Keeps config loading separate from dictionary resource lookup.
  - Uses UTF-16-capable file checks on Windows for internal config and resource paths.
- ResourceProvider.hpp, ResourceProvider.cpp
  - Provides ResourceProvider and FilesystemResourceProvider.
  - FilesystemResourceProvider searches configured resource directories in order and returns a resolved path for lower-level dictionary loaders.
  - Embedded hosts can combine application, plugin, and system OpenCC data directories without changing config JSON.

## Segmentation

- Segmentation.hpp, Segmentation.cpp
  - Base interface for segmenters.
- MaxMatchSegmentation.hpp, MaxMatchSegmentation.cpp
  - Maximum forward matching segmenter used by normal OpenCC configs.
  - Uses dictionary prefix matches to keep phrases intact.
- PluginSegmentation.hpp, PluginSegmentation.cpp
  - Runtime-loaded segmentation plugin support.
  - Used by the Jieba plugin.
- Segments.hpp
  - Segment container used between segmenters, conversions, and inspection output.

## Conversion

- Converter.hpp, Converter.cpp
  - Owns a segmenter and a conversion chain.
  - Provides high-level string and buffer conversion.
- ConversionChain.hpp, ConversionChain.cpp
  - Ordered list of conversion stages.
- Conversion.hpp, Conversion.cpp
  - One dictionary-backed conversion stage.
- ConversionInspection.hpp
  - Data structures returned by inspection mode.

The core conversion path depends on segmentation and longest-prefix dictionary matching. Character-by-character replacement is not equivalent to OpenCC behavior because phrase priority and multi-stage conversion order matter.

# Dictionaries

## Interfaces and Shared Types

- Dict.hpp, Dict.cpp
  - Abstract dictionary interface.
  - Supports exact match, prefix match, all-prefix match, and enumeration.
- DictEntry.hpp, DictEntry.cpp
  - Key/value entry representation.
- PrefixMatch.hpp, PrefixMatch.cpp
  - Prefix match result.
- Lexicon.hpp, Lexicon.cpp
  - In-memory collection of dictionary entries.
- SerializableDict.hpp
  - Template helpers for loading serialized dictionaries from files.
- SerializedValues.hpp, SerializedValues.cpp
  - Compact storage for candidate value lists used by .ocd2.

## Implementations

- TextDict.hpp, TextDict.cpp
  - Tab-delimited text dictionary.
  - Useful for source data and tests.
- MarisaDict.hpp, MarisaDict.cpp
  - Default .ocd2 dictionary format.
  - Uses marisa-trie for compact prefix lookup.
- DartsDict.hpp, DartsDict.cpp
  - Legacy .ocd dictionary format.
  - Requires Darts support.
- BinaryDict.hpp, BinaryDict.cpp
  - Legacy binary payload support used with Darts serialization.
- DictGroup.hpp, DictGroup.cpp
  - Ordered group of dictionaries.
  - Tries dictionaries in sequence and returns the first usable match.
- DictConverter.hpp, DictConverter.cpp
  - Converts dictionary files between supported formats.

# Public APIs

## C++ API

- SimpleConverter.hpp, SimpleConverter.cpp
  - High-level C++ wrapper around Config and Converter.
  - Accepts a config name/path, optional search paths, or an explicit ResourceProvider.
  - Throws C++ exceptions on failures.

## C API

- opencc.h
  - Stable C ABI for downstream users and bindings.
  - Exposes opencc_open, opencc_open_w, opencc_convert_utf8, opencc_convert_utf8_free, opencc_close, and error helpers.

Windows path semantics need care:

- opencc_open_w(const wchar_t*) is the explicit UTF-16 Windows API.
- opencc_open(const char*) keeps the historical Windows/MSVC narrow-string behavior. Do not silently change its encoding contract without a migration plan.
- New Windows path-taking C APIs should use explicit names such as *_utf8 or *_w rather than relying on ambiguous char* semantics.

## Python Extension

- py_opencc.cpp
  - Python module binding built on top of the C++ core.

# Command-Line Tools

The native CLI tools live under src/tools.

- CommandLine.cpp
  - Small executable entry point.
  - On Windows/MSVC, obtains command-line arguments through wide Windows APIs and converts them to UTF-8 before dispatching to the CLI core.
- CommandLineMain.hpp, CommandLineMain.cpp
  - Main opencc command implementation.
  - Handles conversion, segmentation/inspection modes, measurement output, stream conversion, and explicit --in-place conversion.
- PlatformIO.hpp, PlatformIO.cpp
  - CLI platform boundary for path-sensitive operations.
  - Handles UTF-8 file open/remove/replace, temporary output files, same-file detection, real path resolution, and Windows argv collection.
- DictConverter.cpp
  - opencc_dict implementation.
- PhraseExtract.cpp
  - opencc_phrase_extract implementation.
- CmdLineOutput.hpp
  - Shared command-line help formatting.

CLI file conversion must remain streaming. Do not replace stream processing with "read whole file into memory" logic. In-place conversion is intentionally opt-in:

- Without --in-place, -i and -o referring to the same actual file is rejected.
- With --in-place, output is written to a temporary file next to the target, then the target is replaced after conversion succeeds.

# Platform and Path Handling

OpenCC uses UTF-8 internally for paths unless an API explicitly documents a different contract. Windows code should convert to UTF-16 at the platform boundary.

Important files:

- UTF8Util.hpp, UTF8Util.cpp
  - UTF-8 helpers and platform string conversion helpers.
- WinUtil.hpp
  - Small Windows-only UTF-8/UTF-16 conversion helpers.
- tools/PlatformIO.*
  - CLI path boundary.

Maintenance rules:

- Do not add raw fopen, std::fstream, stat, std::tmpnam, or narrow Win32 path calls to new Windows-sensitive paths.
- Prefer existing platform helpers or add a clearly named boundary helper.
- Keep public API encoding contracts explicit.
- Validate Windows path changes with real Windows CI. Zig cross-compilation is useful for compile/link coverage, but it does not execute Windows runtime path behavior.

# Plugins

- plugin/OpenCCPlugin.h
  - C plugin ABI used by loadable segmentation plugins.
- PluginSegmentation.*
  - Host-side plugin loader and adapter.

The Jieba plugin lives outside src under plugins/jieba.

# Tests

Most core modules have adjacent *Test.cpp files in this directory. Important test groups include:

- ConfigTest.cpp
  - Config search paths and Unicode config path handling.
- SimpleConverterTest.cpp
  - C++ wrapper behavior and C API basics.
- Conversion*Test.cpp
  - Conversion and inspection behavior.
- MaxMatchSegmentationTest.cpp
  - Segmenter behavior.
- MarisaDictTest.cpp, TextDictTest.cpp, DictGroupTest.cpp
  - Dictionary implementations.
- UTF8*Test.cpp
  - UTF-8 slicing and utility behavior.

CLI tests live in test/CommandLineConvertTest.cpp because they execute the built command-line binary. They cover streaming behavior, Unicode paths, measurement output, inspection modes, and in-place conversion safety.

# Build Integration

The source tree is built through both CMake and Bazel:

- src/CMakeLists.txt
- src/BUILD.bazel
- src/tools/CMakeLists.txt
- src/tools/BUILD.bazel

When adding or renaming source files, update both build systems and any direct cross-build scripts that carry explicit source lists.