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# TsFile C++ Document

<p align="center">
  <img src="https://www.apache.org/logos/originals/tsfile.svg"
       alt="TsFile Logo"
       width="400"/>
</p>

## Introduction


This directory contains the C++ implementation of TsFile. The C++ version currently supports the query and write functions of TsFile, including time filtering queries.

The source code can be found in the `./src` directory. C/C++ examples are located in the `./examples` directory, and a benchmark for TsFile_cpp can be found in the `./bench_mark` directory. Additionally, a C function wrapper is available in the `./src/cwrapper` directory, which the Python tool relies on.

## How to make contributions

We use `clang-format` to ensure that our C++ code adheres to a consistent set of rules defined in `./clang-format`. This is similar to the Google style.

`mvn spotless` uses `clang-format v17.0.6` for C++ code formatting. Please make sure the `clang-format` in your `PATH` matches this version before submitting code.

How to install `clang-format v17.0.6`:

- macOS

```bash
brew install llvm@17
ln -sf /opt/homebrew/opt/llvm@17/bin/clang-format /opt/homebrew/bin/clang-format
```

- Windows

```bash
choco install llvm --version 17.0.6 --force
```

You can verify the installed version with:

```bash
clang-format --version
```

To format the C++ code, run:

```bash
mvn spotless:apply -P with-cpp
```

If you need to skip code formatting temporarily, you can add `-Dspotless.skip=true`, for example:

```bash
mvn package -P with-cpp clean verify -Dspotless.skip=true
```

We welcome any bug reports. You can open an issue with a title starting with [CPP] to describe the bug, like: https://github.com/apache/tsfile/issues/94

## Build

### Requirements

```bash
sudo apt-get update
sudo apt-get install -y cmake make g++ clang-format libuuid-dev
```

To build tsfile, you can run: `bash build.sh`. If you have Maven tools, you can run: `mvn package -P with-cpp clean verify`. Then, you can find the shared object at `./build`.

Before you submit your code to GitHub, please ensure that the `mvn` compilation is correct.

If you compile using MinGW on windows and encounter an error, you can try replacing MinGW with the following version that we have tried without problems:

* GCC 14.2.0 (with **POSIX** threads) + LLVM/Clang/LLD/LLDB 18.1.8 + MinGW-w64 12.0.0 UCRT - release 1
* GCC 12.2.0 + LLVM/Clang/LLD/LLDB 16.0.0 + MinGW-w64 10.0.0 (UCRT) - release 5
* GCC 12.2.0 + LLVM/Clang/LLD/LLDB 16.0.0 + MinGW-w64 10.0.0 (MSVCRT) - release 5
* GCC 11.2.0 + MinGW-w64 10.0.0 (MSVCRT) - release 1

### configure the cross-compilation toolchain

Modify the Toolchain File `cmake/ToolChain.cmake`, define the following variables:

- `CMAKE_C_COMPILER`: Specify the path to the C compiler.
- `CMAKE_CXX_COMPILER`: Specify the path to the C++ compiler.
- `CMAKE_FIND_ROOT_PATH`: Set the root path for the cross-compilation environment (e.g., the directory of the cross-compilation toolchain).

In the `cpp/` directory, run the following commands to create the build directory and start the compilation:
```
mkdir build && cd build
cmake .. -DToolChain=ON
make
```

## Parallel Write

TsFile C++ supports thread pool-based parallel column encoding for the table write path (`write_table`). When enabled, each column (time and value columns) is written in parallel using precomputed page boundaries, while maintaining aligned page sealing across columns.

### Build Options

Parallel write is controlled by the `ENABLE_THREADS` CMake option (ON by default):

```bash
cmake .. -DENABLE_THREADS=ON   # enable (default)
cmake .. -DENABLE_THREADS=OFF  # disable — all thread code is stripped at compile time
```

### Runtime Configuration

```cpp
#include "common/global.h"

// Enable or disable parallel write at runtime (auto-disabled on single-core machines)
storage::set_parallel_write_enabled(true);

// Set the number of worker threads (must be called before creating TsFileWriter)
storage::set_write_thread_count(4);
```

By default, parallel write is enabled when the machine has more than one CPU core, and the thread count is set to the number of hardware cores (capped at 64).

## Use TsFile

You can find examples on how to read and write data in `demo_read.cpp` and `demo_write.cpp` located under `./examples/cpp_examples`. There are also examples under `./examples/c_examples`on how to use a C-style API to read and write data in a C environment. You can run `bash build.sh` under `./examples` to generate an executable output under `./examples/build`.
