C API

In this section, we describe how to use the C API of sherpa-ncnn.

Specifically, we will describe:

How to generate required files

How to use pkg-config with sherpa-ncnn

Generate required files

Before using the C API of sherpa-ncnn, we need to first build required libraries. You can choose either to build static libraries or shared libraries.

Build shared libraries

Assume that we want to put library files and header files in the directory /tmp/sherpa-ncnn/shared:

git clone https://github.com/k2-fsa/sherpa-ncnn
cd sherpa-ncnn
mkdir build-shared
cd build-shared

cmake \
  -DSHERPA_NCNN_ENABLE_C_API=ON \
  -DCMAKE_BUILD_TYPE=Release \
  -DBUILD_SHARED_LIBS=ON \
  -DCMAKE_INSTALL_PREFIX=/tmp/sherpa-ncnn/shared \
  ..

make -j6
make install

You should find the following files inside /tmp/sherpa-ncnn/shared:

$ tree /tmp/sherpa-ncnn/shared/
/tmp/sherpa-ncnn/shared/
├── bin
│   ├── sherpa-ncnn
│   └── sherpa-ncnn-microphone
├── include
│   └── sherpa-ncnn
│       └── c-api
│           └── c-api.h
├── lib
│   ├── libkaldi-native-fbank-core.dylib
│   ├── libncnn.dylib
│   ├── libsherpa-ncnn-c-api.dylib
│   └── libsherpa-ncnn-core.dylib
└── sherpa-ncnn.pc

5 directories, 8 files

$ tree /tmp/sherpa-ncnn/shared/
/tmp/sherpa-ncnn/shared/
├── bin
│   ├── sherpa-ncnn
│   └── sherpa-ncnn-microphone
├── include
│   └── sherpa-ncnn
│       └── c-api
│           └── c-api.h
├── lib
│   ├── libkaldi-native-fbank-core.so
│   ├── libncnn.so
│   ├── libsherpa-ncnn-c-api.so
│   └── libsherpa-ncnn-core.so
└── sherpa-ncnn.pc

5 directories, 8 files

Build static libraries

Assume that we want to put library files and header files in the directory /tmp/sherpa-ncnn/static:

git clone https://github.com/k2-fsa/sherpa-ncnn
cd sherpa-ncnn
mkdir build-static
cd build-static

cmake \
  -DSHERPA_NCNN_ENABLE_C_API=ON \
  -DCMAKE_BUILD_TYPE=Release \
  -DBUILD_SHARED_LIBS=OFF \
  -DCMAKE_INSTALL_PREFIX=/tmp/sherpa-ncnn/static \
  ..

make -j6
make install

You should find the following files in /tmp/sherpa-ncnn/static:

$ tree /tmp/sherpa-ncnn/static/
/tmp/sherpa-ncnn/static/
├── bin
│   ├── sherpa-ncnn
│   └── sherpa-ncnn-microphone
├── include
│   └── sherpa-ncnn
│       └── c-api
│           └── c-api.h
├── lib
│   ├── libkaldi-native-fbank-core.a
│   ├── libncnn.a
│   ├── libsherpa-ncnn-c-api.a
│   └── libsherpa-ncnn-core.a
└── sherpa-ncnn.pc

5 directories, 8 files

Build decode-file-c-api.c with generated files

To build the following file:

https://github.com/k2-fsa/sherpa-ncnn/blob/master/c-api-examples/decode-file-c-api.c

We can use:

export PKG_CONFIG_PATH=/tmp/sherpa-ncnn/static:$PKG_CONFIG_PATH

cd ./c-api-examples
gcc -o decode-file-c-api $(pkg-config --cflags sherpa-ncnn) ./decode-file-c-api.c $(pkg-config --libs sherpa-ncnn)

export PKG_CONFIG_PATH=/tmp/sherpa-ncnn/shared:$PKG_CONFIG_PATH

cd ./c-api-examples
gcc -o decode-file-c-api $(pkg-config --cflags sherpa-ncnn) ./decode-file-c-api.c $(pkg-config --libs sherpa-ncnn)