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Example usage in unit test.

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Alex Helfet 2017-03-23 20:12:44 +00:00
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README.md
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@ -4,15 +4,78 @@ capnpc-c
This is a C plugin for [Cap'n Proto](http://kentonv.github.io/capnproto), an
efficient protocol for sharing data and capabilities.
This is only the plugin, to properly make use of it you need to download, build
and install capnpc and then build and install this project and then you can
utilize it as:
This is only the code generator plugin, to properly make use of it you
need to download, build and install capnpc and then build and install
this project and then you can utilize it as:
capnpc compiler/test.capnp -oc
```sh
capnpc compiler/test.capnp -oc
```
[![Build Status](https://travis-ci.org/opensourcerouting/c-capnproto.svg?branch=master)](https://travis-ci.org/opensourcerouting/c-capnproto)
## status
## Building on Linux
```sh
git clone https://github.com/opensourcerouting/c-capnproto
cd c-capnproto
git submodule update --init --recursive
autoreconf -f -i -s
./configure
make
make check
```
## Usage
### Generating C code from a `.capnp` schema file
The `compiler` directory contains the C language plugin (`capnpc-c`) for use with the `capnp` tool: https://capnproto.org/capnp-tool.html.
`capnp` will by default search `$PATH` for `capnpc-c` - if it's on your PATH, you can generate code for your schema as follows:
```sh
capnp compile -o c myschema.capnp
```
Otherwise, you can specify the path to the c plugin:
```sh
capnp compile -o ./capnpc-c myschema.capnp
```
`capnp` generates a C struct that corresponds to each capn proto struct, along with read/write functions that convert to/from capn proto form.
If you want accessor functions for struct members, use attribute `fieldgetset` in your `.capnp` file as follows:
```capnp
using C = import "${c-capnproto}/compiler/c.capnp";
$C.fieldgetset;
struct MyStruct {}
```
### Example C code
See the unit tests in [`tests/example-test.cpp`](tests/example-test.cpp). The example schema file is [`tests/example.capnp`](tests/example.capnp). The tests are written in C++, but only use C features.
You need to compile these runtime library files and link them into your own project's binaries:
* [`lib/capn.c`](lib/capn.c)
* [`lib/capn-malloc.c`](lib/capn-malloc.c)
* [`lib/capn-stream.c`](lib/capn-stream.c)
Your include path must contain the runtime library directory [`lib`](lib). Header file [`lib/capnp_c.h`](lib/capnp_c.h) contains the public interfaces of the library.
For further reference, please see the other unit tests in [`tests`](tests), and header file [`lib/capnp_c.h`](lib/capnp_c.h).
The project [`quagga-capnproto`](https://github.com/opensourcerouting/quagga-capnproto) uses `c-capnproto` and contains some good examples, as found with [this github repository search](https://github.com/opensourcerouting/quagga-capnproto/search?utf8=%E2%9C%93&q=capn&type=):
* Serialization in function [`bgp_notify_send()`](https://github.com/opensourcerouting/quagga-capnproto/blob/27061648f3418fac0d217b16a46add534343e841/bgpd/bgp_zmq.c#L81-L96) in file `quagga-capnproto/bgpd/bgp_zmq.c`
* Deserialization in function [`qzc_callback()`](https://github.com/opensourcerouting/quagga-capnproto/blob/27061648f3418fac0d217b16a46add534343e841/lib/qzc.c#L249-L257) in file `quagga-capnproto/lib/qzc.c`
## Status
This is a merge of 3 forks of [James McKaskill's great
work](https://github.com/jmckaskill/c-capnproto), which has been untouched for
@ -21,33 +84,3 @@ a while:
- [liamstask's fork](https://github.com/liamstask/c-capnproto)
- [baruch's fork](https://github.com/baruch/c-capnproto)
- [kylemanna's fork](https://github.com/kylemanna/c-capnproto)
## usage
The `compiler` directory contains the C language plugin (`capnpc-c`) for use with the `capnp` tool: https://capnproto.org/capnp-tool.html.
`capnp` will by default search `$PATH` for `capnpc-c` - if it's on your PATH, you can generate code for your schema as follows:
$ capnp compile -o c myschema.capnp
Otherwise, you can specify the path to the c plugin:
$ capnp compile -o ./capnpc-c myschema.capnp
`capnp` generates a C struct that corresponds to each capn proto struct, along with read/write functions that convert to/from capn proto form.
TBD whether it will make sense in the future to provide accessor functions for struct members, rather than converting entire structs.
## building on linux
```
git clone https://github.com/opensourcerouting/c-capnproto
cd c-capnproto
git submodule update --init --recursive
autoreconf -f -i -s
./configure
make
make check
```