# C/C++ quickstart

This is a ~60-second round-trip in C/C++: snapshot a directory, `push` it to a
local `file://` store, then `pull` it back and confirm the ID matches. Snapshot
IDs are 64-character lowercase hex and are bit-identical to the CLI and every
other binding.

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## 1. Install

Build the `snapdir-ffi` C ABI from crates.io and compile against `snapdir.hpp` —
see [Install snapdir for C/C++](/install/cpp/) for the full recipe:

```sh
cargo build --release                       # -> target/release/libsnapdir_ffi.a
cbindgen --config cbindgen.toml --crate snapdir-ffi --output snapdir.h .
g++ -std=c++20 roundtrip.cpp -I. -L. -lsnapdir_ffi -lpthread -ldl -lm -o roundtrip
```

## 2. Snapshot + push

Compute the snapshot ID of a directory, then push it to a local store. The store
URI is always an argument; `file://$PWD/store` needs no setup.

```cpp
#include <snapdir.hpp>
#include <cstdlib>
#include <iostream>
#include <string>

int main() {
    const std::string dir   = "./my-dir";
    const std::string store = std::string("file://") + std::getenv("PWD") + "/store";

    // Synchronous id — the 64-char lowercase hex snapshot id.
    std::cout << "id:   " << snapdir::id(dir) << '\n';

    // Async push returns std::future<std::string>; .get() resolves or throws.
    const std::string id = snapdir::push(dir, store).get();
    std::cout << "push: " << id << '\n';   // <snapshot-id>
}
```

## 3. Pull it back

Pull the snapshot into a fresh directory and recompute its ID — it matches the
one you pushed.

```cpp
snapdir::pull(id, store, "./restored").get();

const std::string back = snapdir::id("./restored");
std::cout << (back == id ? "match" : "MISMATCH") << ": " << back << '\n';
```

The `id` you get here is the same snapshot id the CLI prints for `snapdir id` and
`snapdir push` — every binding agrees byte-for-byte.