file_alloc 0.1.2

# `file_alloc`

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跨平台、高性能、兼容性好的文件大小分配库

- **跨平台**：支持 Windows、Linux、MacOS
- **高性能**：优先使用 fallocate 高速分配
- **兼容性好**：支持自动回退到全部写 0
- **取消安全**：可用随时中断分配
- **轻量**：只依赖与 `tokio`、`rustix`、`windows-sys`

```rust
use file_alloc::{init_fast_alloc, FileAlloc};

#[tokio::main]
async fn main() -> std::io::Result<()> {
    init_fast_alloc(); // 必须在打开文件前调用，否则无法享受快分配

    let temp_file = tempfile::NamedTempFile::new()?;
    let mut file = tokio::fs::File::options()
        .read(true)
        .write(true)
        .open(temp_file.path())
        .await?;

    let target_size = 5 * 1024 * 1024;
    file.allocate(target_size).await?; // 文件预分配

    let metadata = file.metadata().await?;
    assert_eq!(metadata.len(), target_size);
    Ok(())
}
```