ntuple 0.7.0

Read and write ntuple ROOT files
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use anyhow::Result;
use std::io::Write;
use std::{env, fs::File, path::PathBuf};

fn main() -> Result<()> {
    compile_ntuple_writer()
}

fn compile_ntuple_writer() -> Result<()> {
    let out_path = PathBuf::from(env::var("OUT_DIR").unwrap());

    let bindings = bindgen::Builder::default()
        .header("src/ntuple.h")
        .parse_callbacks(Box::new(bindgen::CargoCallbacks))
        .allowlist_function("ntuple_create_reader")
        .allowlist_function("ntuple_read_event")
        .allowlist_function("ntuple_num_events")
        .allowlist_function("ntuple_delete_reader")
        .allowlist_function("ntuple_create_writer")
        .allowlist_function("ntuple_write_event")
        .allowlist_function("ntuple_delete_writer")
        .newtype_enum("ReadStatus")
        .newtype_enum("WriteResult")
        .generate()
        .expect("Failed to generate ntuple writer bindings");

    bindings
        .write_to_file(out_path.join("ntuple.rs"))
        .expect("Failed to write ntuple bindings!");

    println!("cargo:rerun-if-changed=src/ntupleevent.h");
    println!("cargo:rerun-if-changed=src/ntuplereader.h");
    println!("cargo:rerun-if-changed=src/ntuplewriter.h");
    println!("cargo:rerun-if-changed=src/root_interface.hh");
    println!("cargo:rerun-if-changed=src/ntuplereader.cc");
    println!("cargo:rerun-if-changed=src/ntuplewriter.cc");
    println!("cargo:rerun-if-changed=src/root_interface.cc");
    let mut cc_cmd = cc::Build::new();
    cc_cmd.cpp(true).files([
        "src/ntuplereader.cc",
        "src/ntuplewriter.cc",
        "src/root_interface.cc",
    ]);

    for flag in get_root_flags("--cflags")? {
        cc_cmd.flag(&flag);
    }

    cc_cmd.compile("ntuplewriter");

    let root_linker_flags = get_root_flags("--libs")?;
    let linker_flags =
        Vec::from_iter(root_linker_flags.iter().map(|f| format!(r#"r"{f}""#)));
    let mut flag_out = File::create(out_path.join("flags.rs"))?;

    writeln!(
        flag_out,
        "pub const ROOT_LINKER_FLAGS: [&str; {}] = [{}];",
        linker_flags.len(),
        linker_flags.join(", ")
    )?;

    for flag in root_linker_flags {
        println!("cargo:rustc-link-arg={flag}");
    }

    Ok(())
}

fn get_root_flags(flags: &str) -> Result<Vec<String>> {
    use anyhow::{bail, Context};
    use std::{process::Command, str::from_utf8};

    const CFG_CMD: &str = "root-config";

    let cmd = format!("{CFG_CMD} {flags}");
    let output = Command::new(CFG_CMD)
        .arg(flags)
        .output()
        .with_context(|| format!("Failed to run `{cmd}`"))?;
    if !output.status.success() {
        if output.stderr.is_empty() {
            bail!("{CFG_CMD} {flags} failed without error messages");
        } else {
            bail!(
                "{CFG_CMD} {flags} failed: {}",
                from_utf8(&output.stderr).unwrap()
            );
        }
    }
    let args = from_utf8(&output.stdout)
        .with_context(|| format!("Failed to convert `{cmd}` output to utf8"))?;
    Ok(args.split_whitespace().map(|arg| arg.to_owned()).collect())
}