view rust/hgcli/src/main.rs @ 38717:aa21a9ad46ea

sparse-revlog: new requirement enabled with format.sparse-revlog

The meaning of the new 'sparse-revlog' requirement is that the revlogs are
allowed to contain wider delta chains with larger holes between the interesting
chunks. These sparse delta chains should be read in several chunks to avoid a
potential explosion of memory usage.

Former version won't know how to read a delta chain in several chunks. They
would keep reading them in a single read, and therefore would be subject to the
potential memory explosion. Hence this new requirement: only versions having
support of sparse-revlog reading should be allowed to read such a revlog.

Implementation of this new algorithm and tools to enable or disable the
requirement will follow in the next changesets.

// main.rs -- Main routines for `hg` program
//
// Copyright 2017 Gregory Szorc <[e-mail]>
//
// This software may be used and distributed according to the terms of the
// GNU General Public License version 2 or any later version.

extern crate libc;
extern crate cpython;
extern crate python27_sys;

use cpython::{NoArgs, ObjectProtocol, PyModule, PyResult, Python};
use libc::{c_char, c_int};

use std::env;
use std::path::PathBuf;
use std::ffi::{CString, OsStr};
#[cfg(target_family = "unix")]
use std::os::unix::ffi::{OsStrExt, OsStringExt};

#[derive(Debug)]
struct Environment {
    _exe: PathBuf,
    python_exe: PathBuf,
    python_home: PathBuf,
    mercurial_modules: PathBuf,
}

/// Run Mercurial locally from a source distribution or checkout.
///
/// hg is <srcdir>/rust/target/<target>/hg
/// Python interpreter is detected by build script.
/// Python home is relative to Python interpreter.
/// Mercurial files are relative to hg binary, which is relative to source root.
#[cfg(feature = "localdev")]
fn get_environment() -> Environment {
    let exe = env::current_exe().unwrap();

    let mut mercurial_modules = exe.clone();
    mercurial_modules.pop(); // /rust/target/<target>
    mercurial_modules.pop(); // /rust/target
    mercurial_modules.pop(); // /rust
    mercurial_modules.pop(); // /

    let python_exe: &'static str = env!("PYTHON_INTERPRETER");
    let python_exe = PathBuf::from(python_exe);

    let mut python_home = python_exe.clone();
    python_home.pop();

    // On Windows, python2.7.exe exists at the root directory of the Python
    // install. Everywhere else, the Python install root is one level up.
    if !python_exe.ends_with("python2.7.exe") {
        python_home.pop();
    }

    Environment {
        _exe: exe.clone(),
        python_exe: python_exe,
        python_home: python_home,
        mercurial_modules: mercurial_modules.to_path_buf(),
    }
}

// On UNIX, platform string is just bytes and should not contain NUL.
#[cfg(target_family = "unix")]
fn cstring_from_os<T: AsRef<OsStr>>(s: T) -> CString {
    CString::new(s.as_ref().as_bytes()).unwrap()
}

// TODO convert to ANSI characters?
#[cfg(target_family = "windows")]
fn cstring_from_os<T: AsRef<OsStr>>(s: T) -> CString {
    CString::new(s.as_ref().to_str().unwrap()).unwrap()
}

// On UNIX, argv starts as an array of char*. So it is easy to convert
// to C strings.
#[cfg(target_family = "unix")]
fn args_to_cstrings() -> Vec<CString> {
    env::args_os()
        .map(|a| CString::new(a.into_vec()).unwrap())
        .collect()
}

// TODO Windows support is incomplete. We should either use env::args_os()
// (or call into GetCommandLineW() + CommandLinetoArgvW()), convert these to
// PyUnicode instances, and pass these into Python/Mercurial outside the
// standard PySys_SetArgvEx() mechanism. This will allow us to preserve the
// raw bytes (since PySys_SetArgvEx() is based on char* and can drop wchar
// data.
//
// For now, we use env::args(). This will choke on invalid UTF-8 arguments.
// But it is better than nothing.
#[cfg(target_family = "windows")]
fn args_to_cstrings() -> Vec<CString> {
    env::args().map(|a| CString::new(a).unwrap()).collect()
}

fn set_python_home(env: &Environment) {
    let raw = cstring_from_os(&env.python_home).into_raw();
    unsafe {
        python27_sys::Py_SetPythonHome(raw);
    }
}

fn update_encoding(_py: Python, _sys_mod: &PyModule) {
    // Call sys.setdefaultencoding("undefined") if HGUNICODEPEDANTRY is set.
    let pedantry = env::var("HGUNICODEPEDANTRY").is_ok();

    if pedantry {
        // site.py removes the sys.setdefaultencoding attribute. So we need
        // to reload the module to get a handle on it. This is a lesser
        // used feature and we'll support this later.
        // TODO support this
        panic!("HGUNICODEPEDANTRY is not yet supported");
    }
}

fn update_modules_path(env: &Environment, py: Python, sys_mod: &PyModule) {
    let sys_path = sys_mod.get(py, "path").unwrap();
    sys_path
        .call_method(py, "insert", (0, env.mercurial_modules.to_str()), None)
        .expect("failed to update sys.path to location of Mercurial modules");
}

fn run() -> Result<(), i32> {
    let env = get_environment();

    //println!("{:?}", env);

    // Tell Python where it is installed.
    set_python_home(&env);

    // Set program name. The backing memory needs to live for the duration of the
    // interpreter.
    //
    // TODO consider storing this in a static or associating with lifetime of
    // the Python interpreter.
    //
    // Yes, we use the path to the Python interpreter not argv[0] here. The
    // reason is because Python uses the given path to find the location of
    // Python files. Apparently we could define our own ``Py_GetPath()``
    // implementation. But this may require statically linking Python, which is
    // not desirable.
    let program_name = cstring_from_os(&env.python_exe).as_ptr();
    unsafe {
        python27_sys::Py_SetProgramName(program_name as *mut i8);
    }

    unsafe {
        python27_sys::Py_Initialize();
    }

    // https://docs.python.org/2/c-api/init.html#c.PySys_SetArgvEx has important
    // usage information about PySys_SetArgvEx:
    //
    // * It says the first argument should be the script that is being executed.
    //   If not a script, it can be empty. We are definitely not a script.
    //   However, parts of Mercurial do look at sys.argv[0]. So we need to set
    //   something here.
    //
    // * When embedding Python, we should use ``PySys_SetArgvEx()`` and set
    //   ``updatepath=0`` for security reasons. Essentially, Python's default
    //   logic will treat an empty argv[0] in a manner that could result in
    //   sys.path picking up directories it shouldn't and this could lead to
    //   loading untrusted modules.

    // env::args() will panic if it sees a non-UTF-8 byte sequence. And
    // Mercurial supports arbitrary encodings of input data. So we need to
    // use OS-specific mechanisms to get the raw bytes without UTF-8
    // interference.
    let args = args_to_cstrings();
    let argv: Vec<*const c_char> = args.iter().map(|a| a.as_ptr()).collect();

    unsafe {
        python27_sys::PySys_SetArgvEx(args.len() as c_int, argv.as_ptr() as *mut *mut i8, 0);
    }

    let result;
    {
        // These need to be dropped before we call Py_Finalize(). Hence the
        // block.
        let gil = Python::acquire_gil();
        let py = gil.python();

        // Mercurial code could call sys.exit(), which will call exit()
        // itself. So this may not return.
        // TODO this may cause issues on Windows due to the CRT mismatch.
        // Investigate if we can intercept sys.exit() or SystemExit() to
        // ensure we handle process exit.
        result = match run_py(&env, py) {
            // Print unhandled exceptions and exit code 255, as this is what
            // `python` does.
            Err(err) => {
                err.print(py);
                Err(255)
            }
            Ok(()) => Ok(()),
        };
    }

    unsafe {
        python27_sys::Py_Finalize();
    }

    result
}

fn run_py(env: &Environment, py: Python) -> PyResult<()> {
    let sys_mod = py.import("sys").unwrap();

    update_encoding(py, &sys_mod);
    update_modules_path(&env, py, &sys_mod);

    // TODO consider a better error message on failure to import.
    let demand_mod = py.import("hgdemandimport")?;
    demand_mod.call(py, "enable", NoArgs, None)?;

    let dispatch_mod = py.import("mercurial.dispatch")?;
    dispatch_mod.call(py, "run", NoArgs, None)?;

    Ok(())
}

fn main() {
    let exit_code = match run() {
        Err(err) => err,
        Ok(()) => 0,
    };

    std::process::exit(exit_code);
}