feat: PrimOp type
(cherry picked from commit 67616c4a55b9d98d716384ffc07d3b3880dd76e4)
This commit is contained in:
Robert Hensing
parent
5c43a28cf0
commit
312c86b811
5 changed files with 233 additions and 84 deletions
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@ -1,3 +1,4 @@
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use crate::primop;
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use crate::value::{Int, Value, ValueType};
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use anyhow::Context as _;
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use anyhow::{bail, Result};
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@ -8,8 +9,7 @@ use nix_store::store::{Store, StoreWeak};
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use nix_util::context::Context;
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use nix_util::string_return::{callback_get_result_string, callback_get_result_string_data};
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use nix_util::{check_call, check_call_opt_key, result_string_init};
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use std::ffi::{c_char, c_int, c_void, CString};
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use std::mem::ManuallyDrop;
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use std::ffi::{c_char, CStr, CString};
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use std::os::raw::c_uint;
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use std::ptr::{null, null_mut, NonNull};
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use std::sync::{Arc, Weak};
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@ -78,7 +78,7 @@ impl Drop for EvalStateRef {
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pub struct EvalState {
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eval_state: Arc<EvalStateRef>,
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store: Store,
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context: Context,
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pub(crate) context: Context,
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}
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impl EvalState {
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pub fn new<'a>(store: Store, lookup_path: impl IntoIterator<Item = &'a str>) -> Result<Self> {
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@ -426,9 +426,23 @@ impl EvalState {
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self.new_value_apply(&f, &f)
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}
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/// Create a new function that is backed by a Rust function.
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/// Create a new Nix function that is implemented by a Rust function.
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/// This is also known as a "primop" in Nix, short for primitive operation.
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/// The `builtins.*` are examples of primops.
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/// Most of the `builtins.*` values are examples of primops, but
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/// `new_value_primop` does not affect `builtins`.
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pub fn new_value_primop(&mut self, primop: primop::PrimOp) -> Result<Value> {
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let value = self.new_value_uninitialized()?;
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unsafe {
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check_call!(raw::init_primop(
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&mut self.context,
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value.raw_ptr(),
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primop.ptr
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))?;
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};
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Ok(value)
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}
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/// A worse quality shortcut for calling [new_value_primop].
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pub fn new_value_function<const N: usize>(
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&mut self,
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name: *const i8,
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@ -443,43 +457,21 @@ impl EvalState {
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}));
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}
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let mut args = Vec::new();
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for _ in 0..N {
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args.push(FUNCTION_ANONYMOUS_ARG.as_ptr());
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}
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args.push(null());
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// This leaks
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let name = unsafe { CStr::from_ptr(name) };
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let user_data = {
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// We'll be leaking this Box.
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// TODO: Use the GC with finalizer, if possible.
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let user_data = ManuallyDrop::new(Box::new(PrimOpContext {
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arity: N,
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function: Box::new(move |eval_state, args| {
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let r = f(eval_state, args.try_into().unwrap());
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r
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}),
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eval_state: self.weak_ref(),
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}));
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user_data.as_ref() as *const PrimOpContext as *mut c_void
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};
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let op = unsafe {
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check_call!(raw::alloc_primop(
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&mut self.context,
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FUNCTION_ADAPTER,
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N as c_int,
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let args: [&CStr; N] = [FUNCTION_ANONYMOUS_ARG.as_ref(); N];
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let prim = primop::PrimOp::new(
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self,
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primop::PrimOpMeta {
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name,
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args.as_mut_ptr(), /* TODO add an extra const to bindings to avoid mut here. */
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FUNCTION_ANONYMOUS_DOC.as_ptr(),
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user_data
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))?
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};
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let value = self.new_value_uninitialized()?;
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// Then use it in a value
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unsafe {
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check_call!(raw::init_primop(&mut self.context, value.raw_ptr(), op))?;
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}
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Ok(value)
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args,
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doc: FUNCTION_ANONYMOUS_DOC.as_ref(),
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},
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f,
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)?;
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self.new_value_primop(prim)
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}
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}
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@ -535,50 +527,6 @@ impl Clone for EvalState {
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}
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}
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/// The user_data for our Nix primops
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struct PrimOpContext {
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arity: usize,
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// Something like Haskell's Dynamic
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function: Box<dyn Fn(&mut EvalState, &[Value]) -> Result<Value>>,
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eval_state: EvalStateWeak,
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}
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unsafe extern "C" fn function_adapter(
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user_data: *mut ::std::os::raw::c_void,
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context_out: *mut raw::c_context,
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_state: *mut raw::EvalState,
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args: *mut *mut raw::Value,
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ret: *mut raw::Value,
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) {
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let primop_info = (user_data as *const PrimOpContext).as_ref().unwrap();
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let mut eval_state = primop_info.eval_state.upgrade().unwrap_or_else(|| {
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panic!("Nix primop called after EvalState was dropped");
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});
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let args_raw_slice = unsafe { std::slice::from_raw_parts(args, primop_info.arity) };
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let args_vec: Vec<Value> = args_raw_slice
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.iter()
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.map(|v| Value::new_borrowed(*v as *mut c_void))
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.collect();
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let args_slice = args_vec.as_slice();
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let r = primop_info.function.as_ref()(&mut eval_state, args_slice);
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match r {
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Ok(v) => unsafe {
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raw::copy_value(context_out, ret, v.raw_ptr());
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},
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Err(e) => unsafe {
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let cstr = CString::new(e.to_string()).unwrap_or_else(|_e| {
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CString::new("<rust nix-expr application error message contained null byte>")
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.unwrap()
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});
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raw::set_err_msg(context_out, raw::NIX_ERR_UNKNOWN, cstr.as_ptr());
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},
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}
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}
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static FUNCTION_ADAPTER: raw::PrimOpFun = Some(function_adapter);
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lazy_static! {
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pub static ref FUNCTION_ANONYMOUS: CString = CString::new("anonymous-primop").unwrap();
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static ref FUNCTION_ANONYMOUS_ARG: CString = CString::new("x").unwrap();
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@ -604,6 +552,7 @@ pub fn test_init() {
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#[cfg(test)]
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mod tests {
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use super::*;
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use cstr::cstr;
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use ctor::ctor;
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use std::collections::HashMap;
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use std::fs::read_dir;
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@ -1498,4 +1447,71 @@ mod tests {
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})
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.unwrap();
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}
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#[test]
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pub fn eval_state_primop_custom() {
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gc_registering_current_thread(|| {
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let store = Store::open("auto", []).unwrap();
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let mut es = EvalState::new(store, []).unwrap();
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let primop = primop::PrimOp::new(
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&mut es,
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primop::PrimOpMeta {
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name: cstr!("frobnicate"),
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doc: cstr!("Frobnicates widgets"),
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args: [cstr!("x"), cstr!("y")],
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},
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Box::new(|es, args| {
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let a = es.require_int(&args[0])?;
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let b = es.require_int(&args[1])?;
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Ok(es.new_value_int(a + b)?)
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}),
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)
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.unwrap();
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let f = es.new_value_primop(primop).unwrap();
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let a = es.new_value_int(2).unwrap();
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let b = es.new_value_int(3).unwrap();
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let fa = es.call(f, a).unwrap();
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let fb = es.call(fa, b).unwrap();
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es.force(&fb).unwrap();
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let t = es.value_type(&fb).unwrap();
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assert!(t == ValueType::Int);
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let i = es.require_int(&fb).unwrap();
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assert!(i == 5);
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})
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.unwrap();
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}
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#[test]
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pub fn eval_state_primop_custom_throw() {
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gc_registering_current_thread(|| {
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let store = Store::open("auto", []).unwrap();
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let mut es = EvalState::new(store, []).unwrap();
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let primop = primop::PrimOp::new(
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&mut es,
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primop::PrimOpMeta {
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name: cstr!("frobnicate"),
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doc: cstr!("Frobnicates widgets"),
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args: [cstr!("x")],
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},
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Box::new(|_es, _args| bail!("The frob unexpectedly fizzled")),
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)
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.unwrap();
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let f = es.new_value_primop(primop).unwrap();
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let a = es.new_value_int(0).unwrap();
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match es.call(f, a) {
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Ok(_) => panic!("expected an error"),
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Err(e) => {
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if !e.to_string().contains("The frob unexpectedly fizzled") {
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eprintln!("unexpected error message: {}", e);
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assert!(false);
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}
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if !e.to_string().contains("frobnicate") {
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eprintln!("unexpected error message: {}", e);
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assert!(false);
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}
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}
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}
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})
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.unwrap();
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}
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}
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@ -1,2 +1,3 @@
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pub mod eval_state;
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pub mod primop;
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pub mod value;
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120
rust/nix-expr/src/primop.rs
Normal file
120
rust/nix-expr/src/primop.rs
Normal file
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@ -0,0 +1,120 @@
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use crate::eval_state::{EvalState, EvalStateWeak};
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use crate::value::Value;
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use anyhow::Result;
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use nix_c_raw as raw;
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use nix_util::check_call;
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use std::ffi::{c_int, c_void, CStr, CString};
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use std::mem::ManuallyDrop;
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use std::ptr::{null, null_mut};
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/// Metadata for a primop, used with `PrimOp::new`.
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pub struct PrimOpMeta<'a, const N: usize> {
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/// Name of the primop. Note that primops do not have to be registered as
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/// builtins. Nonetheless, a name is required for documentation purposes, e.g.
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/// :doc in the repl.
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pub name: &'a CStr,
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/// Documentation for the primop. This is displayed in the repl when using
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/// :doc. The format is markdown.
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pub doc: &'a CStr,
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/// The number of arguments the function takes, as well as names for the
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/// arguments, to be presented in the documentation (if applicable, e.g.
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/// :doc in the repl).
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pub args: [&'a CStr; N],
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}
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pub struct PrimOp {
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pub(crate) ptr: *mut raw::PrimOp,
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}
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impl Drop for PrimOp {
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fn drop(&mut self) {
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unsafe {
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raw::gc_decref(null_mut(), self.ptr as *mut c_void);
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}
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}
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}
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impl PrimOp {
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pub fn new<const N: usize>(
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eval_state: &mut EvalState,
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meta: PrimOpMeta<N>,
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f: Box<dyn Fn(&mut EvalState, &[Value; N]) -> Result<Value>>,
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) -> Result<PrimOp> {
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let mut args = Vec::new();
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for arg in meta.args {
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args.push(arg.as_ptr());
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}
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args.push(null());
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// Primops weren't meant to be dynamically created, as of writing.
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// This leaks, and so do the primop fields in Nix internally.
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let user_data = {
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// We'll be leaking this Box.
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// TODO: Use the GC with finalizer, if possible.
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let user_data = ManuallyDrop::new(Box::new(PrimOpContext {
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arity: N,
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function: Box::new(move |eval_state, args| {
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let r = f(eval_state, args.try_into().unwrap());
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r
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}),
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eval_state: eval_state.weak_ref(),
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}));
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user_data.as_ref() as *const PrimOpContext as *mut c_void
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};
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let op = unsafe {
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check_call!(raw::alloc_primop(
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&mut eval_state.context,
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FUNCTION_ADAPTER,
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N as c_int,
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meta.name.as_ptr(),
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args.as_mut_ptr(), /* TODO add an extra const to bindings to avoid mut here. */
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meta.doc.as_ptr(),
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user_data
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))?
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};
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Ok(PrimOp { ptr: op })
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}
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}
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/// The user_data for our Nix primops
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struct PrimOpContext {
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arity: usize,
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function: Box<dyn Fn(&mut EvalState, &[Value]) -> Result<Value>>,
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eval_state: EvalStateWeak,
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}
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unsafe extern "C" fn function_adapter(
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user_data: *mut ::std::os::raw::c_void,
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context_out: *mut raw::c_context,
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_state: *mut raw::EvalState,
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args: *mut *mut raw::Value,
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ret: *mut raw::Value,
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) {
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let primop_info = (user_data as *const PrimOpContext).as_ref().unwrap();
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let mut eval_state = primop_info.eval_state.upgrade().unwrap_or_else(|| {
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panic!("Nix primop called after EvalState was dropped");
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});
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let args_raw_slice = unsafe { std::slice::from_raw_parts(args, primop_info.arity) };
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let args_vec: Vec<Value> = args_raw_slice
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.iter()
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.map(|v| Value::new_borrowed(*v))
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.collect();
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let args_slice = args_vec.as_slice();
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let r = primop_info.function.as_ref()(&mut eval_state, args_slice);
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match r {
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Ok(v) => unsafe {
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raw::copy_value(context_out, ret, v.raw_ptr());
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},
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Err(e) => unsafe {
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let cstr = CString::new(e.to_string()).unwrap_or_else(|_e| {
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CString::new("<rust nix-expr application error message contained null byte>")
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.unwrap()
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});
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raw::set_err_msg(context_out, raw::err_NIX_ERR_UNKNOWN, cstr.as_ptr());
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},
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}
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}
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static FUNCTION_ADAPTER: raw::PrimOpFun = Some(function_adapter);
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