Files
nix-js/fix-runtime/src/value.rs
T

778 lines
22 KiB
Rust

use std::cell::RefCell;
use std::fmt;
use std::marker::PhantomData;
use std::mem::size_of;
use std::ops::Deref;
use fix_bytecode::Continuation;
use fix_lang::*;
use fix_macros::unelide_lifetimes;
use gc_arena::barrier::Unlock;
use gc_arena::collect::Trace;
use gc_arena::{Collect, Gc, GcRefLock, Mutation, RefLock};
use smallvec::SmallVec;
use string_interner::Symbol;
use string_interner::symbol::SymbolU32;
use crate::boxing::{RawBox, RawStore, RawTag, Value as RawValue};
use crate::string_context::StringContext;
mod private {
pub trait Cealed {}
}
pub trait ValueVariant<'gc>: private::Cealed {
#[expect(
private_bounds,
reason = "Storable is a sealed implementation detail of the value system"
)]
type Ty: Storable + 'gc;
const TYPE: NixType;
}
trait Storable: private::Cealed {
fn is(raw: &RawBox) -> bool;
fn to_raw_box(self) -> RawBox;
/// # Safety
///
/// `raw` must represent a valid `Self`.
unsafe fn from_raw_box(raw: RawBox) -> Self;
}
macro_rules! define_value_types {
(
inline { $($itype:ty => $itag:path, $ity:path, $iname:literal;)* }
gc { $($gtype:ty => $gtag:path, $gty:path, $gname:literal;)* }
) => {
$(
impl Storable for $itype {
#[inline(always)]
fn is(value: &RawBox) -> bool {
value.tag() == Some($itag)
}
#[inline(always)]
fn to_raw_box(self) -> RawBox {
RawBox::from_value(RawValue::store($itag, self))
}
#[inline(always)]
unsafe fn from_raw_box(raw: RawBox) -> Self {
// SAFETY: the caller guarantees `raw` represents a valid
// `Self` of this inline type, so it holds a `Value` (making
// `value()` `Some`) whose payload decodes to this type.
unsafe { <Self as RawStore>::from_val(raw.value().unwrap_unchecked()) }
}
}
impl private::Cealed for $itype {}
impl<'gc> ValueVariant<'gc> for $itype {
type Ty = $itype;
const TYPE: NixType = $ity;
}
impl<'gc> TryFrom<Value<'gc>> for $itype {
type Error = ();
fn try_from(val: Value<'gc>) -> Result<Self, Self::Error> {
<Self as Storable>::is(&val.raw)
// SAFETY: `is` returned true, so `val.raw` represents a
// valid `Self` of this GC type.
.then(|| unsafe { <Self as Storable>::from_raw_box(val.raw) })
.ok_or(())
}
}
)*
$(
impl Storable for Gc<'_, $gtype> {
#[inline(always)]
fn is(value: &RawBox) -> bool {
value.tag() == Some($gtag)
}
#[inline(always)]
fn to_raw_box(self) -> RawBox {
RawBox::from_value(RawValue::store($gtag, Gc::as_ptr(self)))
}
#[inline(always)]
unsafe fn from_raw_box(raw: RawBox) -> Self {
// SAFETY: the caller guarantees `raw` represents a valid
// `Self` of this GC type, so it holds a `Value` (making
// `value()` `Some`) whose payload is the pointer originally
// produced by `Gc::as_ptr` in `to_raw_box`.
unsafe { Gc::from_ptr(<*mut $gtype as RawStore>::from_val(raw.value().unwrap_unchecked())) }
}
}
impl<'gc> TryFrom<Value<'gc>> for Gc<'gc, unelide_lifetimes!('gc; $gtype)> {
type Error = ();
fn try_from(val: Value<'gc>) -> Result<Self, Self::Error> {
<Self as Storable>::is(&val.raw)
// SAFETY: `is` returned true, so `val.raw` represents a
// valid `Self` of this GC type.
.then(|| unsafe { <Self as Storable>::from_raw_box(val.raw) })
.ok_or(())
}
}
impl private::Cealed for Gc<'_, $gtype> {}
impl private::Cealed for $gtype {}
impl<'gc> ValueVariant<'gc> for unelide_lifetimes!('gc; $gtype) {
type Ty = Gc<'gc, unelide_lifetimes!('gc; $gtype)>;
const TYPE: NixType = $gty;
}
)*
const _: () = assert!(size_of::<Value<'static>>() == 8);
$(const _: () = assert!(size_of::<$itype>() <= 6);)*
const _: () = {
let tags: &[(bool, u8)] = &[$(RawTag::neg_val($itag)),*, $(RawTag::neg_val($gtag)),*];
let mut mask_false: u8 = 0;
let mut mask_true: u8 = 0;
let mut i = 0;
while i < tags.len() {
#[expect(clippy::indexing_slicing, reason = "loop condition guarantees `i < tags.len()`")]
let (neg, val) = tags[i];
let bit = 1 << val;
if neg {
assert!(mask_true & bit == 0, "duplicate true tag id");
mask_true |= bit;
} else {
assert!(mask_false & bit == 0, "duplicate false tag id");
mask_false |= bit;
}
i += 1;
}
};
// SAFETY: `trace` visits every reachable `Gc` pointer: for each GC
// tag it downcasts to the concrete `Gc` type and forwards `trace`,
// while inline tags hold no GC pointers and need no tracing.
unsafe impl<'gc> Collect<'gc> for Value<'gc> {
const NEEDS_TRACE: bool = true;
fn trace<T: Trace<'gc>>(&self, cc: &mut T) {
let Some(tag) = self.raw.tag() else { return };
match tag {
$($gtag => unsafe {
// SAFETY: `tag` matched `$gtag`, so `downcast` to the
// corresponding GC type is guaranteed to be `Some`.
self.downcast::<$gtype>().unwrap_unchecked().trace(cc)
},)*
$($itag => (),)*
_ => unreachable!("invalid value tag"),
}
}
}
impl fmt::Debug for Value<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
match self.tag() {
// SAFETY: `tag()` is `None`, meaning the `RawBox` holds a
// float, so `float()` is guaranteed to be `Some`.
None => write!(f, "Float({:?})", unsafe {
self.raw.float().unwrap_unchecked()
}),
// SAFETY: `tag()` matched `$itag`, so `downcast` to the
// corresponding inline type is guaranteed to be `Some`.
$(Some($itag) => write!(f, "{}({:?})", $iname, unsafe {
self.downcast::<$itype>().unwrap_unchecked()
}),)*
$(Some($gtag) =>
write!(f, "{}(..)", $gname),)*
_ => unreachable!("invalid value tag"),
}
}
}
};
}
define_value_types! {
inline {
i32 => RawTag::P1, NixType::Int, "SmallInt";
bool => RawTag::P2, NixType::Bool, "Bool";
Null => RawTag::P3, NixType::Null, "Null";
StringId => RawTag::P4, NixType::String, "SmallString";
PrimOp => RawTag::P5, NixType::PrimOp, "PrimOp";
Path => RawTag::P6, NixType::Path, "Path";
}
gc {
i64 => RawTag::P7, NixType::Int, "BigInt";
NixString => RawTag::N1, NixType::String, "String";
AttrSet<'_> => RawTag::N2, NixType::AttrSet, "AttrSet";
List<'_> => RawTag::N3, NixType::List, "List";
Thunk<'_> => RawTag::N4, NixType::Thunk, "Thunk";
Closure<'_> => RawTag::N5, NixType::Closure, "Closure";
PrimOpApp<'_> => RawTag::N6, NixType::PrimOpApp, "PrimOpApp";
}
}
impl private::Cealed for f64 {}
impl Storable for f64 {
#[inline(always)]
fn is(value: &RawBox) -> bool {
value.is_float()
}
#[inline(always)]
fn to_raw_box(self) -> RawBox {
RawBox::from_float(self)
}
#[inline(always)]
unsafe fn from_raw_box(raw: RawBox) -> Self {
// SAFETY: the caller guarantees `raw` represents a valid `f64`, so
// `float()` is guaranteed to be `Some`.
unsafe { raw.float().copied().unwrap_unchecked() }
}
}
impl<'gc> ValueVariant<'gc> for f64 {
type Ty = f64;
const TYPE: NixType = NixType::Float;
}
impl<'gc, T: Storable + 'gc> From<T> for Value<'gc> {
fn from(value: T) -> Self {
Value::new(value)
}
}
/// # Nix runtime value representation
///
/// NaN-boxed value fitting in 8 bytes.
#[derive(Copy, Clone)]
#[repr(transparent)]
pub struct Value<'gc> {
raw: RawBox,
_marker: PhantomData<Gc<'gc, ()>>,
}
impl Default for Value<'_> {
#[inline(always)]
fn default() -> Self {
Self::new(Null)
}
}
impl<'gc> Value<'gc> {
#[inline(always)]
const fn tag(self) -> Option<RawTag> {
self.raw.tag()
}
}
impl<'gc> Value<'gc> {
#[inline]
#[expect(
private_bounds,
reason = "Storable is a sealed implementation detail of the value system"
)]
pub fn new<T: Storable>(val: T) -> Self {
Self {
raw: val.to_raw_box(),
_marker: PhantomData,
}
}
#[inline]
pub fn make_int(val: i64, mc: &Mutation<'gc>) -> Self {
if val >= i32::MIN as i64 && val <= i32::MAX as i64 {
Value::new(val as i32)
} else {
Value::new(Gc::new(mc, val))
}
}
#[inline]
pub fn is<T: ValueVariant<'gc>>(self) -> bool {
T::Ty::is(&self.raw)
}
#[inline]
pub fn downcast<T: ValueVariant<'gc>>(self) -> Option<T::Ty> {
self.is::<T>()
// SAFETY: `is::<T>()` returned true, so `self.raw` represents a
// valid `T::Ty`.
.then(|| unsafe { T::Ty::from_raw_box(self.raw) })
}
#[inline]
pub fn to_bits(self) -> u64 {
self.raw.to_bits()
}
#[inline]
pub fn downcast_num(self) -> Option<NixNum> {
if let Some(i) = self.downcast::<i32>() {
Some(NixNum::Int(i as i64))
} else if let Some(gc_i) = self.downcast::<i64>() {
Some(NixNum::Int(*gc_i))
} else {
self.downcast::<f64>().map(NixNum::Float)
}
}
#[inline]
pub fn restrict(self) -> Result<StrictValue<'gc>, Gc<'gc, Thunk<'gc>>> {
if let Some(thunk) = self.downcast::<Thunk>() {
Err(thunk)
} else {
Ok(StrictValue(self))
}
}
#[inline]
#[expect(
clippy::unreachable,
reason = "the preceding `if`/`else if` chain exhausts every registered value tag"
)]
pub fn ty(self) -> NixType {
if self.is::<f64>() {
NixType::Float
} else if self.is::<i32>() || self.is::<i64>() {
NixType::Int
} else if self.is::<bool>() {
NixType::Bool
} else if self.is::<Null>() {
NixType::Null
} else if self.is::<StringId>() {
NixType::String
} else if self.is::<PrimOp>() {
NixType::PrimOp
} else if self.is::<NixString>() {
NixType::String
} else if self.is::<Path>() {
NixType::Path
} else if self.is::<AttrSet>() {
NixType::AttrSet
} else if self.is::<List>() {
NixType::List
} else if self.is::<Thunk>() {
NixType::Thunk
} else if self.is::<Closure>() {
NixType::Closure
} else if self.is::<PrimOpApp>() {
NixType::PrimOpApp
} else {
unreachable!("value has no recognized type tag")
}
}
#[inline]
pub fn expect<T: ValueVariant<'gc>>(self) -> Result<T::Ty, NixType> {
self.downcast::<T>().ok_or_else(|| self.ty())
}
#[inline]
pub fn expect_num(self) -> Result<NixNum, NixType> {
self.downcast_num().ok_or_else(|| self.ty())
}
}
#[derive(Copy, Clone, Default)]
#[repr(transparent)]
pub struct StaticValue(Value<'static>);
impl<'gc> From<StaticValue> for Value<'gc> {
#[inline]
fn from(value: StaticValue) -> Self {
// SAFETY: StaticValue is guaranteed to not contain any `Gc`.
unsafe { std::mem::transmute::<Value<'static>, Value<'gc>>(value.0) }
}
}
impl StaticValue {
#[inline]
#[expect(
private_bounds,
reason = "Storable is a sealed implementation detail of the value system"
)]
pub fn new<T: Storable + 'static>(val: T) -> Self {
Self(Value::new(val))
}
#[inline]
pub fn is<T: ValueVariant<'static>>(self) -> bool {
self.0.is::<T>()
}
#[inline]
pub fn downcast<T: ValueVariant<'static>>(self) -> Option<T::Ty> {
self.0.downcast::<T>()
}
#[inline]
pub fn to_bits(self) -> u64 {
self.0.raw.to_bits()
}
}
#[derive(Clone, Copy, Debug)]
pub struct Null;
impl RawStore for Null {
fn to_val(self, value: &mut RawValue) {
value.set_data([0; 6]);
}
fn from_val(_: &RawValue) -> Self {
Self
}
}
impl RawStore for StringId {
fn to_val(self, value: &mut RawValue) {
(self.0.to_usize() as u32).to_val(value);
}
fn from_val(value: &RawValue) -> Self {
Self(
SymbolU32::try_from_usize(u32::from_val(value) as usize)
.expect("failed to read StringId from Value"),
)
}
}
/// A canonicalized absolute path. Inline value carrying an interned
/// `StringId` whose contents are the path's absolute, dot-resolved form.
#[derive(Clone, Copy, Debug, PartialEq, Eq)]
pub struct Path(pub StringId);
impl RawStore for Path {
fn to_val(self, value: &mut RawValue) {
self.0.to_val(value);
}
fn from_val(value: &RawValue) -> Self {
Self(StringId::from_val(value))
}
}
#[derive(Collect)]
#[collect(require_static)]
pub struct NixString {
data: Box<str>,
context: StringContext,
}
impl NixString {
pub fn new(s: impl Into<Box<str>>) -> Self {
Self {
data: s.into(),
context: StringContext::new(),
}
}
/// Construct a `NixString` whose `context` is already sorted+deduped.
/// The caller is responsible for invariant maintenance.
pub fn with_context(s: impl Into<Box<str>>, context: StringContext) -> Self {
Self {
data: s.into(),
context,
}
}
pub fn as_str(&self) -> &str {
&self.data
}
pub fn context(&self) -> &StringContext {
&self.context
}
pub fn has_context(&self) -> bool {
!self.context.is_empty()
}
}
impl fmt::Debug for NixString {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&self.data, f)
}
}
#[derive(Collect, Debug, Default)]
#[collect(no_drop)]
pub struct AttrSet<'gc> {
pub entries: SmallVec<[(StringId, Value<'gc>); 4]>,
}
impl<'gc> AttrSet<'gc> {
pub fn from_sorted_unchecked(entries: SmallVec<[(StringId, Value<'gc>); 4]>) -> Self {
debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
Self { entries }
}
#[expect(
clippy::indexing_slicing,
reason = "index comes from a successful `binary_search_by_key`, so it is a valid entry index"
)]
pub fn lookup(&self, key: StringId) -> Option<Value<'gc>> {
self.entries
.binary_search_by_key(&key, |(k, _)| *k)
.ok()
.map(|i| self.entries[i].1)
}
pub fn has(&self, key: StringId) -> bool {
self.entries.binary_search_by_key(&key, |(k, _)| *k).is_ok()
}
#[expect(
clippy::indexing_slicing,
reason = "`i`/`j` stay strictly below their lengths inside the loop, and the trailing slices use those in-bounds cursors as start indices"
)]
pub fn merge(&self, other: &Self, mc: &Mutation<'gc>) -> Gc<'gc, Self> {
use std::cmp::Ordering::*;
debug_assert!(self.entries.is_sorted_by_key(|(key, _)| *key));
debug_assert!(other.entries.is_sorted_by_key(|(key, _)| *key));
let mut entries = SmallVec::new();
let mut i = 0;
let mut j = 0;
while i < self.entries.len() && j < other.entries.len() {
match self.entries[i].0.cmp(&other.entries[j].0) {
Less => {
entries.push(self.entries[i]);
i += 1;
}
Greater => {
entries.push(other.entries[j]);
j += 1;
}
Equal => {
entries.push(other.entries[j]);
i += 1;
j += 1;
}
}
}
entries.extend(other.entries[j..].iter().cloned());
entries.extend(self.entries[i..].iter().cloned());
debug_assert!(entries.is_sorted_by_key(|(key, _)| *key));
Gc::new(mc, AttrSet { entries })
}
}
#[derive(Collect, Debug, Default)]
#[repr(transparent)]
#[collect(no_drop)]
pub struct List<'gc> {
pub inner: RefLock<SmallVec<[Value<'gc>; 4]>>,
}
impl<'gc> List<'gc> {
pub fn new(mc: &Mutation<'gc>, data: SmallVec<[Value<'gc>; 4]>) -> Gc<'gc, Self> {
Gc::new(
mc,
Self {
inner: RefLock::new(data),
},
)
}
pub fn new_gc(mc: &Mutation<'gc>) -> Gc<'gc, Self> {
Gc::new(mc, Self::default())
}
}
impl<'gc> Unlock for List<'gc> {
type Unlocked = RefCell<SmallVec<[Value<'gc>; 4]>>;
unsafe fn unlock_unchecked(&self) -> &Self::Unlocked {
// SAFETY: the caller upholds the `Unlock` contract (mutation happens
// behind a write barrier); we forward that obligation to the inner
// `RefLock`'s `unlock_unchecked`.
unsafe { self.inner.unlock_unchecked() }
}
}
pub type Thunk<'gc> = RefLock<ThunkState<'gc>>;
#[derive(Collect, Debug)]
#[collect(no_drop)]
pub enum ThunkState<'gc> {
Pending { ip: usize, env: GcEnv<'gc> },
Apply { func: Value<'gc>, arg: Value<'gc> },
Blackhole,
Evaluated(StrictValue<'gc>),
}
#[derive(Collect, Debug)]
#[collect(no_drop)]
pub struct Env<'gc> {
pub locals: SmallVec<[Value<'gc>; 4]>,
pub prev: Option<GcEnv<'gc>>,
}
pub type GcEnv<'gc> = GcRefLock<'gc, Env<'gc>>;
#[derive(Collect, Debug)]
#[collect(no_drop)]
pub struct WithEnv<'gc> {
pub env: Value<'gc>,
pub prev: Option<GcWithEnv<'gc>>,
}
pub type GcWithEnv<'gc> = Gc<'gc, WithEnv<'gc>>;
impl<'gc> Env<'gc> {
pub fn empty() -> Self {
Env {
locals: SmallVec::new(),
prev: None,
}
}
#[expect(
clippy::indexing_slicing,
reason = "`locals` was just created with `1 + n_locals` elements, so index 0 is always valid"
)]
pub fn with_arg(arg: Value<'gc>, n_locals: u32, prev: Gc<'gc, RefLock<Env<'gc>>>) -> Self {
let mut locals = smallvec::smallvec![Value::default(); 1 + n_locals as usize];
locals[0] = arg;
Env {
locals,
prev: Some(prev),
}
}
}
#[derive(Collect, Debug)]
#[collect(no_drop)]
pub struct Closure<'gc> {
pub ip: u32,
pub n_locals: u32,
pub env: Gc<'gc, RefLock<Env<'gc>>>,
pub pattern: Option<Gc<'gc, PatternInfo>>,
}
#[derive(Collect, Debug)]
#[collect(require_static)]
pub struct PatternInfo {
pub required: SmallVec<[StringId; 4]>,
pub optional: SmallVec<[StringId; 4]>,
pub ellipsis: bool,
pub param_spans: Box<[(StringId, u32)]>,
}
#[repr(packed, Rust)]
#[derive(Clone, Copy, Debug, Collect)]
#[collect(require_static)]
pub struct PrimOp {
pub id: BuiltinId,
pub arity: u8,
pub dispatch_ip: u32,
}
impl From<BuiltinId> for PrimOp {
fn from(id: BuiltinId) -> Self {
let BuiltinInfo { arity, .. } = id.info();
let dispatch_ip = Continuation::entry_for_builtin(id).ip();
Self {
id,
arity,
dispatch_ip,
}
}
}
impl RawStore for PrimOp {
fn to_val(self, value: &mut RawValue) {
let bytes = self.dispatch_ip.to_le_bytes();
value.set_data([
self.id as u8,
self.arity,
bytes[0],
bytes[1],
bytes[2],
bytes[3],
]);
}
fn from_val(value: &RawValue) -> Self {
let [id, arity, bytes @ ..] = *value.data();
Self {
id: BuiltinId::try_from(id).expect("invalid BuiltinId"),
arity,
dispatch_ip: u32::from_le_bytes(bytes),
}
}
}
#[derive(Collect, Debug)]
#[collect(no_drop)]
pub struct PrimOpApp<'gc> {
pub primop: PrimOp,
pub arity: u8,
pub args: [Value<'gc>; 3],
}
#[derive(Copy, Clone, Default, Collect)]
#[repr(transparent)]
#[collect(no_drop)]
pub struct StrictValue<'gc>(Value<'gc>);
impl<'gc> StrictValue<'gc> {
#[inline]
pub fn relax(self) -> Value<'gc> {
self.0
}
}
impl<'gc> Deref for StrictValue<'gc> {
type Target = Value<'gc>;
#[inline]
fn deref(&self) -> &Value<'gc> {
&self.0
}
}
impl<'gc> From<StrictValue<'gc>> for Value<'gc> {
fn from(value: StrictValue<'gc>) -> Self {
value.0
}
}
impl fmt::Debug for StrictValue<'_> {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
fmt::Debug::fmt(&self.0, f)
}
}
#[derive(Clone, Copy, Debug, PartialEq, Eq, Collect)]
#[collect(require_static)]
pub enum NixType {
Int,
Float,
Bool,
Null,
String,
Path,
AttrSet,
List,
Thunk,
Closure,
PrimOp,
PrimOpApp,
}
impl NixType {
pub fn display(self) -> &'static str {
use NixType::*;
match self {
Int => "an integer",
Float => "a float",
Bool => "a boolean",
Null => "null",
String => "a string",
Path => "a path",
AttrSet => "a set",
List => "a list",
Thunk => "a thunk",
Closure => "a function",
PrimOp => "a built-in function",
PrimOpApp => "a partially applied built-in function",
}
}
}
impl std::fmt::Display for NixType {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
write!(f, "{}", self.display())
}
}
pub enum NixNum {
Int(i64),
Float(f64),
}