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dictdatatype.rs
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318 lines (282 loc) · 9.39 KB
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use crate::obj::objbool;
use crate::pyhash;
use crate::pyobject::{IdProtocol, PyObjectRef, PyResult};
use crate::vm::VirtualMachine;
/// Ordered dictionary implementation.
/// Inspired by: https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html
/// And: https://www.youtube.com/watch?v=p33CVV29OG8
/// And: http://code.activestate.com/recipes/578375/
use std::collections::{hash_map::DefaultHasher, HashMap};
use std::hash::{Hash, Hasher};
/// hash value of an object returned by __hash__
type HashValue = pyhash::PyHash;
/// index calculated by resolving collision
type HashIndex = pyhash::PyHash;
/// entry index mapped in indices
type EntryIndex = usize;
#[derive(Clone)]
pub struct Dict<T = PyObjectRef> {
size: usize,
indices: HashMap<HashIndex, EntryIndex>,
entries: Vec<Option<DictEntry<T>>>,
}
impl<T> Default for Dict<T> {
fn default() -> Self {
Dict {
size: 0,
indices: HashMap::new(),
entries: Vec::new(),
}
}
}
#[derive(Clone)]
struct DictEntry<T> {
hash: HashValue,
key: PyObjectRef,
value: T,
}
#[derive(Debug)]
pub struct DictSize {
size: usize,
entries_size: usize,
}
impl<T: Clone> Dict<T> {
fn unchecked_push(
&mut self,
hash_index: HashIndex,
hash_value: HashValue,
key: &PyObjectRef,
value: T,
) {
let entry = DictEntry {
hash: hash_value,
key: key.clone(),
value,
};
let entry_index = self.entries.len();
self.entries.push(Some(entry));
self.indices.insert(hash_index, entry_index);
self.size += 1;
}
fn unchecked_delete(&mut self, entry_index: EntryIndex) {
self.entries[entry_index] = None;
self.size -= 1;
}
/// Store a key
pub fn insert(&mut self, vm: &VirtualMachine, key: &PyObjectRef, value: T) -> PyResult<()> {
match self.lookup(vm, key)? {
LookupResult::Existing(index) => {
// Update existing key
if let Some(ref mut entry) = self.entries[index] {
entry.value = value;
Ok(())
} else {
panic!("Lookup returned invalid index into entries!");
}
}
LookupResult::NewIndex {
hash_index,
hash_value,
} => {
// New key:
self.unchecked_push(hash_index, hash_value, key, value);
Ok(())
}
}
}
pub fn contains(&self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<bool> {
if let LookupResult::Existing(_) = self.lookup(vm, key)? {
Ok(true)
} else {
Ok(false)
}
}
fn unchecked_get(&self, index: EntryIndex) -> T {
if let Some(entry) = &self.entries[index] {
entry.value.clone()
} else {
panic!("Lookup returned invalid index into entries!");
}
}
/// Retrieve a key
pub fn get(&self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<Option<T>> {
if let LookupResult::Existing(index) = self.lookup(vm, key)? {
Ok(Some(self.unchecked_get(index)))
} else {
Ok(None)
}
}
pub fn clear(&mut self) {
self.entries.clear();
self.indices.clear();
self.size = 0
}
/// Delete a key
pub fn delete(&mut self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<()> {
if self.delete_if_exists(vm, key)? {
Ok(())
} else {
Err(vm.new_key_error(key.clone()))
}
}
pub fn delete_if_exists(&mut self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<bool> {
if let LookupResult::Existing(entry_index) = self.lookup(vm, key)? {
self.unchecked_delete(entry_index);
Ok(true)
} else {
Ok(false)
}
}
pub fn delete_or_insert(
&mut self,
vm: &VirtualMachine,
key: &PyObjectRef,
value: T,
) -> PyResult<()> {
match self.lookup(vm, &key)? {
LookupResult::Existing(entry_index) => self.unchecked_delete(entry_index),
LookupResult::NewIndex {
hash_value,
hash_index,
} => self.unchecked_push(hash_index, hash_value, &key, value),
};
Ok(())
}
pub fn len(&self) -> usize {
self.size
}
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn size(&self) -> DictSize {
DictSize {
size: self.size,
entries_size: self.entries.len(),
}
}
pub fn next_entry(&self, position: &mut EntryIndex) -> Option<(&PyObjectRef, &T)> {
while *position < self.entries.len() {
if let Some(DictEntry { key, value, .. }) = &self.entries[*position] {
*position += 1;
return Some((key, value));
}
*position += 1;
}
None
}
pub fn has_changed_size(&self, position: &DictSize) -> bool {
position.size != self.size || self.entries.len() != position.entries_size
}
pub fn keys<'a>(&'a self) -> Box<Iterator<Item = PyObjectRef> + 'a> {
Box::new(
self.entries
.iter()
.filter_map(|v| v.as_ref().and_then(|v| Some(v.key.clone()))),
)
}
/// Lookup the index for the given key.
fn lookup(&self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<LookupResult> {
let hash_value = collection_hash(vm, key)?;
let perturb = hash_value;
let mut hash_index: HashIndex = hash_value;
loop {
if self.indices.contains_key(&hash_index) {
// Now we have an index, lets check the key.
let index = self.indices[&hash_index];
if let Some(entry) = &self.entries[index] {
// Okay, we have an entry at this place
if entry.key.is(key) {
// Literally the same object
break Ok(LookupResult::Existing(index));
} else if entry.hash == hash_value {
if do_eq(vm, &entry.key, key)? {
break Ok(LookupResult::Existing(index));
} else {
// entry mismatch.
}
} else {
// entry mismatch.
}
} else {
// Removed entry, continue search...
}
} else {
// Hash not in table, we are at free slot now.
break Ok(LookupResult::NewIndex {
hash_value,
hash_index,
});
}
// Update i to next probe location:
hash_index = hash_index
.wrapping_mul(5)
.wrapping_add(perturb)
.wrapping_add(1);
// warn!("Perturb value: {}", i);
}
}
/// Retrieve and delete a key
pub fn pop(&mut self, vm: &VirtualMachine, key: &PyObjectRef) -> PyResult<T> {
if let LookupResult::Existing(index) = self.lookup(vm, key)? {
let value = self.unchecked_get(index);
self.unchecked_delete(index);
Ok(value)
} else {
Err(vm.new_key_error(key.clone()))
}
}
pub fn pop_front(&mut self) -> Option<(PyObjectRef, T)> {
let mut entry_index = 0;
match self.next_entry(&mut entry_index) {
Some((key, value)) => {
let item = (key.clone(), value.clone());
self.unchecked_delete(entry_index - 1);
Some(item)
}
None => None,
}
}
}
enum LookupResult {
NewIndex {
hash_value: HashValue,
hash_index: HashIndex,
}, // return not found, index into indices
Existing(EntryIndex), // Existing record, index into entries
}
fn collection_hash(vm: &VirtualMachine, object: &PyObjectRef) -> PyResult<HashValue> {
let raw_hash = vm._hash(object)?;
let mut hasher = DefaultHasher::new();
raw_hash.hash(&mut hasher);
Ok(hasher.finish() as HashValue)
}
/// Invoke __eq__ on two keys
fn do_eq(vm: &VirtualMachine, key1: &PyObjectRef, key2: &PyObjectRef) -> Result<bool, PyObjectRef> {
let result = vm._eq(key1.clone(), key2.clone())?;
objbool::boolval(vm, result)
}
#[cfg(test)]
mod tests {
use super::{Dict, VirtualMachine};
#[test]
fn test_insert() {
let mut vm = VirtualMachine::new();
let mut dict = Dict::default();
assert_eq!(0, dict.len());
let key1 = vm.new_bool(true);
let value1 = vm.new_str("abc".to_string());
dict.insert(&mut vm, &key1, value1.clone()).unwrap();
assert_eq!(1, dict.len());
let key2 = vm.new_str("x".to_string());
let value2 = vm.new_str("def".to_string());
dict.insert(&mut vm, &key2, value2.clone()).unwrap();
assert_eq!(2, dict.len());
dict.insert(&mut vm, &key1, value2.clone()).unwrap();
assert_eq!(2, dict.len());
dict.delete(&mut vm, &key1).unwrap();
assert_eq!(1, dict.len());
dict.insert(&mut vm, &key1, value2).unwrap();
assert_eq!(2, dict.len());
assert_eq!(true, dict.contains(&mut vm, &key1).unwrap());
}
}