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dictdatatype.rs
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218 lines (195 loc) · 6.61 KB
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use crate::obj::objbool;
use crate::obj::objint;
use crate::pyobject::{IdProtocol, PyObjectRef, PyResult};
use crate::vm::VirtualMachine;
use num_traits::ToPrimitive;
/// 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::HashMap;
pub struct Dict {
size: usize,
indices: HashMap<usize, usize>,
entries: Vec<Option<DictEntry>>,
}
struct DictEntry {
hash: usize,
key: PyObjectRef,
value: PyObjectRef,
}
impl Dict {
pub fn new() -> Self {
Dict {
size: 0,
indices: HashMap::new(),
entries: Vec::new(),
}
}
/// Store a key
pub fn insert(
&mut self,
vm: &mut VirtualMachine,
key: &PyObjectRef,
value: PyObjectRef,
) -> 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:
let entry = DictEntry {
hash: hash_value,
key: key.clone(),
value,
};
let index = self.entries.len();
self.entries.push(Some(entry));
self.indices.insert(hash_index, index);
self.size += 1;
Ok(())
}
}
}
pub fn contains(&self, vm: &mut VirtualMachine, key: &PyObjectRef) -> PyResult<bool> {
if let LookupResult::Existing(_index) = self.lookup(vm, key)? {
Ok(true)
} else {
Ok(false)
}
}
/// Retrieve a key
pub fn get(&self, vm: &mut VirtualMachine, key: &PyObjectRef) -> PyResult {
if let LookupResult::Existing(index) = self.lookup(vm, key)? {
if let Some(entry) = &self.entries[index] {
Ok(entry.value.clone())
} else {
panic!("Lookup returned invalid index into entries!");
}
} else {
let key_repr = vm.to_pystr(key)?;
Err(vm.new_value_error(format!("Key not found: {}", key_repr)))
}
}
/// Delete a key
pub fn delete(&mut self, vm: &mut VirtualMachine, key: &PyObjectRef) -> PyResult<()> {
if let LookupResult::Existing(index) = self.lookup(vm, key)? {
self.entries[index] = None;
self.size -= 1;
Ok(())
} else {
let key_repr = vm.to_pystr(key)?;
Err(vm.new_value_error(format!("Key not found: {}", key_repr)))
}
}
pub fn len(&self) -> usize {
self.size
}
pub fn is_empty(&self) -> bool {
self.len() == 0
}
pub fn get_items(&self) -> Vec<(PyObjectRef, PyObjectRef)> {
self.entries
.iter()
.filter(|e| e.is_some())
.map(|e| e.as_ref().unwrap())
.map(|e| (e.key.clone(), e.value.clone()))
.collect()
}
/// Lookup the index for the given key.
fn lookup(&self, vm: &mut VirtualMachine, key: &PyObjectRef) -> PyResult<LookupResult> {
let hash_value = calc_hash(vm, key)?;
let perturb = hash_value;
let mut hash_index: usize = 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);
}
}
}
enum LookupResult {
NewIndex {
hash_value: usize,
hash_index: usize,
}, // return not found, index into indices
Existing(usize), // Existing record, index into entries
}
fn calc_hash(vm: &mut VirtualMachine, key: &PyObjectRef) -> PyResult<usize> {
let hash = vm.call_method(key, "__hash__", vec![])?;
Ok(objint::get_value(&hash).to_usize().unwrap())
}
/// Invoke __eq__ on two keys
fn do_eq(
vm: &mut VirtualMachine,
key1: &PyObjectRef,
key2: &PyObjectRef,
) -> Result<bool, PyObjectRef> {
let result = vm._eq(key1, key2.clone())?;
Ok(objbool::get_value(&result))
}
#[cfg(test)]
mod tests {
use super::{Dict, VirtualMachine};
#[test]
fn test_insert() {
let mut vm = VirtualMachine::new();
let mut dict = Dict::new();
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());
}
}