use prolog_parser::ast::*;
use prolog::instructions::*;
use std::collections::{HashMap, VecDeque};
use std::hash::Hash;
#[derive(Clone, Copy)]
enum IntIndex {
External(usize), Fail, Internal(usize)
}
pub struct CodeOffsets {
flags: MachineFlags,
pub constants: HashMap<Constant, ThirdLevelIndex>,
pub lists: ThirdLevelIndex,
pub structures: HashMap<(ClauseName, usize), ThirdLevelIndex>
}
impl CodeOffsets {
pub fn new(flags: MachineFlags) -> Self {
CodeOffsets {
flags,
constants: HashMap::new(),
lists: Vec::new(),
structures: HashMap::new()
}
}
fn cap_choice_seq_with_trust(prelude: &mut ThirdLevelIndex) {
prelude.last_mut().map(|instr| {
match instr {
&mut IndexedChoiceInstruction::Retry(i) =>
*instr = IndexedChoiceInstruction::Trust(i),
_ => {}
};
});
}
fn add_index(is_first_index: bool, index: usize) -> IndexedChoiceInstruction {
if is_first_index {
IndexedChoiceInstruction::Try(index)
} else {
IndexedChoiceInstruction::Retry(index)
}
}
pub fn index_term(&mut self, first_arg: &Term, index: usize)
{
match first_arg {
&Term::Clause(_, ref name, ref terms, _) => {
let code = self.structures.entry((name.clone(), terms.len()))
.or_insert(Vec::new());
let is_initial_index = code.is_empty();
code.push(Self::add_index(is_initial_index, index));
},
&Term::Cons(..) => {
let is_initial_index = self.lists.is_empty();
self.lists.push(Self::add_index(is_initial_index, index));
},
&Term::Constant(_, Constant::String(_))
if self.flags.double_quotes.is_chars() => { let is_initial_index = self.lists.is_empty();
self.lists.push(Self::add_index(is_initial_index, index));
},
&Term::Constant(_, ref constant) => {
let code = self.constants.entry(constant.clone())
.or_insert(Vec::new());
let is_initial_index = code.is_empty();
code.push(Self::add_index(is_initial_index, index));
},
_ => {}
};
}
fn second_level_index<Index>(indices: HashMap<Index, ThirdLevelIndex>, prelude: &mut CodeDeque)
-> HashMap<Index, IntIndex>
where Index: Eq + Hash
{
let mut index_locs = HashMap::new();
for (key, mut code) in indices.into_iter() {
if code.len() > 1 {
index_locs.insert(key, IntIndex::Internal(prelude.len()));
Self::cap_choice_seq_with_trust(&mut code);
prelude.extend(code.into_iter().map(|code| Line::from(code)));
} else {
code.first().map(|i| {
index_locs.insert(key, IntIndex::External(i.offset()));
});
}
}
index_locs
}
fn no_indices(&self) -> bool {
let no_constants = self.constants.is_empty();
let no_structures = self.structures.is_empty();
let no_lists = self.lists.is_empty();
no_constants && no_structures && no_lists
}
fn flatten_index<Index>(index: HashMap<Index, IntIndex>, len: usize)
-> HashMap<Index, usize>
where Index: Eq + Hash
{
let mut flattened_index = HashMap::new();
for (key, int_index) in index.into_iter() {
match int_index {
IntIndex::External(offset) => {
flattened_index.insert(key, offset + len + 1);
},
IntIndex::Internal(offset) => {
flattened_index.insert(key, offset + 1);
},
_ => {}
};
}
flattened_index
}
fn adjust_internal_index(index: IntIndex) -> IntIndex
{
match index {
IntIndex::Internal(o) => IntIndex::Internal(o + 1),
IntIndex::External(o) => IntIndex::External(o),
_ => IntIndex::Fail
}
}
fn switch_on_constant(con_ind: HashMap<Constant, ThirdLevelIndex>, prelude: &mut CodeDeque)
-> IntIndex
{
let con_ind = Self::second_level_index(con_ind, prelude);
if con_ind.len() > 1 {
let index = Self::flatten_index(con_ind, prelude.len());
let instr = IndexingInstruction::SwitchOnConstant(index.len(), index);
prelude.push_front(Line::from(instr));
IntIndex::Internal(1)
} else {
con_ind.values().next()
.map(|index| Self::adjust_internal_index(*index))
.unwrap_or(IntIndex::Fail)
}
}
fn switch_on_structure(str_ind: HashMap<(ClauseName, usize), ThirdLevelIndex>,
prelude: &mut CodeDeque)
-> IntIndex
{
let str_ind = Self::second_level_index(str_ind, prelude);
if str_ind.len() > 1 {
let index = Self::flatten_index(str_ind, prelude.len());
let instr = IndexingInstruction::SwitchOnStructure(index.len(), index);
prelude.push_front(Line::from(instr));
IntIndex::Internal(1)
} else {
str_ind.values().next()
.map(|index| Self::adjust_internal_index(*index))
.unwrap_or(IntIndex::Fail)
}
}
fn switch_on_list(mut lists: ThirdLevelIndex, prelude: &mut CodeDeque) -> IntIndex
{
if lists.len() > 1 {
Self::cap_choice_seq_with_trust(&mut lists);
prelude.extend(lists.into_iter().map(|i| Line::from(i)));
IntIndex::Internal(0)
} else {
lists.first()
.map(|i| IntIndex::External(i.offset()))
.unwrap_or(IntIndex::Fail)
}
}
fn switch_on_str_offset_from(str_loc: IntIndex, prelude_len: usize, con_loc: IntIndex)
-> usize
{
match str_loc {
IntIndex::External(o) => o + prelude_len + 1,
IntIndex::Fail => 0,
IntIndex::Internal(_) => match con_loc {
IntIndex::Internal(_) => 2,
_ => 1
}
}
}
fn switch_on_con_offset_from(con_loc: IntIndex, prelude_len: usize) -> usize
{
match con_loc {
IntIndex::External(offset) => offset + prelude_len + 1,
IntIndex::Fail => 0,
IntIndex::Internal(offset) => offset,
}
}
fn switch_on_lst_offset_from(lst_loc: IntIndex, prelude_len: usize, lst_offset: usize)
-> usize
{
match lst_loc {
IntIndex::External(o) => o + prelude_len + 1,
IntIndex::Fail => 0,
IntIndex::Internal(_) => prelude_len - lst_offset + 1
}
}
pub fn add_indices(self, code: &mut Code, mut code_body: Code)
{
if self.no_indices() {
*code = code_body;
return;
}
let mut prelude = VecDeque::new();
let lst_loc = Self::switch_on_list(self.lists, &mut prelude);
let lst_offset = prelude.len();
let str_loc = Self::switch_on_structure(self.structures, &mut prelude);
let con_loc = Self::switch_on_constant(self.constants, &mut prelude);
let prelude_length = prelude.len();
for (index, line) in prelude.iter_mut().enumerate() {
match line {
&mut Line::IndexedChoice(IndexedChoiceInstruction::Try(ref mut i))
| &mut Line::IndexedChoice(IndexedChoiceInstruction::Retry(ref mut i))
| &mut Line::IndexedChoice(IndexedChoiceInstruction::Trust(ref mut i)) =>
*i += prelude_length - index,
_ => {}
}
}
let str_loc = Self::switch_on_str_offset_from(str_loc, prelude.len(), con_loc);
let con_loc = Self::switch_on_con_offset_from(con_loc, prelude.len());
let lst_loc = Self::switch_on_lst_offset_from(lst_loc, prelude.len(), lst_offset);
let switch_instr = IndexingInstruction::SwitchOnTerm(prelude.len() + 1,
con_loc,
lst_loc,
str_loc);
prelude.push_front(Line::from(switch_instr));
*code = Vec::from(prelude);
code.append(&mut code_body);
}
}