add multifile and module scoped predicates

src/prolog/machine/code_walker.rs

@@ -0,0 +1,81 @@
+use crate::prolog::instructions::*;
+
+use std::collections::VecDeque;
+
+fn scan_for_trust_me(code: &Code, jmp_offsets: &mut VecDeque<usize>, after_idx: &mut usize) {
+    for (idx, instr) in code[*after_idx..].iter().enumerate() {
+        match instr {
+            &Line::Choice(ChoiceInstruction::TrustMe)
+          | &Line::IndexedChoice(IndexedChoiceInstruction::Trust(..)) => {
+                *after_idx += idx;
+                return;
+            }
+            &Line::Control(ControlInstruction::JmpBy(_, offset, ..)) => {
+                jmp_offsets.push_back(*after_idx + idx + offset)
+            }
+            _ => {}
+        }
+    }
+}
+
+fn capture_next_range(code: &Code, queue: &mut VecDeque<usize>, last_idx: &mut usize) {
+    loop {
+        match &code[*last_idx] {
+            &Line::Choice(ChoiceInstruction::TryMeElse(..))
+          | &Line::IndexedChoice(IndexedChoiceInstruction::Try(..)) => {
+                    *last_idx += 1;
+                    scan_for_trust_me(code, queue, last_idx);
+                }
+            &Line::Control(ControlInstruction::JmpBy(_, offset, _, false)) => {
+                queue.push_back(*last_idx + offset);
+                *last_idx += 1;
+            }
+            &Line::Control(ControlInstruction::JmpBy(_, offset, _, true)) => {
+                queue.push_back(*last_idx + offset);
+                break;
+            }
+            &Line::Control(ControlInstruction::Proceed)
+          | &Line::Control(ControlInstruction::CallClause(_, _, _, true, _)) =>
+                break,
+            _ =>
+                *last_idx += 1,
+        };
+    }
+}
+
+/* This function walks the code of a single predicate, supposed to
+ * begin in code at the offset p. Each instruction is passed to the
+ * walker function.
+ */
+pub fn walk_code(code: &Code, p: usize, mut walker: impl FnMut(&Line))
+{
+    let mut queue = VecDeque::from(vec![p]);
+
+    while let Some(first_idx) = queue.pop_front() {
+        let mut last_idx = first_idx;
+
+        capture_next_range(code, &mut queue, &mut last_idx);
+
+        for instr in &code[first_idx .. last_idx + 1] {
+            walker(instr);
+        }
+    }
+}
+
+/* A function for code walking that might result in modification to
+ * the code. Otherwise identical to walk_code.
+ */
+pub fn walk_code_mut(code: &mut Code, p: usize, mut walker: impl FnMut(&mut Line))
+{
+    let mut queue = VecDeque::from(vec![p]);
+
+    while let Some(first_idx) = queue.pop_front() {
+        let mut last_idx = first_idx;
+
+        capture_next_range(code, &mut queue, &mut last_idx);
+
+        for instr in &mut code[first_idx .. last_idx + 1] {
+            walker(instr);
+        }
+    }
+}