From f4ced467e4859bfe9c83c1a5f355dc81baae7b26 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ond=C5=99ej=20Hru=C5=A1ka?= <ondra@ondrovo.com>
Date: Tue, 6 Oct 2020 12:18:07 +0200
Subject: [PATCH] add rpush and rpop stack instructions

---
 crsn_stacks/src/defs.rs  |  2 +
 crsn_stacks/src/exec.rs  | 89 +++++++++++++++++++++++++---------------
 crsn_stacks/src/parse.rs | 14 +++++++
 examples/stacks.csn      | 22 ++++++++++
 4 files changed, 95 insertions(+), 32 deletions(-)

diff --git a/crsn_stacks/src/defs.rs b/crsn_stacks/src/defs.rs
index c85ad4f..ddef1db 100644
--- a/crsn_stacks/src/defs.rs
+++ b/crsn_stacks/src/defs.rs
@@ -5,4 +5,6 @@ pub enum StackOp {
     NewStack { dst: Wr },
     Push { obj: RdObj, src: Rd },
     Pop { dst: Wr, obj: RdObj },
+    ReversePush { obj: RdObj, src: Rd },
+    ReversePop { dst: Wr, obj: RdObj },
 }
diff --git a/crsn_stacks/src/exec.rs b/crsn_stacks/src/exec.rs
index b574306..1d29106 100644
--- a/crsn_stacks/src/exec.rs
+++ b/crsn_stacks/src/exec.rs
@@ -10,6 +10,7 @@ use crate::defs::StackOp;
 use crsn::sexp::Sexp;
 use crsn::sexp;
 use crsn::utils::A;
+use crsn::asm::data::{RdObj, Rd, Wr};
 
 #[derive(Debug, Default)]
 struct Stacks {
@@ -28,40 +29,20 @@ impl OpTrait for StackOp {
                 state.write(*dst, id)?;
             }
             StackOp::Push { obj, src } => {
-                state.clear_status();
-                let handle = state.read_obj(*obj)?;
-                let val = state.read(*src)?;
-
-                let stacks: &mut Stacks = state.ext_mut();
-                stacks.store.get_mut(&handle)
-                    .ok_or_else(|| Fault::ObjectNotExist(handle))?
-                    .push_back(val);
+                prepare_push(state, obj, src,
+                             |stack, val| stack.push_back(val))?;
+            }
+            StackOp::ReversePush { obj, src } => {
+                prepare_push(state, obj, src,
+                             |stack, val| stack.push_front(val))?;
             }
             StackOp::Pop { dst, obj } => {
-                state.clear_status();
-                let handle = state.read_obj(*obj)?;
-
-                let stacks: &mut Stacks = state.ext_mut();
-                let stack = stacks.store.get_mut(&handle)
-                    .ok_or_else(|| Fault::ObjectNotExist(handle))?;
-
-                let val = stack.pop_back();
-
-                if stack.is_empty() {
-                    state.set_flag(Cond::Zero, true);
-                }
-
-                let val = match val {
-                    None => {
-                        state.set_flag(Cond::Overflow, true);
-                        0
-                    }
-                    Some(val) => {
-                        val
-                    }
-                };
-
-                state.write(*dst, val)?;
+                prepare_pop(state, dst, obj,
+                            |stack| stack.pop_back())?;
+            }
+            StackOp::ReversePop { dst, obj } => {
+                prepare_pop(state, dst, obj,
+                            |stack| stack.pop_front())?;
             }
         }
 
@@ -73,11 +54,55 @@ impl OpTrait for StackOp {
             StackOp::NewStack { dst } => sexp::list(&[A("stack"), A(dst)]),
             StackOp::Push { obj, src } => sexp::list(&[A("push"), A(obj), A(src)]),
             StackOp::Pop { dst, obj } => sexp::list(&[A("pop"), A(dst), A(obj)]),
+            StackOp::ReversePush { obj, src } => sexp::list(&[A("rpush"), A(obj), A(src)]),
+            StackOp::ReversePop { dst, obj } => sexp::list(&[A("rpop"), A(dst), A(obj)]),
         }
     }
 }
 
+
 pub(crate) fn drop_obj(state: &mut RunState, handle: Value) -> Result<Option<()>, Fault> {
     let stacks: &mut Stacks = state.ext_mut();
     Ok(stacks.store.remove(&handle).map(|_| ()))
 }
+
+fn prepare_push(mut state: &mut RunState, obj: &RdObj, src: &Rd, pushfn : impl FnOnce(&mut VecDeque<Value>, Value) -> ()) -> Result<(), Fault> {
+    state.clear_status();
+    let handle = state.read_obj(*obj)?;
+    let val = state.read(*src)?;
+
+    let stacks: &mut Stacks = state.ext_mut();
+    let mutable = stacks.store.get_mut(&handle)
+        .ok_or_else(|| Fault::ObjectNotExist(handle))?;
+
+    pushfn(mutable, val);
+    Ok(())
+}
+
+fn prepare_pop(state: &mut RunState, dst: &Wr, obj: &RdObj, popfn : impl FnOnce(&mut VecDeque<Value>) -> Option<Value>) -> Result<(), Fault> {
+    state.clear_status();
+    let handle = state.read_obj(*obj)?;
+
+    let stacks: &mut Stacks = state.ext_mut();
+    let stack = stacks.store.get_mut(&handle)
+        .ok_or_else(|| Fault::ObjectNotExist(handle))?;
+
+    let val = popfn(stack);
+
+    if stack.is_empty() {
+        state.set_flag(Cond::Zero, true);
+    }
+
+    let val = match val {
+        None => {
+            state.set_flag(Cond::Overflow, true);
+            0
+        }
+        Some(val) => {
+            val
+        }
+    };
+
+    state.write(*dst, val)?;
+    Ok(())
+}
diff --git a/crsn_stacks/src/parse.rs b/crsn_stacks/src/parse.rs
index 55da319..b1206e3 100644
--- a/crsn_stacks/src/parse.rs
+++ b/crsn_stacks/src/parse.rs
@@ -27,6 +27,20 @@ pub(crate) fn parse<'a>(keyword: &str, mut args: TokenParser<'a>) -> Result<Pars
             }
         }
 
+        "rpush" => {
+            StackOp::ReversePush {
+                obj: args.next_rdobj()?,
+                src: args.next_rd()?,
+            }
+        }
+
+        "rpop" => {
+            StackOp::ReversePop {
+                dst: args.next_wr()?,
+                obj: args.next_rdobj()?,
+            }
+        }
+
         _other => {
             return Ok(ParseRes::Unknown(args));
         }
diff --git a/examples/stacks.csn b/examples/stacks.csn
index 9c37a9b..a828235 100644
--- a/examples/stacks.csn
+++ b/examples/stacks.csn
@@ -10,5 +10,27 @@
     (pop r1 @r0)
     (cmp r1 1 (ne? (fault)))
 
+    ; test reverse push
+    (push @r0 1)
+    (push @r0 7)
+    (rpush @r0 8)
+
+    (pop r1 @r0)
+    (cmp r1 7 (ne? (fault)))
+
+    (pop r1 @r0)
+    (cmp r1 1 (ne? (fault)))
+
+    (pop r1 @r0)
+    (cmp r1 8 (ne? (fault)))
+
+    ; test reverse pop
+
+    (push @r0 1000)
+    (push @r0 2000)
+
+    (rpop r1 @r0)
+    (cmp r1 1000 (ne? (fault)))
+
     (drop @r0)
 )