From b3cf9ccb9dec4351187a90459c3c6104f168b59a Mon Sep 17 00:00:00 2001
From: Guanqun Lu <guanqun.lu@gmail.com>
Date: Thu, 2 Aug 2018 16:04:43 +0800
Subject: [PATCH 1/2] implement extend() and remove one TODO

---
 src/runner.rs | 46 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 41 insertions(+), 5 deletions(-)

diff --git a/src/runner.rs b/src/runner.rs
index 5a9ec84..3a69350 100644
--- a/src/runner.rs
+++ b/src/runner.rs
@@ -1,5 +1,6 @@
 use std::ops;
 use std::{u32, usize};
+use std::cmp;
 use std::fmt;
 use std::iter::repeat;
 use parity_wasm::elements::Local;
@@ -1109,11 +1110,7 @@ impl FunctionContext {
 			.map(RuntimeValue::default)
 			.collect::<Vec<_>>();
 
-		// TODO: Replace with extend.
-		for local in locals {
-			value_stack.push(local)
-				.map_err(|_| TrapKind::StackOverflow)?;
-		}
+		value_stack.extend(&locals)?;
 
 		self.is_initialized = true;
 		Ok(())
@@ -1263,8 +1260,47 @@ impl ValueStack {
 		Ok(())
 	}
 
+	#[inline]
+	fn extend(&mut self, values: &[RuntimeValue]) -> Result<(), TrapKind> {
+		let len = cmp::min(values.len(), self.buf.len() - self.sp);
+		self.buf[self.sp..(self.sp+len)].copy_from_slice(&values[..len]);
+		self.sp += len;
+		if len < values.len() {
+			Err(TrapKind::StackOverflow)
+		} else {
+			Ok(())
+		}
+	}
+
 	#[inline]
 	fn len(&self) -> usize {
 		self.sp
 	}
 }
+
+#[cfg(test)]
+mod tests {
+	use super::ValueStack;
+	use value::RuntimeValue;
+
+	#[test]
+	fn test_stack_extend() {
+		let mut stack = ValueStack::with_limit(5);
+		let values = vec![RuntimeValue::I32(1), RuntimeValue::I32(2), RuntimeValue::I32(3),
+			RuntimeValue::I32(4), RuntimeValue::I32(5)];
+
+		assert!(stack.extend(&values).is_ok());
+		assert_eq!(stack.len(), 5);
+
+		assert!(stack.push(RuntimeValue::I32(6)).is_err());
+
+		// check each elements
+		assert_eq!(stack.pop(), RuntimeValue::I32(5));
+		assert_eq!(stack.pop(), RuntimeValue::I32(4));
+		assert_eq!(stack.pop(), RuntimeValue::I32(3));
+		assert_eq!(stack.pop(), RuntimeValue::I32(2));
+		assert_eq!(stack.pop(), RuntimeValue::I32(1));
+
+		assert_eq!(stack.len(), 0);
+	}
+}

From 039c75589ca4030896a973a13acbc383148f8aed Mon Sep 17 00:00:00 2001
From: Guanqun Lu <guanqun.lu@gmail.com>
Date: Tue, 18 Sep 2018 23:32:35 +0800
Subject: [PATCH 2/2] fix according to the comments

---
 src/runner.rs | 48 +++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/src/runner.rs b/src/runner.rs
index 3a69350..2d7c53a 100644
--- a/src/runner.rs
+++ b/src/runner.rs
@@ -1,6 +1,5 @@
 use std::ops;
 use std::{u32, usize};
-use std::cmp;
 use std::fmt;
 use std::iter::repeat;
 use parity_wasm::elements::Local;
@@ -1262,13 +1261,15 @@ impl ValueStack {
 
 	#[inline]
 	fn extend(&mut self, values: &[RuntimeValue]) -> Result<(), TrapKind> {
-		let len = cmp::min(values.len(), self.buf.len() - self.sp);
-		self.buf[self.sp..(self.sp+len)].copy_from_slice(&values[..len]);
-		self.sp += len;
-		if len < values.len() {
-			Err(TrapKind::StackOverflow)
+		let avail_len = self.buf.len() - self.sp;
+		let to_copy_len = values.len();
+
+		if to_copy_len <= avail_len {
+		    self.buf[self.sp..(self.sp+to_copy_len)].copy_from_slice(&values[..to_copy_len]);
+		    self.sp += to_copy_len;
+		    Ok(())
 		} else {
-			Ok(())
+		    Err(TrapKind::StackOverflow)
 		}
 	}
 
@@ -1286,8 +1287,13 @@ mod tests {
 	#[test]
 	fn test_stack_extend() {
 		let mut stack = ValueStack::with_limit(5);
-		let values = vec![RuntimeValue::I32(1), RuntimeValue::I32(2), RuntimeValue::I32(3),
-			RuntimeValue::I32(4), RuntimeValue::I32(5)];
+		let values = vec![
+			RuntimeValue::I32(1),
+			RuntimeValue::I32(2),
+			RuntimeValue::I32(3),
+			RuntimeValue::I32(4),
+			RuntimeValue::I32(5)
+		];
 
 		assert!(stack.extend(&values).is_ok());
 		assert_eq!(stack.len(), 5);
@@ -1303,4 +1309,28 @@ mod tests {
 
 		assert_eq!(stack.len(), 0);
 	}
+
+	#[test]
+	fn test_stack_extend_overflow() {
+		let mut stack = ValueStack::with_limit(4);
+		let values = vec![
+			RuntimeValue::I32(1),
+			RuntimeValue::I32(2),
+			RuntimeValue::I32(3),
+			RuntimeValue::I32(4),
+			RuntimeValue::I32(5)
+		];
+
+		assert!(stack.extend(&values).is_err());
+		assert_eq!(stack.len(), 0);
+
+		assert!(stack.push(RuntimeValue::I32(6)).is_ok());
+
+		assert_eq!(stack.len(), 1);
+
+		// check each elements
+		assert_eq!(stack.pop(), RuntimeValue::I32(6));
+
+		assert_eq!(stack.len(), 0);
+	}
 }