Added helper to create Vec with a given size

src/common/mod.rs

@@ -30,3 +30,10 @@ pub trait HasLen {
 }
 
 
+pub fn create_vec_with_len<T>(capacity: usize) -> Vec<T> {
+    let mut v = Vec::with_capacity(capacity);
+    unsafe {
+        v.set_len(capacity);
+    }
+    v
+}

src/datastruct/stacker/heap.rs

@@ -1,5 +1,6 @@
 use std::cell::UnsafeCell;
 use std::mem;
+use common::create_vec_with_len;
 use std::ptr;
 
 /// `BytesRef` refers to a slice in tantivy's custom `Heap`.
@@ -109,11 +110,7 @@ struct InnerHeap {
 /// We use this unsafe trick to make unit test
 /// way faster.
 fn allocate_fast(num_bytes: usize) -> Vec<u8> {
-    let mut buffer = Vec::with_capacity(num_bytes);
-    unsafe {
-        buffer.set_len(num_bytes);
-    }
-    buffer
+    create_vec_with_len(num_bytes)
 }
 
 impl InnerHeap {

src/schema/term.rs

@@ -1,6 +1,7 @@
 use std::fmt;
 
 use common::BinarySerializable;
+use common::create_vec_with_len;
 use byteorder::{BigEndian, ByteOrder};
 use super::Field;
 use std::str;
@@ -44,8 +45,7 @@ impl Term {
     /// The first byte is `1`, and the 4 following bytes are that of the u32.
     pub fn from_field_u32(field: Field, val: u32) -> Term {
         const U32_TERM_LEN: usize = 1 + 4;
-        let mut buffer = Vec::with_capacity(U32_TERM_LEN);
-        unsafe { buffer.set_len(U32_TERM_LEN) };
+        let mut buffer = create_vec_with_len(U32_TERM_LEN);
         buffer[0] = field.0;
         // we want BigEndian here to have lexicographic order
         // match the natural order of vals.