Implement both extension and shrinking of buffers.

1 files changed, 41 insertions, 13 deletions

diff --git a/vespalib/src/tests/alloc/alloc_test.cpp b/vespalib/src/tests/alloc/alloc_test.cpp
index 6950287edb1..03d600c6559 100644
--- a/vespalib/src/tests/alloc/alloc_test.cpp
+++ b/vespalib/src/tests/alloc/alloc_test.cpp
@@ -103,23 +103,51 @@ TEST("rounding of large mmaped buffer") {
 }
 
 TEST("heap alloc can not be extended") {
-   Alloc buf = Alloc::allocHeap(100);
-   void * oldPtr = buf.get();
-   EXPECT_EQUAL(100, buf.size());
-   EXPECT_FALSE(buf.resize_inplace(101));
-   EXPECT_EQUAL(oldPtr, buf.get());
-   EXPECT_EQUAL(100, buf.size());
+    Alloc buf = Alloc::allocHeap(100);
+    void * oldPtr = buf.get();
+    EXPECT_EQUAL(100, buf.size());
+    EXPECT_FALSE(buf.resize_inplace(101));
+    EXPECT_EQUAL(oldPtr, buf.get());
+    EXPECT_EQUAL(100, buf.size());
 }
 
-TEST("mmap alloc can be extended") {
-   Alloc buf = Alloc::allocMMap(100);
-   void * oldPtr = buf.get();
-   EXPECT_EQUAL(4096, buf.size());
-   EXPECT_TRUE(buf.resize_inplace(4097));
-   EXPECT_EQUAL(oldPtr, buf.get());
-   EXPECT_EQUAL(8192, buf.size());
+TEST("mmap alloc can be extended if room") {
+    Alloc reserved = Alloc::allocMMap(100);
+    Alloc buf = Alloc::allocMMap(100);
+
+    // Normally mmapping starts at the top and grows down in address space.
+    // The there is no room to extend the last mapping.
+    // So in order to verify this we first mmap a reserved area that we unmap
+    // before we test extension.
+    EXPECT_GREATER(reserved.get(), buf.get());
+    EXPECT_EQUAL(reserved.get(), static_cast<const char *>(buf.get()) + buf.size());
+    {
+        Alloc().swap(reserved);
+    }
+
+    void * oldPtr = buf.get();
+    EXPECT_EQUAL(4096, buf.size());
+    EXPECT_TRUE(buf.resize_inplace(4097));
+    EXPECT_EQUAL(oldPtr, buf.get());
+    EXPECT_EQUAL(8192, buf.size());
 }
 
+TEST("heap alloc can not be shrinked") {
+    Alloc buf = Alloc::allocHeap(101);
+    void * oldPtr = buf.get();
+    EXPECT_EQUAL(101, buf.size());
+    EXPECT_FALSE(buf.resize_inplace(100));
+    EXPECT_EQUAL(oldPtr, buf.get());
+    EXPECT_EQUAL(101, buf.size());
+}
 
+TEST("mmap alloc can be shrinked") {
+    Alloc buf = Alloc::allocMMap(4097);
+    void * oldPtr = buf.get();
+    EXPECT_EQUAL(8192, buf.size());
+    EXPECT_TRUE(buf.resize_inplace(4095));
+    EXPECT_EQUAL(oldPtr, buf.get());
+    EXPECT_EQUAL(4096, buf.size());
+}
 
 TEST_MAIN() { TEST_RUN_ALL(); }