Use minimum size of 64 bytes for buffers.

This avoids an infinite loop in reserve_space(). See #202.
osmcode · Mar 31, 2017 · 7685449 · 7685449
1 parent 3c82892
commit 7685449
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Showing 2 changed files with 29 additions and 5 deletions.
diff --git a/include/osmium/memory/buffer.hpp b/include/osmium/memory/buffer.hpp
@@ -119,6 +119,15 @@ namespace osmium {
             auto_grow m_auto_grow{auto_grow::no};
             std::function<void(Buffer&)> m_full;
 
+            static size_t calculate_capacity(size_t capacity) noexcept {
+                // The majority of all Nodes will fit into this size.
+                constexpr static const size_t min_capacity = 64;
+                if (capacity < min_capacity) {
+                    return min_capacity;
+                }
+                return capacity;
+            }
+
         public:
 
             /**
@@ -198,13 +207,13 @@ namespace osmium {
              *         of the alignment.
              */
             explicit Buffer(size_t capacity, auto_grow auto_grow = auto_grow::yes) :
-                m_memory(new unsigned char[capacity]),
+                m_memory(new unsigned char[calculate_capacity(capacity)]),
                 m_data(m_memory.get()),
-                m_capacity(capacity),
+                m_capacity(calculate_capacity(capacity)),
                 m_written(0),
                 m_committed(0),
                 m_auto_grow(auto_grow) {
-                if (capacity % align_bytes != 0) {
+                if (m_capacity % align_bytes != 0) {
                     throw std::invalid_argument("buffer capacity needs to be multiple of alignment");
                 }
             }

diff --git a/test/t/memory/test_buffer_basics.cpp b/test/t/memory/test_buffer_basics.cpp
@@ -6,8 +6,8 @@ TEST_CASE("Buffer basics") {
 
     osmium::memory::Buffer invalid_buffer1;
     osmium::memory::Buffer invalid_buffer2;
-    osmium::memory::Buffer empty_buffer1(1024);
-    osmium::memory::Buffer empty_buffer2(2048);
+    osmium::memory::Buffer empty_buffer1{1024};
+    osmium::memory::Buffer empty_buffer2{2048};
 
     REQUIRE(!invalid_buffer1);
     REQUIRE(!invalid_buffer2);
@@ -32,3 +32,18 @@ TEST_CASE("Buffer basics") {
 
 }
 
+TEST_CASE("Buffer with zero size") {
+    osmium::memory::Buffer buffer{0};
+    REQUIRE(buffer.capacity() == 64);
+}
+
+TEST_CASE("Buffer with less than minimum size") {
+    osmium::memory::Buffer buffer{63};
+    REQUIRE(buffer.capacity() == 64);
+}
+
+TEST_CASE("Buffer with minimum size") {
+    osmium::memory::Buffer buffer{64};
+    REQUIRE(buffer.capacity() == 64);
+}
+