From cab874305f4ee88a7c0ec06b5bdf3a4f90a1b041 Mon Sep 17 00:00:00 2001
From: Josh Holtrop <jholtrop@gmail.com>
Date: Sun, 17 Jul 2016 20:43:18 -0400
Subject: [PATCH] add PagedBuffer; use own main() for tests

---
 src/core/PagedBuffer.h       | 79 ++++++++++++++++++++++++++++++++++++
 test/src/main.cc             |  9 ++++
 test/src/test_PagedBuffer.cc | 45 ++++++++++++++++++++
 wscript                      |  3 +-
 4 files changed, 134 insertions(+), 2 deletions(-)
 create mode 100644 src/core/PagedBuffer.h
 create mode 100644 test/src/main.cc
 create mode 100644 test/src/test_PagedBuffer.cc

diff --git a/src/core/PagedBuffer.h b/src/core/PagedBuffer.h
new file mode 100644
index 0000000..0ba04b0
--- /dev/null
+++ b/src/core/PagedBuffer.h
@@ -0,0 +1,79 @@
+#ifndef PAGEDBUFFER_H
+#define PAGEDBUFFER_H
+
+#include "System.h"
+#include <vector>
+#include <stdint.h>
+
+template <typename T>
+class PagedBuffer
+{
+public:
+    /**
+     * Create a PagedBuffer.
+     *
+     * Note: sizeof(T) must be a power of 2. A single page can hold
+     * System::page_size / sizeof(T) entries.
+     */
+    PagedBuffer<T>()
+    {
+        static_assert((sizeof(T) & (sizeof(T) - 1)) == 0,
+                      "sizeof(T) must be a power of 2");
+        m_size = 0u;
+    }
+
+    ~PagedBuffer<T>()
+    {
+        for (auto it : m_pages)
+        {
+            System::free_pages(it, 1);
+        }
+    }
+
+    const T & operator[](unsigned int index) const
+    {
+        while (index >= (m_pages.size() * n_per_page()))
+        {
+            grow();
+        }
+        return m_pages[page_index(index)][index_in_page(index)];
+    }
+
+    T & operator[](unsigned int index)
+    {
+        while (index >= (m_pages.size() * n_per_page()))
+        {
+            grow();
+        }
+        return m_pages[page_index(index)][index_in_page(index)];
+    }
+
+    size_t size() { return m_size; }
+
+protected:
+    unsigned int n_per_page()
+    {
+        return System::page_size / sizeof(T);
+    }
+
+    unsigned int page_index(unsigned int index)
+    {
+        return index / n_per_page();
+    }
+
+    unsigned int index_in_page(unsigned int index)
+    {
+        return index % n_per_page();
+    }
+
+    void grow()
+    {
+        m_pages.push_back((T *)System::alloc_pages(1));
+        m_size += n_per_page();
+    }
+
+    std::vector<T *> m_pages;
+    unsigned long m_size;
+};
+
+#endif
diff --git a/test/src/main.cc b/test/src/main.cc
new file mode 100644
index 0000000..55fc515
--- /dev/null
+++ b/test/src/main.cc
@@ -0,0 +1,9 @@
+#include "gtest/gtest.h"
+#include "System.h"
+
+int main(int argc, char * argv[])
+{
+    ::testing::InitGoogleTest(&argc, argv);
+    System::init();
+    return RUN_ALL_TESTS();
+}
diff --git a/test/src/test_PagedBuffer.cc b/test/src/test_PagedBuffer.cc
new file mode 100644
index 0000000..4d1bb93
--- /dev/null
+++ b/test/src/test_PagedBuffer.cc
@@ -0,0 +1,45 @@
+#include "gtest/gtest.h"
+#include "PagedBuffer.h"
+
+struct X
+{
+    uint64_t a;
+    uint32_t b;
+    uint32_t c;
+};
+
+struct Y
+{
+    uint32_t a;
+    uint32_t b;
+};
+
+TEST(PagedBufferTest, empty_paged_buffer_has_size_0)
+{
+    PagedBuffer<X> pbx;
+    ASSERT_EQ(0u, pbx.size());
+
+    PagedBuffer<Y> pby;
+    ASSERT_EQ(0u, pby.size());
+}
+
+TEST(PagedBufferTest, allows_adding_elements)
+{
+    PagedBuffer<X> pbx;
+
+    for (uint32_t i = 0u; i < 1000u; i++)
+    {
+        X x = {i, 2u * i, 4u * i};
+        pbx[i] = x;
+    }
+
+    ASSERT_GE(pbx.size(), 1000u);
+
+    for (uint32_t i = 0u; i < 1000u; i++)
+    {
+        const X & x = pbx[i];
+        ASSERT_EQ(i, x.a);
+        ASSERT_EQ(2u * i, x.b);
+        ASSERT_EQ(4u * i, x.c);
+    }
+}
diff --git a/wscript b/wscript
index d293d99..137488a 100644
--- a/wscript
+++ b/wscript
@@ -33,8 +33,7 @@ def build(bld):
         test_libs += ["pthread"]
     test_sources = bld.path.ant_glob("src/core/**/*.cc")
     test_sources += bld.path.ant_glob("test/src/**/*.cc")
-    test_sources += ["libs/googletest/src/gtest-all.cc",
-                     "libs/googletest/src/gtest_main.cc"]
+    test_sources += ["libs/googletest/src/gtest-all.cc"]
     test_includes = ["src/core"]
     test_includes += ["libs/googletest/include", "libs/googletest"]
     bld(features = "cxx cxxprogram",