Add StackAllocator (#450)

modules/common/chowdsp_data_structures/Structures/chowdsp_StackAllocator.h

@@ -0,0 +1,86 @@
+#pragma once
+
+#include <vector>
+
+namespace chowdsp
+{
+/** A simple stack allocator */
+class StackAllocator
+{
+public:
+    StackAllocator() = default;
+
+    StackAllocator (const StackAllocator&) = delete;
+    StackAllocator& operator= (const StackAllocator&) = delete;
+
+    StackAllocator (StackAllocator&&) noexcept = default;
+    StackAllocator& operator= (StackAllocator&&) noexcept = default;
+
+    /** Re-allocates the internal buffer with a given number of bytes */
+    void reset (size_t new_size_bytes)
+    {
+        clear();
+        raw_data.resize (new_size_bytes, {});
+    }
+
+    /** Resets the allocator */
+    void clear() noexcept
+    {
+        bytes_used = 0;
+    }
+
+    /** Returns the number of bytes currently being used */
+    [[nodiscard]] size_t get_bytes_used() const noexcept { return bytes_used; }
+
+    /** Allocates a given number of bytes */
+    void* allocate_bytes (size_t num_bytes) noexcept
+    {
+        if (bytes_used + num_bytes > raw_data.size())
+            return nullptr;
+
+        auto* pointer = raw_data.data() + bytes_used;
+        bytes_used += num_bytes;
+        return pointer;
+    }
+
+    /** Allocates space for some number of objects of type T */
+    template <typename T, typename IntType>
+    T* allocate (IntType num_Ts) noexcept
+    {
+        return static_cast<T*> (allocate_bytes ((size_t) num_Ts * sizeof (T)));
+    }
+
+    /** Returns a pointer to the internal buffer with a given offset in bytes */
+    template <typename T, typename IntType>
+    T* data (IntType offset_bytes) noexcept
+    {
+        return reinterpret_cast<T*> (raw_data.data() + offset_bytes);
+    }
+
+    /**
+     * Creates a "frame" for the allocator.
+     * Once the frame goes out of scope, the allocator will be reset
+     * to whatever it's state was at the beginning of the frame.
+     */
+    struct StackAllocatorFrame
+    {
+        explicit StackAllocatorFrame (StackAllocator& allocator)
+            : alloc (allocator),
+              bytes_used_at_start (alloc.bytes_used)
+        {
+        }
+
+        ~StackAllocatorFrame()
+        {
+            alloc.bytes_used = bytes_used_at_start;
+        }
+
+        StackAllocator& alloc;
+        const size_t bytes_used_at_start;
+    };
+
+private:
+    std::vector<std::byte> raw_data {};
+    size_t bytes_used = 0;
+};
+} // namespace chowdsp

modules/common/chowdsp_data_structures/chowdsp_data_structures.h

@@ -29,6 +29,7 @@ BEGIN_JUCE_MODULE_DECLARATION
 #include "Structures/chowdsp_OptionalPointer.h"
 #include "Structures/chowdsp_RawObject.h"
 #include "Structures/chowdsp_SmallVector.h"
+#include "Structures/chowdsp_StackAllocator.h"
 #include "Structures/chowdsp_StringLiteral.h"
 
 #include "Helpers/chowdsp_Iterators.h"

tests/common_tests/chowdsp_data_structures_test/CMakeLists.txt

@@ -9,6 +9,7 @@ target_sources(chowdsp_data_structures_test
         LocalPointerTest.cpp
         OptionalPointerTest.cpp
         SmallVectorTest.cpp
+        StackAllocatorTest.cpp
         StringLiteralTest.cpp
         TupleHelpersTest.cpp
         VectorHelpersTest.cpp

tests/common_tests/chowdsp_data_structures_test/StackAllocatorTest.cpp

@@ -0,0 +1,39 @@
+#include <CatchUtils.h>
+#include <chowdsp_data_structures/chowdsp_data_structures.h>
+
+TEST_CASE ("Stack Allocator Test", "[common][data-structures]")
+{
+    chowdsp::StackAllocator allocator;
+    allocator.reset (150);
+
+    // allocate doubles
+    {
+        auto* some_doubles = allocator.allocate<double> (10);
+        REQUIRE ((void*) some_doubles == allocator.data<void> (0));
+        REQUIRE (allocator.get_bytes_used() == 80);
+    }
+
+    // allocate ints
+    {
+        auto* some_ints = allocator.allocate<int32_t> (10);
+        REQUIRE ((void*) some_ints == allocator.data<void> (80));
+        REQUIRE (allocator.get_bytes_used() == 120);
+    }
+
+    // allocate with stack frame
+    {
+        chowdsp::StackAllocator::StackAllocatorFrame frame { allocator };
+        auto* some_chars = allocator.allocate<char> (30);
+        juce::ignoreUnused (some_chars);
+        REQUIRE (allocator.get_bytes_used() == 150);
+    }
+
+    REQUIRE (allocator.get_bytes_used() == 120);
+
+    // overfull allocation
+    REQUIRE (allocator.allocate<double> (100) == nullptr);
+
+    // clear allocator
+    allocator.clear();
+    REQUIRE (allocator.get_bytes_used() == 0);
+}