add missing buffer.hpp

include/llmr/geometry/buffer.hpp

@@ -0,0 +1,73 @@
+#ifndef LLMR_GEOMETRY_BUFFER
+#define LLMR_GEOMETRY_BUFFER
+
+#include <cstdlib>
+#include <cassert>
+#include <llmr/platform/gl.hpp>
+
+namespace llmr {
+
+template <
+    size_t itemSize,
+    int bufferType = GL_ARRAY_BUFFER,
+    size_t defaultLength = 8192
+>
+class Buffer {
+public:
+    ~Buffer() {
+        if (array) {
+            free(array);
+            array = nullptr;
+        }
+        if (buffer != 0) {
+            glDeleteBuffers(1, &buffer);
+            buffer = 0;
+        }
+    }
+
+    inline size_t index() const {
+        return pos / itemSize;
+    }
+
+    void bind() {
+        if (buffer == 0) {
+            glGenBuffers(1, &buffer);
+            glBindBuffer(bufferType, buffer);
+            glBufferData(bufferType, pos, array, GL_STATIC_DRAW);
+            free(array);
+            array = nullptr;
+        } else {
+            glBindBuffer(bufferType, buffer);
+        }
+    }
+
+protected:
+    // increase the buffer size by at least /required/ bytes.
+    void *addElement() {
+        assert("Buffer is already bound to GPU" && buffer == 0);
+        if (length < pos + itemSize) {
+            while (length < pos + itemSize) length += defaultLength;
+            array = realloc(array, length);
+            assert("Buffer reallocation failed" && array != nullptr);
+        }
+        pos += itemSize;
+        return static_cast<char *>(array) + (pos - itemSize);
+    }
+
+private:
+    // CPU buffer
+    void *array = nullptr;
+
+    // Byte position where we are writing.
+    size_t pos = 0;
+
+    // Number of bytes that are valid in this buffer.
+    size_t length = 0;
+
+    // GL buffer ID
+    uint32_t buffer = 0;
+};
+
+}
+
+#endif