BFFramework/BFFramework/Classes/PQGPUImage/Source/FramebufferCache.swift

#if os(Linux)
    #if GLES
        import COpenGLES.gles2
    #else
        import COpenGL
    #endif
#else
    #if GLES
        import OpenGLES
    #else
        import OpenGL.GL3
    #endif
#endif

// TODO: Add mechanism to purge framebuffers on low memory

public class FramebufferCache {
    var framebufferCache = [Int64: [Framebuffer]]()
    let context: OpenGLContext

    init(context: OpenGLContext) {
        self.context = context
    }

    public func requestFramebufferWithProperties(orientation: ImageOrientation, size: GLSize, textureOnly: Bool = false, minFilter: Int32 = GL_LINEAR, magFilter: Int32 = GL_LINEAR, wrapS: Int32 = GL_CLAMP_TO_EDGE, wrapT: Int32 = GL_CLAMP_TO_EDGE, internalFormat: Int32 = GL_RGBA, format: Int32 = GL_BGRA, type: Int32 = GL_UNSIGNED_BYTE, stencil: Bool = false) -> Framebuffer {
        let hash = hashForFramebufferWithProperties(orientation: orientation, size: size, textureOnly: textureOnly, minFilter: minFilter, magFilter: magFilter, wrapS: wrapS, wrapT: wrapT, internalFormat: internalFormat, format: format, type: type, stencil: stencil)
        let framebuffer: Framebuffer

        if framebufferCache.count > 20 {
            debugPrint("WARNING: Runaway framebuffer cache with size: \(framebufferCache.count)")
        }

        if (framebufferCache[hash]?.count ?? -1) > 0 {
            // debugPrint("Restoring previous framebuffer")
            framebuffer = framebufferCache[hash]!.removeLast()
            framebuffer.orientation = orientation
        } else {
            do {
                // debugPrint("Generating new framebuffer at size: \(size)")

                framebuffer = try Framebuffer(context: context, orientation: orientation, size: size, textureOnly: textureOnly, minFilter: minFilter, magFilter: magFilter, wrapS: wrapS, wrapT: wrapT, internalFormat: internalFormat, format: format, type: type, stencil: stencil)
                framebuffer.cache = self
            } catch {
                fatalError("Could not create a framebuffer of the size (\(size.width), \(size.height)), error: \(error)")
            }
        }
        return framebuffer
    }

    public func purgeAllUnassignedFramebuffers() {
        framebufferCache.removeAll()
#if os(iOS)
        CVOpenGLESTextureCacheFlush(sharedImageProcessingContext.coreVideoTextureCache, 0);
        print("release buffer")
#endif
    }

    func returnToCache(_ framebuffer: Framebuffer) {
        // sprint("Returning to cache: \(framebuffer)")
        context.runOperationSynchronously {
            if self.framebufferCache[framebuffer.hash] != nil {
                self.framebufferCache[framebuffer.hash]!.append(framebuffer)
            } else {
                self.framebufferCache[framebuffer.hash] = [framebuffer]
            }
        }
    }
}