From fce7639c905486f0fd98082abc46f90f6b62e078 Mon Sep 17 00:00:00 2001
From: Zaggy1024 <zaggy1024@gmail.com>
Date: Sun, 6 Nov 2022 15:27:50 -0600
Subject: [PATCH] LibVideo: Put motion vector or reference frame pairs in a
 struct

Since these two types are often passed around as a pair, it's easier to
handle them with a simple pair struct, at least for now. Once things
are fully being passed around as parameters wherever possible, it may
be good to change this type for something more generalized.
---
 Userland/Libraries/LibVideo/VP9/Context.h | 33 +++++++++++++++++++++++
 Userland/Libraries/LibVideo/VP9/Parser.h  | 31 ++++++++++-----------
 2 files changed, 49 insertions(+), 15 deletions(-)
 create mode 100644 Userland/Libraries/LibVideo/VP9/Context.h

diff --git a/Userland/Libraries/LibVideo/VP9/Context.h b/Userland/Libraries/LibVideo/VP9/Context.h
new file mode 100644
index 0000000000..758ce39e04
--- /dev/null
+++ b/Userland/Libraries/LibVideo/VP9/Context.h
@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2021, Hunter Salyer <thefalsehonesty@gmail.com>
+ * Copyright (c) 2022, Gregory Bertilson <zaggy1024@gmail.com>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#include "Enums.h"
+#include "MotionVector.h"
+
+namespace Video::VP9 {
+
+template<typename T>
+struct Pair {
+    T a;
+    T b;
+
+    T& operator[](size_t index)
+    {
+        if (index == 0)
+            return a;
+        if (index == 1)
+            return b;
+        VERIFY_NOT_REACHED();
+    }
+};
+
+typedef Pair<ReferenceFrameType> ReferenceFramePair;
+typedef Pair<MotionVector> MotionVectorPair;
+
+}
diff --git a/Userland/Libraries/LibVideo/VP9/Parser.h b/Userland/Libraries/LibVideo/VP9/Parser.h
index d86751d052..b8a8299e92 100644
--- a/Userland/Libraries/LibVideo/VP9/Parser.h
+++ b/Userland/Libraries/LibVideo/VP9/Parser.h
@@ -16,6 +16,7 @@
 #include <LibVideo/DecoderError.h>
 
 #include "BitStream.h"
+#include "Context.h"
 #include "LookupTables.h"
 #include "MotionVector.h"
 #include "ProbabilityTables.h"
@@ -233,7 +234,7 @@ private:
     // The column to use for getting partition tree probability lookups.
     u32 m_col { 0 };
     TXSize m_tx_size { TX_4x4 };
-    ReferenceFrameType m_ref_frame[2];
+    ReferenceFramePair m_ref_frame;
     bool m_is_inter { false };
     bool m_is_compound { false };
     PredictionMode m_default_intra_mode { PredictionMode::DcPred };
@@ -243,18 +244,18 @@ private:
     u8 m_num_4x4_h { 0 };
     PredictionMode m_uv_mode { 0 }; // FIXME: Is u8 the right size?
     Vector<Array<PredictionMode, 4>> m_sub_modes;
-    ReferenceFrameType m_left_ref_frame[2];
-    ReferenceFrameType m_above_ref_frame[2];
+    ReferenceFramePair m_left_ref_frame;
+    ReferenceFramePair m_above_ref_frame;
     bool m_left_intra { false };
     bool m_above_intra { false };
     bool m_left_single { false };
     bool m_above_single { false };
     // The current block's interpolation filter.
     InterpolationFilter m_interp_filter { EightTap };
-    MotionVector m_mv[2];
-    MotionVector m_near_mv[2];
-    MotionVector m_nearest_mv[2];
-    MotionVector m_best_mv[2];
+    MotionVectorPair m_mv;
+    MotionVectorPair m_near_mv;
+    MotionVectorPair m_nearest_mv;
+    MotionVectorPair m_best_mv;
     // FIXME: Move these to a struct to store together in one array.
     Gfx::Size<u32> m_ref_frame_size[NUM_REF_FRAMES];
     bool m_ref_subsampling_x[NUM_REF_FRAMES];
@@ -271,7 +272,7 @@ private:
     TXMode m_tx_mode;
     ReferenceMode m_reference_mode;
     ReferenceFrameType m_comp_fixed_ref;
-    ReferenceFrameType m_comp_var_ref[2];
+    ReferenceFramePair m_comp_var_ref;
     MotionVector m_block_mvs[2][4];
     Vector<u8> m_prev_segment_ids;
 
@@ -280,15 +281,15 @@ private:
     Vector<u32> m_mi_sizes;
     Vector<PredictionMode> m_y_modes;
     Vector<u8> m_segment_ids;
-    Vector<Array<ReferenceFrameType, 2>> m_ref_frames;
-    Vector<Array<ReferenceFrameType, 2>> m_prev_ref_frames;
-    Vector<Array<MotionVector, 2>> m_mvs;
-    Vector<Array<MotionVector, 2>> m_prev_mvs;
-    MotionVector m_candidate_mv[2];
-    ReferenceFrameType m_candidate_frame[2];
+    Vector<ReferenceFramePair> m_ref_frames;
+    Vector<ReferenceFramePair> m_prev_ref_frames;
+    Vector<MotionVectorPair> m_mvs;
+    Vector<MotionVectorPair> m_prev_mvs;
+    MotionVectorPair m_candidate_mv;
+    ReferenceFramePair m_candidate_frame;
     Vector<Array<Array<MotionVector, 4>, 2>> m_sub_mvs;
     u8 m_ref_mv_count { 0 };
-    MotionVector m_ref_list_mv[2];
+    MotionVectorPair m_ref_list_mv;
     bool m_use_prev_frame_mvs;
     Vector<InterpolationFilter> m_interp_filters;
     // Indexed by ReferenceFrame enum.