1 files changed, 124 insertions, 0 deletions
diff --git a/src/video_core/texture/etc1.cpp b/src/video_core/texture/etc1.cpp
new file mode 100644
index 000000000..af60cde1e
--- /dev/null
+++ b/src/video_core/texture/etc1.cpp
@@ -0,0 +1,124 @@
+// Copyright 2017 Citra Emulator Project
+// Licensed under GPLv2 or any later version
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <array>
+#include "common/bit_field.h"
+#include "common/color.h"
+#include "common/common_types.h"
+#include "common/math_util.h"
+#include "common/vector_math.h"
+#include "video_core/texture/etc1.h"
+
+namespace Pica {
+namespace Texture {
+
+namespace {
+
+constexpr std::array<u8[2], 8> etc1_modifier_table = {{
+    {2, 8}, {5, 17}, {9, 29}, {13, 42}, {18, 60}, {24, 80}, {33, 106}, {47, 183},
+}};
+
+union ETC1Tile {
+    u64 raw;
+
+    // Each of these two is a collection of 16 bits (one per lookup value)
+    BitField<0, 16, u64> table_subindexes;
+    BitField<16, 16, u64> negation_flags;
+
+    unsigned GetTableSubIndex(unsigned index) const {
+        return (table_subindexes >> index) & 1;
+    }
+
+    bool GetNegationFlag(unsigned index) const {
+        return ((negation_flags >> index) & 1) == 1;
+    }
+
+    BitField<32, 1, u64> flip;
+    BitField<33, 1, u64> differential_mode;
+
+    BitField<34, 3, u64> table_index_2;
+    BitField<37, 3, u64> table_index_1;
+
+    union {
+        // delta value + base value
+        BitField<40, 3, s64> db;
+        BitField<43, 5, u64> b;
+
+        BitField<48, 3, s64> dg;
+        BitField<51, 5, u64> g;
+
+        BitField<56, 3, s64> dr;
+        BitField<59, 5, u64> r;
+    } differential;
+
+    union {
+        BitField<40, 4, u64> b2;
+        BitField<44, 4, u64> b1;
+
+        BitField<48, 4, u64> g2;
+        BitField<52, 4, u64> g1;
+
+        BitField<56, 4, u64> r2;
+        BitField<60, 4, u64> r1;
+    } separate;
+
+    const Math::Vec3<u8> GetRGB(unsigned int x, unsigned int y) const {
+        int texel = 4 * x + y;
+
+        if (flip)
+            std::swap(x, y);
+
+        // Lookup base value
+        Math::Vec3<int> ret;
+        if (differential_mode) {
+            ret.r() = static_cast<int>(differential.r);
+            ret.g() = static_cast<int>(differential.g);
+            ret.b() = static_cast<int>(differential.b);
+            if (x >= 2) {
+                ret.r() += static_cast<int>(differential.dr);
+                ret.g() += static_cast<int>(differential.dg);
+                ret.b() += static_cast<int>(differential.db);
+            }
+            ret.r() = Color::Convert5To8(ret.r());
+            ret.g() = Color::Convert5To8(ret.g());
+            ret.b() = Color::Convert5To8(ret.b());
+        } else {
+            if (x < 2) {
+                ret.r() = Color::Convert4To8(static_cast<u8>(separate.r1));
+                ret.g() = Color::Convert4To8(static_cast<u8>(separate.g1));
+                ret.b() = Color::Convert4To8(static_cast<u8>(separate.b1));
+            } else {
+                ret.r() = Color::Convert4To8(static_cast<u8>(separate.r2));
+                ret.g() = Color::Convert4To8(static_cast<u8>(separate.g2));
+                ret.b() = Color::Convert4To8(static_cast<u8>(separate.b2));
+            }
+        }
+
+        // Add modifier
+        unsigned table_index =
+            static_cast<int>((x < 2) ? table_index_1.Value() : table_index_2.Value());
+
+        int modifier = etc1_modifier_table[table_index][GetTableSubIndex(texel)];
+        if (GetNegationFlag(texel))
+            modifier *= -1;
+
+        ret.r() = MathUtil::Clamp(ret.r() + modifier, 0, 255);
+        ret.g() = MathUtil::Clamp(ret.g() + modifier, 0, 255);
+        ret.b() = MathUtil::Clamp(ret.b() + modifier, 0, 255);
+
+        return ret.Cast<u8>();
+    }
+};
+
+} // anonymous namespace
+
+Math::Vec3<u8> SampleETC1Subtile(u64 value, unsigned int x, unsigned int y) {
+    ETC1Tile tile{value};
+    return tile.GetRGB(x, y);
+}
+
+} // namespace Texture
+} // namespace Pica