Introduce a TextureDSP module

This module implements generic texture decompression from different
families (DXTC, RGTC, BCn) and texture compression DXTC 1, 3, and 5.
Signed-off-by: Vittorio Giovara <vittorio.giovara@gmail.com>

configure

@@ -1626,6 +1626,8 @@ CONFIG_EXTRA="
     sinewin
     snappy
     startcode
+    texturedsp
+    texturedspenc
     tpeldsp
     videodsp
     vp3dsp

libavcodec/Makefile

@@ -93,6 +93,8 @@ OBJS-$(CONFIG_RDFT)                    += rdft.o $(RDFT-OBJS-yes)
 OBJS-$(CONFIG_SINEWIN)                 += sinewin.o
 OBJS-$(CONFIG_SNAPPY)                  += snappy.o
 OBJS-$(CONFIG_STARTCODE)               += startcode.o
+OBJS-$(CONFIG_TEXTUREDSP)              += texturedsp.o
+OBJS-$(CONFIG_TEXTUREDSPENC)           += texturedspenc.o
 OBJS-$(CONFIG_TPELDSP)                 += tpeldsp.o
 OBJS-$(CONFIG_VIDEODSP)                += videodsp.o
 OBJS-$(CONFIG_VP3DSP)                  += vp3dsp.o

libavcodec/texturedsp.h

+/*
+ * Texture block module
+ * Copyright (C) 2015 Vittorio Giovara <vittorio.giovara@gmail.com>
+ *
+ * This file is part of Libav.
+ *
+ * Libav is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * Libav is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file
+ * Texture block (4x4) module
+ *
+ * References:
+ *   https://www.opengl.org/wiki/S3_Texture_Compression
+ *   https://www.opengl.org/wiki/Red_Green_Texture_Compression
+ *   https://msdn.microsoft.com/en-us/library/bb694531%28v=vs.85%29.aspx
+ *
+ * All functions return how much data has been written or read.
+ *
+ * Pixel input or output format is always AV_PIX_FMT_RGBA.
+ */
+
+#ifndef AVCODEC_TEXTUREDSP_H
+#define AVCODEC_TEXTUREDSP_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#define TEXTURE_BLOCK_W 4
+#define TEXTURE_BLOCK_H 4
+
+typedef struct TextureDSPContext {
+    int (*dxt1_block)  (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt1a_block) (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt2_block)  (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt3_block)  (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt4_block)  (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt5_block)  (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt5y_block) (uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxt5ys_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*rgtc1s_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*rgtc1u_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*rgtc2s_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*rgtc2u_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+    int (*dxn3dc_block)(uint8_t *dst, ptrdiff_t stride, const uint8_t *block);
+} TextureDSPContext;
+
+void ff_texturedsp_init(TextureDSPContext *c);
+void ff_texturedspenc_init(TextureDSPContext *c);
+
+#endif /* AVCODEC_TEXTUREDSP_H */