avcodec/g2meet, mjpegdec: Factor out common VLC initialization code

While just at it, remove the nb_codes parameter: It is redundant
(the number of codes is implicitly contained in the array containing how
many entries of a specific size there are) and for this reason it might
even be wrong, so it is better to check what is actually used instead.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

5 files changed, 77 insertions, 72 deletions

diff --git a/libavcodec/Makefile b/libavcodec/Makefile
index db8e4fd254..379c91af8c 100644
--- a/libavcodec/Makefile
+++ b/libavcodec/Makefile
@@ -342,7 +342,7 @@ OBJS-$(CONFIG_FMVC_DECODER)            += fmvc.o
 OBJS-$(CONFIG_FOURXM_DECODER)          += 4xm.o
 OBJS-$(CONFIG_FRAPS_DECODER)           += fraps.o
 OBJS-$(CONFIG_FRWU_DECODER)            += frwu.o
-OBJS-$(CONFIG_G2M_DECODER)             += g2meet.o elsdec.o
+OBJS-$(CONFIG_G2M_DECODER)             += g2meet.o elsdec.o mjpegdec_common.o
 OBJS-$(CONFIG_G723_1_DECODER)          += g723_1dec.o g723_1.o \
                                           acelp_vectors.o celp_filters.o celp_math.o
 OBJS-$(CONFIG_G723_1_ENCODER)          += g723_1enc.o g723_1.o \
@@ -451,7 +451,7 @@ OBJS-$(CONFIG_METASOUND_DECODER)       += metasound.o metasound_data.o \
                                           twinvq.o
 OBJS-$(CONFIG_MICRODVD_DECODER)        += microdvddec.o ass.o
 OBJS-$(CONFIG_MIMIC_DECODER)           += mimic.o
-OBJS-$(CONFIG_MJPEG_DECODER)           += mjpegdec.o
+OBJS-$(CONFIG_MJPEG_DECODER)           += mjpegdec.o mjpegdec_common.o
 OBJS-$(CONFIG_MJPEG_QSV_DECODER)       += qsvdec.o
 OBJS-$(CONFIG_MJPEG_ENCODER)           += mjpegenc.o mjpegenc_common.o \
                                           mjpegenc_huffman.o
diff --git a/libavcodec/g2meet.c b/libavcodec/g2meet.c
index 70dc8c72a3..68b1b9dc74 100644
--- a/libavcodec/g2meet.c
+++ b/libavcodec/g2meet.c
@@ -41,6 +41,7 @@
 #include "internal.h"
 #include "jpegtables.h"
 #include "mjpeg.h"
+#include "mjpegdec.h"
 
 #define EPIC_PIX_STACK_SIZE 1024
 #define EPIC_PIX_STACK_MAX  (EPIC_PIX_STACK_SIZE - 1)
@@ -159,45 +160,24 @@ typedef struct G2MContext {
     int        cursor_hot_x, cursor_hot_y;
 } G2MContext;
 
-static av_cold int build_vlc(VLC *vlc, const uint8_t *bits_table,
-                             const uint8_t *val_table, int nb_codes,
-                             int is_ac)
-{
-    uint8_t  huff_size[256] = { 0 };
-    uint16_t huff_code[256];
-    uint16_t huff_sym[256];
-    int i;
-
-    ff_mjpeg_build_huffman_codes(huff_size, huff_code, bits_table, val_table);
-
-    for (i = 0; i < 256; i++)
-        huff_sym[i] = i + 16 * is_ac;
-
-    if (is_ac)
-        huff_sym[0] = 16 * 256;
-
-    return ff_init_vlc_sparse(vlc, 9, nb_codes, huff_size, 1, 1,
-                              huff_code, 2, 2, huff_sym, 2, 2, 0);
-}
-
 static av_cold int jpg_init(AVCodecContext *avctx, JPGContext *c)
 {
     int ret;
 
-    ret = build_vlc(&c->dc_vlc[0], avpriv_mjpeg_bits_dc_luminance,
-                    avpriv_mjpeg_val_dc, 12, 0);
+    ret = ff_mjpeg_build_vlc(&c->dc_vlc[0], avpriv_mjpeg_bits_dc_luminance,
+                             avpriv_mjpeg_val_dc, 0, avctx);
     if (ret)
         return ret;
-    ret = build_vlc(&c->dc_vlc[1], avpriv_mjpeg_bits_dc_chrominance,
-                    avpriv_mjpeg_val_dc, 12, 0);
+    ret = ff_mjpeg_build_vlc(&c->dc_vlc[1], avpriv_mjpeg_bits_dc_chrominance,
+                             avpriv_mjpeg_val_dc, 0, avctx);
     if (ret)
         return ret;
-    ret = build_vlc(&c->ac_vlc[0], avpriv_mjpeg_bits_ac_luminance,
-                    avpriv_mjpeg_val_ac_luminance, 251, 1);
+    ret = ff_mjpeg_build_vlc(&c->ac_vlc[0], avpriv_mjpeg_bits_ac_luminance,
+                             avpriv_mjpeg_val_ac_luminance, 1, avctx);
     if (ret)
         return ret;
-    ret = build_vlc(&c->ac_vlc[1], avpriv_mjpeg_bits_ac_chrominance,
-                    avpriv_mjpeg_val_ac_chrominance, 251, 1);
+    ret = ff_mjpeg_build_vlc(&c->ac_vlc[1], avpriv_mjpeg_bits_ac_chrominance,
+                             avpriv_mjpeg_val_ac_chrominance, 1, avctx);
     if (ret)
         return ret;
 
diff --git a/libavcodec/mjpegdec.c b/libavcodec/mjpegdec.c
index 66dc79529c..256393a68f 100644
--- a/libavcodec/mjpegdec.c
+++ b/libavcodec/mjpegdec.c
@@ -51,40 +51,6 @@
 #include "bytestream.h"
 
 
-static void build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table)
-{
-    for (int i = 1, k = 0; i <= 16; i++) {
-        int nb = bits_table[i];
-        for (int j = 0; j < nb;j++) {
-            huff_size[k] = i;
-            k++;
-        }
-    }
-}
-
-static int build_vlc(VLC *vlc, const uint8_t *bits_table,
-                     const uint8_t *val_table, int nb_codes,
-                     int is_ac, void *logctx)
-{
-    uint8_t huff_size[256];
-    uint16_t huff_sym[256];
-    int i;
-
-    av_assert0(nb_codes <= 256);
-
-    build_huffman_codes(huff_size, bits_table);
-
-    for (i = 0; i < nb_codes; i++) {
-        huff_sym[i] = val_table[i] + 16 * is_ac;
-
-        if (is_ac && !val_table[i])
-            huff_sym[i] = 16 * 256;
-    }
-
-    return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1,
-                                    huff_sym, 2, 2, 0, 0, logctx);
-}
-
 static int init_default_huffman_tables(MJpegDecodeContext *s)
 {
     static const struct {
@@ -110,9 +76,9 @@ static int init_default_huffman_tables(MJpegDecodeContext *s)
     int i, ret;
 
     for (i = 0; i < FF_ARRAY_ELEMS(ht); i++) {
-        ret = build_vlc(&s->vlcs[ht[i].class][ht[i].index],
-                        ht[i].bits, ht[i].values, ht[i].length,
-                        ht[i].class == 1, s->avctx);
+        ret = ff_mjpeg_build_vlc(&s->vlcs[ht[i].class][ht[i].index],
+                                 ht[i].bits, ht[i].values,
+                                 ht[i].class == 1, s->avctx);
         if (ret < 0)
             return ret;
 
@@ -307,14 +273,14 @@ int ff_mjpeg_decode_dht(MJpegDecodeContext *s)
         ff_free_vlc(&s->vlcs[class][index]);
         av_log(s->avctx, AV_LOG_DEBUG, "class=%d index=%d nb_codes=%d\n",
                class, index, n);
-        if ((ret = build_vlc(&s->vlcs[class][index], bits_table, val_table,
-                             n, class > 0, s->avctx)) < 0)
+        if ((ret = ff_mjpeg_build_vlc(&s->vlcs[class][index], bits_table,
+                                      val_table, class > 0, s->avctx)) < 0)
             return ret;
 
         if (class > 0) {
             ff_free_vlc(&s->vlcs[2][index]);
-            if ((ret = build_vlc(&s->vlcs[2][index], bits_table, val_table,
-                                 n, 0, s->avctx)) < 0)
+            if ((ret = ff_mjpeg_build_vlc(&s->vlcs[2][index], bits_table,
+                                          val_table, 0, s->avctx)) < 0)
                 return ret;
         }
 
diff --git a/libavcodec/mjpegdec.h b/libavcodec/mjpegdec.h
index a824b5029c..732aeab994 100644
--- a/libavcodec/mjpegdec.h
+++ b/libavcodec/mjpegdec.h
@@ -161,6 +161,8 @@ typedef struct MJpegDecodeContext {
     void *hwaccel_picture_private;
 } MJpegDecodeContext;
 
+int ff_mjpeg_build_vlc(VLC *vlc, const uint8_t *bits_table,
+                       const uint8_t *val_table, int is_ac, void *logctx);
 int ff_mjpeg_decode_init(AVCodecContext *avctx);
 int ff_mjpeg_decode_end(AVCodecContext *avctx);
 int ff_mjpeg_receive_frame(AVCodecContext *avctx, AVFrame *frame);
diff --git a/libavcodec/mjpegdec_common.c b/libavcodec/mjpegdec_common.c
new file mode 100644
index 0000000000..701ddfec06
--- /dev/null
+++ b/libavcodec/mjpegdec_common.c
@@ -0,0 +1,57 @@
+/*
+ * MJPEG decoder VLC code
+ * Copyright (c) 2000, 2001 Fabrice Bellard
+ * Copyright (c) 2003 Alex Beregszaszi
+ * Copyright (c) 2003-2004 Michael Niedermayer
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <stdint.h>
+#include "libavutil/avassert.h"
+#include "mjpegdec.h"
+#include "vlc.h"
+
+static int build_huffman_codes(uint8_t *huff_size, const uint8_t *bits_table)
+{
+    int nb_codes = 0;
+    for (int i = 1, j = 0; i <= 16; i++) {
+        nb_codes += bits_table[i];
+        av_assert1(nb_codes <= 256);
+        for (; j < nb_codes; j++)
+            huff_size[j] = i;
+    }
+    return nb_codes;
+}
+
+int ff_mjpeg_build_vlc(VLC *vlc, const uint8_t *bits_table,
+                       const uint8_t *val_table, int is_ac, void *logctx)
+{
+    uint8_t huff_size[256];
+    uint16_t huff_sym[256];
+    int nb_codes = build_huffman_codes(huff_size, bits_table);
+
+    for (int i = 0; i < nb_codes; i++) {
+        huff_sym[i] = val_table[i] + 16 * is_ac;
+
+        if (is_ac && !val_table[i])
+            huff_sym[i] = 16 * 256;
+    }
+
+    return ff_init_vlc_from_lengths(vlc, 9, nb_codes, huff_size, 1,
+                                    huff_sym, 2, 2, 0, 0, logctx);
+}