From d7ad70e33b6f3ced421d2be67a067d0940682bb0 Mon Sep 17 00:00:00 2001
From: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
Date: Thu, 25 Jun 2020 13:20:19 +0200
Subject: avcodec/bitstream: Avoid allocation when creating VLC tables

Reviewed-by: Michael Niedermayer <michael@niedermayer.cc>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
---
 libavcodec/bitstream.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/libavcodec/bitstream.c b/libavcodec/bitstream.c
index 53a2db7451..d379dbc0e8 100644
--- a/libavcodec/bitstream.c
+++ b/libavcodec/bitstream.c
@@ -285,7 +285,6 @@ int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
     vlc->bits = nb_bits;
     if (flags & INIT_VLC_USE_NEW_STATIC) {
         av_assert0(nb_codes + 1 <= FF_ARRAY_ELEMS(localbuf));
-        buf = localbuf;
         localvlc = *vlc_arg;
         vlc = &localvlc;
         vlc->table_size = 0;
@@ -293,11 +292,13 @@ int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
         vlc->table           = NULL;
         vlc->table_allocated = 0;
         vlc->table_size      = 0;
-
+    }
+    if (nb_codes + 1 > FF_ARRAY_ELEMS(localbuf)) {
         buf = av_malloc_array((nb_codes + 1), sizeof(VLCcode));
         if (!buf)
             return AVERROR(ENOMEM);
-    }
+    } else
+        buf = localbuf;
 
 
     av_assert0(symbols_size <= 2 || !symbols);
@@ -309,7 +310,7 @@ int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
             continue;                                                       \
         if (buf[j].bits > 3*nb_bits || buf[j].bits>32) {                    \
             av_log(NULL, AV_LOG_ERROR, "Too long VLC (%d) in init_vlc\n", buf[j].bits);\
-            if (!(flags & INIT_VLC_USE_NEW_STATIC))                         \
+            if (buf != localbuf)                                            \
                 av_free(buf);                                               \
             return AVERROR(EINVAL);                                         \
         }                                                                   \
@@ -317,7 +318,7 @@ int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
         if (buf[j].code >= (1LL<<buf[j].bits)) {                            \
             av_log(NULL, AV_LOG_ERROR, "Invalid code %"PRIx32" for %d in "  \
                    "init_vlc\n", buf[j].code, i);                           \
-            if (!(flags & INIT_VLC_USE_NEW_STATIC))                         \
+            if (buf != localbuf)                                            \
                 av_free(buf);                                               \
             return AVERROR(EINVAL);                                         \
         }                                                                   \
@@ -346,7 +347,8 @@ int ff_init_vlc_sparse(VLC *vlc_arg, int nb_bits, int nb_codes,
         av_assert0(ret >= 0);
         *vlc_arg = *vlc;
     } else {
-        av_free(buf);
+        if (buf != localbuf)
+            av_free(buf);
         if (ret < 0) {
             av_freep(&vlc->table);
             return ret;
-- 
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