From 5ba8c3a0ed0e43e6418eabdf8af9549c9e806382 Mon Sep 17 00:00:00 2001
From: "Ronald S. Bultje" <rsbultje@gmail.com>
Date: Mon, 27 Mar 2017 11:24:43 -0400
Subject: [PATCH] dirac: make initialization of arithmetic coder tables
 threadsafe.

---
 libavcodec/dirac_arith.c | 15 ++++++++++-----
 libavcodec/dirac_arith.h |  1 +
 libavcodec/diracdec.c    |  9 ++++++++-
 3 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/libavcodec/dirac_arith.c b/libavcodec/dirac_arith.c
index bf913928b3..7eb9bd60b2 100644
--- a/libavcodec/dirac_arith.c
+++ b/libavcodec/dirac_arith.c
@@ -83,6 +83,16 @@ const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT] = {
 
 int16_t ff_dirac_prob_branchless[256][2];
 
+av_cold void ff_dirac_init_arith_tables(void)
+{
+    int i;
+
+    for (i = 0; i < 256; i++) {
+        ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
+        ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
+    }
+}
+
 void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length)
 {
     int i;
@@ -106,11 +116,6 @@ void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length)
     c->counter = -16;
     c->range   = 0xffff;
 
-    for (i = 0; i < 256; i++) {
-        ff_dirac_prob_branchless[i][0] =  ff_dirac_prob[255-i];
-        ff_dirac_prob_branchless[i][1] = -ff_dirac_prob[i];
-    }
-
     for (i = 0; i < DIRAC_CTX_COUNT; i++)
         c->contexts[i] = 0x8000;
 }
diff --git a/libavcodec/dirac_arith.h b/libavcodec/dirac_arith.h
index 003430a48d..24a7ca390e 100644
--- a/libavcodec/dirac_arith.h
+++ b/libavcodec/dirac_arith.h
@@ -190,6 +190,7 @@ static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ct
     return ret;
 }
 
+void ff_dirac_init_arith_tables(void);
 void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length);
 
 #endif /* AVCODEC_DIRAC_ARITH_H */
diff --git a/libavcodec/diracdec.c b/libavcodec/diracdec.c
index e0604af103..202ae94922 100644
--- a/libavcodec/diracdec.c
+++ b/libavcodec/diracdec.c
@@ -26,6 +26,7 @@
  * @author Marco Gerards <marco@gnu.org>, David Conrad, Jordi Ortiz <nenjordi@gmail.com>
  */
 
+#include "libavutil/thread.h"
 #include "avcodec.h"
 #include "get_bits.h"
 #include "bytestream.h"
@@ -379,10 +380,12 @@ static void free_sequence_buffers(DiracContext *s)
     av_freep(&s->mcscratch);
 }
 
+static AVOnce dirac_arith_init = AV_ONCE_INIT;
+
 static av_cold int dirac_decode_init(AVCodecContext *avctx)
 {
     DiracContext *s = avctx->priv_data;
-    int i;
+    int i, ret;
 
     s->avctx = avctx;
     s->frame_number = -1;
@@ -404,6 +407,9 @@ static av_cold int dirac_decode_init(AVCodecContext *avctx)
             return AVERROR(ENOMEM);
         }
     }
+    ret = ff_thread_once(&dirac_arith_init, ff_dirac_init_arith_tables);
+    if (ret != 0)
+        return AVERROR_UNKNOWN;
 
     return 0;
 }
@@ -2299,5 +2305,6 @@ AVCodec ff_dirac_decoder = {
     .close          = dirac_decode_end,
     .decode         = dirac_decode_frame,
     .capabilities   = AV_CODEC_CAP_DELAY | AV_CODEC_CAP_SLICE_THREADS | AV_CODEC_CAP_DR1,
+    .caps_internal  = FF_CODEC_CAP_INIT_THREADSAFE,
     .flush          = dirac_decode_flush,
 };