[FFmpeg-devel] [PATCH] avutil/aes: use pthread_once to fill the static tables

[James Almer]

Signed-off-by: James Almer <jamr...@gmail.com>
---
 libavutil/aes.c | 53 ++++++++++++++++++++++++++++---------------------
 1 file changed, 30 insertions(+), 23 deletions(-)

diff --git a/libavutil/aes.c b/libavutil/aes.c
index 1f4cceb700..5f31412149 100644
--- a/libavutil/aes.c
+++ b/libavutil/aes.c
@@ -29,6 +29,7 @@
 #include "intreadwrite.h"
 #include "macros.h"
 #include "mem.h"
+#include "thread.h"
 
 const int av_aes_size= sizeof(AVAES);
 
@@ -197,6 +198,34 @@ static void init_multbl2(uint32_t tbl[][256], const int 
c[4],
     }
 }
 
+static AVOnce aes_static_init = AV_ONCE_INIT;
+
+static void aes_init_static(void)
+{
+    uint8_t log8[256];
+    uint8_t alog8[512];
+    int i, j = 1;
+
+    for (i = 0; i < 255; i++) {
+        alog8[i] = alog8[i + 255] = j;
+        log8[j] = i;
+        j ^= j + j;
+        if (j > 255)
+            j ^= 0x11B;
+    }
+    for (i = 0; i < 256; i++) {
+        j = i ? alog8[255 - log8[i]] : 0;
+        j ^= (j << 1) ^ (j << 2) ^ (j << 3) ^ (j << 4);
+        j = (j ^ (j >> 8) ^ 99) & 255;
+        inv_sbox[j] = i;
+        sbox[i]     = j;
+    }
+    init_multbl2(dec_multbl, (const int[4]) { 0xe, 0x9, 0xd, 0xb },
+                 log8, alog8, inv_sbox);
+    init_multbl2(enc_multbl, (const int[4]) { 0x2, 0x1, 0x1, 0x3 },
+                 log8, alog8, sbox);
+}
+
 // this is based on the reference AES code by Paulo Barreto and Vincent Rijmen
 int av_aes_init(AVAES *a, const uint8_t *key, int key_bits, int decrypt)
 {
@@ -204,34 +233,12 @@ int av_aes_init(AVAES *a, const uint8_t *key, int 
key_bits, int decrypt)
     uint8_t tk[8][4];
     int KC = key_bits >> 5;
     int rounds = KC + 6;
-    uint8_t log8[256];
-    uint8_t alog8[512];
 
     a->crypt = decrypt ? aes_decrypt : aes_encrypt;
     if (ARCH_X86)
         ff_init_aes_x86(a, decrypt);
 
-    if (!enc_multbl[FF_ARRAY_ELEMS(enc_multbl) - 
1][FF_ARRAY_ELEMS(enc_multbl[0]) - 1]) {
-        j = 1;
-        for (i = 0; i < 255; i++) {
-            alog8[i] = alog8[i + 255] = j;
-            log8[j] = i;
-            j ^= j + j;
-            if (j > 255)
-                j ^= 0x11B;
-        }
-        for (i = 0; i < 256; i++) {
-            j = i ? alog8[255 - log8[i]] : 0;
-            j ^= (j << 1) ^ (j << 2) ^ (j << 3) ^ (j << 4);
-            j = (j ^ (j >> 8) ^ 99) & 255;
-            inv_sbox[j] = i;
-            sbox[i]     = j;
-        }
-        init_multbl2(dec_multbl, (const int[4]) { 0xe, 0x9, 0xd, 0xb },
-                     log8, alog8, inv_sbox);
-        init_multbl2(enc_multbl, (const int[4]) { 0x2, 0x1, 0x1, 0x3 },
-                     log8, alog8, sbox);
-    }
+    ff_thread_once(&aes_static_init, aes_init_static);
 
     if (key_bits != 128 && key_bits != 192 && key_bits != 256)
         return AVERROR(EINVAL);
-- 
2.49.0

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