improve CRC API

 - don't export any global var
 - provide either generated or hardcoded tables

Originally committed as revision 11409 to svn://svn.ffmpeg.org/ffmpeg/trunk

configure

@@ -132,6 +132,7 @@ show_help(){
   echo "  --disable-ffserver       disable ffserver build"
   echo "  --disable-ffplay         disable ffplay build"
   echo "  --enable-small           optimize for size instead of speed"
+  echo "  --enable-hardcoded-tables use hardcoded tables instead of runtime generation"
   echo "  --enable-memalign-hack   emulate memalign, interferes with memory debuggers"
   echo "  --disable-encoder=NAME   disables encoder NAME"
   echo "  --enable-encoder=NAME    enables encoder NAME"
@@ -629,6 +630,7 @@ CONFIG_LIST="
     gpl
     gprof
     gray
+    hardcoded_tables
     ipv6
     liba52
     liba52bin

libavcodec/ac3dec.c

@@ -1110,7 +1110,7 @@ static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
 
     /* check for crc mismatch */
     if(avctx->error_resilience > 0) {
-        if(av_crc(av_crc8005, 0, &buf[2], s->frame_size-2)) {
+        if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
             av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
             return -1;
         }

libavcodec/ac3enc.c

@@ -1141,13 +1141,16 @@ static int output_frame_end(AC3EncodeContext *s)
     /* Now we must compute both crcs : this is not so easy for crc1
        because it is at the beginning of the data... */
     frame_size_58 = (frame_size >> 1) + (frame_size >> 3);
-    crc1 = bswap_16(av_crc(av_crc8005, 0, frame + 4, 2 * frame_size_58 - 4));
+    crc1 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
+                           frame + 4, 2 * frame_size_58 - 4));
     /* XXX: could precompute crc_inv */
     crc_inv = pow_poly((CRC16_POLY >> 1), (16 * frame_size_58) - 16, CRC16_POLY);
     crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
     AV_WB16(frame+2,crc1);
 
-    crc2 = bswap_16(av_crc(av_crc8005, 0, frame + 2 * frame_size_58, (frame_size - frame_size_58) * 2 - 2));
+    crc2 = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
+                           frame + 2 * frame_size_58,
+                           (frame_size - frame_size_58) * 2 - 2));
     AV_WB16(frame+2*frame_size-2,crc2);
 
     //    printf("n=%d frame_size=%d\n", n, frame_size);

libavcodec/flac.c

@@ -558,7 +558,8 @@ static int decode_frame(FLACContext *s, int alloc_data_size)
     }
 
     skip_bits(&s->gb, 8);
-    crc8= av_crc(av_crc07, 0, s->gb.buffer, get_bits_count(&s->gb)/8);
+    crc8 = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0,
+                  s->gb.buffer, get_bits_count(&s->gb)/8);
     if(crc8){
         av_log(s->avctx, AV_LOG_ERROR, "header crc mismatch crc=%2X\n", crc8);
         return -1;

libavcodec/flacenc.c

@@ -1283,7 +1283,8 @@ static void output_frame_header(FlacEncodeContext *s)
         put_bits(&s->pb, 16, s->sr_code[1]);
     }
     flush_put_bits(&s->pb);
-    crc = av_crc(av_crc07, 0, s->pb.buf, put_bits_count(&s->pb)>>3);
+    crc = av_crc(av_crc_get_table(AV_CRC_8_ATM), 0,
+                 s->pb.buf, put_bits_count(&s->pb)>>3);
     put_bits(&s->pb, 8, crc);
 }
 
@@ -1425,7 +1426,8 @@ static void output_frame_footer(FlacEncodeContext *s)
 {
     int crc;
     flush_put_bits(&s->pb);
-    crc = bswap_16(av_crc(av_crc8005, 0, s->pb.buf, put_bits_count(&s->pb)>>3));
+    crc = bswap_16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
+                          s->pb.buf, put_bits_count(&s->pb)>>3));
     put_bits(&s->pb, 16, crc);
     flush_put_bits(&s->pb);
 }

libavcodec/utils.c

@@ -1247,17 +1247,6 @@ unsigned avcodec_build( void )
   return LIBAVCODEC_BUILD;
 }
 
-static void init_crcs(void){
-#if LIBAVUTIL_VERSION_INT  < (50<<16)
-    av_crc04C11DB7= av_mallocz_static(sizeof(AVCRC) * 257);
-    av_crc8005    = av_mallocz_static(sizeof(AVCRC) * 257);
-    av_crc07      = av_mallocz_static(sizeof(AVCRC) * 257);
-#endif
-    av_crc_init(av_crc04C11DB7, 0, 32, AV_CRC_32_IEEE, sizeof(AVCRC)*257);
-    av_crc_init(av_crc8005    , 0, 16, AV_CRC_16     , sizeof(AVCRC)*257);
-    av_crc_init(av_crc07      , 0,  8, AV_CRC_8_ATM  , sizeof(AVCRC)*257);
-}
-
 void avcodec_init(void)
 {
     static int inited = 0;
@@ -1267,7 +1256,6 @@ void avcodec_init(void)
     inited = 1;
 
     dsputil_static_init();
-    init_crcs();
 }
 
 void avcodec_flush_buffers(AVCodecContext *avctx)

libavformat/aviobuf.c

@@ -318,7 +318,7 @@ static void fill_buffer(ByteIOContext *s)
 }
 
 unsigned long ff_crc04C11DB7_update(unsigned long checksum, const uint8_t *buf, unsigned int len){
-    return av_crc(av_crc04C11DB7, checksum, buf, len);
+    return av_crc(av_crc_get_table(AV_CRC_32_IEEE), checksum, buf, len);
 }
 
 unsigned long get_checksum(ByteIOContext *s){

libavformat/mpegts.c

@@ -262,7 +262,8 @@ static void write_section_data(AVFormatContext *s, MpegTSFilter *tss1,
     if (tss->section_h_size != -1 && tss->section_index >= tss->section_h_size) {
         tss->end_of_section_reached = 1;
         if (!tss->check_crc ||
-            av_crc(av_crc04C11DB7, -1, tss->section_buf, tss->section_h_size) == 0)
+            av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1,
+                   tss->section_buf, tss->section_h_size) == 0)
             tss->section_cb(tss1, tss->section_buf, tss->section_h_size);
     }
 }

libavformat/mpegtsenc.c

@@ -43,7 +43,7 @@ static void mpegts_write_section(MpegTSSection *s, uint8_t *buf, int len)
     unsigned char *q;
     int first, b, len1, left;
 
-    crc = bswap_32(av_crc(av_crc04C11DB7, -1, buf, len - 4));
+    crc = bswap_32(av_crc(av_crc_get_table(AV_CRC_32_IEEE), -1, buf, len - 4));
     buf[len - 4] = (crc >> 24) & 0xff;
     buf[len - 3] = (crc >> 16) & 0xff;
     buf[len - 2] = (crc >> 8) & 0xff;

libavutil/crc.c

@@ -21,16 +21,21 @@
 #include "common.h"
 #include "crc.h"
 
-#if LIBAVUTIL_VERSION_INT  < (50<<16)
-AVCRC *av_crcEDB88320;
-AVCRC *av_crc04C11DB7;
-AVCRC *av_crc8005    ;
-AVCRC *av_crc07      ;
+#ifdef CONFIG_HARDCODED_TABLES
+#include "crc_data.h"
 #else
-AVCRC av_crcEDB88320[257];
-AVCRC av_crc04C11DB7[257];
-AVCRC av_crc8005    [257];
-AVCRC av_crc07      [257];
+static struct {
+    uint8_t  le;
+    uint8_t  bits;
+    uint32_t poly;
+} av_crc_table_params[AV_CRC_MAX] = {
+    [AV_CRC_8_ATM]      = { 0,  8,       0x07 },
+    [AV_CRC_16_ANSI]    = { 0, 16,     0x8005 },
+    [AV_CRC_16_CCITT]   = { 0, 16,     0x1021 },
+    [AV_CRC_32_IEEE]    = { 0, 32, 0x04C11DB7 },
+    [AV_CRC_32_IEEE_LE] = { 1, 32, 0xEDB88320 },
+};
+static AVCRC av_crc_table[AV_CRC_MAX][257];
 #endif
 
 /**
@@ -79,6 +84,24 @@ int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size){
     return 0;
 }
 
+/**
+ * Get an initialized standard CRC table.
+ * @param crc_id ID of a standard CRC
+ * @return a pointer to the CRC table or NULL on failure
+ */
+const AVCRC *av_crc_get_table(AVCRCId crc_id){
+#ifndef CONFIG_HARDCODED_TABLES
+    if (!av_crc_table[crc_id][sizeof(av_crc_table[crc_id])-1])
+        if (av_crc_init(av_crc_table[crc_id],
+                        av_crc_table_params[crc_id].le,
+                        av_crc_table_params[crc_id].bits,
+                        av_crc_table_params[crc_id].poly,
+                        sizeof(av_crc_table[crc_id])) < 0)
+            return NULL;
+#endif
+    return av_crc_table[crc_id];
+}
+
 /**
  * Calculate the CRC of a block
  * @param crc CRC of previous blocks if any or initial value for CRC.
@@ -110,18 +133,18 @@ uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t le
 main(void){
     uint8_t buf[1999];
     int i;
-    int p[4][4]={{1, 32, AV_CRC_32_IEEE_LE, 0x3D5CDD04},
-                 {0, 32, AV_CRC_32_IEEE   , 0xC0F5BAE0},
-                 {0, 16, AV_CRC_16        , 0x1FBB    },
-                 {0,  8, AV_CRC_8_ATM     , 0xE3      },};
-    AVCRC ctx[1 ? 1024:257];
+    int p[4][3]={{AV_CRC_32_IEEE_LE, 0xEDB88320, 0x3D5CDD04},
+                 {AV_CRC_32_IEEE   , 0x04C11DB7, 0xC0F5BAE0},
+                 {AV_CRC_16_ANSI   , 0x8005,     0x1FBB    },
+                 {AV_CRC_8_ATM     , 0x07,       0xE3      },};
+    const AVCRC *ctx;
 
     for(i=0; i<sizeof(buf); i++)
         buf[i]= i+i*i;
 
     for(i=0; i<4; i++){
-        av_crc_init(ctx, p[i][0], p[i][1], p[i][2], sizeof(ctx));
-        printf("crc %08X =%X\n", p[i][2], av_crc(ctx, 0, buf, sizeof(buf)));
+        ctx = av_crc_get_table(p[i][0]);
+        printf("crc %08X =%X\n", p[i][1], av_crc(ctx, 0, buf, sizeof(buf)));
     }
 }
 #endif

libavutil/crc.h

@@ -26,26 +26,17 @@
 
 typedef uint32_t AVCRC;
 
-#define AV_CRC_8_ATM      0x07
-#define AV_CRC_16         0x8005
-#define AV_CRC_16_CCITT   0x1021
-#define AV_CRC_32_IEEE    0x04C11DB7L
-//! reversed bitorder version of AV_CRC_32_IEEE
-#define AV_CRC_32_IEEE_LE 0xEDB88320L
-
-#if LIBAVUTIL_VERSION_INT  < (50<<16)
-extern AVCRC *av_crcEDB88320;
-extern AVCRC *av_crc04C11DB7;
-extern AVCRC *av_crc8005    ;
-extern AVCRC *av_crc07      ;
-#else
-extern AVCRC av_crcEDB88320[];
-extern AVCRC av_crc04C11DB7[];
-extern AVCRC av_crc8005    [];
-extern AVCRC av_crc07      [];
-#endif
+typedef enum {
+    AV_CRC_8_ATM,
+    AV_CRC_16_ANSI,
+    AV_CRC_16_CCITT,
+    AV_CRC_32_IEEE,
+    AV_CRC_32_IEEE_LE,  /*< reversed bitorder version of AV_CRC_32_IEEE */
+    AV_CRC_MAX,         /*< not part of public API! don't use outside lavu */
+}AVCRCId;
 
 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
+const AVCRC *av_crc_get_table(AVCRCId crc_id);
 uint32_t av_crc(const AVCRC *ctx, uint32_t start_crc, const uint8_t *buffer, size_t length);
 
 #endif /* FFMPEG_CRC_H */