[FFmpeg-devel] [RFC][PATCH 1/3] lavu: Add av_crc2() and av_crc_init2()

[James Almer]

Functionally the same as av_crc() and av_crc_init(), but
supporting CRCs of up to 64 bits.

Signed-off-by: James Almer <jamrial at gmail.com>
---
 libavutil/crc.c | 33 ++++++++++++++++++++++++---------
 libavutil/crc.h |  7 ++++++-
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/libavutil/crc.c b/libavutil/crc.c
index aeb9e46..792e898 100644
--- a/libavutil/crc.c
+++ b/libavutil/crc.c
@@ -29,7 +29,7 @@
 static struct {
     uint8_t  le;
     uint8_t  bits;
-    uint32_t poly;
+    uint64_t poly;
 } av_crc_table_params[AV_CRC_MAX] = {
     [AV_CRC_8_ATM]      = { 0,  8,       0x07 },
     [AV_CRC_16_ANSI]    = { 0, 16,     0x8005 },
@@ -42,10 +42,18 @@ static AVCRC av_crc_table[AV_CRC_MAX][257];
 
 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
 {
-    unsigned i, j;
-    uint32_t c;
+    if(bits > 32 || poly >= (1LL << bits))
+        return -1;
+
+    return av_crc_init2(ctx, le, bits, poly, ctx_size);
+}
+
+int av_crc_init2(AVCRC *ctx, int le, int bits, uint64_t poly, int ctx_size)
+{
+    unsigned j;
+    uint64_t i, c;
 
-    if (bits < 8 || bits > 32 || poly >= (1LL << bits))
+    if (bits < 8 || bits > 64)
         return -1;
     if (ctx_size != sizeof(AVCRC) * 257 && ctx_size != sizeof(AVCRC) * 1024)
         return -1;
@@ -56,9 +64,9 @@ int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size)
                 c = (c >> 1) ^ (poly & (-(c & 1)));
             ctx[i] = c;
         } else {
-            for (c = i << 24, j = 0; j < 8; j++)
-                c = (c << 1) ^ ((poly << (32 - bits)) & (((int32_t) c) >> 31));
-            ctx[i] = av_bswap32(c);
+            for (c = i << 56, j = 0; j < 8; j++)
+                c = (c << 1) ^ ((poly << (64 - bits)) & (((int64_t) c) >> 63));
+            ctx[i] = av_bswap64(c);
         }
     }
     ctx[256] = 1;
@@ -77,7 +85,7 @@ const AVCRC *av_crc_get_table(AVCRCId crc_id)
 {
 #if !CONFIG_HARDCODED_TABLES
     if (!av_crc_table[crc_id][FF_ARRAY_ELEMS(av_crc_table[crc_id]) - 1])
-        if (av_crc_init(av_crc_table[crc_id],
+        if (av_crc_init2(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,
@@ -90,6 +98,12 @@ const AVCRC *av_crc_get_table(AVCRCId crc_id)
 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                 const uint8_t *buffer, size_t length)
 {
+    return (uint32_t)av_crc2(ctx, crc, buffer, length);
+}
+
+uint64_t av_crc2(const AVCRC *ctx, uint64_t crc,
+                 const uint8_t *buffer, size_t length)
+{
     const uint8_t *end = buffer + length;
 
 #if !CONFIG_SMALL
@@ -101,8 +115,9 @@ uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
             crc ^= av_le2ne32(*(const uint32_t *) buffer); buffer += 4;
             crc = ctx[3 * 256 + ( crc        & 0xFF)] ^
                   ctx[2 * 256 + ((crc >> 8 ) & 0xFF)] ^
+                                 (crc >> 32)          ^
                   ctx[1 * 256 + ((crc >> 16) & 0xFF)] ^
-                  ctx[0 * 256 + ((crc >> 24)       )];
+                  ctx[0 * 256 + ((crc >> 24) & 0xFF)];
         }
     }
 #endif
diff --git a/libavutil/crc.h b/libavutil/crc.h
index 2bdfca8..ca693a2 100644
--- a/libavutil/crc.h
+++ b/libavutil/crc.h
@@ -25,7 +25,7 @@
 #include <stddef.h>
 #include "attributes.h"
 
-typedef uint32_t AVCRC;
+typedef uint64_t AVCRC;
 
 typedef enum {
     AV_CRC_8_ATM,
@@ -52,6 +52,8 @@ typedef enum {
  * @param ctx_size size of ctx in bytes
  * @return <0 on failure
  */
+int av_crc_init2(AVCRC *ctx, int le, int bits, uint64_t poly, int ctx_size);
+
 int av_crc_init(AVCRC *ctx, int le, int bits, uint32_t poly, int ctx_size);
 
 /**
@@ -68,6 +70,9 @@ const AVCRC *av_crc_get_table(AVCRCId crc_id);
  *
  * @see av_crc_init() "le" parameter
  */
+uint64_t av_crc2(const AVCRC *ctx, uint64_t crc,
+                 const uint8_t *buffer, size_t length) av_pure;
+
 uint32_t av_crc(const AVCRC *ctx, uint32_t crc,
                 const uint8_t *buffer, size_t length) av_pure;
 
-- 
1.7.12.4