lavu/hash: add hash_final helpers.

The helpers use local memory to compute the final hash,
making AV_HASH_MAX_SIZE safe to use.

doc/APIchanges

@@ -15,6 +15,9 @@ libavutil:     2012-10-22
 
 API changes, most recent first:
 
+2014-04-29 - xxxxxxx - lavu 52.80.0 - hash.h
+  Add av_hash_final_bin(), av_hash_final_hex() and av_hash_final_b64().
+
 2014-03-07 - 8b2a130 - lavc 55.50.0 / 55.53.100 - dxva2.h
   Add FF_DXVA2_WORKAROUND_INTEL_CLEARVIDEO for old Intel GPUs.
 

libavutil/hash.c

@@ -29,6 +29,7 @@
 #include "sha512.h"
 
 #include "avstring.h"
+#include "base64.h"
 #include "error.h"
 #include "intreadwrite.h"
 #include "mem.h"
@@ -196,6 +197,40 @@ void av_hash_final(AVHashContext *ctx, uint8_t *dst)
     }
 }
 
+void av_hash_final_bin(struct AVHashContext *ctx, uint8_t *dst, int size)
+{
+    uint8_t buf[AV_HASH_MAX_SIZE];
+    unsigned rsize = av_hash_get_size(ctx);
+
+    av_hash_final(ctx, buf);
+    memcpy(dst, buf, FFMIN(size, rsize));
+    if (size > rsize)
+        memset(dst + rsize, 0, size - rsize);
+}
+
+void av_hash_final_hex(struct AVHashContext *ctx, uint8_t *dst, int size)
+{
+    uint8_t buf[AV_HASH_MAX_SIZE];
+    unsigned rsize = av_hash_get_size(ctx), i;
+
+    av_hash_final(ctx, buf);
+    for (i = 0; i < FFMIN(rsize, size / 2); i++)
+        snprintf(dst + i * 2, size - i * 2, "%02x", buf[i]);
+}
+
+void av_hash_final_b64(struct AVHashContext *ctx, uint8_t *dst, int size)
+{
+    uint8_t buf[AV_HASH_MAX_SIZE], b64[AV_BASE64_SIZE(AV_HASH_MAX_SIZE)];
+    unsigned rsize = av_hash_get_size(ctx), osize;
+
+    av_hash_final(ctx, buf);
+    av_base64_encode(b64, sizeof(b64), buf, rsize);
+    osize = AV_BASE64_SIZE(rsize);
+    memcpy(dst, b64, FFMIN(osize, size));
+    if (size < osize)
+        dst[size - 1] = 0;
+}
+
 void av_hash_freep(AVHashContext **ctx)
 {
     if (*ctx)

libavutil/hash.h

@@ -82,6 +82,28 @@ void av_hash_update(struct AVHashContext *ctx, const uint8_t *src, int len);
  */
 void av_hash_final(struct AVHashContext *ctx, uint8_t *dst);
 
+/**
+ * Finalize a hash context and compute the actual hash value.
+ * If size is smaller than the hash size, the hash is truncated;
+ * if size is larger, the buffer is padded with 0.
+ */
+void av_hash_final_bin(struct AVHashContext *ctx, uint8_t *dst, int size);
+
+/**
+ * Finalize a hash context and compute the actual hash value as a hex string.
+ * The string is always 0-terminated.
+ * If size is smaller than 2 * hash_size + 1, the hex string is truncated.
+ */
+void av_hash_final_hex(struct AVHashContext *ctx, uint8_t *dst, int size);
+
+/**
+ * Finalize a hash context and compute the actual hash value as a base64 string.
+ * The string is always 0-terminated.
+ * If size is smaller than AV_BASE64_SIZE(hash_size), the base64 string is
+ * truncated.
+ */
+void av_hash_final_b64(struct AVHashContext *ctx, uint8_t *dst, int size);
+
 /**
  * Free hash context.
  */

libavutil/version.h

@@ -56,7 +56,7 @@
  */
 
 #define LIBAVUTIL_VERSION_MAJOR  52
-#define LIBAVUTIL_VERSION_MINOR  79
+#define LIBAVUTIL_VERSION_MINOR  80
 #define LIBAVUTIL_VERSION_MICRO 100
 
 #define LIBAVUTIL_VERSION_INT   AV_VERSION_INT(LIBAVUTIL_VERSION_MAJOR, \