avutil/log: Replace addresses in log output with simple ids

..and individual numbering. The benefits are:

- Smaller log file sizes
- The disambiguation is much easier to recognize and to follow
- It eventually allows comparing and viewing log file diffs
  without almost every line being different due to those addresses

Signed-off-by: softworkz <softworkz@hotmail.com>

Author: softworkz

libavutil/log.c

@@ -57,6 +57,55 @@ static AVMutex mutex = AV_MUTEX_INITIALIZER;
 
 static int av_log_level = AV_LOG_INFO;
 static int flags;
+static int nb_class_ids;
+
+#define NB_CLASS_IDS 1000
+static struct class_ids {
+    void *avcl;
+    uint64_t class_hash;
+    unsigned id;
+} class_ids[NB_CLASS_IDS];
+
+static uint64_t fnv_hash(const char *str)
+{
+    // FNV-1a 64-bit hash algorithm
+    uint64_t hash = 0xcbf29ce484222325ULL;
+    while (*str) {
+        hash ^= (unsigned char)*str++;
+        hash *= 0x100000001b3ULL;
+    }
+    return hash;
+}
+
+static unsigned get_class_id(void* avcl)
+{
+    AVClass* avc = avcl ? *(AVClass **) avcl : NULL;
+    const char* class_name = avc->item_name(avcl);
+    unsigned i, nb_ids = 0;
+    uint64_t class_hash;
+
+    for (i = 0; i < NB_CLASS_IDS && class_ids[i].avcl; i++) {
+        if (class_ids[i].avcl == avcl)
+            return class_ids[i].id;
+    }
+
+    class_hash = fnv_hash(avc->class_name);
+
+    for (i = 0; i < NB_CLASS_IDS; i++) {
+        if (class_ids[i].class_hash == class_hash)
+            nb_ids++;
+
+        if (!class_ids[i].avcl) {
+            class_ids[i].avcl = avcl;
+            class_ids[i].class_hash = class_hash;
+            class_ids[i].id = nb_ids;
+            return class_ids[i].id;
+        }
+    }
+
+    // exceeded NB_CLASS_IDS entries in class_ids[]
+    return 0;
+}
 
 #define NB_LEVELS 8
 #if defined(_WIN32) && HAVE_SETCONSOLETEXTATTRIBUTE && HAVE_GETSTDHANDLE
@@ -331,13 +380,13 @@ static void format_line(void *avcl, int level, const char *fmt, va_list vl,
             AVClass** parent = *(AVClass ***) (((uint8_t *) avcl) +
                                    avc->parent_log_context_offset);
             if (parent && *parent) {
-                av_bprintf(part+0, "[%s @ %p] ",
-                           item_name(parent, *parent), parent);
+                av_bprintf(part+0, "[%s #%u] ",
+                           item_name(parent, *parent), get_class_id(parent));
                 if(type) type[0] = get_category(parent);
             }
         }
-        av_bprintf(part+1, "[%s @ %p] ",
-                   item_name(avcl, avc), avcl);
+        av_bprintf(part+1, "[%s #%u] ",
+                   item_name(avcl, avc), get_class_id(avcl));
         if(type) type[1] = get_category(avcl);
     }