HLLSELFTEST command implemented.

To test the bitfield array of counters set/get macros from the Redis Tcl
suite is hard, so a specialized command that is able to test the
internals was developed.

src/Makefile

@@ -107,7 +107,7 @@ endif
 
 REDIS_SERVER_NAME=redis-server
 REDIS_SENTINEL_NAME=redis-sentinel
-REDIS_SERVER_OBJ=adlist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o
+REDIS_SERVER_OBJ=adlist.o ae.o anet.o dict.o redis.o sds.o zmalloc.o lzf_c.o lzf_d.o pqsort.o zipmap.o sha1.o ziplist.o release.o networking.o util.o object.o db.o replication.o rdb.o t_string.o t_list.o t_set.o t_zset.o t_hash.o config.o aof.o pubsub.o multi.o debug.o sort.o intset.o syncio.o cluster.o crc16.o endianconv.o slowlog.o scripting.o bio.o rio.o rand.o memtest.o crc64.o bitops.o sentinel.o notify.o setproctitle.o blocked.o hyperloglog.o
 REDIS_CLI_NAME=redis-cli
 REDIS_CLI_OBJ=anet.o sds.o adlist.o redis-cli.o zmalloc.o release.o anet.o ae.o crc64.o
 REDIS_BENCHMARK_NAME=redis-benchmark

src/hyperloglog.c

@@ -53,6 +53,7 @@
 
 #define REDIS_HLL_REGISTERS 16384
 #define REDIS_HLL_BITS 6
+#define REDIS_HLL_REGISTER_MAX ((1<<REDIS_HLL_BITS)-1)
 #define REDIS_HLL_SIZE ((REDIS_HLL_REGISTERS*REDIS_HLL_BITS+7)/8)
 
 /* =========================== Low level bit macros ========================= */
@@ -158,18 +159,60 @@
 
 /* Set the value of the register at position 'regnum' to 'val'.
  * 'p' is an array of unsigned bytes. */
-#define HLL_SET_REGISTER(val,p,regnum) do { \
+#define HLL_SET_REGISTER(p,regnum,val) do { \
     int _byte = regnum*REDIS_HLL_BITS/8; \
     int _leftshift = regnum*REDIS_HLL_BITS&7; \
     int _rightshift = 8 - _leftshift; \
-    unsigned int m1 = 255, m2 = (1<<REDIS_HLL_BITS)-1; \
-    p[byte] &= m1 << _rightshift; \
-    p[byte] |= val >> _leftshift; \
-    p[byte+1] &= ~(m2 << _rightshift); \
-    p[byte+1] |= val << _rightshift; \
+    unsigned int m1 = 255, m2 = REDIS_HLL_REGISTER_MAX; \
+    p[_byte] &= m1 << _rightshift; \
+    p[_byte] |= val >> _leftshift; \
+    p[_byte+1] &= ~(m2 << _rightshift); \
+    p[_byte+1] |= val << _rightshift; \
 } while(0)
 
 /* ========================= HyperLogLog algorithm  ========================= */
 
 /* ========================== HyperLogLog commands ========================== */
 
+/* This command performs a self-test of the HLL registers implementation.
+ * Something that is not easy to test from within the outside.
+ *
+ * The test is conceived to test that the different counters of our data
+ * structure are accessible and that setting their values both result in
+ * the correct value to be retained and not affect adjacent values. */
+
+#define REDIS_HLL_TEST_CYCLES 1000
+void hllSelftestCommand(redisClient *c) {
+    int j, i;
+    sds bitcounters = sdsnewlen(NULL,REDIS_HLL_SIZE);
+    uint8_t bytecounters[REDIS_HLL_REGISTERS];
+
+    for (j = 0; j < REDIS_HLL_TEST_CYCLES; j++) {
+        /* Set the HLL counters and an array of unsigned byes of the
+         * same size to the same set of random values. */
+        for (i = 0; i < REDIS_HLL_REGISTERS; i++) {
+            unsigned int r = rand() & REDIS_HLL_REGISTER_MAX;
+
+            bytecounters[i] = r;
+            HLL_SET_REGISTER(bitcounters,i,r);
+        }
+        /* Check that we are able to retrieve the same values. */
+        for (i = 0; i < REDIS_HLL_REGISTERS; i++) {
+            unsigned int val;
+
+            HLL_GET_REGISTER(val,bitcounters,i);
+            if (val != bytecounters[i]) {
+                addReplyErrorFormat(c,
+                    "TESTFAILED Register %d should be %d but is %d",
+                    i, (int) bytecounters[i], (int) val);
+                goto cleanup;
+            }
+        }
+    }
+
+    /* Success! */
+    addReply(c,shared.ok);
+
+cleanup:
+    sdsfree(bitcounters);
+}

src/redis.c

@@ -267,7 +267,8 @@ struct redisCommand redisCommandTable[] = {
     {"bitop",bitopCommand,-4,"wm",0,NULL,2,-1,1,0,0},
     {"bitcount",bitcountCommand,-2,"r",0,NULL,1,1,1,0,0},
     {"bitpos",bitposCommand,-3,"r",0,NULL,1,1,1,0,0},
-    {"wait",waitCommand,3,"rs",0,NULL,0,0,0,0,0}
+    {"wait",waitCommand,3,"rs",0,NULL,0,0,0,0,0},
+    {"hllselftest",hllSelftestCommand,1,"r",0,NULL,0,0,0,0,0},
 };
 
 struct evictionPoolEntry *evictionPoolAlloc(void);

src/redis.h

@@ -1447,6 +1447,7 @@ void bitcountCommand(redisClient *c);
 void bitposCommand(redisClient *c);
 void replconfCommand(redisClient *c);
 void waitCommand(redisClient *c);
+void hllSelftestCommand(redisClient *c);
 
 #if defined(__GNUC__)
 void *calloc(size_t count, size_t size) __attribute__ ((deprecated));