Added scan implementation to module api.

The implementation expose the following new functions:
1. RedisModule_CursorCreate - allow to create a new cursor object for
keys scanning
2. RedisModule_CursorRestart - restart an existing cursor to restart the
scan
3. RedisModule_CursorDestroy - destroy an existing cursor
4. RedisModule_Scan - scan keys

The RedisModule_Scan function gets a cursor object, a callback and void*
(used as user private data).
The callback will be called for each key in the database proving the key
name and the value as RedisModuleKey.

3 files changed, 82 insertions, 1 deletions

diff --git a/tests/modules/Makefile b/tests/modules/Makefile
index 9e27758a2..07c3cb829 100644
--- a/tests/modules/Makefile
+++ b/tests/modules/Makefile
@@ -19,7 +19,8 @@ TEST_MODULES = \
     propagate.so \
     misc.so \
     hooks.so \
-    blockonkeys.so
+    blockonkeys.so \
+    scan.so
 
 .PHONY: all
 
diff --git a/tests/modules/scan.c b/tests/modules/scan.c
new file mode 100644
index 000000000..21071720a
--- /dev/null
+++ b/tests/modules/scan.c
@@ -0,0 +1,62 @@
+#define REDISMODULE_EXPERIMENTAL_API
+#include "redismodule.h"
+
+#include <string.h>
+#include <assert.h>
+#include <unistd.h>
+
+#define UNUSED(V) ((void) V)
+
+typedef struct scan_pd{
+        size_t nkeys;
+        RedisModuleCtx *ctx;
+} scan_pd;
+
+void scan_callback(void *privdata, RedisModuleString* keyname, RedisModuleKey* key){
+    scan_pd* pd = privdata;
+    RedisModule_ReplyWithArray(pd->ctx, 2);
+
+    RedisModule_ReplyWithString(pd->ctx, keyname);
+    if(key && RedisModule_KeyType(key) == REDISMODULE_KEYTYPE_STRING){
+        size_t len;
+        char * data = RedisModule_StringDMA(key, &len, REDISMODULE_READ);
+        RedisModule_ReplyWithStringBuffer(pd->ctx, data, len);
+    }else{
+        RedisModule_ReplyWithNull(pd->ctx);
+    }
+    pd->nkeys++;
+}
+
+int scan_keys_values(RedisModuleCtx *ctx, RedisModuleString **argv, int argc)
+{
+    scan_pd pd = {
+            .nkeys = 0,
+            .ctx = ctx,
+    };
+
+    RedisModule_ReplyWithArray(ctx, REDISMODULE_POSTPONED_ARRAY_LEN);
+
+    RedisModuleCursor* cursor = RedisModule_CursorCreate();
+    while(RedisModule_Scan(ctx, cursor, scan_callback, &pd));
+    RedisModule_CursorDestroy(cursor);
+
+    RedisModule_ReplySetArrayLength(ctx, pd.nkeys);
+    return 0;
+}
+
+int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
+    UNUSED(argv);
+    UNUSED(argc);
+    if (RedisModule_Init(ctx, "scan", 1, REDISMODULE_APIVER_1)== REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    if (RedisModule_CreateCommand(ctx, "scan.scankeysvalues", scan_keys_values, "", 0, 0, 0) == REDISMODULE_ERR)
+        return REDISMODULE_ERR;
+
+    return REDISMODULE_OK;
+}
+
+
+
+
+
diff --git a/tests/unit/moduleapi/scan.tcl b/tests/unit/moduleapi/scan.tcl
new file mode 100644
index 000000000..5a77e8195
--- /dev/null
+++ b/tests/unit/moduleapi/scan.tcl
@@ -0,0 +1,18 @@
+set testmodule [file normalize tests/modules/scan.so]
+
+proc count_log_message {pattern} {
+    set result [exec grep -c $pattern < [srv 0 stdout]]
+}
+
+start_server {tags {"modules"}} {
+    r module load $testmodule
+
+    test {Module scan} {
+        # the module create a scan command which also return values
+        r set x 1
+        r set y 2
+        r set z 3
+        lsort [r scan.scankeysvalues]
+    } {{x 1} {y 2} {z 3}}
+
+}
\ No newline at end of file