Redis Functions - Introduce script unit.

Script unit is a new unit located on script.c.
Its purpose is to provides an API for functions (and eval)
to interact with Redis. Interaction includes mostly
executing commands, but also functionalities like calling
Redis back on long scripts or check if the script was killed.

The interaction is done using a scriptRunCtx object that
need to be created by the user and initialized using scriptPrepareForRun.

Detailed list of functionalities expose by the unit:
1. Calling commands (including all the validation checks such as
   acl, cluster, read only run, ...)
2. Set Resp
3. Set Replication method (AOF/REPLICATION/NONE)
4. Call Redis back to on long running scripts to allow Redis reply
   to clients and perform script kill

The commit introduce the new unit and uses it on eval commands to
interact with Redis.

1 files changed, 96 insertions, 0 deletions

diff --git a/src/script.h b/src/script.h
new file mode 100644
index 000000000..4d5e92966
--- /dev/null
+++ b/src/script.h
@@ -0,0 +1,96 @@
+/*
+ * Copyright (c) 2009-2021, Redis Ltd.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ *   * Redistributions of source code must retain the above copyright notice,
+ *     this list of conditions and the following disclaimer.
+ *   * Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *   * Neither the name of Redis nor the names of its contributors may be used
+ *     to endorse or promote products derived from this software without
+ *     specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+ * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#ifndef __SCRIPT_H_
+#define __SCRIPT_H_
+
+/*
+ * Script.c unit provides an API for functions and eval 
+ * to interact with Redis. Interaction includes mostly
+ * executing commands, but also functionalities like calling
+ * Redis back on long scripts or check if the script was killed.
+ *
+ * The interaction is done using a scriptRunCtx object that
+ * need to be created by the user and initialized using scriptPrepareForRun.
+ *
+ * Detailed list of functionalities expose by the unit:
+ * 1. Calling commands (including all the validation checks such as
+ *    acl, cluster, read only run, ...)
+ * 2. Set Resp
+ * 3. Set Replication method (AOF/REPLICATION/NONE)
+ * 4. Call Redis back to on long running scripts to allow Redis reply
+ *    to clients and perform script kill
+ */
+
+/*
+ * scriptInterrupt function will return one of those value,
+ *
+ * - SCRIPT_KILL - kill the current running script.
+ * - SCRIPT_CONTINUE - keep running the current script.
+ */
+#define SCRIPT_KILL 1
+#define SCRIPT_CONTINUE 2
+
+/* runCtx flags */
+#define SCRIPT_WRITE_DIRTY            (1ULL<<0) /* indicate that the current script already performed a write command */
+#define SCRIPT_RANDOM_DIRTY           (1ULL<<1) /* indicate that the current script already performed a random reply command.
+                                                   Thanks to this flag we'll raise an error every time a write command
+                                                   is called after a random command and prevent none deterministic
+                                                   replication or AOF. */
+#define SCRIPT_MULTI_EMMITED          (1ULL<<2) /* indicate that we already wrote a multi command to replication/aof */
+#define SCRIPT_TIMEDOUT               (1ULL<<3) /* indicate that the current script timedout */
+#define SCRIPT_KILLED                 (1ULL<<4) /* indicate that the current script was marked to be killed */
+#define SCRIPT_READ_ONLY              (1ULL<<5) /* indicate that the current script should only perform read commands */
+#define SCRIPT_EVAL_REPLICATION       (1ULL<<6) /* mode for eval, indicate that we replicate the
+                                                   script invocation and not the effects */
+typedef struct scriptRunCtx scriptRunCtx;
+
+struct scriptRunCtx {
+    const char *funcname;
+    client *c;
+    client *original_client;
+    int flags;
+    int repl_flags;
+    monotime start_time;
+    mstime_t snapshot_time;
+};
+
+void scriptPrepareForRun(scriptRunCtx *r_ctx, client *engine_client, client *caller, const char *funcname);
+void scriptResetRun(scriptRunCtx *r_ctx);
+int scriptSetResp(scriptRunCtx *r_ctx, int resp);
+int scriptSetRepl(scriptRunCtx *r_ctx, int repl);
+void scriptCall(scriptRunCtx *r_ctx, robj **argv, int argc, sds *err);
+int scriptInterrupt(scriptRunCtx *r_ctx);
+void scriptKill(client *c);
+int scriptIsRunning();
+int scriptIsTimedout();
+client* scriptGetClient();
+mstime_t scriptTimeSnapshot();
+
+#endif /* __SCRIPT_H_ */