DOC-4996 added reply table for RESP2

Author: andy-stark-redis

content/develop/clients/hiredis/issue-commands.md

@@ -41,7 +41,7 @@ command. For example, to issue the command:
 SET foo bar
 ```
 
-you would use (with an existing `redisContext* c`):
+you would use the following command with an existing `redisContext* c`:
 
 ```c
 redisReply *reply = redisCommand(c, "SET foo bar");
@@ -59,4 +59,81 @@ char *myValue = "Hello";
 redisReply *reply = redisCommand(c, "SET key:%s %s", myKeyNumber, myValue);
 ```
 
+You may need to include binary data in the command (for example, to store
+[vector embeddings]({{< relref "/develop/interact/search-and-query/advanced-concepts/vectors" >}})
+in fields of a [hash]({{< relref "/develop/data-types/hashes" >}})) object.
+To do this, use the `%b` format specifier and pass a pointer to the
+data buffer, followed by a `size_t` value indicating its length in bytes.
+As the example below shows, you can freely mix `%s` and `%b` specifiers
+in the same format string.
 
+```c
+char *entryNumber = "1";
+char *embedding = "<binary data>";
+char *url = "https://redis.io/";
+size_t embLength = 13;
+
+redisReply *reply = redisCommand(c,
+    "HSET entry:%s embedding %b  url %s",
+    entryNumber,
+    embedding, embLength,
+    url
+);
+```
+
+The `redisCommand()` function has a variant `redisCommandArgv()`:
+
+```c
+void *redisCommandArgv(redisContext *c, int argc, const char **argv, const size_t *argvlen);
+```
+
+This doesn't take a format string but instead builds the command from an array
+of strings passed in the `argv` parameter.
+
+Use the `argc` value to
+specify the length of this array and the `argvlen` array to specify
+the lengths of each of the strings in the array. If you pass `NULL`
+for `argvlen` then the function will attempt to use `strlen()` to
+get the length of each string. However, this will not work if any of
+the strings contains binary data, so you should pass `argvlen`
+explicitly in this case. The example below shows how to use
+`redisCommandArgv()` with a simple command:
+
+```c
+const char *argv[3] = { "SET", "greeting", "hello"};
+int argc = 3;
+const size_t argvlen[] = {3, 8, 5};
+
+redisReply *reply = redisCommandArgv(c, argc, argv, argvlen);
+```
+
+## Handle replies
+
+The `redisCommand()` and `redisCommandArgv()` functions return
+a pointer to a `redisReply` object. This type supports all
+reply formats defined in the
+[RESP2 and RESP3]({{< relref "/develop/reference/protocol-spec#resp-protocol-description" >}})
+protocols, so its content varies greatly between calls.
+
+You can find the reply format for a command at the end of its
+reference page in the RESP2/RESP3 Reply section (for example, the
+[`INCRBY`]({{< relref "/commands/incrby" >}}) page shows that the
+command has an integer result). You can also determine the format
+using the `type` field of the reply object. This contains a
+different integer value for each type, and `hiredis.h` defines
+constants for each type (for example `REDIS_REPLY_STRING`).
+
+The `redisReply` struct has several fields to contain different
+types of replies, with different fields being set depending on
+the value of the `type` field. The table below shows the type
+constants, the corresponding reply type, and the fields you can
+use to access the reply value:
+
+| Constant | Type | Relevant fields of `redisReply` | RESP protocol |
+| :- | :- |:- | :- |
+| `REDIS_REPLY_STATUS` | [Simple string]({{< relref "/develop/reference/protocol-spec#simple-strings" >}}) | `reply->str`: the string value (`char*`)<br/> `reply->len`: the string length (`size_t`) | 2 |
+| `REDIS_REPLY_ERROR` | [Simple string]({{< relref "/develop/reference/protocol-spec#simple-strings" >}}) | `reply->str`: the string value (`char*`)<br/> `reply->len`: the string length (`size_t`) | 2 |
+| `REDIS_REPLY_INTEGER` | [Integer]({{< relref "/develop/reference/protocol-spec#integers" >}}) | `reply->integer`: the integer value (`long long`)| 2 |
+| `REDIS_REPLY_NIL` | [Null]({{< relref "/develop/reference/protocol-spec#nulls" >}}) | No data | 2 |
+| `REDIS_REPLY_STRING` | [Bulk string]({{< relref "/develop/reference/protocol-spec#bulk-strings" >}}) |`reply->str`: the string value (`char*`)<br/> `reply->len`: the string length (`size_t`) | 2 |
+| `REDIS_REPLY_ARRAY` | [Array]({{< relref "/develop/reference/protocol-spec#arrays" >}}) | `reply->elements`: number of elements (`size_t`)<br/> `reply->element`: array elements (`redisReply`) | 2 |