redis-cli: Better --json Unicode support and --quoted-json (#10286)

Normally, `redis-cli` escapes non-printable data received from Redis, using a custom scheme (which is also used to handle quoted input). When using `--json` this is not desired as it is not compatible with RFC 7159, which specifies JSON strings are assumed to be Unicode and how they should be escaped.

This commit changes `--json` to follow RFC 7159, which means that properly encoded Unicode strings in Redis will result with a valid Unicode JSON.

However, this introduces a new problem with `--json` and data that is not valid Unicode (e.g., random binary data, text that follows other encoding, etc.). To address this, we add `--quoted-json` which produces JSON strings that follow the original redis-cli quoting scheme.

For example, a value that consists of only null (0x00) bytes will show up as:
* `"\u0000\u0000\u0000"` when using `--json`
* `"\\x00\\x00\\x00"` when using `--quoted-json`

1 files changed, 25 insertions, 0 deletions

diff --git a/src/cli_common.c b/src/cli_common.c
index 7064a096b..6d627d2b4 100644
--- a/src/cli_common.c
+++ b/src/cli_common.c
@@ -371,3 +371,28 @@ void freeCliConnInfo(cliConnInfo connInfo){
     if (connInfo.auth) sdsfree(connInfo.auth);
     if (connInfo.user) sdsfree(connInfo.user);
 }
+
+/*
+ * Escape a Unicode string for JSON output (--json), following RFC 7159:
+ * https://datatracker.ietf.org/doc/html/rfc7159#section-7
+*/
+sds escapeJsonString(sds s, const char *p, size_t len) {
+    s = sdscatlen(s,"\"",1);
+    while(len--) {
+        switch(*p) {
+        case '\\':
+        case '"':
+            s = sdscatprintf(s,"\\%c",*p);
+            break;
+        case '\n': s = sdscatlen(s,"\\n",2); break;
+        case '\f': s = sdscatlen(s,"\\f",2); break;
+        case '\r': s = sdscatlen(s,"\\r",2); break;
+        case '\t': s = sdscatlen(s,"\\t",2); break;
+        case '\b': s = sdscatlen(s,"\\b",2); break;
+        default:
+            s = sdscatprintf(s,(*p >= 0 && *p <= 0x1f) ? "\\u%04x" : "%c",*p);
+        }
+        p++;
+    }
+    return sdscatlen(s,"\"",1);
+}