[Fix] Fix learning with long prefixes

Issue: #4786
Closes: #4786

src/libstat/backends/redis_backend.cxx

@@ -645,6 +645,58 @@ void rspamd_redis_close(gpointer p)
 	delete ctx;
 }
 
+static constexpr auto
+msgpack_emit_str(const std::string_view st, char *out) -> std::size_t
+{
+	auto len = st.size();
+	constexpr const unsigned char fix_mask = 0xA0, l8_ch = 0xd9, l16_ch = 0xda, l32_ch = 0xdb;
+	auto blen = 0;
+	if (len <= 0x1F) {
+		blen = 1;
+		out[0] = (len | fix_mask) & 0xff;
+	}
+	else if (len <= 0xff) {
+		blen = 2;
+		out[0] = l8_ch;
+		out[1] = len & 0xff;
+	}
+	else if (len <= 0xffff) {
+		uint16_t bl = GUINT16_TO_BE(len);
+
+		blen = 3;
+		out[0] = l16_ch;
+		memcpy(&out[1], &bl, sizeof(bl));
+	}
+	else {
+		uint32_t bl = GUINT32_TO_BE(len);
+
+		blen = 5;
+		out[0] = l32_ch;
+		memcpy(&out[1], &bl, sizeof(bl));
+	}
+
+	memcpy(&out[blen], st.data(), st.size());
+
+	return blen + len;
+}
+
+static constexpr auto
+msgpack_str_len(std::size_t len) -> std::size_t
+{
+	if (len <= 0x1F) {
+		return 1 + len;
+	}
+	else if (len <= 0xff) {
+		return 2 + len;
+	}
+	else if (len <= 0xffff) {
+		return 3 + len;
+	}
+	else {
+		return 4 + len;
+	}
+}
+
 /*
  * Serialise stat tokens to message pack
  */
@@ -654,9 +706,12 @@ rspamd_redis_serialize_tokens(struct rspamd_task *task, const gchar *prefix, GPt
 	/* Each token is int64_t that requires 10 bytes (2 int32_t) + 4 bytes array len + 1 byte array magic */
 	char max_int64_str[] = "18446744073709551615";
 	auto prefix_len = strlen(prefix);
-	auto req_len = tokens->len * (sizeof(max_int64_str) + prefix_len + 1) + 5;
+	std::size_t req_len = 5;
 	rspamd_token_t *tok;
 
+	/* Calculate required length */
+	req_len += tokens->len * (msgpack_str_len(sizeof(max_int64_str) + prefix_len) + 1);
+
 	auto *buf = (gchar *) rspamd_mempool_alloc(task->task_pool, req_len);
 	auto *p = buf;
 
@@ -668,16 +723,16 @@ rspamd_redis_serialize_tokens(struct rspamd_task *task, const gchar *prefix, GPt
 	*p++ = (gchar) ((tokens->len >> 8) & 0xff);
 	*p++ = (gchar) (tokens->len & 0xff);
 
+
 	int i;
+	auto numbuf_len = sizeof(max_int64_str) + prefix_len + 1;
+	auto *numbuf = (char *) g_alloca(numbuf_len);
+
 	PTR_ARRAY_FOREACH(tokens, i, tok)
 	{
-		auto numbuf_len = sizeof(max_int64_str) + prefix_len + 1;
-		auto *numbuf = (char *) g_alloca(numbuf_len);
-		auto r = rspamd_snprintf(numbuf, numbuf_len, "%s_%uL", prefix, tok->data);
-		*p++ = (gchar) ((r & 0xff) | 0xa0);
-
-		memcpy(p, numbuf, r);
-		p += r;
+		std::size_t r = rspamd_snprintf(numbuf, numbuf_len, "%s_%uL", prefix, tok->data);
+		auto shift = msgpack_emit_str({numbuf, r}, p);
+		p += shift;
 	}
 
 	*ser_len = p - buf;
@@ -692,52 +747,6 @@ rspamd_redis_serialize_text_tokens(struct rspamd_task *task, GPtrArray *tokens,
 	auto req_len = 5; /* Messagepack array prefix */
 	int i;
 
-	constexpr const auto msgpack_str_len = [](std::size_t len) {
-		if (len <= 0x1F) {
-			return 1 + len;
-		}
-		else if (len <= 0xff) {
-			return 2 + len;
-		}
-		else if (len <= 0xffff) {
-			return 3 + len;
-		}
-		else {
-			return 4 + len;
-		}
-	};
-	constexpr const auto msgpack_emit_str = [](const std::string_view st, char *out) -> size_t {
-		auto len = st.size();
-		constexpr const unsigned char fix_mask = 0xA0, l8_ch = 0xd9, l16_ch = 0xda, l32_ch = 0xdb;
-		auto blen = 0;
-		if (len <= 0x1F) {
-			blen = 1;
-			out[0] = (len | fix_mask) & 0xff;
-		}
-		else if (len <= 0xff) {
-			blen = 2;
-			out[0] = l8_ch;
-			out[1] = len & 0xff;
-		}
-		else if (len <= 0xffff) {
-			uint16_t bl = GUINT16_TO_BE(len);
-
-			blen = 3;
-			out[0] = l16_ch;
-			memcpy(&out[1], &bl, sizeof(bl));
-		}
-		else {
-			uint32_t bl = GUINT32_TO_BE(len);
-
-			blen = 5;
-			out[0] = l32_ch;
-			memcpy(&out[1], &bl, sizeof(bl));
-		}
-
-		memcpy(&out[blen], st.data(), st.size());
-
-		return blen + len;
-	};
 	/*
 	 * First we need to determine the requested length
 	 */