u_json: Add array helper.

src/xrt/auxiliary/util/u_json.c

@@ -1,10 +1,49 @@
-// Copyright 2019, Collabora, Ltd.
+// Copyright 2019-2020, Collabora, Ltd.
 // SPDX-License-Identifier: BSL-1.0
 /*!
  * @file
  * @brief  Tiny JSON wrapper around cJSON.
  * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @author Ryan Pavlik <ryan.pavlik@collabora.com>
  * @ingroup aux_util
  */
 
+#include "u_json.h"
+
 #include "cjson/cJSON.c"
+
+size_t
+u_json_get_double_array(const cJSON *json_array,
+                        double *out_array,
+                        size_t max_size)
+{
+	if (!json_array) {
+		return 0;
+	}
+	if (!out_array) {
+		return 0;
+	}
+	if (!cJSON_IsArray(json_array)) {
+		return 0;
+	}
+	if (max_size == 0) {
+		return 0;
+	}
+	size_t i = 0;
+	const cJSON *elt;
+	cJSON_ArrayForEach(elt, json_array)
+	{
+		if (!cJSON_IsNumber(elt)) {
+			fprintf(stderr,
+			        "warning: u_json_get_double_array got a "
+			        "non-number in a numeric array");
+			return i;
+		}
+		out_array[i] = elt->valuedouble;
+		++i;
+		if (i == max_size) {
+			break;
+		}
+	}
+	return i;
+}

src/xrt/auxiliary/util/u_json.h

@@ -1,9 +1,10 @@
-// Copyright 2019, Collabora, Ltd.
+// Copyright 2019-2020, Collabora, Ltd.
 // SPDX-License-Identifier: BSL-1.0
 /*!
  * @file
  * @brief  Tiny JSON wrapper around cJSON header.
  * @author Jakob Bornecrantz <jakob@collabora.com>
+ * @author Ryan Pavlik <ryan.pavlik@collabora.com>
  * @ingroup aux_util
  */
 
@@ -12,3 +13,21 @@
 #include "xrt/xrt_compiler.h"
 
 #include "cjson/cJSON.h"
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif // __cplusplus
+
+/*!
+ * @brief Parse up to max_size doubles from a JSON array.
+ *
+ * @return the number of elements set.
+ */
+size_t
+u_json_get_double_array(const cJSON *json_array,
+                        double *out_array,
+                        size_t max_size);
+#ifdef __cplusplus
+} // extern "C"
+#endif // __cplusplus