Made stylistic edits to list_files function

include/pros/misc.hpp

@@ -601,7 +601,7 @@ std::int32_t list_files_raw(const char* path, char* buffer, int32_t len);
  *  DO NOT PREPEND YOUR PATHS WITH "/usd/"
  * 
  * \return vector of std::string of file names, if error occurs, returns vector containing
- * one element specifying the error state
+ * two elements, first element is "ERROR" and second element is the error message
  * 
  * \b Example
  * \code
@@ -610,12 +610,20 @@ std::int32_t list_files_raw(const char* path, char* buffer, int32_t len);
  *	std::vector<std::string> files = pros::usd::list_files("/");
  *	pros::delay(200);
  *	// Given vector of std::string file names, print each file name
- *  // Note that if there is an error, the vector will contain one element, which
- *  // is the error state
- *  // Print each file name
- *	for (std::string& file : files) {
- *		std::cout << file << std::endl;
- *	}
+ *  // Note that if there is an error, the vector will contain two elements,
+ *  // first element is "ERROR" and second element is the error message
+ * 
+ * 	// Check if error occurred
+ *  if (file_list.front().start_with("ERROR")) {
+ *  	// deal with error
+ *  }
+ *  else {
+ * 		// file list returned is valid
+ *  	// Print each file name
+ *		for (std::string& file : files) {
+ *			std::cout << file << std::endl;
+ *		}
+ *  }
  * }
  * \endcode
 */

src/devices/vdml_usd.cpp

@@ -28,22 +28,26 @@ std::int32_t list_files_raw(const char* path, char* buffer, int32_t len) {
 std::vector<std::string> list_files(const char* path) {
 	std::vector<std::string> files = {};
 	// malloc buffer to store file names
-	char *buffer = (char *) malloc(10000);
+	size_t buffer_size = 10000;
+	char *buffer = (char *) malloc(buffer_size);
 	if (buffer == NULL) {
 		// try again smaller buffer to see if that works
-		buffer = (char *) malloc(500);
+		buffer_size = 500;
+		buffer = (char *) malloc(buffer_size);
 		if (buffer == NULL) {
 			// if still fails, return vector containing error state
 			// set errno to ENOMEM
 			errno = ENOMEM;
+			files.push_back("ERROR");
 			files.push_back("not enough memory to get file names");
 			return files;
 		}
 	}
 	// Call the C function
-	int32_t success = usd_list_files_raw(path, buffer, 10000);
+	int32_t success = usd_list_files_raw(path, buffer, buffer_size);
 	// Check if call successful, if error return vector containing error state
 	if (success == PROS_ERR) {
+		files.push_back("ERROR");
 		// Check errno to see which error state occurred
 		// push back error state to files vector as std::string
 		if (errno == EINVAL || errno == ENOENT) {
@@ -62,14 +66,16 @@ std::vector<std::string> list_files(const char* path) {
 	// delimter_pos is the position of the delimiter '\n'
 	// index of which character to start substr from
 	// file_name used to store each file name
-	size_t delimiter_pos, index = 0;
+	size_t delimiter_pos = 0;
+	size_t index = 0;
 	std::string_view file_name;
 
 	// Loop until delimiter '\n' can not be found anymore
 	while ((delimiter_pos = str.find('\n', index)) != std::string::npos) {
 		// file_name is the string from the beginning of str to the first '\n', excluding '\n'
 		file_name = std::string_view(str.data() + index, delimiter_pos - index);
-		// Add token to files vector
+		// This is point where content of the std::string_view file name is copied to its
+		// own std::string and added to the files vector
 		files.emplace_back(file_name);
 		// Increment index to start substr from
 		index = delimiter_pos + 1;