Using C++ to program, read random contents from a file in the main have been written, requires to a function follow the steps:

Given:

std::string encode_char(std::string block, char payload); char decode_char(std::string block); int find_boundary(std::string message, int start); std::string encode_string(std::string message, std::string payload); std::string decode_string(std::string message); std::string read_file(std::string filename); void write_file(std::string filename, std::string message);

decode_string

decode_string(message) ret = "" start = 0 infinite loop block_length = find_boundary(message, start) // Ensure we have enough to make a block if block_length == -1 throw an error block = substring of message starting at start, block_length characters in length c = decode_char(block) // Check for null terminator if c == '\0' break; append c to ret increment start by block_length return ret