when to use writeUTF() and writeUTFBytes() in ByteArray of AS3

Question

I am trying to create a file format for myself, so i was forming the header for my file. To write a known length string into a ByteArray, which method should i use, writeUTF() or writeUTFBytes().

From the Flex 3 language ref, it tells me that writeUTF() prepends the length of the string and throws a RangeError whereas writeUTFBytes() does not.

Any suggessions would be appreciated.

Answer 1

The only difference between the two is that writeUTFBytes() doesn't prepend the message with the length of the string (The RangeError is because 65535 is the highest number you can store in 16 bits)

Where you'd use one over the other depends on what you're doing. For example, I use writeUTFBytes() when copying a XML object over to be compressed. In this case, I don't care about the length of the string, and it'd introduce something extra to the code.

writeUTF() can be useful if you're writing a streaming/network server, where as you prefix the message length to the message, you know how many bytes to stream on the other end before the end of the message. e.g., I have 200 bytes worth of message. I read the length (16-bit integer), which tells me the message is 100 bytes. I read in 100 bytes and I know it's a complete message. Everything after is another message. If the message length said the message was 300 bytes, then I'd know I'd have to wait a bit before I have the full message.

Answer 2

I think i have found the solution myself. It came to me when i was coding to read back the data. The corresponding functions to read from a bytearray readUTF() and readUTFBytes(length:uint) requires the length to be passed to it.

So if you know the length of the string that you are gonna write, you can use writeUTFBytes() and use readUTFBytes() with that size. Else you can use readUTF(), letting as3 write the size of the data which can be read back without any need to know the length of the string while using readUTF().

Hope this might be useful to some one as well.