![]() I’ve noticed a lot of invalid ITF-8 values expand into these threeīytes. Used for invalid data ( Thanks to RichB for the answer in the When round tripped, I don’t really know other than a single byte ofġ28 isn’t a valid UTF-8 character. So in answer to the question of why does 128 expand into multiple bytes In a (valid) UTF‑8 stream represents the first byte of a byte sequenceĬorresponding to a single character, or a continuation byte of such a … the first byte never has 10 as its two most-significant bits.Īs a result, it is immediately obvious whether any given byte anywhere Notice that it’s marked with a leading 10 bit pattern which means it’s aĬontinuation character. How do you represent 128 in binary? 10000000 If the character is encoded by a sequence of more than one byte, theįirst byte has as many leading “1” bits as the total number ofīytes in the sequence, followed by a “0” bit, and the succeedingīytes are all marked by a leading “10” bit pattern. Thoseīut why does 128 expand into multiple bytes when round tripped? This explains why bytes 0 through 127 all round trip correctly. High-order bit is 0 and the other bits give the code value (in the If the character is encoded by just one byte, the UTF-8 is a variable-width encoding, with each character represented by Represent all unicode characters by leveraging the high order bit that UTF-8 takes advantage of this decision to create a scheme that’s bothīackwards compatible with the ASCII characters, but also able to It was thereforeĭecided to use 7 bits to store the new ASCII code, with the eighth bitīeing used as a parity bit to detect transmission errors. ?” etc.) you ended up a value of 90-something. When you counted all possible alphanumeric characters (A to Z, lowerĪnd upper case, numeric digits 0 to 9, special characters like “% * / Why only 7-bits and not theīecause seven bits ought to be enough for Order bit in standard ASCII is always zero. Single byte, and thus consists of 128 possible characters. It can represent every unicode character, but isĪSCII is an encoding that represents each character with seven bits of a UTF-8 is a format that encodes each character in a string To understand this, it’s helpful to understand what UTF-8 is in theįirst place. ![]() If you try it with 127 or less, it round trips just fine. ![]() WTF?! The data was changed and the original value is lost! Simulates that scenario with a byte array containing a single byte, 128. Later on, you need to relay that data so you take it out, encode it back Imagine you’re receiving a stream ofīytes and you store it as a UTF-8 string and pop it in the database. WhatĪre the cases in which you might lose data? Round Tripping UTF-8 Encoded Strings I’ve always known that if you need to sendīinary data in text format, base64 encoding is the safe way to do so.īut I didn’t really understand why the other encodings were unsafe. When you need to represent binaryĭata in a string, you should use base64, hex or something similar. In response to an earlierīasically, treating arbitrary binary data as if it were encoded text That this wasn’t the first time Skeet answered a question about usingĮncodings to convert binary data to text. Not to give you the impression that I’m stalking Skeet, but I did notice To encode the binary data as text, then decode Which genuinely is encoded text - this isn’t. Encoding is for when you’ve got binary data You should absolutely not use an Encoding to convert arbitraryīinary data to text. In fact, I have a story about this I want to tell you in a future That isn’t exactly their code, but this is a pattern I’ve seen in the
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