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.
#Trim nul codepoints code
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
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Order bit in standard ASCII is always zero.
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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
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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