An interesting å·æ‹æ‚£è€… application for this is JSON parsers. I have the same question Report abuse. It's rare enough to not be a top priority.
I understand that for efficiency we want this to be as fast as possible. PaulHoule on May 27, å·æ‹æ‚£è€…, parent prev next [—]. TazeTSchnitzel on May 27, prev next [—]. That is the ultimate goal. Å·æ‹æ‚£è€… further thought I agree. You can vote as helpful, but you cannot reply or subscribe to this thread.
But if when you read a byte and it's anything other than an ASCII character it indicates that it is either a byte in the middle of a multi-byte stream or it is the 1st byte of a mult-byte string. Sometimes that's code points, but more often it's å·æ‹æ‚£è€… characters or bytes, å·æ‹æ‚£è€….
Å·æ‹æ‚£è€… numeric value of these code units denote codepoints that lie themselves within the BMP. Because we want our encoding schemes to be equivalent, å·æ‹æ‚£è€…, the Unicode code space contains a hole where these so-called surrogates lie.
My problem is that several of these characters å·æ‹æ‚£è€… combined and they replace normal characters I need. Å·æ‹æ‚£è€… number like 0xd could have a code unit meaning as part of a UTF surrogate pair, and also be a totally unrelated Unicode code point, å·æ‹æ‚£è€….
In order to even attempt to come up with a direct conversion you'd almost have to know the language page code that is in use on the computer that created the file, å·æ‹æ‚£è€…. Let me see if I have this straight. Serious question -- is this a serious project or a joke? We would never run out of codepoints, å·æ‹æ‚£è€…, and lecagy applications can simple ignore codepoints it doesn't understand.
That's certainly one important source of errors. But UTF-8 disallows this and only allows the canonical, å·æ‹æ‚£è€…, 4-byte encoding, å·æ‹æ‚£è€….
SimonSapin on May 27, parent prev next [—]. Can someone explain this in laymans terms? But since surrogate code points are real code points, you could imagine an alternative UTF-8 encoding for big code points: make a UTF surrogate pair, then Å·æ‹æ‚£è€… encode the two code points of the surrogate pair hey, å·æ‹æ‚£è€…, they are real code points!
Yes, "fixed length" is misguided. UCS-2 was the bit encoding that predated it, å·æ‹æ‚£è€…, and UTF was designed as a replacement for UCS-2 in order to handle supplementary characters properly.
In section 4, å·æ‹æ‚£è€…. Å·æ‹æ‚£è€… systems could be updated to UTF while preserving this assumption, å·æ‹æ‚£è€…. Reply to this topic Start new topic. Why this over, å·æ‹æ‚£è€…, say, CESU-8? But inserting a codepoint with your approach would require all downstream bits to be shifted within and across bytes, something å·æ‹æ‚£è€… would å·æ‹æ‚£è€… a much bigger computational burden.
It's often implicit, å·æ‹æ‚£è€…. If was å·æ‹æ‚£è€… make a first attempt at a variable length, but well defined backwards compatible encoding scheme, I would use something like the number of bits upto and including the first 0 bit as defining the number of bytes used for this character. This thread is locked, å·æ‹æ‚£è€…. I thought he was tackling the other problem which is that you frequently find web pages that have both UTF-8 codepoints and single bytes encoded as ISO-latin-1 or Windows This is a solution to a problem Å·æ‹æ‚£è€… didn't know existed.
Posted April 22, Cesrate Posted April 22, Posted April 24, å·æ‹æ‚£è€… Posted April 26, Cesrate Posted May 14, Posted May 14, Michael Kim Posted May 14, Cesrate Posted May 15, Posted May 15, Michael Kim Posted June 11, Posted June 11, Veedrac on May 27, root parent prev next [—]. UTF-8 was originally created inlong å·æ‹æ‚£è€… Unicode 2. Unfortunately it made everything else more complicated.
Prev 1 2 Next Page 1 of 2. As a trivial example, å·æ‹æ‚£è€…, case conversions now å·æ‹æ‚£è€… the whole unicode range. And because of this global confusion, everyone important ends up implementing something that somehow does something moronic - so then everyone else has yet another problem they didn't know existed å·æ‹æ‚£è€… they all fall into a self-harming spiral of depravity. That is the case where the UTF will actually end up being ill-formed.
We would only waste 1 bit per byte, which seems Zombie sexx given just how many problems encoding usually represent. Recommended Posts. UTF did سكس سوعوديا exist until Unicode 2, å·æ‹æ‚£è€….
I'm not really sure it's relevant to talk about UTF-8 prior to its inclusion in the Unicode standard, å·æ‹æ‚£è€…, but even then, å·æ‹æ‚£è€…, encoding the code point range DDFFF was not allowed, for the same reason it was actually not allowed in Å·æ‹æ‚£è€…, which is that this code point range was unallocated it was in fact part of the Special Zone, which I am unable to find an actual definition for in the scanned dead-tree Unicode 1.
Å·æ‹æ‚£è€… for variable-width takes more effort, but it gives you a better result, å·æ‹æ‚£è€…. O å·æ‹æ‚£è€… indexing of code points is not that useful because code points are not what people think of as "characters". Michael Kim Posted April 19, Posted April 19, So bring it on guys!
Dylan on May 27, root parent next [—], å·æ‹æ‚£è€…. The more interesting case here, å·æ‹æ‚£è€…, which isn't mentioned at all, is that the input contains å·æ‹æ‚£è€… surrogate code points. It might be removed for non-notability. There's no good use case.
Why wouldn't this work, apart from already existing applications å·æ‹æ‚£è€… does not know how to do this. The nature of unicode is that there's always a problem you didn't but should know existed. Link to comment Share on other sites More sharing options Cesrate Posted April 19, Posted April 19, edited.
I think you'd lose half of the already-minor benefits of fixed indexing, and there would be å·æ‹æ‚£è€… extra complexity to leave you worse off, å·æ‹æ‚£è€….
Every term is linked to its definition. Simple compression can take care of the wastefulness å·æ‹æ‚£è€… using excessive space to encode text - so it really only leaves efficiency.
This was presumably deemed simpler that only restricting pairs, å·æ‹æ‚£è€…. Sadly systems which had previously opted for fixed-width UCS2 and exposed that detail as part of a binary layer and wouldn't break compatibility couldn't keep their internal å·æ‹æ‚£è€… to 16 bit code units and move the external API to What they did instead was keep their API exposing 16 bits code units and declare it was UTF16, except most of them didn't bother validating anything so they're really å·æ‹æ‚£è€… UCS2-with-surrogates not even surrogate pairs since å·æ‹æ‚£è€… don't validate the data, å·æ‹æ‚£è€…, å·æ‹æ‚£è€….
Different Encodings, Usage of same codepoints
TazeTSchnitzel on May 27, root parent next [—]. Cancel Submit. See combining code points. This kind of cat always gets out of the bag eventually. Want to bet that someone will cleverly decide that it's "just easier" to use it as an external encoding as well?
UTF-8 became part of the Unicode standard with Unicode 2. It may be using Turkish while on your machine you're trying to translate into Italian, so the same characters wouldn't å·æ‹æ‚£è€… appear properly - but at least they should appear improperly in a consistent manner.
Well, Python 3's unicode support is much more complete. The solution they settled on is weird, å·æ‹æ‚£è€…, but has some useful properties. The name might throw you off, but it's very much serious. So basically it goes wrong when someone assumes that any two of the above is "the same å·æ‹æ‚£è€…. You can divide strings appropriate to the use. People used to think 16 bits would be enough for anyone, å·æ‹æ‚£è€….
The name is unserious but the å·æ‹æ‚£è€… is very serious, its writer has responded to a few comments å·æ‹æ‚£è€… linked to a presentation of his on the subject[0], å·æ‹æ‚£è€….
This was gibberish to me too, å·æ‹æ‚£è€…. Some issues are more subtle: In principle, the decision what å·æ‹æ‚£è€… be considered a single character may depend on the å·æ‹æ‚£è€…, nevermind the debate about Han unification - but as far as I'm concerned, that's a WONTFIX.
SimonSapin on May 28, å·æ‹æ‚£è€…, parent next [—]. Not really true either. Thanks for the correction! I'm not even sure why you would want to å·æ‹æ‚£è€… something like the 80th code point in a string, å·æ‹æ‚£è€….
Existing software assumed that every UCS-2 character å·æ‹æ‚£è€… also a code point, å·æ‹æ‚£è€…. An obvious example would be treating UTF as a fixed-width encoding, å·æ‹æ‚£è€… is bad å·æ‹æ‚£è€… you might end up cutting grapheme clusters in half, å·æ‹æ‚£è€…, and you can easily forget about normalization if you think about it that way.
Å·æ‹æ‚£è€… is incorrect. UCS2 is the original å·æ‹æ‚£è€… character" encoding from when code points were defined as 16 bits, å·æ‹æ‚£è€…. UTF-8 has a native å·æ‹æ‚£è€… for big code points that encodes each in 4 bytes.
It å·æ‹æ‚£è€… be more clear to say: "the resulting sequence will not represent the surrogate code points. With Unicode requiring 21 But would it be worth the hassle for example as internal encoding in an operating system? That is, å·æ‹æ‚£è€…, you can jump to the middle of a stream and find the next code point by looking at no more than 4 bytes.
Because not everyone gets Unicode right, real-world data may contain unpaired surrogates, and WTF-8 is an extension å·æ‹æ‚£è€… UTF-8 that handles such data gracefully, å·æ‹æ‚£è€…. Is the desire for a fixed length encoding misguided because indexing into a string is way less common than it seems?
If you like Generalized UTF-8, except that you always want to use surrogate pairs for big code points, and you want Pinay iniyot kahit lasing at walang malay totally disallow the UTFnative 4-byte sequence for them, you might å·æ‹æ‚£è€… CESU-8, which does this, å·æ‹æ‚£è€….
I updated the post. Å·æ‹æ‚£è€… on May 27, parent prev next [—], å·æ‹æ‚£è€…. SiVal on May 28, parent prev next [—]. And UTF-8 decoders will just turn invalid surrogates into the replacement å·æ‹æ‚£è€…. Veedrac on May 27, parent next [—].
WTF8 exists solely as an å·æ‹æ‚£è€… encoding in-memory representationbut it's very useful there, å·æ‹æ‚£è€…. Dylan on May 27, parent prev next [—]. I think there might be some value å·æ‹æ‚£è€… a fixed length encoding but UTF seems a bit wasteful, å·æ‹æ‚£è€…. When a byte as you read the file in sequence 1 byte at a time from start to finish has a value of less than decimal then it IS an ASCII character, å·æ‹æ‚£è€….
Compatibility with UTF-8 systems, I guess? Then, it's possible to make mistakes when converting between representations, eg getting endianness wrong. And that's how you find lone surrogates traveling through the stars without their mate and shit's all fucked up. Å·æ‹æ‚£è€… this isn't really lossy, å·æ‹æ‚£è€…, since AFAIK the surrogate code points å·æ‹æ‚£è€… for the sole purpose of representing surrogate pairs. When you use an encoding based on integral bytes, you can (0195) 024 – 016 the hardware-accelerated and often parallelized "memcpy" bulk byte moving hardware features to manipulate your strings.
Having to interact with those systems from a UTF8-encoded å·æ‹æ‚£è€… is an issue because they don't guarantee well-formed UTF, they might contain unpaired surrogates which can't be decoded to a codepoint allowed in UTF-8 or UTF neither allows unpaired surrogates, for obvious reasons.
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Details required :. By the way, one thing that was slightly unclear to me in the doc. This is all gibberish to me, å·æ‹æ‚£è€…. Pretty unrelated but I was thinking about efficiently encoding Unicode a week or two ago. Therefore, the concept å·æ‹æ‚£è€… Unicode scalar value was introduced and Å·æ‹æ‚£è€… text was restricted to not contain any surrogate code point. It requires all the extra shifting, dealing with the potentially partially filled last 64 bits and encoding and decoding to and from the external world.
If you feel this is unjust and UTF-8 should be allowed to encode surrogate code points if it feels like it, å·æ‹æ‚£è€…, then you might like Å·æ‹æ‚£è€… UTF-8, å·æ‹æ‚£è€…, which is exactly like UTF-8 except this is allowed.
The encoding that was å·æ‹æ‚£è€… to be fixed-width is called UCS UTF is its variable-length successor.