UTF-8, UTF-16, and UTF-32

What are the differences between UTF-8, UTF-16, and UTF-32?

I understand that they will all store Unicode, and that each uses a different number of bytes to represent a character. Is there an advantage to choosing one over the other?

回答1

UTF-8 has an advantage in the case where ASCII characters represent the majority of characters in a block of text, because UTF-8 encodes these into 8 bits (like ASCII). It is also advantageous in that a UTF-8 file containing only ASCII characters has the same encoding as an ASCII file.

UTF-16 is better where ASCII is not predominant, since it uses 2 bytes per character, primarily. UTF-8 will start to use 3 or more bytes for the higher order characters where UTF-16 remains at just 2 bytes for most characters.

UTF-32 will cover all possible characters in 4 bytes. This makes it pretty bloated. I can't think of any advantage to using it.

 

回答2

n short:

• UTF-8: Variable-width encoding, backwards compatible with ASCII. ASCII characters (U+0000 to U+007F) take 1 byte, code points U+0080 to U+07FF take 2 bytes, code points U+0800 to U+FFFF take 3 bytes, code points U+10000 to U+10FFFF take 4 bytes. Good for English text, not so good for Asian text.
• UTF-16: Variable-width encoding. Code points U+0000 to U+FFFF take 2 bytes, code points U+10000 to U+10FFFF take 4 bytes. Bad for English text, good for Asian text.
• UTF-32: Fixed-width encoding. All code points take four bytes. An enormous memory hog, but fast to operate on. Rarely used.

In long: see Wikipedia: UTF-8, UTF-16, and UTF-32.

 

回答3

• UTF-8 is variable 1 to 4 bytes.

• UTF-16 is variable 2 or 4 bytes.

• UTF-32 is fixed 4 bytes.

Note: UTF-8 can take 1 to 6 bytes with latest convention: https://lists.gnu.org/archive/html/help-flex/2005-01/msg00030.html