If you think you have one, you are probably wrong. I'm yet to see a single valid reason to ever do so. macOS automatically converts the a umlaut to the three byte sequence.First of all, you can't index directly into a Unicode string because it's a terrible idea. Under Linux and BSD you can create a filename with both encodings. For example the filename 'ä.txt' can be encoded in Unicode with two different sequences (#$C3#$A4 and 'a'#$CC#$88). The file functions of the FileUtil unit also take care of macOS specific behaviour: macOS normalizes filenames. It is not specific to any encoding but Unicode in general.
This is not automatically handled by the RTL. one of the string contains decomposed characters, while the other uses the direct codes for the same letter. procedure IterateUTF8Codepoints ( const AnUTF8String : string ) var p : PChar unicode : Cardinal CPLen : integer begin p := PChar ( AnUTF8String ) repeat unicode := UTF8CodepointToUnicode ( p, CPLen ) writeln ( 'Unicode=', unicode ) inc ( p, CPLen ) until ( CPLen = 0 ) or ( unicode = 0 ) end Decomposed charactersĭue to the ambiguity of Unicode, compare functions and Pos() might show unexpected behavior when e.g. Searching for a valid UTF-8 string with Pos will always return a valid UTF-8 byte position:
iterate over codepoints or characters - useful for graphical components like SynEdit, for example when you want to know the third printed character on the screen.ĭue to the special nature of UTF8 you can simply use the normal string functions for searching a sub-string. iterate over bytes - useful for searching a substring or when looking only at the ASCII characters in the UTF8 string, for example when parsing XML files. If you want to iterate over codepoints of a UTF-8 string, there are basically two ways: This is not something specific to UTF-8, the Unicode standard is complex and the word "character" is ambiguous. Simply iterating over characters as if the string was an array of equal sized elements does not work with Unicode. Many (Unix-related) operating systems use UTF-8 natively. Processing the data directly as UTF-8 eliminates useless conversions. Most textual data moving in internet is encoded as UTF-8. ITERATE OVER STRING ANDROID CODEPOINTS CODE
For UTF-16 there is plenty of sloppy code which assumes codepoints to be fixed width. Code that deals with codepoints must always be done right with UTF-8 because multi-byte codepoints are common. (D800 range signals first surrogate, DC00 range signals second part of surrogate) Note that similar integrity features are also exists in UTF-16. This allows using the old fast string functions like Pos() and Copy() in many situations.
A byte at a certain position in a multi-byte sequence can never be confused with the other bytes. 
You can always find the start of a multi-byte codepoint even if you jumped to a random byte position. The integrity of multi-byte data can be verified from the number of '1'-bits at the beginning of each byte. However that backwards compatibility does not extend to code, since code has to be recrafted to avoid mangling utf8 strings. ASCII is also used in markup language tags and other metadata which gives UTF-8 an advantage with any language. It is backwards compatible with ASCII and produces compact data for western languages. The design of UTF-8 has some benefits over other encodings : 4 bytes : 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx. With multi-byte codepoints the number of 1’s in the leading byte determines the number of bytes the codepoint occupies. 2.8 Showing codepoints with UTF8CharacterToUnicodeīytes starting with '0' (0xxxxxxx) are reserved for ASCII-compatible single byte characters. 2.6 Accessing bytes inside one UTF8 codepoint. 2.5 Iterating over string analysing individual codepoints. 2.4 Iterating over string looking for Unicode characters or text. 2.3 Iterating over string looking for ASCII characters.
0 kommentar(er)
