utils.utf8sub
Summary
Returns a substring of a UTF-8 string
Prototype
s = utils.utf8sub (str, start, end)Description
Returns a substring of the UTF-8 string, starting at index 'start' and ending at index 'end'. Both may be negative to indicate counting from the right. The end point is optional and defaults to -1, which is the entire rest of the string.
For strings where each character has a character code of < 128, the behaviour is identical to string.sub:
utils.utf8sub ("ABCDEF", 2, 3) --> BC
utils.utf8sub ("ABCDEF", 3) --> CDEF
utils.utf8sub ("ABCDEF", -1) --> F
The above examples are straight "ASCII" strings (ie. each byte is < 128), however the behaviour is different to string.sub with UTF-8 strings. For example:
utils.utf8sub (utils.fromhex ("C686C689C69C"), 1, 2) --> (hex) C686C689
utils.utf8sub (utils.fromhex ("C686C689C69C"), -1, -1) --> (hex) C69C
For Unicode characters (ie. whose character code is >= 128 and <= 255) then the function calculates the number of bytes that each "Unicode code point" will require, and count each one as a "column".
The supplied string must be valid UTF-8. If not, the function returns nil followed by the byte position in error.See Also ...
Topics
Lua base functions
Lua bc (big number) functions
Lua bit manipulation functions
Lua coroutine functions
Lua debug functions
Lua io functions
Lua LPEG library
Lua math functions
Lua os functions
Lua package functions
Lua PCRE regular expression functions
Lua script extensions
Lua string functions
Lua table functions
Lua utilities
ScriptingLua functions
utils.base64decode (Decode a string which was base-64 encoded)
utils.base64encode (Encode a string with base-64 encoding)
utils.choose (Display a combo box with choices in it)
utils.compress (Compress a string)
utils.decompress (Decompress a string)
utils.directorypicker (Invokes the Windows standard "directory picker" dialog box)
utils.editbox (Display a large message box and get free-format reply)
utils.edit_distance (Returns the Levenshtein Edit Distance between two words)
utils.filepicker (Invokes the Windows standard "file picker" dialog box)
utils.fontpicker (Invokes the Windows standard "font picker" dialog box)
utils.fromhex (Convert a string from hex)
utils.functionlist (Returns a table of MUSHclient world function names)
utils.getfontfamilies (Returns all fonts available to Windows)
utils.hash (Hash a string, returning the hex codes)
utils.info (Information about directories, locale, etc.)
utils.inputbox (Display a message box and get free-format reply)
utils.listbox (Display a dialog box with choices in it in a single selection list box)
utils.md5 (Hash a string using the 128-bit MD5 algorithm)
utils.metaphone (Returns metaphones (sound-alike codes) for the supplied word)
utils.msgbox (Display a message box and get a response)
utils.multilistbox (Display a dialog box with choices in it in a multiple selection list box)
utils.readdir (Read a disk directory into a table)
utils.sha256 (Hash a string using a 256-bit hash)
utils.spellcheckdialog (Spell-checker dialog)
utils.split (Split a delimited string into a table)
utils.tohex (Convert a string into hex)
utils.umsgbox (Display a message box and get a response (Unicode))
utils.utf8decode (Encodes a series of Unicode codes into a UTF-8 string)
utils.utf8encode (Encodes a series of Unicode codes into a UTF-8 string)
utils.utf8valid (Checks if a UTF-8 string is valid)
utils.xmlread (Parses an XML string into a nested table)(Help topic: lua=utils.utf8sub)
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