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77 lines
3.8 KiB
Text
77 lines
3.8 KiB
Text
-------------------------------------------------------------------------------
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-- UTF-8 Support.
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-- This library provides basic support for UTF-8 encoding.
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-- It provides all its functions inside the table utf8.
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-- This library does not provide any support for Unicode other than the handling of the encoding.
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-- Any operation that needs the meaning of a character, such as character classification, is outside its scope.
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--
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-- Unless stated otherwise, all functions that expect a byte position as a parameter assume that
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-- the given position is either the start of a byte sequence or one plus the length of the subject string.
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-- As in the string library, negative indices count from the end of the string.
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-- @module utf8
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-------------------------------------------------------------------------------
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-- Receives zero or more integers, converts each one to its
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-- corresponding UTF-8 byte sequence, and returns a string with the concatenation
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-- of all these sequences.
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-- @function [parent=#utf8] char
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-- @param ... zero or more integers.
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-- @return #string
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-------------------------------------------------------------------------------
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-- The pattern which matches exactly one UTF-8 byte sequence, assuming that
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-- the subject is a valid UTF-8 string.
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-- @function [parent=#utf8] charpattern
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-- @return #string
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-------------------------------------------------------------------------------
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-- Returns values so that the construction
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--
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-- for p, c in utf8.codes(s) do body end
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--
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-- will iterate over all characters in string s, with p being the position (in bytes)
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-- and c the code point of each character.
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-- It raises an error if it meets any invalid byte sequence.
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-- @function [parent=#utf8] codes
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-- @param #string s string to handle.
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-------------------------------------------------------------------------------
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-- Returns the codepoints (as integers) from all characters in s that start
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-- between byte position i and j (both included). The default for i is 1 and for j is i.
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-- It raises an error if it meets any invalid byte sequence.
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-- @function [parent=#utf8] codepoint
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-- @param #string s string to handle
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-- @param #number i the initial position (default value is 1)
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-- @param #number j the final position (default value is i)
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-- @return #number the codepoints of each character in s
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-------------------------------------------------------------------------------
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-- Returns the number of UTF-8 characters in string s that start
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-- between positions i and j (both inclusive).
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-- The default for i is 1 and for j is -1.
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-- If it finds any invalid byte sequence,
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-- returns a false value plus the position of the first invalid byte.
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-- @function [parent=#utf8] len
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-- @param #string s string to handle
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-- @param #number i the initial position (default value is 1)
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-- @param #number j the final position (default value is -1)
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-- @return #number the number of utf8 characters in s
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-------------------------------------------------------------------------------
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-- Returns the position (in bytes) where the encoding of the n-th character of s
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-- (counting from position i) starts. A negative n gets characters before position i.
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-- The default for i is 1 when n is non-negative and #s + 1 otherwise,
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-- so that utf8.offset(s, -n) gets the offset of the n-th character from the end of the string.
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-- If the specified character is neither in the subject nor right after its end, the function returns nil.
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--
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-- As a special case, when n is 0 the function returns the
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-- start of the encoding of the character that contains the i-th byte of s.
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--
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-- This function assumes that s is a valid UTF-8 string.
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-- @function [parent=#utf8] offset
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-- @param #string s string to handle
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-- @param #number n the n-th character
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-- @param #number i the initial position (default value is 1 if n is is non-negative and #s + 1 otherwise)
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-- @return #number
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return nil
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