mirror of
https://github.com/appgurueu/modlib.git
synced 2024-07-02 14:20:25 +02:00
102 lines
3.1 KiB
Lua
102 lines
3.1 KiB
Lua
local assert, error, select, string_char, table_concat
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= assert, error, select, string.char, table.concat
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local utf8 = {}
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-- Overly permissive pattern that greedily matches a single UTF-8 codepoint
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utf8.charpattern = "[%z-\127\194-\253][\128-\191]*"
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function utf8.is_valid_codepoint(codepoint)
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-- Must be in bounds & must not be a surrogate
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return codepoint <= 0x10FFFF and (codepoint < 0xD800 or codepoint > 0xDFFF)
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end
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local function utf8_bytes(codepoint)
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if codepoint <= 0x007F then
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return codepoint
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end if codepoint <= 0x7FF then
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local payload_2 = codepoint % 0x40
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codepoint = (codepoint - payload_2) / 0x40
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return 0xC0 + codepoint, 0x80 + payload_2
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end if codepoint <= 0xFFFF then
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local payload_3 = codepoint % 0x40
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codepoint = (codepoint - payload_3) / 0x40
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local payload_2 = codepoint % 0x40
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codepoint = (codepoint - payload_2) / 0x40
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return 0xE0 + codepoint, 0x80 + payload_2, 0x80 + payload_3
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end if codepoint <= 0x10FFFF then
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local payload_4 = codepoint % 0x40
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codepoint = (codepoint - payload_4) / 0x40
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local payload_3 = codepoint % 0x40
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codepoint = (codepoint - payload_3) / 0x40
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local payload_2 = codepoint % 0x40
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codepoint = (codepoint - payload_2) / 0x40
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return 0xF0 + codepoint, 0x80 + payload_2, 0x80 + payload_3, 0x80 + payload_4
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end error"codepoint out of range"
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end
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function utf8.char(...)
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local n_args = select("#", ...)
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if n_args == 0 then
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return
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end if n_args == 1 then
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return string_char(utf8_bytes(...))
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end
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local chars = {}
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for i = 1, n_args do
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chars[i] = string_char(utf8_bytes(select(i, ...)))
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end
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return table_concat(chars)
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end
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local function utf8_next_codepoint(str, i)
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local first_byte = str:byte(i)
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if first_byte < 0x80 then
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return i + 1, first_byte
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end
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local len, head_bits
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if first_byte >= 0xC0 and first_byte <= 0xDF then -- 110_00000 to 110_11111
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len, head_bits = 2, first_byte % 0x20 -- last 5 bits
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elseif first_byte >= 0xE0 and first_byte <= 0xEF then -- 1110_0000 to 1110_1111
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len, head_bits = 3, first_byte % 0x10 -- last 4 bits
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elseif first_byte >= 0xF0 and first_byte <= 0xF7 then -- 11110_000 to 11110_111
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len, head_bits = 4, first_byte % 0x8 -- last 3 bits
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else error"invalid UTF-8" end
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local codepoint = 0
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local pow = 1
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for j = i + len - 1, i + 1, -1 do
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local byte = assert(str:byte(j), "invalid UTF-8")
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local val_bits = byte % 0x40 -- extract last 6 bits xxxxxx from 10xxxxxx
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assert(byte - val_bits == 0x80) -- assert that first two bits are 10
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codepoint = codepoint + val_bits * pow
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pow = pow * 0x40
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end
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return i + len, codepoint + head_bits * pow
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end
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function utf8.codepoint(str, i, j)
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i, j = i or 1, j or #str
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if i > j then return end
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local codepoint
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i, codepoint = utf8_next_codepoint(str, i)
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assert(i - j <= 1, "invalid UTF-8")
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return codepoint, utf8.codepoint(str, i)
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end
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-- Iterator to loop over the UTF-8 characters as `index, codepoint`
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function utf8.codes(text, i)
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i = i or 1
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return function()
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if i > #text then
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return
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end
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local prev_index = i
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local codepoint
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i, codepoint = utf8_next_codepoint(text, i)
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return prev_index, codepoint
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end
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end
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return utf8 |