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---Helper utils
--@module utils
local bit, ffi = require "bit", require "ffi"
local band, bor, rshift, lshift = bit.band, bit.bor, bit.rshift, bit.lshift
-- -- TODO use rgb as the return value from the matcher functions
-- -- instead of the rgb_hex. Can be the highlight key as well
-- -- when you shift it left 8 bits. Use the lower 8 bits for
-- -- indicating which highlight mode to use.
-- ffi.cdef [[
-- typedef struct { uint8_t r, g, b; } colorizer_rgb;
-- ]]
-- local rgb_t = ffi.typeof 'colorizer_rgb'
-- Create a lookup table where the bottom 4 bits are used to indicate the
-- category and the top 4 bits are the hex value of the ASCII byte.
local BYTE_CATEGORY = ffi.new "uint8_t[256]"
local CATEGORY_DIGIT = lshift(1, 0)
local CATEGORY_ALPHA = lshift(1, 1)
local CATEGORY_HEX = lshift(1, 2)
local CATEGORY_ALPHANUM = bor(CATEGORY_ALPHA, CATEGORY_DIGIT)
-- do not run the loop multiple times
local b = string.byte
for i = 0, 255 do
local v = 0
-- Digit is bit 1
if i >= b "0" and i <= b "9" then
v = bor(v, lshift(1, 0))
v = bor(v, lshift(1, 2))
v = bor(v, lshift(i - b "0", 4))
end
local lowercase = bor(i, 0x20)
-- Alpha is bit 2
if lowercase >= b "a" and lowercase <= b "z" then
v = bor(v, lshift(1, 1))
if lowercase <= b "f" then
v = bor(v, lshift(1, 2))
v = bor(v, lshift(lowercase - b "a" + 10, 4))
end
end
BYTE_CATEGORY[i] = v
end
---Obvious.
---@param byte number
---@return boolean
local function byte_is_alphanumeric(byte)
local category = BYTE_CATEGORY[byte]
return band(category, CATEGORY_ALPHANUM) ~= 0
end
---Obvious.
---@param byte number
---@return boolean
local function byte_is_hex(byte)
return band(BYTE_CATEGORY[byte], CATEGORY_HEX) ~= 0
end
---Merge two tables.
--
-- todo: Remove this and use `vim.tbl_deep_extend`
---@return table
local function merge(...)
local res = {}
for i = 1, select("#", ...) do
local o = select(i, ...)
if type(o) ~= "table" then
return {}
end
for k, v in pairs(o) do
res[k] = v
end
end
return res
end
--- Obvious.
---@param byte number
---@return number
local function parse_hex(byte)
return rshift(BYTE_CATEGORY[byte], 4)
end
--- Obvious.
---@param v string
---@return number|nil
local function percent_or_hex(v)
if v:sub(-1, -1) == "%" then
return tonumber(v:sub(1, -2)) / 100 * 255
end
local x = tonumber(v)
if x > 255 then
return
end
return x
end
--- @export
return {
byte_is_alphanumeric = byte_is_alphanumeric,
byte_is_hex = byte_is_hex,
merge = merge,
parse_hex = parse_hex,
percent_or_hex = percent_or_hex,
}
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