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---Helper function to parse argb
local bit = require "bit"
local floor, min = math.floor, math.min
local band, rshift, lshift = bit.band, bit.rshift, bit.lshift
local utils = require "colorizer.utils"
local byte_is_alphanumeric = utils.byte_is_alphanumeric
local byte_is_hex = utils.byte_is_hex
local parse_hex = utils.parse_hex
local parser = {}
local ARGB_MINIMUM_LENGTH = #"0xAARRGGBB" - 1
---parse for 0xaarrggbb and return rgb hex.
-- a format used in android apps
---@param line string: line to parse
---@param i number: index of line from where to start parsing
---@return number|nil: index of line where the hex value ended
---@return string|nil: rgb hex value
function parser.argb_hex_parser(line, i)
if #line < i + ARGB_MINIMUM_LENGTH then
return
end
local j = i + 2
local n = j + 8
local alpha
local v = 0
while j <= min(n, #line) do
local b = line:byte(j)
if not byte_is_hex(b) then
break
end
if j - i <= 3 then
alpha = parse_hex(b) + lshift(alpha or 0, 4)
else
v = parse_hex(b) + lshift(v, 4)
end
j = j + 1
end
if #line >= j and byte_is_alphanumeric(line:byte(j)) then
return
end
local length = j - i
if length ~= 10 then
return
end
alpha = tonumber(alpha) / 255
local r = floor(band(rshift(v, 16), 0xFF) * alpha)
local g = floor(band(rshift(v, 8), 0xFF) * alpha)
local b = floor(band(v, 0xFF) * alpha)
local rgb_hex = string.format("%02x%02x%02x", r, g, b)
return length, rgb_hex
end
return parser.argb_hex_parser
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