1 files changed, 106 insertions, 0 deletions
diff --git a/lua/colorizer/utils.lua b/lua/colorizer/utils.lua
new file mode 100644
index 0000000..0cb09ee
--- /dev/null
+++ b/lua/colorizer/utils.lua
@@ -0,0 +1,106 @@
+---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,
+}