pretty/cdata.lua

-- Import

local ffi = require 'ffi'
local bit = require 'bit'

-- Constants

--------------------------------------------------------------------------------
-- Util

local NUMBER_TO_HEX = {
	[00] = '0', [01] = '1', [02] = '2', [03] = '3', [04] = '4', [05] = '5',
	[06] = '6', [07] = '7', [08] = '8', [09] = '9', [10] = 'A', [11] = 'B',
	[12] = 'C', [13] = 'D', [14] = 'E', [15] = 'F',
}

local function to_hex (val, nr_elements, element_size)
	local l = {}
	for i = 0, nr_elements - 1 do
		local v = val[i]
		l[#l+1] = bit.tohex(v, -2*element_size)
		l[#l+1] = ' '
	end
	l[#l] = nil
	return table.concat(l, '')
end

local function is_nice_unicode_string (str)
	-- TODO... Maybe also look into a purely binary oriented representation.
	return false
end

local function is_nice_ascii_string (str)
	for i = 1, #str do
		local byte = str:byte(i)
		if not (32 <= byte and byte <= 126) then  return false  end
	end
	return true
end

local function get_type_and_size_of_singular ( ctype )
	local nr_elements, layers  =  1, 0
	while true do
		local etype, elements  =  ctype:match('(.+)%[(%d*)%]$')
		if not elements then  break  end
		ctype, nr_elements  =  etype, nr_elements * elements
		layers = layers + 1
	end
	return ctype, nr_elements, layers
end

--------------------------------------------------------------------------------

local CDATA_REPR_MATCHER = 'cdata<(.+)>: (0x%w+)'

local function format_cdata (value, options, depth, l, format_value)

	local native_repr  =  tostring(value)
	local data_length  =  ffi.sizeof(value)
	local ctype, addr  =  native_repr:match(CDATA_REPR_MATCHER)

	-- Is void  pointer?
	if ctype == 'void *' then
		local address_pointing_at = tonumber(ffi.cast('int', value))
		l[#l+1] = 'void pointer to ' .. addr
		return ;
	end

	-- Is normal pointer?
	if ctype:match('%*$') then
		if type(value[0]) ~= 'cdata' then
			-- Data presentable in Lua, refered to by pointers?
			l[#l+1] = 'pointer to '
			return format_value(value[0], options, depth, l)
		else
			l[#l+1] = '* '
			return format_cdata(value[0], options, depth, l, format_value)
		end
	end

	l[#l+1] = 'cdata {'
	--l[#l+1] = '\n\tnative = \''   .. native_repr .. '\','
	l[#l+1] = '\n\ttype   = '   .. ctype .. ','
	l[#l+1] = '\n\taddr   = '   .. addr .. ','
	if data_length then
		-- Size
		local str = ffi.string(value, data_length)
		l[#l+1] = '\n\tsize   = '   .. data_length .. ','

		-- Element size and type
		local element_type, nr_elements, nr_layers  =  get_type_and_size_of_singular(ctype)
		local element_size = data_length / nr_elements
		l[#l+1] = '\n\tnr_e   = ' .. nr_elements .. ','
		l[#l+1] = '\n\ttype_e = '   .. element_type .. ','
		l[#l+1] = '\n\tsize_e = '   .. element_size .. ','

		-- If can be expressed as string, express it as string.
		if is_nice_ascii_string(str) or is_nice_unicode_string(str) then
			local string_or_unicode = is_nice_ascii_string(str) and 'ascii' or 'utf8 '
			l[#l+1] = '\n\t'..string_or_unicode..'    = ' .. str .. ','
		end
		--
		if nr_layers == 1 then
			-- Only a single level of arrays
			l[#l+1] = '\n\thex    = ' .. to_hex(value, nr_elements, element_size) .. ','
		end

	end
	l[#l+1] = '\n}'
end

return format_cdata