New unicode.lua library. Supports utf-8 and UTF-16

nselib/unicode.lua

@@ -0,0 +1,199 @@
+---
+-- Library methods for handling unicode strings.
+--
+-- @author Daniel Miller
+-- @copyright Same as Nmap--See http://nmap.org/book/man-legal.html
+
+
+local bit = require "bit"
+local bin = require "bin"
+local string = require "string"
+local table = require "table"
+local stdnse = require "stdnse"
+local unittest = require "unittest"
+_ENV = stdnse.module("json", stdnse.seeall)
+
+-- Localize a few functions for a tiny speed boost, since these will be looped
+-- over every char of a string
+local band = bit.band
+local lshift = bit.lshift
+local rshift = bit.rshift
+local byte = string.byte
+local char = string.char
+local pack = bin.pack
+local unpack = bin.unpack
+
+
+---Decode a buffer containing Unicode data.
+--@param buf The string/buffer to be decoded
+--@param decoder A Unicode decoder function (such as utf8_dec)
+--@param bigendian For encodings that care about byte-order (such as UTF-16),
+--                 set this to true to force big-endian byte order. Default:
+--                 false (little-endian)
+--@return A list-table containing the code points as numbers
+function decode(buf, decoder, bigendian)
+  local cp = {}
+  local pos = 1
+  while pos < #buf do
+    pos, cp[#cp+1] = decoder(buf, pos, bigendian)
+  end
+  return cp
+end
+
+---Encode a list of Unicode code points
+--@param list A list-table of code points as numbers
+--@param encoder A Unicode encoder function (such as utf8_enc)
+--@param bigendian For encodings that care about byte-order (such as UTF-16),
+--                 set this to true to force big-endian byte order. Default:
+--                 false (little-endian)
+--@return An encoded string
+function encode(list, encoder, bigendian)
+  local buf = {}
+  for i, cp in ipairs(list) do
+    buf[i] = encoder(cp, bigendian)
+  end
+  return table.concat(buf, "")
+end
+
+---Encode a Unicode code point to UTF-16. See RFC 2781.
+-- Windows OS prior to Windows 2000 only supports UCS-2, so beware using this
+-- function to encode code points above 0xFFFF.
+--@param cp The Unicode code point as a number
+--@param bigendian Set this to true to encode big-endian UTF-16. Default is
+--                 false (little-endian)
+--@return A string containing the code point in UTF-16 encoding.
+function utf16_enc(cp, bigendian)
+  local fmt = "<S"
+  if bigendian then
+    fmt = ">S"
+  end
+
+  if cp % 1.0 ~= 0.0 or cp < 0 then
+    -- Only defined for nonnegative integers.
+    return nil
+  elseif cp <= 0xFFFF then
+    return pack(fmt, cp)
+  elseif cp <= 0x10FFFF then
+    cp = cp - 0x10000
+    return pack(fmt .. fmt, 0xD800 + rshift(cp, 10), 0xDC00 + band(cp, 0x3FF))
+  else
+    return nil
+  end
+end
+
+---Decodes a UTF-16 character.
+-- Does not check that the returned code point is a real character.
+-- Specifically, it can be fooled by out-of-order lead- and trail-surrogate
+-- characters.
+--@param buf A string containing the character
+--@param pos The index in the string where the character begins
+--@param bigendian Set this to true to encode big-endian UTF-16. Default is
+--                 false (little-endian)
+--@return pos The index in the string where the character ended
+--@return cp The code point of the character as a number
+function utf16_dec(buf, pos, bigendian)
+  local fmt = "<S"
+  if bigendian then
+    fmt = ">S"
+  end
+
+  local cp
+  pos, cp = unpack(fmt, buf, pos)
+  if cp >= 0xD800 and cp <= 0xDFFF then
+    local high = lshift(cp - 0xD800, 10)
+    pos, cp = unpack(fmt, buf, pos)
+    cp = 0x10000 + high + cp - 0xDC00
+  end
+  return pos, cp
+end
+
+---Encode a Unicode code point to UTF-8. See RFC 3629.
+-- Does not check that cp is a real character; that is, doesn't exclude the
+-- surrogate range U+D800 - U+DFFF and a handful of others.
+--@param cp The Unicode code point as a number
+--@return A string containing the code point in UTF-8 encoding.
+function utf8_enc(cp)
+  local bytes = {}
+  local n, mask
+
+  if cp % 1.0 ~= 0.0 or cp < 0 then
+    -- Only defined for nonnegative integers.
+    return nil
+  elseif cp <= 0x7F then
+    -- Special case of one-byte encoding.
+    return char(cp)
+  elseif cp <= 0x7FF then
+    n = 2
+    mask = 0xC0
+  elseif cp <= 0xFFFF then
+    n = 3
+    mask = 0xE0
+  elseif cp <= 0x10FFFF then
+    n = 4
+    mask = 0xF0
+  else
+    return nil
+  end
+
+  while n > 1 do
+    bytes[n] = char(0x80 + band(cp, 0x3F))
+    cp = rshift(cp, 6)
+    n = n - 1
+  end
+  bytes[1] = char(mask + cp)
+
+  return table.concat(bytes)
+end
+
+---Decodes a UTF-8 character.
+-- Does not check that the returned code point is a real character.
+--@param buf A string containing the character
+--@param pos The index in the string where the character begins
+--@return pos The index in the string where the character ended
+--@return cp The code point of the character as a number
+function utf8_dec(buf, pos)
+  pos = pos or 1
+  local n, mask
+  local bv = byte(buf, pos)
+  if bv <= 0x7F then
+    return pos+1, bv
+  elseif bv <= 0xDF then
+    --110xxxxx 10xxxxxx
+    n = 1
+    mask = 0xC0
+  elseif bv <= 0xEF then
+    --1110xxxx 10xxxxxx 10xxxxxx
+    n = 2
+    mask = 0xE0
+  elseif bv <= 0xF7 then
+    --11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
+    n = 3
+    mask = 0xF0
+  else
+    return nil
+  end
+
+  local cp = bv - mask
+
+  for i = 1, n do
+    bv = band(byte(buf, pos + i), 0x3F)
+    cp = lshift(cp, 6) + bv
+  end
+
+  return pos + 1 + n, cp
+end
+
+test_suite = unittest.TestSuite:new()
+test_suite:add_test(function()
+    local pos, cp = utf8_dec("\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E")
+    return pos == 4 and cp == 0x65E5, string.format("Expected 4, 0x65E5; got %d, 0x%x", pos, cp)
+  end, "utf8_dec")
+
+test_suite:add_test(unittest.equal(encode({0x65E5,0x672C,0x8A9E}, utf8_enc), "\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E"),"encode utf-8")
+test_suite:add_test(unittest.equal(encode({0x12345,61,82,97}, utf16_enc), "\x08\xD8\x45\xDF=\0R\0a\0"),"encode utf-16")
+test_suite:add_test(unittest.equal(encode({0x12345,61,82,97}, utf16_enc, true), "\xD8\x08\xDF\x45\0=\0R\0a"),"encode utf-16, big-endian")
+test_suite:add_test(unittest.table_equal(decode("\xE6\x97\xA5\xE6\x9C\xAC\xE8\xAA\x9E", utf8_dec), {0x65E5,0x672C,0x8A9E}),"decode utf-8")
+test_suite:add_test(unittest.table_equal(decode("\x08\xD8\x45\xDF=\0R\0a\0", utf16_dec), {0x12345,61,82,97}),"decode utf-16")
+test_suite:add_test(unittest.table_equal(decode("\xD8\x08\xDF\x45\0=\0R\0a", utf16_dec, true), {0x12345,61,82,97}),"decode utf-16, big-endian")
+
+return _ENV