davidxifeng

Keybase proof

I hereby claim:

• I am davidfeng on github.
• I am davidfeng (https://keybase.io/davidfeng) on keybase.
• I have a public key ASAVA-RbCz8YZU5tKQt1QuSu7y6cULUvX-fSutmFkKeI7Qo

To claim this, I am signing this object:

davidxifeng

Exploiting Lua 5.1 on 32-bit Windows

The following Lua program generates a Lua bytecode program called ignore-unsigned-sga.fnt, which in turn loads a DLL from within an extremely locked down Lua 5.1 sandbox in a program called RelicCOH2.exe. The remainder of this document attempts to explain how this program works by a whirlwind tour of relevent bits of the Lua 5.1 virtual machine.

if string.dump(function()end):sub(1, 12) ~= "\27Lua\81\0\1\4\4\4\8\0" then
  error("This generator requires a 32-bit version of Lua 5.1")
end

local function outer()
  local magic -- In bytecode, the stack slot corresponding to this local is changed

davidxifeng

local print = print
local tconcat = table.concat
local tinsert = table.insert
local srep = string.rep
local type = type
local pairs = pairs
local tostring = tostring
local next = next

davidxifeng

系统开发

1. 什么是自旋锁 spin lock? 什么是互斥锁? 各有什么特点,应用在何种场景?
2. compare and swap (cas)是什么? 原子操作, 编译器(gcc) 固有指令
3. 读写锁 (锁定读, 锁定写, 未加锁 3种状态) 共享-独占锁

图形学

1. 仿射变换 齐次坐标空间
2. 贝塞儿曲线 二次/三次 特点 应用 true type, 矢量图, 曲面

Lua

davidxifeng

import qualified Data.HashSet as HS
import Data.Hashable

-- 2014-07-25 20:27:29
-- TODO custom HashSet with special ``insert`` ``fromListWith`` ...

data Test = A Int | B Double | C Char | D
    deriving (Show)

instance Eq Test where

davidxifeng

import Data.Csv
import Control.Monad
import Control.Applicative

-- 2014-07-24 15:26:22 fail and mzero

data Test = A | B | C
    deriving (Show, Read)

instance FromField Test where

davidxifeng

#!/bin/sh

# Shell script to install your public key on a remote machine
# Takes the remote machine name as an argument.
# Obviously, the remote machine must accept password authentication,
# or one of the other keys in your ssh-agent, for this to work.

ID_FILE="${HOME}/.ssh/id_rsa.pub"

if [ "-i" = "$1" ]; then

davidxifeng

{-# LANGUAGE DeriveDataTypeable #-}
{-# LANGUAGE OverloadedStrings #-}
{-# LANGUAGE RecordWildCards #-}
import Network.Wai
import Control.Exception (Exception, throwIO, assert)
import Control.Applicative ((<$>))
import Control.Monad (when, forever, unless)
import Data.Typeable (Typeable)
import Network.HTTP.Types (status200, status404)
import Network.Wai.Handler.Warp (run)

davidxifeng

测试使用gist

你好

I love Haskell.

davidxifeng

################ Lispy: Scheme Interpreter in Python
 
## (c) Peter Norvig, 2010; See http://norvig.com/lispy.html
 
################ Symbol, Procedure, Env classes
 
from __future__ import division
 
Symbol = str