1. Introduction of the script files.

 In /cocci directory, there are six script files and two subdirectory that are important to know (ignore the rest):

 (1)/testdir: A directory that stors the files that are to parsed. Any file in this directoy or subdirectoy will be parsed.

 (2)startcocci_linux.sh: Shellscript to start the parsing. This script will clearn the files that are left from the last parsing and invoke the right cocci script(pattern_match_linux.cocci) to parse the source files. This one is specifc for Linux and Android source code.

 (3)startcocci_freebsd.sh: Shellscript of starting the parsing. This script will clearn the files that are left from the last parsing and invoke the right cocci script(pattern_match_fressbsd.cocci) to parse the source files. This one is specifc for FreeBSD source code.

 (4)pattern_match_linux.cocci: Coccinelle script file that stores the rules we added for the pattern matching. This one is specific for Linux and Android, because they use the same transfer functions.

 (5)pattern_match_FreeBSD.cocci: Coccinelle script file that stores the rules we added for the pattern matching. This one is specific for FreeBSD, because it uses different transfer functions.

 (6)copy_files.py: Python script that helps to copy the suspicious souce code files to a specifc subdirectory, so as to facilitate the manual analysis.

 (7)/outcome: This directory will be created after parsing, and suspicous source files will be copied here for manual analysis.

 (8)resut.txt: This file will be created after parsing, reports and statistical data will be stored in this file.

 (9)readme.txt: Instructions and decriptions.

2. Description of Coccinelle rules.

 There totally two Coccinelle rule files (pattern_match_linux.cocci, pattern_match_FreeBSD.cocci) in this method, which are basically the same except useing different transfer functions to match. These file consist of the following:

(1) function print_and_log() prints and stores the results of the parsing to specific files and directory.

(2) function post_match_process() filters out some coner cases after the coccinelle pattern matching, so as to reduce the false positives.

(3)rule 1 ~ rule 6 are the coccinelle rules defined to match different double fetch situations. These rules will be matched one by one, and matching stops once a rule is matched. 
	The "..." in the code stands for any statements in the source code; 
	The "|" stands for a disjunction, each item is used to match until one is matched.
	Key workd "when != " after "..." represents the situations that shouldn't be included.


3. How to use.
(1) Install Coccinelle on the machine.
  Mac OS:  “brew install coccinelle”
  Ubuntu:  “apt-get install coccinelle”

(2) Copy the files that are to be parsed to /testdir

(3) Run “./startcocci_linux.sh”  for Linux or Android parsing
    Run “./startcocci_freebsd.sh”  for FreeBSD parsing 

(4) Check the result from result.txt

(5) See the corresponding source files from /outcome