#!/bin/bash
  
  # objdiff - a small script for validating that a commit or series of commits
  # didn't change object code.
  #
  # Copyright 2014, Jason Cooper <jason@lakedaemon.net>
  #
  # Licensed under the terms of the GNU GPL version 2
  
  # usage example:
  #
  # $ git checkout COMMIT_A
  # $ <your fancy build command here>
  # $ ./scripts/objdiff record path/to/*.o
  #
  # $ git checkout COMMIT_B
  # $ <your fancy build command here>
  # $ ./scripts/objdiff record path/to/*.o
  #
  # $ ./scripts/objdiff diff COMMIT_A COMMIT_B
  # $
  
  # And to clean up (everything is in .tmp_objdiff/*)
  # $ ./scripts/objdiff clean all
  #
  # Note: 'make mrproper' will also remove .tmp_objdiff

  SRCTREE=$(cd $(git rev-parse --show-toplevel 2>/dev/null); pwd)

  if [ -z "$SRCTREE" ]; then
  	echo >&2 "ERROR: Not a git repository."

  	exit 1
  fi

  TMPD=$SRCTREE/.tmp_objdiff

  usage() {

  	echo >&2 "Usage: $0 <command> <args>"
  	echo >&2 "  record    <list of object files or directories>"
  	echo >&2 "  diff      <commitA> <commitB>"
  	echo >&2 "  clean     all | <commit>"

  	exit 1
  }

  get_output_dir() {
  	dir=${1%/*}
  
  	if [ "$dir" = "$1" ]; then
  		dir=.
  	fi
  
  	dir=$(cd $dir; pwd)
  
  	echo $TMPD/$CMT${dir#$SRCTREE}
  }
  
  do_objdump() {
  	dir=$(get_output_dir $1)
  	base=${1##*/}

  	stripped=$dir/${base%.o}.stripped

  	dis=$dir/${base%.o}.dis
  
  	[ ! -d "$dir" ] && mkdir -p $dir
  
  	# remove addresses for a cleaner diff
  	# http://dummdida.tumblr.com/post/60924060451/binary-diff-between-libc-from-scientificlinux-and

  	$STRIP -g $1 -R __bug_table -R .note -R .comment -o $stripped
  	$OBJDUMP -D $stripped | sed -e "s/^[[:space:]]\+[0-9a-f]\+//" -e "s:^$stripped:$1:" > $dis

  }

  dorecord() {
  	[ $# -eq 0 ] && usage
  
  	FILES="$*"
  
  	CMT="`git rev-parse --short HEAD`"

  	STRIP="${CROSS_COMPILE}strip"

  	OBJDUMP="${CROSS_COMPILE}objdump"

  	for d in $FILES; do
  		if [ -d "$d" ]; then
  			for f in $(find $d -name '*.o')
  			do
  				do_objdump $f
  			done
  		else
  			do_objdump $d
  		fi

  	done
  }
  
  dodiff() {
  	[ $# -ne 2 ] && [ $# -ne 0 ] && usage
  
  	if [ $# -eq 0 ]; then
  		SRC="`git rev-parse --short HEAD^`"
  		DST="`git rev-parse --short HEAD`"
  	else
  		SRC="`git rev-parse --short $1`"
  		DST="`git rev-parse --short $2`"
  	fi
  
  	DIFF="`which colordiff`"
  
  	if [ ${#DIFF} -eq 0 ] || [ ! -x "$DIFF" ]; then
  		DIFF="`which diff`"
  	fi
  
  	SRCD="$TMPD/$SRC"
  	DSTD="$TMPD/$DST"
  
  	if [ ! -d "$SRCD" ]; then

  		echo >&2 "ERROR: $SRCD doesn't exist"

  		exit 1
  	fi
  
  	if [ ! -d "$DSTD" ]; then

  		echo >&2 "ERROR: $DSTD doesn't exist"

  		exit 1
  	fi
  
  	$DIFF -Nurd $SRCD $DSTD
  }
  
  doclean() {
  	[ $# -eq 0 ] && usage
  	[ $# -gt 1 ] && usage
  
  	if [ "x$1" = "xall" ]; then
  		rm -rf $TMPD/*
  	else
  		CMT="`git rev-parse --short $1`"
  
  		if [ -d "$TMPD/$CMT" ]; then
  			rm -rf $TMPD/$CMT
  		else

  			echo >&2 "$CMT not found"

  		fi
  	fi
  }
  
  [ $# -eq 0 ] &&	usage
  
  case "$1" in
  	record)
  		shift
  		dorecord $*
  		;;
  	diff)
  		shift
  		dodiff $*
  		;;
  	clean)
  		shift
  		doclean $*
  		;;
  	*)

  		echo >&2 "Unrecognized command '$1'"

  		exit 1
  		;;
  esac