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#! /bin/bash

########################################################################

#

# File:    reg_search

# Author:  Janis Johnson 

# Date:    2002/12/15

#

# Search for a small time interval within a range of dates in which

# results for a test changed, using a binary search.  The functionality

# for getting sources, building the component to test, and running the

# test are in other scripts that are run from here.  Before the search

# begins, we verify that we get the expected behavior for the first and

# last dates.

#

# Define these in a file whose name is the argument to this script:

#   LOW_DATE:   Date string recognized by the date command (local time).

#   HIGH_DATE:  Date string recognized by the date command (local time).

#   REG_UPDATE: Pathname of script to update your source tree; returns

#               zero for success, nonzero for failure.

#   REG_BUILD:  Pathname of script to build enough of the product to run

#               the test; returns zero for success, nonzero for failure.

#   REG_TEST:   Pathname of script to run the test; returns 1 if we

#               should search later dates, 0 if we should search earlier

#               dates.

# Optional:

#   DELTA:      Search to an interval within this many seconds; default

#               is one hour (although 300 works well).

#   REG_FINISH  Pathname of script to call at the end with the two final

#               dates as arguments.

#   SKIP_LOW    If 1, skip verifying the low date of the range;

#               define this only if you're restarting and have already

#               tested the low date.

#   SKIP_HIGH   If 1, skip verifying the high date of the range;

#               define this only if you're restarting and have already

#               tested the high date.

#   FIRST_MID   Use this as the first midpoint, to avoid a midpoint that

#               is known not to build.

#   HAS_CHANGES Pathname of script to report whether the current date has

#               no differences from one of the ends of the current range

#               to skip unnecessary build and testing; default is "true".

#   VERBOSITY   Default is 0, to print only errors and final message.

#   DATE_IN_MSG If set to anything but 0, include the time and date in

#               messages.

#

#

#

# Copyright (c) 2002, 2003, 2005 Free Software Foundation, Inc.

#

# This file is free software; you can redistribute it and/or modify

# it under the terms of the GNU General Public License as published by

# the Free Software Foundation; either version 2 of the License, or

# (at your option) any later version.

#

# This program is distributed in the hope that it will be useful,

# but WITHOUT ANY WARRANTY; without even the implied warranty of

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

# GNU General Public License for more details.

#

# For a copy of the GNU General Public License, write the the

# Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,

# Boston, MA 02110-1301, USA.

#

########################################################################

########################################################################

# Functions

########################################################################

# Issue a message if its verbosity level is high enough.

msg() {

  test ${1} -gt ${VERBOSITY}  && return

  if [ "x${DATE_IN_MSG}" = "x" ]; then

    echo "${2}"

  else

    echo "`${DATE}`  ${2}"

  fi

}

# Issue an error message and exit with a non-zero status.  If there

# is a valid current range whose end points have been tested, report

# it so the user can start again from there.

error() {

  msg 0 "error: ${1}"

  test ${VALID_RANGE} -eq 1 && \

    echo "current range:"

    echo "LOW_DATE=\"${LATER_THAN}\""

    echo "HIGH_DATE=\"${EARLIER_THAN}\""

  exit 1

}

# Turn seconds since the epoch into a date we can use with source

# control tools and report to the user.

make_date() {

  MADE_DATE="`${DATE} -u +\"%Y-%m-%d %H:%M %Z\" --date \"1970-01-01 ${1} seconds\"`" \

    || error "make_date: date command failed"

}

# Build the components to test using sources as of a particular date and

# run a test case.  Pass each of the scripts the date that we're

# testing; the first one needs it, the others can ignore it if they want.

process_date() {

  TEST_DATE="${1}"

  ${REG_UPDATE} "${TEST_DATE}" || error "source update failed for ${TEST_DATE}"

  # If we're already in a valid range, skip this date if there are no

  # differences from either end of the range and adjust LATER.

  if [ ${VALID_RANGE} = 1 ]; then

    ${HAS_CHANGES} "${TEST_DATE}" "${LATER_THAN}" "${EARLIER_THAN}"

    RET=$?

    case ${RET} in

    0) ;;

    1) LATER=1; return;;

    2) LATER=0; return;;

    *) error "process_date: unexpected return value from ${HAS_CHANGES}";;

    esac

  fi

  ${REG_BUILD} "${TEST_DATE}"  || error "build failed for ${TEST_DATE}"

  ${REG_TEST} "${TEST_DATE}"

  LATER=$?

}

# Perform a binary search on dates within the range specified by

# the arguments, bounded by the number of seconds in DELTA.

search_dates() {

  let LOW=$1

  let HIGH=$2

  let DIFF=HIGH-LOW

  # Get the date in the middle of the range; MID is in seconds since

  # the epoch, DATE is readable by humans and tools.  The user can

  # override the initial mid date if it is known to have problems,

  # e.g., if a build fails for that date.

  if [ ${FIRST_MID} -ne 0 ]; then

    let MID=${FIRST_MID}

  else

    let MID=LOW/2+HIGH/2

  fi

  while [ ${DIFF} -ge ${DELTA} ]; do

    make_date ${MID}

    TEST_DATE="${MADE_DATE}"

    # Test it.

    process_date "${TEST_DATE}"

    # Narrow the search based on the outcome of testing DATE.

    if [ ${LATER} -eq 1 ]; then

      msg 1 "search dates later than \"${TEST_DATE}\""

      LATER_THAN="${TEST_DATE}"

      let LOW=MID

    else

      msg 1 "search dates earlier than \"${TEST_DATE}\""

      EARLIER_THAN="${TEST_DATE}"

      let HIGH=MID

    fi

    let DIFF=HIGH-LOW

    let MID=LOW/2+HIGH/2

  done

}

########################################################################

# Main program (so to speak)

########################################################################

# If DATE isn't defined, use the default date command; the configuration

# file can override this.

if [ "x${DATE}" = "x" ]; then

  DATE=date

fi

# The error function uses this.

VALID_RANGE=0

# Process the configuration file.

if [ $# != 1 ]; then

  echo Usage: $0 config_file

  exit 1

fi

CONFIG=${1}

if [ ! -f ${CONFIG} ]; then

  error "configuration file ${CONFIG} does not exist"

fi

# OK, the config file exists.  Source it, make sure required parameters

# are defined and their files exist, and give default values to optional

# parameters.

. ${CONFIG}

test "x${REG_UPDATE}" = "x" && error "REG_UPDATE is not defined"

test "x${REG_BUILD}" = "x" && error "REG_BUILD is not defined"

test "x${REG_TEST}" = "x" && error "REG_TEST is not defined"

test -x ${REG_TEST} || error "REG_TEST is not an executable file"

test "x${SKIP_LOW}" = "x" && SKIP_LOW=0

test "x${SKIP_HIGH}" = "x" && SKIP_HIGH=0

test "x${DELTA}" = "x" && DELTA=3600

test "x${VERBOSITY}" = "x" && VERBOSITY=0

test "x${HAS_CHANGES}" = "x" && HAS_CHANGES=true

test "x${REG_FINISH}" = "x" && REG_FINISH=true

msg 2 "LOW_DATE   = ${LOW_DATE}"

msg 2 "HIGH_DATE  = ${HIGH_DATE}"

msg 2 "REG_UPDATE = ${REG_UPDATE}"

msg 2 "REG_BUILD  = ${REG_BUILD}"

msg 2 "REG_TEST   = ${REG_TEST}"

msg 2 "SKIP_LOW   = ${SKIP_LOW}"

msg 2 "SKIP_HIGH  = ${SKIP_HIGH}"

msg 2 "FIRST_MID  = ${FIRST_MID}"

msg 2 "VERBOSITY  = ${VERBOSITY}"

msg 2 "DELTA      = ${DELTA}"

# Verify that DELTA is at least two minutes.

test ${DELTA} -lt 120 && \

  error "DELTA is ${DELTA}, must be at least 120 (two minutes)"

# Change the dates into seconds since the epoch.  This uses an extension

# in GNU date.

LOW_DATE=`${DATE} +%s --date "${LOW_DATE}"` || \

  error "date command failed for \"${LOW_DATE}\""

HIGH_DATE=`${DATE} +%s --date "${HIGH_DATE}"` || \

  error "date command failed for \"${LOW_DATE}\""

# If FIRST_MID was defined, convert it and make sure it's in the range.

if [ "x${FIRST_MID}" != "x" ]; then

  FIRST_MID=`${DATE} +%s --date "${FIRST_MID}"` || \

    error "date command failed for \"${FIRST_MID}\""

  test ${FIRST_MID} -le ${LOW_DATE}  && \

    error "FIRST_MID date is earlier than LOW_DATE"

  test ${FIRST_MID} -ge ${HIGH_DATE} && \

    error "FIRST_MID is later than HIGH_DATE"

else

  FIRST_MID=0

fi

# Keep track of the bounds of the range where the test behavior changes,

# using a human-readable version of each date.

make_date ${LOW_DATE}

LATER_THAN="${MADE_DATE}"

make_date ${HIGH_DATE}

EARLIER_THAN="${MADE_DATE}"

msg 2 "LATER_THAN   = ${LATER_THAN}"

msg 2 "EARLIER_THAN = ${EARLIER_THAN}"

# Verify that the range isn't backwards.

test ${LOW_DATE} -lt ${HIGH_DATE} || error "date range is backwards"

# Verify that the first and last date in the range get the results we

# expect.  If not, quit, because any of several things could be wrong.

if [ ${SKIP_LOW} -eq 0 ]; then

  process_date "${LATER_THAN}"

  test ${LATER} -ne 1 && \

    error "unexpected result for low date ${LATER_THAN}"

  msg 1 "result for low date is as expected"

fi

if [ ${SKIP_HIGH} -eq 0 ]; then

  process_date "${EARLIER_THAN}"

  test ${LATER} -ne 0 && \

    error "unexpected result for high date ${EARLIER_THAN}"

  msg 1 "result for high date is as expected"

fi

# Search within the range, now that we know that the end points are valid.

VALID_RANGE=1

search_dates ${LOW_DATE} ${HIGH_DATE}

# Report the range that's left to investigate.

echo "Continue search between ${LATER_THAN} and ${EARLIER_THAN}"

# Invoke the optional script to report additional information about

# changes between the two dates.

${REG_FINISH} "${LATER_THAN}" "${EARLIER_THAN}"