From 4206374f370afe25cb35777d1fe6fe0d298a59ef Mon Sep 17 00:00:00 2001
From: Ole Tange <ole@tange.dk>
Date: Sat, 15 Aug 2020 23:48:47 +0200
Subject: [PATCH] binsearch: Initial version.

---
 Makefile            |  29 ++++++-----
 binsearch/binsearch | 122 ++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 137 insertions(+), 14 deletions(-)
 create mode 100755 binsearch/binsearch

diff --git a/Makefile b/Makefile
index 33a94eb..8d672a4 100644
--- a/Makefile
+++ b/Makefile
@@ -1,19 +1,20 @@
-CMD = blink 2grep 2search burncpu drac duplicate-packets em encdir	\
-	field forever fxkill G gitnext gitundo goodpasswd histogram	\
-	mtrr mirrorpdf neno off parsort pdfman pidcmd pidtree		\
-	plotpipe puniq ramusage rand rclean rina rn rrm seekmaniac	\
-	shython sound-reload splitvideo stdout swapout T teetime	\
-	timestamp tracefile transpose upsidedown vid			\
+CMD = binsearch blink 2grep 2search burncpu drac duplicate-packets em	\
+	encdir field forever fxkill G gitnext gitundo goodpasswd	\
+	histogram mtrr mirrorpdf neno off parsort pdfman pidcmd		\
+	pidtree plotpipe puniq ramusage rand rclean rina rn rrm		\
+	seekmaniac shython sound-reload splitvideo stdout swapout T	\
+	teetime timestamp tracefile transpose upsidedown vid		\
 	w4it-for-port-open whitehash wifi-reload wssh ytv yyyymmdd
 
-all: blink/blink.1 2search/2grep.1 2search/2search.1			\
-	burncpu/burncpu.1 drac/drac.1 encdir/encdir.1 field/field.1	\
-	G/G.1 gitnext/gitnext.1 gitundo/gitundo.1			\
-	goodpasswd/goodpasswd.1 histogram/histogram.1			\
-	mirrorpdf/mirrorpdf.1 neno/neno.1 off/off.1 parsort/parsort.1	\
-	pdfman/pdfman.1 pidcmd/pidcmd.1 pidtree/pidtree.1		\
-	plotpipe/plotpipe.1 puniq/puniq.1 rand/rand.1 rina/rina.1	\
-	rn/rn.1 rrm/rrm.1 seekmaniac/seekmaniac.1 shython/shython.1	\
+all: binsearch/binsearch.1 blink/blink.1 2search/2grep.1		\
+	2search/2search.1 burncpu/burncpu.1 drac/drac.1			\
+	encdir/encdir.1 field/field.1 G/G.1 gitnext/gitnext.1		\
+	gitundo/gitundo.1 goodpasswd/goodpasswd.1			\
+	histogram/histogram.1 mirrorpdf/mirrorpdf.1 neno/neno.1		\
+	off/off.1 parsort/parsort.1 pdfman/pdfman.1 pidcmd/pidcmd.1	\
+	pidtree/pidtree.1 plotpipe/plotpipe.1 puniq/puniq.1		\
+	rand/rand.1 rina/rina.1 rn/rn.1 rrm/rrm.1			\
+	seekmaniac/seekmaniac.1 shython/shython.1			\
 	sound-reload/sound-reload.1 splitvideo/splitvideo.1		\
 	stdout/stdout.1 teetime/teetime.1 timestamp/timestamp.1		\
 	tracefile/tracefile.1 transpose/transpose.1 T/T.1		\
diff --git a/binsearch/binsearch b/binsearch/binsearch
new file mode 100755
index 0000000..a0d7017
--- /dev/null
+++ b/binsearch/binsearch
@@ -0,0 +1,122 @@
+#!/bin/bash
+
+: <<'=cut'
+=encoding utf8
+
+=head1 NAME
+
+binsearch - do binary search to find a numeric limit 
+
+
+=head1 SYNOPSIS
+
+B<binsearch> I<command>
+
+
+=head1 DESCRIPTION
+
+B<binsearch> runs I<command> with a single number. It returns highest
+value that I<command> succeeds for.
+
+
+=head1 EXAMPLES
+
+=head2 Test a bash function
+
+  . $(which binsearch)
+  singleecho() {
+    /bin/echo $(perl -e 'print "x"x'$1) >/dev/null
+  }
+  binsearch singleecho
+
+
+=head1 AUTHOR
+
+Copyright (C) 2020 Ole Tange,
+http://ole.tange.dk and Free Software Foundation, Inc.
+
+
+=head1 LICENSE
+
+Copyright (C) 2012 Free Software Foundation, Inc.
+
+This program 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 3 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.
+
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+=head1 SEE ALSO
+
+B<eval>(1)
+
+=cut
+
+
+# Example: find the max line length
+#
+# singleecho() {
+#     /bin/echo $(perl -e 'print "x"x'$1) >/dev/null
+# }
+# 
+# multiecho() {
+#     /bin/echo $(perl -e 'print "x "x'$(($1/2)) ) >/dev/null
+# }
+#
+# binsearch singleecho
+
+binsearch() {
+    _binsearch() {
+	low=$1
+	high=$2
+	# echo $low-$high
+	if [ $low -gt $(($high - 2)) ]; then
+	    return
+	fi
+	shift
+	shift
+	middle=$(( ( $low + $high ) / 2 ))
+	if eval "$@ $middle" ; then
+	    low=$middle
+	else
+	    high=$middle
+	fi
+	_binsearch $low $high "$@"
+    }
+    
+    low=1
+    # If function(1) = false: run 'not function()' instead
+    if eval "$@ $low" ; then
+	not=''
+    else
+	not='!'
+    fi
+    # exponential search for the first value that is false
+    # low = previous value (function($low) == true)
+    # high = low * 2 (function($high) == false)
+    high=$low
+    while eval "$not" "$@ $high" 2>/dev/null ; do
+	low=$high
+	high=$(( $high*2 ))
+    done
+    # echo "low: $low high: $high not: $not"
+    _binsearch $low $high "$not $@" 2>/dev/null
+    echo $low
+}
+
+if [ -z "$@" ] ; then
+    # source the bash function
+    # . $(which binsearch)
+    true
+else
+    # binsearch command
+    binsearch "$@"
+fi