From 839953f1113c70d13560bfd05c5e52139c7f562f Mon Sep 17 00:00:00 2001
From: Florian Pritz <bluewind@xinu.at>
Date: Fri, 6 Apr 2012 23:37:32 +0200
Subject: pkgdelta: implement requirments for delta generation

Big deltas or deltas for very small packages are not needed so we should
check that and not generate any.

Signed-off-by: Florian Pritz <bluewind@xinu.at>
Signed-off-by: Dan McGee <dan@archlinux.org>
---
 doc/pkgdelta.8.txt     | 12 +++++++++++-
 scripts/pkgdelta.sh.in | 52 +++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 60 insertions(+), 4 deletions(-)

diff --git a/doc/pkgdelta.8.txt b/doc/pkgdelta.8.txt
index 3804c5d9..5913dba6 100644
--- a/doc/pkgdelta.8.txt
+++ b/doc/pkgdelta.8.txt
@@ -11,7 +11,7 @@ pkgdelta - package delta generation utility
 
 Synopsis
 --------
-'pkgdelta' [-q] <package1> <package2>
+'pkgdelta' [options] <package1> <package2>
 
 
 Description
@@ -27,6 +27,16 @@ significantly.
 
 Options
 -------
+*--max-delta-size <ratio>*::
+	Only create delta files if the delta is smaller than ratio * package_size.
+	Possible values: 0.0 to 2.0.
+	Recommended values: 0.2 to 0.9.
+	Default value: 0.7
+
+*--min-pkg-size <size>*::
+	Minimal size of the package file in bytes to be considered for delta creation.
+	Default value: 1048576 bytes = 1MiB
+
 *-q, \--quiet*::
 	Be quiet. Do not output anything but warnings and errors.
 
diff --git a/scripts/pkgdelta.sh.in b/scripts/pkgdelta.sh.in
index 511910ba..66ee35ec 100644
--- a/scripts/pkgdelta.sh.in
+++ b/scripts/pkgdelta.sh.in
@@ -30,6 +30,13 @@ myver='@PACKAGE_VERSION@'
 
 QUIET=0
 
+# minimal of package before deltas are generated (bytes)
+min_pkg_size=$((1024*1024))
+
+# percent of new package above which the delta will be discarded
+max_delta_size=70
+
+
 # ensure we have a sane umask set
 umask 0022
 
@@ -46,6 +53,8 @@ This delta file can then be added to a database using repo-add.\n\n")"
 	echo
 	printf -- "$(gettext "Options:\n")"
 	printf -- "  -q                ""$(gettext "quiet\n")"
+	printf -- "  --min-pkg-size    ""$(gettext "minimal of package before deltas are generated (bytes)\n")"
+	printf -- "  --max-delta-size  ""$(gettext "percent of new package above which the delta will be discarded\n")"
 }
 
 version() {
@@ -56,6 +65,10 @@ This is free software; see the source for copying conditions.\n\
 There is NO WARRANTY, to the extent permitted by law.\n")"
 }
 
+isnumeric() {
+	[[ $1 != *[!0-9]* ]]
+}
+
 read_pkginfo()
 {
 	pkgname= pkgver= arch=
@@ -96,6 +109,13 @@ create_xdelta()
 	newver="$pkgver"
 	newarch="$arch"
 
+	pkgsize="$(@SIZECMD@ -L "$newfile")"
+
+	if ((pkgsize < min_pkg_size)); then
+		msg "$(gettext "Skipping delta creation for small package: %s - size %s")" "$newname" "$pkgsize"
+		return 0
+	fi
+
 	if [[ $oldname != "$newname" ]]; then
 		error "$(gettext "The package names don't match : '%s' and '%s'")" "$oldname" "$newname"
 		return 1
@@ -119,10 +139,19 @@ create_xdelta()
 	if (( ret )); then
 		error "$(gettext "Delta could not be created.")"
 		return 1
-	else
-		msg "$(gettext "Generated delta : '%s'")" "$deltafile"
-		(( QUIET )) && echo "$deltafile"
 	fi
+
+	deltasize="$(@SIZECMD@ -L "$deltafile")"
+
+	if ((max_delta_size * pkgsize / 100 < deltasize)); then
+		msg "$(gettext "Delta package larger than maximum size. Removing.")"
+		rm -f "$deltafile"
+		return 0
+	fi
+
+	msg "$(gettext "Generated delta : '%s'")" "$deltafile"
+	(( QUIET )) && echo "$deltafile"
+
 	return 0
 }
 
@@ -134,6 +163,23 @@ while (( $# )); do
 		-h|--help)    usage; exit 0 ;;
 		-V|--version) version; exit 0 ;;
 		-q|--quiet) QUIET=1;;
+		--min-pkg-size)
+			if ! isnumeric "$2"; then
+				echo "invalid argument '$2' for option -- '$1'"
+				exit 1
+			fi
+			min_pkg_size=$2
+			shift
+			;;
+		--max-delta-size)
+			arg=$(echo "$2" | awk '{print $1 * 100}')
+			if ! isnumeric "$arg" || (($arg > 200)); then
+				echo "invalid argument '$2' for option -- '$1'"
+				exit 1
+			fi
+			max_delta_size=$arg
+			shift
+			;;
 		--) shift; args+=("$@"); break 2 ;;
 		-*) echo "invalid option -- '$1'"; usage; exit 1 ;;
 		*) args+=("$1");;
-- 
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