From a39c3c4520ecea31cf85d31741275657268a8cc8 Mon Sep 17 00:00:00 2001
From: Andrew Cady <d@jerkface.net>
Date: Wed, 30 Aug 2017 20:20:27 -0400
Subject: selfstrap: substantially improve performance

---
 multistrap/selfstrap | 41 +++++++++++++++++++++--------------------
 1 file changed, 21 insertions(+), 20 deletions(-)

diff --git a/multistrap/selfstrap b/multistrap/selfstrap
index 265049b..88dc07e 100755
--- a/multistrap/selfstrap
+++ b/multistrap/selfstrap
@@ -124,7 +124,7 @@ parse_apt_noact_line()
     return 1
 }
 
-extract_dpkg_info()
+dpkg_extract_with_info()
 {
     local deb="$1" TARGET="$2" multiarch="$3" command PKG
     PKG=${deb##*/}
@@ -137,9 +137,10 @@ f=$TARGET/var/lib/dpkg/info/$PKG.${TAR_FILENAME#./}
 cat > "$f"
 chmod $TAR_MODE "$f"
 '
-    (export PKG TARGET
-     dpkg --ctrl-tarfile "$deb" | tar -x --to-command "$command")
-    dpkg --fsys-tarfile "$deb" | tar -t | sed 's?^\.??; s?^/$?/.?; s?/$??' > "$TARGET/var/lib/dpkg/info/$PKG.list"
+    (export PKG TARGET; dpkg --ctrl-tarfile "$deb" | tar -x --to-command "$command")
+    dpkg --fsys-tarfile "$deb" |
+        (cd "$TARGET" && tar -xv) |
+        sed 's?^\.??; s?^/$?/.?; s?/$??' > "$TARGET/var/lib/dpkg/info/$PKG.list"
 
 }
 
@@ -148,11 +149,7 @@ apt_run_inst()
     apt_get -s -yqq install "$@" | while read line; do
         parse_apt_noact_line "$line" || die "unexpected output from apt-get: $line"
         export DPKG_MAINTSCRIPT_PACKAGE="$package" DPKG_MAINTSCRIPT_ARCH="$arch"
-        if is_multiarch_same "$package"; then
-            multiarch=":$arch"
-        else
-            multiarch=
-        fi
+        is_multiarch_same "$package" && multiarch=":$arch" || multiarch=
         case "$action" in
             Inst)
                 export DPKG_MAINTSCRIPT_NAME=preinst
@@ -189,11 +186,12 @@ apt_extract()
         case "$action" in
             Inst)
                 printf 'Extracting %s\n' "${deb##*/}" >&2
-                dpkg-deb --extract "$deb" "$rootfs"
 
                 if [ "$EXTRACT_DPKG_INFO" ]; then
                     is_multiarch_same "$package" && multiarch=":$arch" || multiarch=
-                    extract_dpkg_info "$deb" "$rootfs" "$multiarch"
+                    dpkg_extract_with_info "$deb" "$rootfs" "$multiarch"
+                else
+                    dpkg-deb --extract "$deb" "$rootfs"
                 fi
                 ;;
             Conf)
@@ -227,13 +225,19 @@ required_packages()
          "$(main_packages_file)" | sort -u
 }
 
-multiarch_same_packages()
+declare -A is_multiarch_same
+multicheck()
 {
-    [ "$multiarch_same_packages" ] || multiarch_same_packages=$(multiarch_same_packages_)
-    echo "$multiarch_same_packages"
+    local m
+    if [ ! "$multichecked" ]; then
+        for m in $(multiarch_same_packages); do
+            is_multiarch_same[$m]=y
+        done
+    fi
+    multichecked=y
 }
 
-multiarch_same_packages_()
+multiarch_same_packages()
 {
     perl -00 -ne \
          '/^Multi-Arch: same/mi || next; /^Package: (.*)$/m && print "$1\n"' \
@@ -242,11 +246,8 @@ multiarch_same_packages_()
 
 is_multiarch_same()
 {
-    local p
-    for p in $(multiarch_same_packages); do
-        [ "$1" = "$p" ] && return
-    done
-    return 1
+    multicheck
+    [ "${is_multiarch_same[$1]}" ]
 }
 
 set -e
-- 
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