some people pointed out typos/bugs, so here's v2
-mike

--- eutils.eclass       14 Dec 2011 17:36:18 -0000      1.372
+++ eutils.eclass       14 Dec 2011 23:46:37 -0000
@@ -100,6 +100,54 @@ esvn_clean() {
        find "$@" -type d -name '.svn' -prune -print0 | xargs -0 rm -rf
 }
 
+# @FUNCTION: estack_push
+# @USAGE: <stack> [items to push]
+# @DESCRIPTION:
+# Push any number of items onto the specified stack.  Pick a name that
+# is a valid variable (i.e. stick to alphanumerics), and push as many
+# items as you like onto the stack at once.
+#
+# The following code snippet will echo 5, then 4, then 3, then ...
+# @CODE
+#              estack_push mystack 1 2 3 4 5
+#              while estack_pop mystack i ; do
+#                      echo ${i}
+#              done
+# @CODE
+estack_push() {
+       [[ $# -eq 0 ]] && die "estack_push: incorrect # of arguments"
+       local stack_name="__ESTACK_$1__" ; shift
+       eval ${stack_name}+=\( \"\$@\" \)
+}
+
+# @FUNCTION: estack_pop
+# @USAGE: <stack> [variable]
+# @DESCRIPTION:
+# Pop a single item off the specified stack.  If a variable is specified,
+# the popped item is stored there.  If no more items are available, return
+# 1, else return 0.  See estack_push for more info.
+estack_pop() {
+       ( [[ $# -eq 0 ]] || [[ $# -gt 2 ]] ) && die "estack_pop: incorrect # of 
arguments"
+
+       # We use the fugly __estack_xxx var names to avoid collision with
+       # passing back the return value.  If we used "local i" and the
+       # caller ran `estack_pop ... i`, we'd end up setting the local
+       # copy of "i" rather than the caller's copy.  The __estack_xxx
+       # garbage is preferable to using $1/$2 everywhere as that is a
+       # bit harder to read.
+       local __estack_name="__ESTACK_$1__" ; shift
+       local __estack_retvar=$1 ; shift
+       eval local __estack_i=\${#${__estack_name}[@]}
+       # Don't warn -- let the caller interpret this as a failure
+       # or as normal behavior (akin to `shift`)
+       [[ $(( --__estack_i )) -eq -1 ]] && return 1
+
+       if [[ -n ${__estack_retvar} ]] ; then
+               eval ${__estack_retvar}=\"\${${__estack_name}[${__estack_i}]}\"
+       fi
+       eval unset ${__estack_name}[${__estack_i}]
+}
+
 # @FUNCTION: eshopts_push
 # @USAGE: [options to `set` or `shopt`]
 # @DESCRIPTION:
@@ -126,15 +174,14 @@ esvn_clean() {
 eshopts_push() {
        # have to assume __ESHOPTS_SAVE__ isn't screwed with
        # as a `declare -a` here will reset its value
-       local i=${#__ESHOPTS_SAVE__[@]}
        if [[ $1 == -[su] ]] ; then
-               __ESHOPTS_SAVE__[$i]=$(shopt -p)
+               estack_push eshopts "$(shopt -p)"
                [[ $# -eq 0 ]] && return 0
                shopt "$@" || die "eshopts_push: bad options to shopt: $*"
        else
-               __ESHOPTS_SAVE__[$i]=$-
+               estack_push eshopts $-
                [[ $# -eq 0 ]] && return 0
                set "$@" || die "eshopts_push: bad options to set: $*"
        fi
 }
 
@@ -144,19 +191,36 @@ eshopts_push() {
 # Restore the shell options to the state saved with the corresponding
 # eshopts_push call.  See that function for more details.
 eshopts_pop() {
-       [[ $# -ne 0 ]] && die "eshopts_pop takes no arguments"
-       local i=$(( ${#__ESHOPTS_SAVE__[@]} - 1 ))
-       [[ ${i} -eq -1 ]] && die "eshopts_{push,pop}: unbalanced pair"
-       local s=${__ESHOPTS_SAVE__[$i]}
-       unset __ESHOPTS_SAVE__[$i]
+       local s
+       estack_pop eshopts s || die "${FUNCNAME}: unbalanced push"
        if [[ ${s} == "shopt -"* ]] ; then
                eval "${s}" || die "eshopts_pop: sanity: invalid shopt options: 
${s}"
        else
                set +$-     || die "eshopts_pop: sanity: invalid shell 
settings: $-"
                set -${s}   || die "eshopts_pop: sanity: unable to restore 
saved shell settings: ${s}"
        fi
 }
 
+# @FUNCTION: eumask_push
+# @USAGE: <new umask>
+# @DESCRIPTION:
+# Set the umask to the new value specified while saving the previous
+# value onto a stack.  Useful for temporarily changing the umask.
+eumask_push() {
+       estack_push eumask "$(umask)"
+       umask "$@" || die "${FUNCNAME}: bad options to umask: $*"
+}
+
+# @FUNCTION: eumask_pop
+# @USAGE:
+# @DESCRIPTION:
+# Restore the previous umask state.
+eumask_pop() {
+       local s
+       estack_pop eumask s || die "${FUNCNAME}: unbalanced push"
+       umask ${s} || die "${FUNCNAME}: sanity: could not restore umask: ${s}"
+}
+
 # @VARIABLE: EPATCH_SOURCE
 # @DESCRIPTION:
 # Default directory to search for patches.

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