# Copyright 1999-2017 Gentoo Foundation # Distributed under the terms of the GNU General Public License v2 # @ECLASS: estack.eclass # @MAINTAINER: # base-system@gentoo.org # @BLURB: stack-like value storage support # @DESCRIPTION: # Support for storing values on stack-like variables. if [[ -z ${_ESTACK_ECLASS} ]]; then # @FUNCTION: estack_push # @USAGE: <stack> [items to push] # @DESCRIPTION: # Push any number of items onto the specified stack. Pick a name that # is a valid variable (i.e. stick to alphanumerics), and push as many # items as you like onto the stack at once. # # The following code snippet will echo 5, then 4, then 3, then ... # @CODE # estack_push mystack 1 2 3 4 5 # while estack_pop mystack i ; do # echo "${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: evar_push # @USAGE: <variable to save> [more vars to save] # @DESCRIPTION: # This let's you temporarily modify a variable and then restore it (including # set vs unset semantics). Arrays are not supported at this time. # # This is meant for variables where using `local` does not work (such as # exported variables, or only temporarily changing things in a func). # # For example: # @CODE # evar_push LC_ALL # export LC_ALL=C # ... do some stuff that needs LC_ALL=C set ... # evar_pop # # # You can also save/restore more than one var at a time # evar_push BUTTERFLY IN THE SKY # ... do stuff with the vars ... # evar_pop # This restores just one var, SKY # ... do more stuff ... # evar_pop 3 # This pops the remaining 3 vars # @CODE evar_push() { local var val for var ; do [[ ${!var+set} == "set" ]] \ && val=${!var} \ || val="unset_76fc3c462065bb4ca959f939e6793f94" estack_push evar "${var}" "${val}" done } # @FUNCTION: evar_push_set # @USAGE: <variable to save> [new value to store] # @DESCRIPTION: # This is a handy shortcut to save and temporarily set a variable. If a value # is not specified, the var will be unset. evar_push_set() { local var=$1 evar_push ${var} case $# in 1) unset ${var} ;; 2) printf -v "${var}" '%s' "$2" ;; *) die "${FUNCNAME}: incorrect # of args: $*" ;; esac } # @FUNCTION: evar_pop # @USAGE: [number of vars to restore] # @DESCRIPTION: # Restore the variables to the state saved with the corresponding # evar_push call. See that function for more details. evar_pop() { local cnt=${1:-bad} case $# in 0) cnt=1 ;; 1) isdigit "${cnt}" || die "${FUNCNAME}: first arg must be a number: $*" ;; *) die "${FUNCNAME}: only accepts one arg: $*" ;; esac local var val while (( cnt-- )) ; do estack_pop evar val || die "${FUNCNAME}: unbalanced push" estack_pop evar var || die "${FUNCNAME}: unbalanced push" [[ ${val} == "unset_76fc3c462065bb4ca959f939e6793f94" ]] \ && unset ${var} \ || printf -v "${var}" '%s' "${val}" done } # @FUNCTION: eshopts_push # @USAGE: [options to `set` or `shopt`] # @DESCRIPTION: # Often times code will want to enable a shell option to change code behavior. # Since changing shell options can easily break other pieces of code (which # assume the default state), eshopts_push is used to (1) push the current shell # options onto a stack and (2) pass the specified arguments to set. # # If the first argument is '-s' or '-u', we assume you want to call `shopt` # rather than `set` as there are some options only available via that. # # A common example is to disable shell globbing so that special meaning/care # may be used with variables/arguments to custom functions. That would be: # @CODE # eshopts_push -o noglob # for x in ${foo} ; do # if ...some check... ; then # eshopts_pop # return 0 # fi # done # eshopts_pop # @CODE eshopts_push() { if [[ $1 == -[su] ]] ; then estack_push eshopts "$(shopt -p)" [[ $# -eq 0 ]] && return 0 shopt "$@" || die "${FUNCNAME}: bad options to shopt: $*" else estack_push eshopts "$(shopt -p -o)" [[ $# -eq 0 ]] && return 0 set "$@" || die "${FUNCNAME}: bad options to set: $*" fi } # @FUNCTION: eshopts_pop # @USAGE: # @DESCRIPTION: # Restore the shell options to the state saved with the corresponding # eshopts_push call. See that function for more details. eshopts_pop() { local s estack_pop eshopts s || die "${FUNCNAME}: unbalanced push" eval "${s}" || die "${FUNCNAME}: sanity: invalid shopt options: ${s}" } # @FUNCTION: eumask_push # @USAGE: <new umask> # @DESCRIPTION: # Set the umask to the new value specified while saving the previous # value onto a stack. Useful for temporarily changing the umask. eumask_push() { estack_push eumask "$(umask)" umask "$@" || die "${FUNCNAME}: bad options to umask: $*" } # @FUNCTION: eumask_pop # @USAGE: # @DESCRIPTION: # Restore the previous umask state. eumask_pop() { [[ $# -eq 0 ]] || die "${FUNCNAME}: we take no options" local s estack_pop eumask s || die "${FUNCNAME}: unbalanced push" umask ${s} || die "${FUNCNAME}: sanity: could not restore umask: ${s}" } # @FUNCTION: isdigit # @USAGE: <number> [more numbers] # @DESCRIPTION: # Return true if all arguments are numbers. isdigit() { local d for d ; do [[ ${d:-bad} == *[!0-9]* ]] && return 1 done return 0 } _ESTACK_ECLASS=1 fi #_ESTACK_ECLASS