Pmodules/libstd.bash

- std::upvar(), std::upvars() added

Pmodules/libstd.bash

@@ -133,6 +133,115 @@ std::read_versions() {
 	done < "${fname}"
 }
 
+#--- upvars.sh ---------------------------------------------------------
+# Bash: Passing variables by reference
+# Copyright (C) 2010 Freddy Vulto
+# Version: upvars-0.9.dev
+# See: http://fvue.nl/wiki/Bash:_Passing_variables_by_reference
+#
+# 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/>.
+
+
+# Assign variable one scope above the caller
+# Usage: local "$1" && upvar $1 "value(s)"
+# Param: $1  Variable name to assign value to
+# Param: $*  Value(s) to assign.  If multiple values, an array is
+#            assigned, otherwise a single value is assigned.
+# NOTE: For assigning multiple variables, use 'upvars'.  Do NOT
+#       use multiple 'upvar' calls, since one 'upvar' call might
+#       reassign a variable to be used by another 'upvar' call.
+# Example: 
+#
+#    f() { local b; g b; echo $b; }
+#    g() { local "$1" && upvar $1 bar; }
+#    f  # Ok: b=bar
+#
+std::upvar() {
+    if unset -v "$1"; then           # Unset & validate varname
+        if (( $# == 2 )); then
+            eval $1=\"\$2\"          # Return single value
+        else
+            eval $1=\(\"\${@:2}\"\)  # Return array
+        fi
+    fi
+}
+
+
+# Assign variables one scope above the caller
+# Usage: local varname [varname ...] && 
+#        upvars [-v varname value] | [-aN varname [value ...]] ...
+# Available OPTIONS:
+#     -aN  Assign next N values to varname as array
+#     -v   Assign single value to varname
+# Return: 1 if error occurs
+# Example:
+#
+#    f() { local a b; g a b; declare -p a b; }
+#    g() {
+#        local c=( foo bar )
+#        local "$1" "$2" && upvars -v $1 A -a${#c[@]} $2 "${c[@]}"
+#    }
+#    f  # Ok: a=A, b=(foo bar)
+#
+std::upvars() {
+    if ! (( $# )); then
+        echo "${FUNCNAME[0]}: usage: ${FUNCNAME[0]} [-v varname"\
+            "value] | [-aN varname [value ...]] ..." 1>&2
+        return 2
+    fi
+    while (( $# )); do
+        case $1 in
+            -a*)
+                # Error checking
+                [[ ${1#-a} ]] || { echo "bash: ${FUNCNAME[0]}: \`$1': missing"\
+                    "number specifier" 1>&2; return 1; }
+                printf %d "${1#-a}" &> /dev/null || { echo "bash:"\
+                    "${FUNCNAME[0]}: \`$1': invalid number specifier" 1>&2
+                    return 1; }
+                # Assign array of -aN elements
+                [[ "$2" ]] && unset -v "$2" && eval $2=\(\"\${@:3:${1#-a}}\"\) && 
+                shift $((${1#-a} + 2)) || { echo "bash: ${FUNCNAME[0]}:"\
+                    "\`$1${2+ }$2': missing argument(s)" 1>&2; return 1; }
+                ;;
+            -v)
+                # Assign single value
+                [[ "$2" ]] && unset -v "$2" && eval $2=\"\$3\" &&
+                shift 3 || { echo "bash: ${FUNCNAME[0]}: $1: missing"\
+                "argument(s)" 1>&2; return 1; }
+                ;;
+            --help) echo "\
+Usage: local varname [varname ...] &&
+   ${FUNCNAME[0]} [-v varname value] | [-aN varname [value ...]] ...
+Available OPTIONS:
+-aN VARNAME [value ...]   assign next N values to varname as array
+-v VARNAME value          assign single value to varname
+--help                    display this help and exit
+--version                 output version information and exit"
+                return 0 ;;
+            --version) echo "\
+${FUNCNAME[0]}-0.9.dev
+Copyright (C) 2010 Freddy Vulto
+License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
+This is free software: you are free to change and redistribute it.
+There is NO WARRANTY, to the extent permitted by law."
+                return 0 ;;
+            *)
+                echo "bash: ${FUNCNAME[0]}: $1: invalid option" 1>&2
+                return 1 ;;
+        esac
+    done
+}
 
 # Local Variables:
 # mode: sh