#!/bin/bash
# Daniel Casimiro <dan.casimiro@gmail.com>
#

# Emulates:  hash[key]=value
# * This function is from:
#     http://tldp.org/LDP/abs/html/contributed-scripts.html#HASHLIB
#
# Params:
# 1 - hash
# 2 - key
# 3 - value
function hash_set {
	eval "${Hash_config_varname_prefix}${1}_${2}=\"${3}\""
}

# Emulates something similar to:
#   foreach($hash as $key => $value) { fun($key,$value); }
# * This function is from:
#     http://tldp.org/LDP/abs/html/contributed-scripts.html#HASHLIB
#
# It is possible to write different variations of this function.
# Here we use a function call to make it as "generic" as possible.
#
# Params:
# 1 - hash
# 2 - function name
function hash_foreach {
	local keyname oldIFS="$IFS"
	IFS=' '
	for i in $(eval "echo \${!${Hash_config_varname_prefix}${1}_*}"); do
		keyname=$(eval "echo \${i##${Hash_config_varname_prefix}${1}_}")
		eval "$2 $keyname \"\$$i\""
	done
	IFS="$oldIFS"
}

# UnionFS requires different versions for different kernels.
# This list is as of 27 October 2006.
# Kernel Version Compatibility:
# Kernel Version 	Unionfs Version
# 2.4.x (x>19) 	1.0.14
# 2.6.x (x<9) 	Not Supported
# 2.6.9 - 2.6.15 	1.1.5
# 2.6.16 	1.2
# 2.6.17 	1.3
# 2.6.18-rc 	CVS Snapshots

# $1 unionfs version
# $2 kernel version regular expression
test_unionfs_version() {
    MYKV=`expr match "${KV}" $2`
    if [ ${MYKV} -gt 0 ]; then
	# The keys cannot contain '.', so underscores are substituted here.
	UNIONFS_VERSION=${1/_/.}
    fi
}

# set kernel versions regular expressions and unionfs versions in config file
# build a hash that maps kernel version re's to unionfs version
# for each hash key, use the value when the key regular expression evals
# true when compared to ${BASEKV}
get_unionfs_version() {
    # Do not support 2.4 kernels yet; just need another RE.
    # The hash is hard coded here, but it could be built from variables defined
    # in /etc/genkernel.conf
    hash_set unionfsversions 1_1_5      "2\.6\.(9|1[0-5])-"
    hash_set unionfsversions 1_2        "2\.6\.16-"
    hash_set unionfsversions 1_3        "2\.6\.17-"

    # Unset the UNIONFS_VERSION that was set in /etc/genkernel.conf
    # This function could check if the variable is set, and then break
    # Or, it could use a different variable name
    UNIONFS_VERSION=
    hash_foreach unionfsversions test_unionfs_version

    if [ -z ${UNIONFS_VERSION} ]; then
	echo "Invalid kernel for UNIONFS!"
	exit 1
    fi
}