LDP/LDP/guide/docbook/abs-guide/Hash.lib

# Hash:
# Hash function library
# Author: Mariusz Gniazdowski <mariusz.gn-at-gmail.com>
# Date: 2005-04-07

# Functions making emulating hashes in Bash a little less painful.


#    Limitations:
#  * Only global variables are supported.
#  * Each hash instance generates one global variable per value.
#  * Variable names collisions are possible
#+   if you define variable like __hash__hashname_key
#  * Keys must use chars that can be part of a Bash variable name
#+   (no dashes, periods, etc.).
#  * The hash is created as a variable:
#    ... hashname_keyname
#    So if somone will create hashes like:
#      myhash_ + mykey = myhash__mykey
#      myhash + _mykey = myhash__mykey
#    Then there will be a collision.
#    (This should not pose a major problem.)


Hash_config_varname_prefix=__hash__


# Emulates:  hash[key]=value
#
# Params:
# 1 - hash
# 2 - key
# 3 - value
function hash_set {
	eval "${Hash_config_varname_prefix}${1}_${2}=\"${3}\""
}


# Emulates:  value=hash[key]
#
# Params:
# 1 - hash
# 2 - key
# 3 - value (name of global variable to set)
function hash_get_into {
	eval "$3=\"\$${Hash_config_varname_prefix}${1}_${2}\""
}


# Emulates:  echo hash[key]
#
# Params:
# 1 - hash
# 2 - key
# 3 - echo params (like -n, for example)
function hash_echo {
	eval "echo $3 \"\$${Hash_config_varname_prefix}${1}_${2}\""
}


# Emulates:  hash1[key1]=hash2[key2]
#
# Params:
# 1 - hash1
# 2 - key1
# 3 - hash2
# 4 - key2
function hash_copy {
eval "${Hash_config_varname_prefix}${1}_${2}\
=\"\$${Hash_config_varname_prefix}${3}_${4}\""
}


# Emulates:  hash[keyN-1]=hash[key2]=...hash[key1]
#
# Copies first key to rest of keys.
#
# Params:
# 1 - hash1
# 2 - key1
# 3 - key2
# . . .
# N - keyN
function hash_dup {
  local hashName="$1" keyName="$2"
  shift 2
  until [ ${#} -le 0 ]; do
    eval "${Hash_config_varname_prefix}${hashName}_${1}\
=\"\$${Hash_config_varname_prefix}${hashName}_${keyName}\""
  shift;
  done;
}


# Emulates:  unset hash[key]
#
# Params:
# 1 - hash
# 2 - key
function hash_unset {
	eval "unset ${Hash_config_varname_prefix}${1}_${2}"
}


# Emulates something similar to:  ref=&hash[key]
#
# The reference is name of the variable in which value is held.
#
# Params:
# 1 - hash
# 2 - key
# 3 - ref - Name of global variable to set.
function hash_get_ref_into {
	eval "$3=\"${Hash_config_varname_prefix}${1}_${2}\""
}


# Emulates something similar to:  echo &hash[key]
#
# That reference is name of variable in which value is held.
#
# Params:
# 1 - hash
# 2 - key
# 3 - echo params (like -n for example)
function hash_echo_ref {
	eval "echo $3 \"${Hash_config_varname_prefix}${1}_${2}\""
}



# Emulates something similar to:  $$hash[key](param1, param2, ...)
#
# Params:
# 1 - hash
# 2 - key
# 3,4, ... - Function parameters
function hash_call {
  local hash key
  hash=$1
  key=$2
  shift 2
  eval "eval \"\$${Hash_config_varname_prefix}${hash}_${key} \\\"\\\$@\\\"\""
}


# Emulates something similar to:  isset(hash[key]) or hash[key]==NULL
#
# Params:
# 1 - hash
# 2 - key
# Returns:
# 0 - there is such key
# 1 - there is no such key
function hash_is_set {
  eval "if [[ \"\${${Hash_config_varname_prefix}${1}_${2}-a}\" = \"a\" && 
  \"\${${Hash_config_varname_prefix}${1}_${2}-b}\" = \"b\" ]]
    then return 1; else return 0; fi"
}


# Emulates something similar to:
#   foreach($hash as $key => $value) { fun($key,$value); }
#
# It is possible to write different variations of this function.
# Here we use a function call to make it as "generic" as possible.
#
# Params:
# 1 - hash
# 2 - function name
function hash_foreach {
  local keyname oldIFS="$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"
}

#  NOTE: In lines 103 and 116, ampersand changed.
#  But, it doesn't matter, because these are comment lines anyhow.