Settings.pm

#-------------------------------------------------------------------------------
#  University of Applied Sciences Technikum Wien
#
#  Department of Embedded Systems
#  http://embsys.technikum-wien.at
#
#  Josef Ressel Center for Verification of Embedded Computing Systems
#  http://vecs.technikum-wien.at
#
#-------------------------------------------------------------------------------
#  File:              Settings.pm
#  Created on:        16.02.2015
#  $LastChangedBy$
#  $LastChangedDate$
#
#  Description:
#
# Contains helper functions to deal with FIJI Settings files.
#-------------------------------------------------------------------------------

## @file Settings.pm
# @brief Contains class \ref FIJI::Settings

## @class FIJI::Settings
#
# @brief Contains helper functions to deal with FIJI Settings files.
package FIJI::Settings;

use strict;
use warnings;

use Scalar::Util 'blessed';
use Log::Log4perl qw(get_logger);
use Scalar::Util "looks_like_number";
use Data::Dumper;
use POSIX qw(ceil);
use List::Util qw(max);
use File::Spec;

use FIJI::ConfigSorted;
use FIJI qw(:all);

## @var @base_resources stores the resource count for default config
my @base_resources;

## @function public new ($phase, $fiji_ini_file, $existing_settings)
# Create a new settings instance.
#
# \param phase Tool flow phase the settings need to be compatible with.
# \param fiji_ini_file (optional) Path to the configuration file to read.
# \param existing_settings (optional) A reference to reuse and return
#        with values read from file. Any contained data will be cleared.
# \returns The new settings instance (or undef in the case of an error)
#          and a diagnostic string describing the reason why it could not be created (undef if successful)
sub new ($;$$) {
    my $logger = get_logger("");
    my ($class, $phase, $fiji_ini_file, $existing_settings) = @_;

    my $fiji_settings_ref;

    # if there is no existing settings instance yet, create one
    if (!defined($existing_settings)) {
        $fiji_settings_ref = {};
        $fiji_settings_ref = bless($fiji_settings_ref, $class);
    } else {
        $fiji_settings_ref = $existing_settings;
    }
    if (!blessed($fiji_settings_ref) || !$fiji_settings_ref->isa("FIJI::Settings")) {
        my $msg;
        if (!defined($existing_settings)) {
            $msg = "Could not create FIJI::Settings instance.";
        } else {
            $msg = "Given settings are not of type FIJI::Settings.";
        }
        $logger->error($msg);
        return (undef, $msg);
    }

    my $warn;
    # If there is a file given, try to read it. Else just create a default instance.
    if (defined($fiji_ini_file)) {
        ($fiji_settings_ref, $warn) = read_settingsfile($phase, $fiji_ini_file, $fiji_settings_ref);
        if (!defined($fiji_settings_ref)) {
            return ($fiji_settings_ref, $warn);
        }
        $fiji_settings_ref->{'filename'} = $fiji_ini_file;
    } else {
        $fiji_settings_ref->{'design'} = {};
        _set_defaults(DESIGNMAP, $fiji_settings_ref->{'design'}, $phase);
        $fiji_settings_ref->{'fius'}     = [];
        $fiji_settings_ref->{'filename'} = File::Spec->curdir();
    }

    @base_resources = _est_resources(DESIGNMAP->{'FREQUENCY'}->{'default'}, DESIGNMAP->{'BAUDRATE'}->{'default'}, DESIGNMAP->{'TIMER_WIDTH'}->{'default'}, DESIGNMAP->{'RESET_DUT_IN_DURATION'}->{'default'}, DESIGNMAP->{'LFSR_WIDTH'}->{'default'}, 1, "logarithmic");

    return ($fiji_settings_ref, $warn);
}

sub _export_value {
    my $logger = get_logger("");
    my ($map_ref, $k, $v_ref) = @_;

    if (defined($map_ref->{$k}->{'type'})) {
        my $orig = ${$v_ref};
        if ($map_ref->{$k}->{'type'} eq 'hexadecimal' || $map_ref->{$k}->{'type'} eq 'lfsrpoly') {
            ${$v_ref} = sprintf("0x%x", $orig);

            # } elsif ($map_ref->{$k}->{'type'} eq 'natural') {
            # } elsif ($map_ref->{$k}->{'type'} eq 'boolean') {
            $logger->trace("Converted value of $k (\"$orig\") to \"${$v_ref}\".") if ($orig ne ${$v_ref});
        } elsif ($map_ref->{$k}->{'type'} eq 'net') {
            # Due to an annoying behavior of Config::Simple we have to enclose
            # escaped identifiers with quotes. These are necessary to preserve spaces.
            if (substr($orig, -1) eq ' ') {
                ${$v_ref} = "\"$orig\"";
            }
        }
    }
}

## @method public save ($fiji_ini_file)
# @brief Store contained FIJI Settings to file.
#
# @attention Will happily overwrite existing files!
#
# @param fiji_ini_file The file name to write the FIJI Settings to.
sub save ($) {
    my $logger = get_logger("");
    my ($self, $fiji_ini_file) = @_;
    return "No file name given" if !defined($fiji_ini_file);

    my $fiji_ini = new FIJI::ConfigSorted(syntax => 'ini');
    my $design_ref;
    my $fiu_cnt = 0;
    foreach my $key (keys %{$self}) {
        my $val = $self->{$key};
        if (ref(\$val) eq "REF") {
            if (ref($val) eq "HASH") {
                if ($key eq "design") {
                    $design_ref = $val;
                    next;
                }
            } elsif (ref($val) eq "ARRAY") {
                if ($key eq "fius") {
                    foreach my $fiu (@{$val}) {
                        my $ini_fiu;

                        foreach my $k (keys(%{$fiu})) {
                            my $ini_name = FIUMAP->{$k}->{'ini_name'};
                            if (!defined($fiu->{$k})) {
                                $logger->debug("Skip saving undefined value of FIU constant with key $ini_name.");
                                next;
                            }

                            # Copy value to new hash with external naming.
                            $ini_fiu->{$ini_name} = $fiu->{$k};

                            # Convert value to external representation
                            _export_value(FIUMAP, $k, \$ini_fiu->{$ini_name});
                            $logger->trace(sprintf("Exporting FIU%d setting %s -> %s (%s -> %s).", $fiu_cnt, $k, $ini_name, defined($fiu->{$k}) ? $fiu->{$k} : "undef", defined($ini_fiu->{$ini_name}) ? $ini_fiu->{$ini_name} : "undef"),);
                        }
                        $fiji_ini->set_block("FIU" . $fiu_cnt++, $ini_fiu);
                    }
                    next;
                }
            }
        } elsif ($key eq "filename") {
            next;
        }

        my $err = "Unknown element found in FIJI Settings: key: \"$key\" val: \"$val\"";
        $logger->error($err);
        return $err;
    }
    $design_ref->{'FIU_NUM'} = $fiu_cnt;
    my $ini_design;
    foreach my $k (keys(%{$design_ref})) {
        my $ini_name = DESIGNMAP->{$k}->{'ini_name'};
        if (!defined($design_ref->{$k})) {
            $logger->debug("Skip saving undefined value of design constant with key $ini_name.");
            next;
        }

        # Copy value to new hash with external naming.
        $ini_design->{$ini_name} = $design_ref->{$k};

        # Convert value to external representation
        _export_value(DESIGNMAP, $k, \$ini_design->{$ini_name});
        $logger->trace(sprintf("Exporting Design setting %s -> %s (%s -> %s).", $k, $ini_name, defined($design_ref->{$k}) ? $design_ref->{$k} : "undef", defined($ini_design->{$ini_name}) ? $ini_design->{$ini_name} : "undef"),);
    }
    $fiji_ini->set_block("CONSTS", $ini_design);

    if (!defined($fiji_ini->write($fiji_ini_file))) {
        my $err = FIJI::ConfigSorted->error();
        $logger->error($err);
        return $err;
    }
    $self->{'filename'} = $fiji_ini_file;
    return undef;
}

## @function public read_settingsfile ($phase, $fiji_ini_file)
# @brief Load the FIJI Settings file containing design and FIU constants.
#
# @param phase  Tool flow phase the settings stored in the given file
#               need to be compatible with.
# @param fiji_ini_file The name of an .ini file with FIJI Settings:
#         - a 'consts' block containing the constants specified by
#           \ref _sanitize_design.
#         - at least one FIU block named "FIU<number>" where "<number>"
#           is a strictly increasing integer starting with 0 containing
#           the constants for the respective FIU, see \ref _sanitize_fiu
#
# @returns a reference to the hash containing the read constants (or undef in the case of an error)
#          and a diagnostic string describing the reason why it could not be created (undef if successful)
sub read_settingsfile ($$$) {
    my $logger = get_logger("");
    my ($phase, $fiji_ini_file, $existing_settings) = @_;
    my $fiji_ini;
    eval { $fiji_ini = new FIJI::ConfigSorted($fiji_ini_file) };    # pesky library tries to die on syntax errors
    if (!defined($fiji_ini)) {
        my $submsg = defined($@) ? $@ : FIJI::ConfigSorted->error();
        if (length($submsg) == 0) {
            $submsg = "Empty file?";
        }
        my $msg = "Could not read config file \"$fiji_ini_file\": $submsg";
        $logger->error($msg);
        return (undef, $msg);
    }

    my $design_ref = $fiji_ini->get_block("CONSTS");
    if (!(%$design_ref)) {
        my $msg = "Could not fetch CONSTS block from config file \"$fiji_ini_file\"";
        $logger->error($msg);
        return (undef, $msg);
    }
    _set_defaults(DESIGNMAP, $design_ref, $phase);

    $design_ref = _rename_import(DESIGNMAP, $design_ref);
    if (!defined($design_ref)) {
        my $msg = "Design constants do not match the FIJI Settings naming scheme.";
        $logger->error($msg);
        return (undef, $msg);
    }

    # Create a new instance or reuse the shallow hull of the existing one
    my $fiji_settings_ref;
    if (!defined($existing_settings)) {
        $fiji_settings_ref = {};
        bless($fiji_settings_ref, "FIJI::Settings");
    } else {
        $fiji_settings_ref = $existing_settings;

        # Clear the hash
        for (keys %$fiji_settings_ref) {
            delete $fiji_settings_ref->{$_};
        }
    }
    if (!blessed($fiji_settings_ref) || !$fiji_settings_ref->isa("FIJI::Settings")) {
        my $msg;
        if (!defined($existing_settings)) {
            $msg = "Could not create FIJI::Settings instance.";
        } else {
            $msg = "Given settings are not of type FIJI::Settings.";
        }
        $logger->error($msg);
        return (undef, $msg);
    }
    $fiji_settings_ref->{'design'} = $design_ref;
    $fiji_settings_ref->{'fius'}   = [];

    # sanitize and validate read design constants
    $design_ref = _sanitize_design($design_ref, $phase);
    if (!ref($design_ref)) {
        $logger->error($design_ref);
        return (undef, $design_ref);
    }

    my $fiu_num = 0;
    my $dup = {};
    my $warn;
    # loop over all read fius
    while (1) {

        my $fiu_name = "FIU" . $fiu_num;
        my $fiu_ref  = $fiji_ini->get_block($fiu_name);
        if (!(%$fiu_ref)) {
            last;
        }
        $fiu_ref = _rename_import(FIUMAP, $fiu_ref);
        if (!defined($design_ref)) {
            my $msg = "FIU constants of $fiu_name do not match the FIJI Settings naming scheme.";
            $logger->error($msg);
            return (undef, $msg);
        }

        my $tmp_fiu = {};
        _set_defaults(FIUMAP, $tmp_fiu, $phase);

        # overwrite default entries
        foreach my $k (keys(%{$fiu_ref})) {
            $tmp_fiu->{$k} = $fiu_ref->{$k};
        }
        $fiu_ref = $tmp_fiu;

        $fiu_ref = _sanitize_fiu($fiu_ref, $phase);
        if (!ref($fiu_ref)) {
            my $msg = "(Some) constants for $fiu_name in FIJI Settings are invalid.";
            $logger->error($msg);
            return (undef, $msg);
        }

        if (defined $dup->{$fiu_ref->{'FIU_NET_NAME'}}) {
            my $msg = "More than one FIU attached to ".$fiu_ref->{'FIU_NET_NAME'};
            $logger->error($msg);
            $warn .= $msg;
        } else {
            $dup->{$fiu_ref->{'FIU_NET_NAME'}} = 1;
        }

        $fiji_settings_ref->{'fius'}->[$fiu_num] = $fiu_ref;
        $fiu_num++;
        $logger->trace("Read in $fiu_name from FIJI Settings file successfully.");
    }

    if ($fiu_num == 0) {
        $logger->debug("Could not fetch any FIU blocks from config file \"$fiji_ini_file\"");
    }

    # FIU_NUM is optional in the Settings file... if it was set check that
    # it corresponds to the number of FIU<number> blocks.
    if (defined($design_ref->{'FIU_NUM'}) && $design_ref->{'FIU_NUM'} != $fiu_num) {
        my $msg = FIU_NUM->{'ini_name'} . " does not match the numbers of FIU blocks found.";
        $logger->error($msg);
        return (undef, $msg);
    } else {
        $design_ref->{'FIU_NUM'} = $fiu_num;    # assume the best if FIU_NUM constant is not given
    }

    splice(@{$fiji_settings_ref->{'fius'}}, $fiu_num);
    $logger->info("Successfully read in design constants and $fiu_num FIU definitions from FIJI Settings file \"$fiji_ini_file\".");
    return ($fiji_settings_ref, $warn);
}

## @method public set_fiu_defaults (%$fiu_ref)
# @brief Overwrite existing fields (if defined) with defaults defined in FIJI.pm.
#
sub set_fiu_defaults ($) {
    my ($self, $consts_ref) = @_;
    return _set_defaults(FIUMAP, $consts_ref);
}

## @function _set_defaults (%$map_ref, %$consts_ref)
# @brief Set defaults according to FIJI.pm.
sub _set_defaults {
    my $logger = get_logger("");
    my ($map_ref, $consts_ref, $phase) = @_;
    foreach my $k (keys(%{$map_ref})) {
        if (exists($map_ref->{$k}->{'default'})) {

            # Set default only if it is not mandatory in the given phase.
            if (defined($phase) && scalar(grep { $_ eq $phase } @{$map_ref->{$k}->{'phases_opt'}}) == 0) {
                next;
            }

            # Also, do not overwrite existing values
            if (defined($consts_ref->{$k})) {
                next;
            }
            $consts_ref->{$k} = $map_ref->{$k}->{default};
            $logger->trace(sprintf("Adding default constant: %s (%s) = %s.", $k, $map_ref->{$k}->{'ini_name'}, $map_ref->{$k}->{default}));
        }
    }
}

sub validate_design_value {
    my ($k, $v_ref) = @_;
    return validate_value(DESIGNMAP, $k, $v_ref);
}

sub validate_fiu_value {
    my ($k, $v_ref) = @_;
    return validate_value(FIUMAP, $k, $v_ref);
}

## @function validate_value (%$map_ref, $k, $$v_ref, $old, $log_func)
#   Do validation (and conversation from external->internal representation)
#
#   \param map_ref  reference to FIJI Settings mappings
#   \param k        key identifying the respective setting
#   \param v_ref    scalar reference to the proposed value (that may be modified)
#   \param dep_ref    scalar reference to a value the proposed value depends on
#   \param old      (optional) previously valid value
#   \param log_func (optional) the (log4perl) log function to use
#                   (defaul is \&Log::Log4perl::Logger::trace)
sub validate_value {
    my $logger = get_logger("");
    my ($map_ref, $k, $v_ref, $dep_ref, $old, $log_func) = @_;
    $log_func = \&Log::Log4perl::Logger::trace if !defined($log_func);
    if (defined($map_ref->{$k}->{'type'})) {
        my $orig = ${$v_ref};

        # @FIXME: check if the constant is depending on another constant, that needs to be enabled.
        # my $dependency = @{$map_ref->{$k}->{'depends_on'}};
        # if (defined($dependency) && defined(@{$map_ref->{$dependency}->{'value'}}
        # }

        if ($map_ref->{$k}->{'type'} eq 'net') {
            # @TODO: check syntax? there is nothing more to do in here unless we supply allowed nets...
            # which is actually possible because the input netlist is stored in the settings as well
        } elsif ($map_ref->{$k}->{'type'} eq 'hexadecimal' || $map_ref->{$k}->{'type'} eq 'lfsrpoly') {
            if ($orig !~ /^(0|(0[xX][[:xdigit:]]+))$/) {
                $log_func->($logger, "$k: $orig does not look like a natural hexadecimal number.");
                return 0;
            }
            ${$v_ref} = hex($orig);

            # Check for natural value range. Should never trigger due to the regex above.
            if (${$v_ref} < 0) {
                $log_func->($logger, "$k: $orig is negative.");
                return 0;
            }
        } elsif ($map_ref->{$k}->{'type'} eq 'natural') {

            # Match hexadecimal, binary, octal and decimal numbers (the latter also in scientific notation)
            if ($orig !~ /^(0|(0(x[0-9a-fA-F]+|[0-7]+))|(0b[01]+)|([1-9][0-9]*(e(-[0-9])?[0-9]+)?))$/) {
                $log_func->($logger, "$k: $orig does not look like a number.");
                return 0;
            }

            # convert non-decimal (hexadecimal, binary, octal) values to decimal
            ${$v_ref} = oct($orig) if $orig =~ /^0/;
            if (!looks_like_number(${$v_ref})) {
                $log_func->($logger, "$k: $orig does not look like a number.");
                return 0;
            }

            # Check for natural value range. Should never trigger due to the regex above.
            if (${$v_ref} < 0) {
                $log_func->($logger, "$k: $orig is negative.");
                return 0;
            }
        } elsif ($map_ref->{$k}->{'type'} eq 'boolean') {

            # convert strings to binary if need be
            if (!defined($orig)) {
                $log_func->($logger, "$k: \"undef\" is not a boolean value.");
                return 0;
            } elsif (lc($orig) eq 'true') {
                $orig = 1;
            } elsif (lc($orig) eq 'false') {
                $orig = 0;
            }
            if (($orig ne '0') && ($orig ne '1')) {
                $log_func->($logger, "$k: \"$orig\" does not look like a boolean value.");
                return 0;
            }

            # ensure proper boolean value, i.e. 0 or 1
            ${$v_ref} = (!!$orig) ? 1 : 0;
        }
        $logger->trace("Converted value of $k (\"$orig\") to \"${$v_ref}\".") if (defined($orig) && $orig ne ${$v_ref});
    }

    if (defined($map_ref->{$k}->{'values'})) {
        my $values_ref = $map_ref->{$k}->{'values'};
        my $dep_val;
        if (ref $dep_ref eq 'SCALAR') {
            $dep_val = $dep_ref;
        }

        if (ref($values_ref) eq 'ARRAY') {

            # Look for given value in allowed values
            if (scalar(grep { $_ eq ${$v_ref} } @{$values_ref}) == 0) {
                $log_func->($logger, "$k: ${$v_ref} is not allowed. Allowed values are: " . join(", ", @{$map_ref->{$k}->{'values'}}));
                return 0;
            }
        } elsif (ref($values_ref) eq 'CODE') {
            if (!$values_ref->(${$v_ref}, $old, $$dep_val)) {
                $log_func->($logger, "$k: ${$v_ref} is not allowed.");
                return 0;
            }
        }
    }
    return 1;
}

# @function _rename_import (%$map_ref, %$consts_ref)
# Rename and convert entries in consts_ref according to map_ref.
#
# This function takes a hash of FIJI Settings and converts its keys
# to the respective internal representation. This allows us to use different
# name representations in the external file than within the implementation.
#
#
# \returns $consts_ref, or undef on errors
sub _rename_import {
    my $logger = get_logger("");
    my ($map_ref, $consts_ref) = @_;
    if (ref($consts_ref) ne 'HASH') {
        $logger->error("Parameter is not a reference to a hash (containing design constants).");
        return undef;
    }

    # Iterating over respective hash from FIJI.pm and rename the entries
    # to match our internal naming scheme.
    foreach my $k (keys(%{$map_ref})) {
        my $ini_name = $map_ref->{$k}->{'ini_name'};
        if (exists($consts_ref->{$ini_name}) && $ini_name ne $k) {
            $consts_ref->{$k} = $consts_ref->{$ini_name};
            $logger->trace(sprintf("Renaming Design setting %s -> %s (=%s).", $ini_name, $k, defined($consts_ref->{$ini_name}) ? $consts_ref->{$ini_name} : "undef"),);
            delete $consts_ref->{$ini_name};
        }
    }
    foreach my $entry_key (keys(%{$consts_ref})) {
        if (!exists($map_ref->{$entry_key})) {
            $logger->debug("Deleting unknown setting %s = %s.", $entry_key, $consts_ref->{$entry_key});
            delete $consts_ref->{$entry_key};
        }
    }

    return $consts_ref;
}

## @function _sanitize_fiu (%$fiu_ref, $phase)
# @brief Convert and sanity check FIJI Settings.
#
# \param fiu_ref a reference to a hash containing FIJI Settings for a
#                single FIU.
# \param phase   the current design phase
#
# \returns A new hash with all constants required in the FIU settings
#          in sanitized form, or undef on errors.
sub _sanitize_fiu {
    my $logger = get_logger("");
    my ($fiu_ref, $phase) = @_;
    if (ref($fiu_ref) ne 'HASH') {
        my $msg = "Parameter is not a reference to a hash (containing FIU constants).";
        $logger->error($msg);
        return $msg;
    }

    $fiu_ref = _validate_hashmap(FIUMAP, $fiu_ref, $phase);
    if (!ref($fiu_ref)) {
        $logger->error("Could not validate Design Constants.");
        return $fiu_ref;
    }

    return $fiu_ref;
}

sub _disabled_via_dependency {
    my ($map_ref, $consts_ref, $k) = @_;
    my $dependency = $map_ref->{$k}->{'depends_on'};
    return defined($dependency) && !$consts_ref->{$dependency};
}

sub _validate_hashmap {
    my $logger = get_logger("");
    my ($map_ref, $consts_ref, $phase) = @_;
    my @map_keys = keys(%{$map_ref});
    foreach my $entry_key (keys(%{$consts_ref})) {
        my $forbidden_by = $map_ref->{$entry_key}->{'forbidden_by'};
        my $ini_name     = $map_ref->{$entry_key}->{'ini_name'};

        if (!exists($map_ref->{$entry_key})) {
            $logger->debug("Deleting unknown setting %s = %s.", $entry_key, $consts_ref->{$entry_key});
            next;
        }

        @map_keys = grep { $_ ne $entry_key } @map_keys;    # mark constant key as done
        if (_disabled_via_dependency($map_ref, $consts_ref, $entry_key)) {
            $logger->debug(sprintf("Key %s is disabled via %s. Skipping validation.", $entry_key, $map_ref->{$entry_key}->{'depends_on'}));
        } elsif (!validate_value($map_ref, $entry_key, \$consts_ref->{$entry_key})) {
            my $msg = sprintf("%s = %s is invalid.", $entry_key, !defined($consts_ref->{$entry_key}) ? "<undef>" : $consts_ref->{$entry_key});
            $logger->error($msg);
            return $msg;
        }

        if (defined($forbidden_by) && $consts_ref->{$entry_key} && $consts_ref->{$forbidden_by}) {
            my $msg = "$entry_key is forbidden when $forbidden_by is enabled";
            $logger->error($msg);
            return $msg;
        }
    }

    if (!defined($phase)) {

        # If there is no phase we are creating an "empty" hash that has
        # all possible defaults set earlier already and the there is
        # nothing we can or should do here.
        return $consts_ref;
    }

    # Iterate over the constants defined in FIJI.pm that apparently are
    # not contained in $consts_ref.
    foreach my $k (@map_keys) {
        my $dependency = $map_ref->{$k}->{'depends_on'};
        if (
            scalar(grep { $_ eq $phase } @{$map_ref->{$k}->{'phases_opt'}}) == 0 &&    # mandatory in current phase
            !_disabled_via_dependency($map_ref, $consts_ref, $k)                       # no dependency or dependency is enabled
           )
        {
            my $msg = "$k is mandatory in phase $phase.";
            $logger->error($msg);
            return $msg;
        }

    }

    # @TODO: implement the same mechanism with forbidden_by

    return $consts_ref;
}

## @function _sanitize_design (%$consts_ref, $phase)
# @brief Sanity check FIJI Design Settings.
#
# The function deals with sanity checks for the values
# themselves. It checks for the following conditions:
#
#   - FIU_NUM: > 0
#   - FIU_CFG_BITS: > 0
#   - TIMER_WIDTH: > 0, <= 16
#   - ID: > 0, < 2^15-1
#   - BAUDRATE: > 0
#
# \param consts_ref a reference to a hash containing some design settings
# \param phase the tool flow phase that defines the rules to check against
#
# \returns The given hash with all constants required in the design
#          settings in sanitized form, or an error message.
sub _sanitize_design {
    my $logger = get_logger("");
    my ($consts_ref, $phase) = @_;
    if (ref($consts_ref) ne 'HASH') {
        my $msg = "Parameter is not a reference to a hash (containing design constants).";
        $logger->error($msg);
        return $msg;
    }

    # check for sane values
    $consts_ref = _validate_hashmap(DESIGNMAP, $consts_ref, $phase);
    if (!ref($consts_ref)) {
        my $msg = "Could not validate Design Constants.";
        $logger->error($msg);
        return "$msg $consts_ref";
    }

    if (($consts_ref->{'FIU_CFG_BITS'} <= 0)) {
        my $msg = "FIU_CFG_BITS is <= 0.";
        $logger->error($msg);
        return $msg;
    }
    if (($consts_ref->{'TIMER_WIDTH'} <= 0) || ($consts_ref->{'TIMER_WIDTH'} > 16)) {
        my $msg = "TIMER_WIDTH is invalid ($consts_ref->{'TIMER_WIDTH'}).";
        $logger->error($msg);
        return $msg;
    }
    if (defined($consts_ref->{'ID'}) && ($consts_ref->{ID} < 0 || $consts_ref->{ID} > (2**16 - 1))) {
        my $msg = "ID is invalid ($consts_ref->{ID}).";
        $logger->error($msg);
        return $msg;
    }
    if (($consts_ref->{'BAUDRATE'} <= 0)) {
        my $msg = "BAUDRATE missing is <= 0.";
        $logger->error($msg);
        return $msg;
    }

    return $consts_ref;
}

sub _log2 {
    my $val = shift;
    return ($val > 0) ? (log($val) / log(2)) : 0;
}

## @function private _est_resources ($FREQUENCY, $BAUD, $TIMER_WIDTH, $RESET_CYCLES, $LFSR_WIDTH, $FIU_NUM, $algo)
# @brief estimates the number of Registers and LUTs to implement FIJI logic with the given settings
#
# The function ant its parameters were determined by experiment & fitted by scipy.optimize.curve_fit
#
# @param FREQUENCY      the clock frequency the FIJI logic will run at in Hz
# @param BAUD           the baud rate for DUT <-> FIJI communication
# @param TIMER_WIDTH    the width of the injection timer (durations) in Bytes
# @param RESET_CYCLES   the number of cycles to apply a FIJI-to-DUT reset
# @param LFSR_WIDTH     width of the LFSR used for stuck-open emulation
# @param FIU_NUM        the number of FIUs in the configuration
#
# @returns ($registers, $lutsum)

sub _est_resources {
    my $logger = get_logger("");
    my ($FREQUENCY, $BAUD, $TIMER_WIDTH, $RESET_CYCLES, $LFSR_WIDTH, $FIU_NUM) = @_;

    # @FIXME where do we put these values? they are likely to change if the VHDL
    # source is changed...

    my $registers;
    my $lut6;
    my $out_of_range = [];

    if ($FREQUENCY < 1000000 || $FREQUENCY > 500000000) {
        $logger->debug("FREQUENCY $FREQUENCY out of range for correct resource estimation (1000000 - 500000000)");
        push @{$out_of_range}, "FREQUENCY";
    }
    if ($BAUD < 9600 || $BAUD > 3000000) {
        $logger->debug("BAUD $BAUD out of range for correct resource estimation (9600 - 3000000)");
        push @{$out_of_range}, "BAUD";
    }
    if ($TIMER_WIDTH < 1 || $TIMER_WIDTH > 8) {
        $logger->debug("TIMER_WIDTH $TIMER_WIDTH out of range for correct resource estimation (1 - 8)");
        push @{$out_of_range}, "TIMER_WIDTH";
    }
    if ($RESET_CYCLES < 1 || $RESET_CYCLES > 16) {
        $logger->debug("RESET_CYCLES $RESET_CYCLES out of range for correct resource estimation (1 - 16)");
        push @{$out_of_range}, "RESET_CYCLES";
    }
    if ($LFSR_WIDTH < 16 || $LFSR_WIDTH > 64) {
        $logger->debug("LFSR_WIDTH $LFSR_WIDTH out of range for correct resource estimation (16 - 64)");
        push @{$out_of_range}, "RESET_CYCLES";
    }
    if ($FIU_NUM < 1 || $FIU_NUM > 64) {
        $logger->debug("FIU_NUM $FIU_NUM out of range for correct resource estimation (1 - 64)");
        push @{$out_of_range}, "FIU_NUM";
    }

    $registers = 8769408455.04;
    $registers += (3.16525787254e-08) * ($FREQUENCY) +    (-8063276676.79) * (2**(-1.60957863771e-17 * $FREQUENCY));
    $registers += (0.000329011902135) * ($BAUD) +         (-705457194.107) * (2**(7.38032560255e-13 * $BAUD));
    $registers += (86.8258719199) *     ($TIMER_WIDTH) +  (-424084.540754) * (2**(0.000218517717305 * $TIMER_WIDTH));
    $registers += (5.02154556118) *     ($RESET_CYCLES) + (51167.4447102) *  (2**(-0.000135580209031 * $RESET_CYCLES));
    $registers += (-5.30893252274) *    ($LFSR_WIDTH) +   (-301970.077109) * (2**(-2.99010866996e-05 * $LFSR_WIDTH));
    $registers += (13.746880792) *      ($FIU_NUM) +      (437.305954808) *  (2**(-0.00583539664462 * $FIU_NUM));

    $lut6 = -1591399138.51;
    $lut6 += (5.65349933334e-06) * ($FREQUENCY) +    (-245548261.879) * (2**(3.26830064347e-14 * $FREQUENCY));
    $lut6 += (-0.0602788840594) *  ($BAUD) +         (1868596655.23) *  (2**(4.65257746085e-11 * $BAUD));
    $lut6 += (9.04974779295) *     ($TIMER_WIDTH) +  (-123738.805411) * (2**(7.77721022021e-07 * $TIMER_WIDTH));
    $lut6 += (0.156780025973) *    ($RESET_CYCLES) + (-176988.018256) * (2**(1e-08 * $RESET_CYCLES));
    $lut6 += (-1.88257966999) *    ($LFSR_WIDTH) +   (-31351130.663) *  (2**(-8.63995764468e-08 * $LFSR_WIDTH));
    $lut6 += (3.95693187928) *     ($FIU_NUM) +      (2718.76465806) *  (2**(-0.000895867386597 * $FIU_NUM));

    return ($registers, $lut6, $out_of_range);
}

## @function public estimate_resources ($settings_ref)
# @brief estimates the resources needed to implement the given settings
#
# @returns a hash with the members 'regs' and 'lut_calc'
#
sub estimate_resources {
    my $logger         = get_logger("");
    my ($settings_ref) = @_;
    my $consts_ref     = $settings_ref->{'design'};
    my $fiu_ref        = $settings_ref->{'fius'};
    my $fiu_num        = @{$fiu_ref};

    my @calcrv = _est_resources($consts_ref->{'FREQUENCY'}, $consts_ref->{'BAUDRATE'}, $consts_ref->{'TIMER_WIDTH'}, $consts_ref->{'RESET_DUT_IN_DURATION'}, $consts_ref->{'LFSR_WIDTH'}, $fiu_num, "logarithmic");

    my $rv = {
        regs         => sprintf("%.2f", $calcrv[0] / $base_resources[0]),
        lut_calc     => sprintf("%.2f", $calcrv[1] / $base_resources[1]),
        out_of_range => $calcrv[2],
    };

    $logger->debug("ESTIMATE: current config will need Base*$rv->{'regs'} registers and Base*$rv->{'lut_calc'} combinational resources");
    return $rv;
}

1;