perf(const): const changed to a singelton

const needds to be accessed all throughout so it has been changed to a singleton to allow for more efficient usage

BREAKING CHANGE: Any previous loads to const will break, also constant->Constant and constants->Constants

src/const/meson.build

@@ -12,6 +12,7 @@ libconst = library('const',
     const_sources, 
     include_directories: include_directories('public'),
     cpp_args: ['-fvisibility=default'],
+    dependencies: [const_dep],
     install : true)
 
 # Make headers accessible

src/const/private/const.cpp

@@ -3,23 +3,22 @@
 #include <vector>
 #include <string>
 #include <fstream>
+#include <sstream>
 #include <set>
 
+
 #include "const.h"
+#include "embedded_constants.h" // Generated at build time by meson
 
-constants::constants() {
-  loaded_ = false;
+Constants::Constants() {
+  loaded_ = initialize();
 }
 
-constants::constants(const std::string& filename) {
-  loaded_ = initialize(filename);
+bool Constants::initialize() {
+  return load();
 }
 
-bool constants::initialize(const std::string& filename) {
-  return load(filename);
-}
-
-constant constants::get(const std::string& name) const {
+Constant Constants::get(const std::string& name) const {
   auto it = constants_.find(name);
   if (it != constants_.end()) {
     return it->second;
@@ -28,15 +27,15 @@ constant constants::get(const std::string& name) const {
   }
 }
 
-constant constants::operator[](const std::string& name) const {
+Constant Constants::operator[](const std::string& name) const {
   return this->get(name);
 }
 
-bool constants::has(const std::string& name) const {
+bool Constants::has(const std::string& name) const {
   return constants_.find(name) != constants_.end();
 }
 
-std::set<std::string> constants::keys() const {
+std::set<std::string> Constants::keys() const {
   std::set<std::string> keys;
   for (const auto& pair : constants_) {
     keys.insert(pair.first);
@@ -44,32 +43,28 @@ std::set<std::string> constants::keys() const {
   return keys;
 }
 
-std::string constants::trim(const std::string& str) {
+std::string Constants::trim(const std::string& str) {
     size_t first = str.find_first_not_of(" \t");
     if (first == std::string::npos) return "";
     size_t last = str.find_last_not_of(" \t");
     return str.substr(first, last - first + 1);
 }
 
-bool constants::load(const std::string& filename) {
-    std::ifstream file(filename);
-    if (!file.is_open()) {
-        std::cerr << "Error: Unable to open file " << filename << std::endl;
-        return false;
-    }
+bool Constants::load() {
+    std::istringstream fileStream(embeddedConstants);
 
     std::string line;
     bool data_section = false;
     int line_count = 0;
 
-    while (std::getline(file, line)) {
+    while (std::getline(fileStream, line)) {
         line_count++;
 
         // Detect start of data section (double divider line)
         if (!data_section) {
             if (line.find("Symbol") != std::string::npos) {  // Find header row
-                std::getline(file, line);  // Skip dashed divider
-                std::getline(file, line);  // Skip second dashed divider
+                std::getline(fileStream, line);  // Skip dashed divider
+                std::getline(fileStream, line);  // Skip second dashed divider
                 data_section = true;
             }
             continue;
@@ -102,10 +97,8 @@ bool constants::load(const std::string& filename) {
         }
 
         // Store in map
-        constants_.emplace(symbol, constant{name, value, uncertainty, unit, reference});
+        constants_.emplace(symbol, Constant{name, value, uncertainty, unit, reference});
     }
-
-    file.close();
     loaded_ = true;
     return true;
 }

src/const/public/const.h

@@ -10,7 +10,7 @@
 /**
  * @brief Structure to hold a constant's details.
  */
-struct constant {
+struct Constant {
   const std::string name;         ///< Name of the constant
   const double value;             ///< Value of the constant
   const double uncertainty;       ///< Uncertainty in the constant's value
@@ -25,13 +25,13 @@ struct constant {
    * @param unit The unit of the constant.
    * @param reference The reference for the constant's value.
    */
-  constant(const std::string& name, double value, double uncertainty, const std::string& unit, const std::string& reference)
+  Constant(const std::string& name, const double value, const double uncertainty, const std::string& unit, const std::string& reference)
     : name(name), value(value), uncertainty(uncertainty), unit(unit), reference(reference) {}
 
   /**
    * @brief overload the << operator for pretty printing
    */
-   friend std::ostream& operator<<(std::ostream& os, const constant& c) {
+   friend std::ostream& operator<<(std::ostream& os, const Constant& c) {
      os << "<" << c.name << ": ";
      os << c.value << "±" << c.uncertainty << " ";
      os << c.unit << " (" << c.reference << ")>\n";
@@ -42,18 +42,28 @@ struct constant {
 /**
  * @brief Class to manage a collection of constants.
  */
-class constants {
+class Constants {
 private:
   bool loaded_ = false; ///< Flag to indicate if constants are loaded
   const int col_widths_[6] = {25, 52, 20, 20, 17, 45}; // From the python script used to generate the constants file
-  std::map<std::string, constant> constants_; ///< Map to store constants by name
+  std::map<std::string, Constant> constants_; ///< Map to store constants by name
 
   /**
-   * @brief Load constants from a file.
-   * @param filename The name of the file to load constants from.
+   * @brief Default constructor. Private to avoid direct instantiation
+   */
+  Constants();
+
+  /**
+   * @brief Load constants from the embedded header file.
    * @return True if loading was successful, false otherwise.
    */
-  bool load(const std::string& filename);
+  bool load();
+
+  /**
+   * @brief Initialize constants.
+   * @return True if initialization was successful, false otherwise.
+   */
+  bool initialize();
 
   /**
    * @brief Trim leading and trailing whitespace from a string.
@@ -63,36 +73,28 @@ private:
   std::string trim(const std::string& str);
 
 public:
-  /**
-   * @brief Default constructor.
-   */
-  constants();
 
   /**
-   * @brief Constructor that initializes constants from a file.
-   * @param filename The name of the file to load constants from.
+   * @brief get instance of constants singelton
+   * @return instance of constants
    */
-  constants(const std::string& filename);
+  static Constants& getInstance() {
+    static Constants instance;
+    return instance;
+  }
 
   /**
    * @brief Check if constants are loaded.
    * @return True if constants are loaded, false otherwise.
    */
-  bool is_loaded() { return loaded_; }
-
-  /**
-   * @brief Initialize constants from a file.
-   * @param filename The name of the file to load constants from.
-   * @return True if initialization was successful, false otherwise.
-   */
-  bool initialize(const std::string& filename);
+  bool isLoaded() { return loaded_; }
 
   /**
    * @brief Get a constant by key.
    * @param key The name of the constant to retrieve.
    * @return The constant associated with the given key.
    */
-  constant get(const std::string& key) const;
+  Constant get(const std::string& key) const;
 
   /**
    * @brief Overloaded subscript operator to access constants by key.
@@ -100,7 +102,7 @@ public:
    * @return The constant associated with the given key.
    * @throws std::out_of_range if the key is not found.
    */
-  constant operator[](const std::string& key) const;
+  Constant operator[](const std::string& key) const;
 
   /**
    * @brief Check if a constant exists by key.

src/meson.build

@@ -1,2 +1,6 @@
+# Build resources first so that all the embedded resources are available to the other targets
+subdir('resources')
+
+# Build the main source code
 subdir('dobj')
 subdir('const')

src/resources/const/format.sh

@@ -0,0 +1,10 @@
+#!/bin/sh
+if [ "$#" -ne 2 ]; then
+    echo "Usage: $0 <input_file> <output_file>"
+    exit 1
+fi
+input_file="$1"
+output_file="$2"
+printf 'const char embeddedConstants[] = R"(' > "$output_file"
+cat "$input_file" >> "$output_file"
+printf ')";\n' >> "$output_file"

src/resources/const/meson.build

@@ -0,0 +1,20 @@
+data_file = files('const.dat')
+command_file = files('format.sh')
+output_file = meson.current_build_dir() + '/embedded_constants.h'
+message('Data file absolute path: ' + data_file[0].full_path())
+message('Meson source directory: ' + meson.current_source_dir())
+message('Meson build directory: ' + meson.current_build_dir())
+
+embedded_constants_h = custom_target('embed_constants',
+    input: data_file,
+    output: 'embedded_constants.h',
+    command: ['sh', '-c', command_file[0].full_path()+' @INPUT@ ' + output_file, '@INPUT@', '@OUTPUT@']
+)
+
+# Ensure the generated header is included
+const_header = include_directories('.')
+
+const_dep = declare_dependency(
+    include_directories: const_header,
+    sources: embedded_constants_h
+)

src/resources/meson.build

@@ -0,0 +1 @@
+subdir('const')