Open CASCADE 基础类(Foundation Classes)

1 介绍(Introduction) 1

如何使用Open CASCADE技术(OCCT)基础类.

This manual explains how to use Open CASCADE Technology (OCCT) Foundation Classes. It provides basic
documentation on foundation classes. For advanced information on foundation classes and their applications, see
our E-learning & Training offerings.

基础类提供了常规目的服务如动态内存管理(由handle管理), 集合, 异常处理, 常规转换, 插件生成.
Foundation Classes provide a variety of general-purpose services such as automated dynamic memory management
(manipulation of objects by handle), collections, exception handling, genericity by down-casting and plug-in
creation.

基础类包括: Foundation Classes include the following:

基类 Root Classes (其它数据类型和类的根基)

Root classes are the basic data types and classes on which all the other classes are built. They provide:
• fundamental types such as Boolean, Character, Integer or Real,
• safe handling of dynamically created objects, ensuring automatic deletion of unreferenced objects (see
Standard_Transient class),
• configurable optimized memory manager increasing the performance of applications that intensively use dynamically created objects,
• extended run-time type information (RTTI) mechanism facilitating the creation of complex programs,
• management of exceptions,
• encapsulation of C++ streams. Root classes are mainly implemented in Standard and MMgt packages.

字符串 Strings

Strings are implemented in the TCollection package.

集合 Collections

集合处理动态增长的聚合数据 Collections are the classes that handle dynamically sized aggregates of data.

Collections include a wide range of generic classes such as run-time sized arrays, lists, stacks, queues, sets and
hash maps. Collections are implemented in the TCollection and NCollection packages.

标准对象集合 Collections of Standard Objects

The TColStd package provides frequently used instantiations of generic classes from the TCollection package with
objects from the Standard package or strings from the TCollection package.

向量和矩阵 Vectors and Matrices

它们提供了常用数学算法和基础计算(加, 乘, 平移, 反转)

These classes provide commonly used mathematical algorithms and basic calculations (addition, multiplication,
transposition, inversion, etc.) involving vectors and matrices.

原始几何类型 Primitive Geometric Types

Open CASCADE Technology primitive geometric types are a STEP-compliant implementation of basic geometric
and algebraic entities. They provide:
• Descriptions of elementary geometric shapes:
• Points,
• Vectors,
• Lines,
• Circles and conics,
• Planes and elementary surfaces,
• Positioning of these shapes in space or in a plane by means of an axis or a coordinate system,
• Definition and application of geometric transformations to these shapes:
• Translations
• Rotations
• Symmetries
• Scaling transformations
• Composed transformations
• Tools (coordinates and matrices) for algebraic computation.

Common Math Algorithms

Open CASCADE Technology common math algorithms provide a C++ implementation of the most frequently used
mathematical algorithms. These include:
• Algorithms to solve a set of linear algebraic equations,
• Algorithms to find the minimum of a function of one or more independent variables,
• Algorithms to find roots of one, or of a set, of non-linear equations,
• Algorithms to find the eigen-values and eigen-vectors of a square matrix.

Exceptions

A hierarchy of commonly used exception classes is provided, all based on class Failure, the root of exceptions.
Exceptions describe exceptional situations, which can arise during the execution of a function. With the raising of
an exception, the normal course of program execution is abandoned. The execution of actions in response to this
situation is called the treatment of the exception.

Quantities

These are various classes supporting date and time information and fundamental types representing most physical
quantities such as length, area, volume, mass, density, weight, temperature, pressure etc.

Application services

Foundation Classes also include implementation of several low-level services that facilitate the creation of customizable
and user-friendly applications with Open CASCADE Technology. These include:
• Unit conversion tools, providing a uniform mechanism for dealing with quantities and associated physical
units: check unit compatibility, perform conversions of values between different units and so on (see package
UnitsAPI);
• Basic interpreter of expressions that facilitates the creation of customized scripting tools, generic definition of
expressions and so on (see package ExprIntrp);
• Tools for dealing with configuration resource files (see package Resource) and customizable message files
(see package Message), making it easy to provide a multi-language support in applications;
• Progress indication and user break interfaces, giving a possibility even for low-level algorithms to communicate
with the user in a universal and convenient way.

2 基础(Basics) 3

This chapter deals with basic services such as library organization, persistence, data types, memory management,
programming with handles, exception handling, genericity by downcasting and plug-in creation.

2.1 库组织(Library organization)  6

This chapter introduces some basic concepts, which are used not only in Foundation Classes, but throughout the
whole OCCT library.

2.1.1 模块和工具Modules and toolkits 6

在物理上, 一个共享库(.so或.dll)表示一个工具箱.

The whole OCCT library is organized in a set of modules. The first module, providing most basic services and used
by all other modules, is called Foundation Classes and described by this manual.
Every module consists primarily of one or several toolkits (though it can also contain executables, resource units
etc.). Physically a toolkit is represented by a shared library (e.g. .so or .dll). The toolkit is built from one or several
packages.

2.1.2 包 Packages 6

语义相关的一些类组成一个包. 如: 一个几何包 会包含点,线,圆类.

通常, 每个类名会有包前缀.

A package groups together a number of classes which have semantic links. For example, a geometry package
would contain Point, Line, and Circle classes. A package can also contain enumerations, exceptions and package
methods (functions). In practice, a class name is prefixed with the name of its package e.g. Geom_Circle. Data
types described in a package may include one or more of the following data types:
• Enumerations
• Object classes
• Exceptions
• Pointers to other object classes Inside a package, two data types cannot bear the same name.

2.1.3 类 Classes 7
2.1.4 继承 Inheritance 8
2.2 数据类型 Data Types 8

在OCCT中, Handles能安全的操作动态对象内存分配与释放.

A variable of a type manipulated by handle which is not attached to an object is said to be null. To reference an
object, we instantiate the class with one of its constructors. For example, in C++:

Handle(myClass) m = new myClass;

In Open CASCADE Technology, the Handles are specific classes that are used to safely manipulate objects allocated
in the dynamic memory by reference, providing reference counting mechanism and automatic destruction of
the object when it is not referenced.

2.2.1 原始类型Primitive Types 9

Table 1: Equivalence between C++ Types and OCCT Primitive Types

C++ Types	OCCT Types
int	Standard_Integer
double	Standard_Real
float	Standard_ShortReal
unsigned int	Standard_Boolean
char	Standard_Character
short	Standard_ExtCharacter
char*	Standard_CString
void*	Standard_Address
short*	Standard_ExtString

2.2.2 值类型 Types manipulated by value  10
2.2.3 引用(handle)类型 Types manipulated by reference (handle)    11
2.2.4 什么时候必须用handle When is it necessary to use a handle? 11
2.3 使用Handles Programming with Handles   12

Class Standard_Transient is a root of a big hierarchy of OCCT classes that are said to be operable by handles.

Handle(Geom_Line) aLine; // "Handle(Geom_Line)" is expanded to "opencascade::handleL<Geom_Line>"

In addition, for standard OCCT classes additional typedef is defined for a handle, as the name of a class prefixed
by Handle_. For instance, the above example can be also coded as:

Handle_Geom_Line aLine; // "Handle_Geom_Line" is typedef to "opencascade::handleL<Geom_Line>"

2.3.1 Handle定义 Handle Definition    12
2.3.2 类型管理 Type Management   12
2.3.3 使用Handles创建对象 Using Handles to Create Objects    14
2.3.4 调用方法 Invoking Methods    14
2.3.5 Handle释放 Handle deallocation   15
2.3.6 循环引用Cycles  16
2.4 内存管理 Memory Management  16
2.4.1 使用内存管理器 Usage of Memory Manager   16
2.4.2 如何配置内存管理器 How to configure the Memory Manager    16
2.4.3 优化技巧 Optimization Techniques    17
2.4.4 优点和drawbacks Benefits and drawbacks    17
2.5 异常 Exceptions    18
2.5.1 介绍 Introduction   18
2.5.2 抛出异常 Raising an Exception  18
2.5.3 处理异常 Handling an Exception 19
2.5.4 多平台实现 Implementation on various platforms.  21
2.6 插件管理 Plug-In Management  22
2.6.1 插件发布 Distribution by Plug-Ins 22

3 集合,字符串,数量和单位转换 Collections, Strings, Quantities and Unit Conversion   24

3.1 集合 Collections    24
3.1.1 总览 Overview    24
3.1.2 一般集合 Generic general-purpose Aggregates 24
3.1.3 一般表 Generic Maps  26
3.1.4 遍历 Iterators 29
3.2 标准对象集合 Collections of Standard Objects 29
3.2.1 总览 Overview    30
3.2.2 描述 Description   30
3.3 NCollections   30
3.3.1 Overview    30
3.3.2 Instantiation of collection classes    31
3.3.3 Arrays and sequences 31
3.3.4 Maps  32
3.3.5 Other collection types  32
3.3.6 Features    34
3.4 字符串 Strings  36
3.4.1 示例 Examples    36
3.4.2 约定 Conversion   37
3.5 数量 Quantities    37
3.6 单位转换 Unit Conversion 38

4 数学基础和算法 Math Primitives and Algorithms   39

4.1 总览 Overview    39
4.2 向量和矩阵 Vectors and Matrices  39
4.3 基础几何类型 Primitive Geometric Types    40
4.4 基础几何类型集合 Collections of Primitive Geometric Types    41
4.5 基本几何库 Basic Geometric Libraries    41
4.6 常用数学算法 Common Math Algorithms    41
4.7 精度 Precision 43
4.7.1 精度包 The Precision package 44
4.7.2 标准精度值 Standard Precision values   44