摘要：
uvm_ voiduvm_ void类是所有uvm类的基类。uvm_ object：uvm_对象类是所有UVMdata和层次结构类的基类。uvm_ Object是uvm中数据和组件的公共基类。它集成了许多东西，如录音机和记者，
| uvm_void | |
| The uvm_void class is the base class for all UVM classes. |
uvm_object:
The uvm_object class is the base class for all UVM data and hierarchical classes.
uvm_object是一个uvm中data和component共同的基类，里边集成了很多东西如recorder，reporter等，还定义了许多公用的接口。该类继承自uvm_void
1. 该类的属性：
static bit use_uvm_seeding = 1;//使能调用uvm的种子机制：
当使能的时候，UVM-based 对象使用它们的type和full hierarchical 名字进行seeded，提高对象的随机稳定性因为他们的名字是固定的
The <uvm_component> class is an example of a type that has a unique instance name.
local string m_leaf_name;//本object的名字
local int m_inst_id;//本inst_id
static protected int m_inst_count = 0;//总共的object数
static uvm_status_container __m_uvm_status_container = new;//一个所有object共享的状态容器
2. 种子机制：
function void uvm_object::reseed ();//use_uvm_seeding使能情况下根据类型和层次化名字生成一个随机的种子，即使用uvm的种子机制
3. 对象身份方法：
1. function void uvm_object::set_name (string name); //设置leaf_name
2. function string uvm_object::get_name ();//返回leaf_name(由new设置或者通过set_name更改)
3. function string uvm_object::get_full_name ();//调用2
1. 返回对象的全部层次名，The default implementation is the same as get_name, as uvm_objects do not inherently possess hierarchy.
2. 如果对象具有层次，比如uvm_components,将会重载默认的那个实现
3. Other objects might be associated with component hierarchy but are not themselves components. For example, uvm_sequence #(REQ,RSP) classes are typically associated with a uvm_sequencer #(REQ,RSP). In this case, it is useful to override get_full_name to return the sequencer’s full name concatenated with the sequence’s name. This provides the sequence a full context, which is useful when debugging.
4. function int uvm_object::get_inst_id();//返回inst_id
5. function int uvm_object::get_inst_count(); //返回inst_count
6. function uvm_object_wrapper uvm_object::get_object_type();//在factory中查找type_name并返回对应的实例
1. get_object_type同get_type是相同的
7. function uvm_object_wrapper uvm_object::get_type();//返回本类型所对应的uvm_object_wrapper
1. 某些object派生的对象都对应一个wrapper来实现对某个对象的create，register到工厂等操作，本函数就是要返回对应的wrapper
2. 返回对象的type-proxy（类型-代理wrapper）. uvm_factory's的type-based 覆盖和创建方法
3. The default implementation of this method produces an error and returns null. To enable use of this method, a user’s subtype must implement a version that returns the subtype’s wrapper.
4. This function is implemented by the `uvm_*_utils macros, if employed.（下面例子中的标红部分由uvm_*utils实现）
举个例子：
class cmd extends uvm_object;
typedef uvm_object_registry #(cmd) type_id;
static function type_id get_type();
return type_id::get();
endfunction
endclass
8. virtual function string get_type_name (); //这个函数返回对象的类型名称,这是通常的类型标识符
1. It is used for various debugging functions in the library, and it is used by the factory for creating objects.
2. This function must be defined in every derived class.
4.创建机制：
1. virtual function uvm_object create ( string name ="" )
1. Every class deriving from uvm_object, directly or indirectly, must implement the create method.
2. virtual function uvm_object clone ()；//克隆方法创建并返回这个对象的精确复制。
5. print方法：
1 .function void uvm_object::print(uvm_printer printer=null);//调用sprint打印本object
1. 如果printer没有提供将会使用uvm_default_printer。
2. See also uvm_line_printer, uvm_tree_printer, and uvm_table_printer for details on the pre-defined printer “policies,” or formatters, provided by the UVM.
3. 自定义打印和sprint 操作，派生类必须覆盖do_print方法和使用提供的打印机政策类格式输出。
4. $fwrite(printer.knobs.mcd,sprint(printer));//主要是调用fwrite函数，打印sprint返回的string
2. function string uvm_object::sprint(uvm_printer printer=null); //调用do_print(printer)打印（主要目的是返回一个string，而不是为了打印）
1. The printer policy will manage all string concatenations and provide the string to sprint to return to the caller.
2. 注意在printer.istop，not at top-level, must be recursing into sub-object调用do_print方法
3.调用printer.emit()实现格式化
3. virtual function void do_print ( uvm_printer printer )
1. The do_print method is the user-definable hook called by print and sprint that allows users to customize what gets printed or sprinted beyond the field information provided by the `uvm_field_* macros, Utility and Field Macros for Components and Objects.
2. printer是policy对象，控制输出的格式和内容
3. To ensure correct print and sprint operation, and to ensure a consistent output format, the printer must be used by all do_print implementations. That is, instead of using $display or string concatenations directly, a do_print implementation must call through the printer’s API to add information to be printed or sprinted.
3. 使用printer提供的api打印
class mytype extends uvm_object;
data_obj data;
int f1;
virtual function void do_print (uvm_printer printer);
super.do_print(printer);
printer.print_int("f1", f1, $bits(f1), DEC);
printer.print_object("data", data);
endfunction
4. convert2string()//This virtual function is a user-definable hook, called directly by the user, that allows users to provide object information in the form of a string.
6. Recording方法：
1.function void uvm_object::record (uvm_recorder recorder=null);//调用do_record做记录
1. A simulator’s recording mechanism is vendor-specific. By providing access via a common interface, the uvm_recorder policy provides vendor-independent access to a simulator’s recording capabilities.
2.function void uvm_object::do_record (uvm_recorder recorder);//null
7. Copy方法：
1.function void uvm_object::copy (uvm_object rhs);
2 .function void uvm_object::do_copy (uvm_object rhs); //null
8. Compare方法：
1. function bit uvm_object::compare (uvm_object rhs,
uvm_comparer comparer=null); //调用比较策略器进行比较
1. The optional comparer argument specifies the comparison policy. It allows you to control some aspects of the comparison operation. It also stores the results of the comparison, such as field-by-field miscompare information and the total number of miscompares. If a compare policy is not provided, then the global uvm_default_comparer policy is used. See uvm_comparer for more information.
2. function bit uvm_object::do_compare (uvm_object rhs,
uvm_comparer comparer);//被1调用
class mytype extends uvm_object;
...
int f1;
virtual function bit do_compare (uvm_object rhs,uvm_comparer comparer);
mytype rhs_;
do_compare = super.do_compare(rhs,comparer);
$cast(rhs_,rhs);
do_compare &= comparer.compare_field_int("f1", f1, rhs_.f1);
endfunction
A derived class implementation must call super.do_compare() to ensure its base class’ properties, if any, are included in the comparison. Also, the rhs argument is provided as a generic uvm_object. Thus, you must $cast it to the type of this object before comparing.
The actual comparison should be implemented using the uvm_comparer object rather than direct field-by-field comparison. This enables users of your class to customize how comparisons are performed and how much miscompare information is collected. See uvm_comparer for more details.
9.Pack方法：
10. Unpack方法：
11.configuration方法：
1.function void uvm_object::set_int_local (string field_name,
uvm_bitstream_t value,
bit recurse=1); //保存一个整数
2.function void uvm_object::set_object_local (string field_name,
uvm_object value,
bit clone=1,
bit recurse=1); //保存一个object
3.function void uvm_object::set_string_local (string field_name,
string value,
bit recurse=1);//保存string
1. These methods provide write access to integral, string, and uvm_object-based properties indexed by a field_name string.
2. Although the object designer implements these methods to provide outside access to one or more properties, they are intended for internal use (e.g., for command-line debugging and auto-configuration) and should not be called directly by the user.