7.2 uvm_resource_db in UVM

uvm_resource_db是一个类型参数化 type-parameterized的类，它是资源数据库顶部的一个方便层(convenience layer)。这个便利层简化了对低级数据库的访问，并且没有添加新功能。因此，uvm_resource_db不是从uvm_resource类派生的。
以下uvm_resource_db类的代码段取自uvm源代码。

class uvm_resource_db #(type T=uvm_object);typedef uvm_resource #(T) rsrc_t;protected function new();endfunctionstatic function rsrc_t get_by_name(string scope, string name,bit rpterr=1);return rsrc_t::get_by_name(scope, name, rpterr);endfunctionstatic function void set(input string scope, input string name,T val, input uvm_object accessor = null);rsrc_t rsrc = new(name, scope);rsrc.write(val, accessor);rsrc.set();...    ...endfunction......
endclass

注：

1. 这个uvm_resource_db类未实例化
2. 它使用一组静态函数来操作资源和资源池。因此，必须使用范围解析操作符( ::)来调用它们。

        例如：uvm_resource_db #（整数）：：设置（…）；

     3. 如果+UVM_RESOURCE_DB_TRACE作为命令行参数提供，它会打印所有资源数据库的访问（写入和读取）。

1. uvm_resource_db methods

所有函数都是下表中提到的静态函数

2. uvm_resource_db example

在下面的示例中，control位存储在数据库中，作为在component_B中为my_component创建对象的启用条件(enable condition)。

名为“control”、类型为bit的新资源将从测试用例添加到资源池中。

uvm_resource_db #(bit)::set("*", "control", 1, this);//where,
//string scope = “*”;
//string name = “control”;
//T val = 1;
//uvm_object accessor =  this;//In component_B, 
if(!uvm_resource_db #(bit)::read_by_name(get_full_name(), "control", ctrl))`uvm_fatal(get_type_name(), "read_by_name failed for resource in this scope");

使用read_by_name静态函数检索资源，该函数在名称为“control”的数据库中查找。如果read_by_name在数据库中找不到“control”字符串名，将报告致命错误。尽管致命检查不是强制性的，但建议将其用于调试目的。一旦表中的查找成功，存储在资源数据库中的值就会在局部变量ctrl中更新。此控制位用于控制my_component对象的创建。

`include "uvm_macros.svh"
import uvm_pkg::*;class component_A #(parameter ID_WIDTH = 8) extends uvm_component;bit [ID_WIDTH-1:0] id;`uvm_component_param_utils(component_A #(ID_WIDTH))function new(string name = "component_A", uvm_component parent = null);super.new(name, parent);id = 1;endfunctionfunction display();`uvm_info(get_type_name(), $sformatf("inside component_A: id = %0d", id), UVM_LOW);endfunction
endclassclass mycomponent #(parameter ID_WIDTH = 8) extends uvm_component;bit [ID_WIDTH-1:0] id;`uvm_component_param_utils(mycomponent #(ID_WIDTH))function new(string name = "mycomponent", uvm_component parent = null);super.new(name, parent);id = 2;endfunctionfunction display();`uvm_info(get_type_name(), $sformatf("inside mycomponent: id = %0d", id), UVM_LOW);endfunction
endclassclass component_B #(int ID_WIDTH = 8) extends component_A #(ID_WIDTH);bit ctrl;bit [ID_WIDTH-1:0] id;mycomponent #(8) my_comp;`uvm_component_param_utils(component_B #(ID_WIDTH))function new(string name = "component_B", uvm_component parent = null);super.new(name, parent);id = 3;endfunctionfunction void build_phase(uvm_phase phase);super.build_phase(phase);if(!uvm_resource_db #(bit)::read_by_name(get_full_name(), "control", ctrl))`uvm_fatal(get_type_name(), "read_by_name failed for resource in this scope");if(ctrl)  my_comp = mycomponent #(8)::type_id::create("my_comp", this);endfunctionfunction display();`uvm_info(get_type_name(), $sformatf("inside component_B: id = %0d, ctrl = %0d", id, ctrl), UVM_LOW);if(ctrl) void'(my_comp.display());endfunction
endclassclass my_test extends uvm_test;bit control;`uvm_component_utils(my_test)component_A #(32) comp_A;component_B #(16) comp_B;function new(string name = "my_test", uvm_component parent = null);super.new(name, parent);endfunctionfunction void build_phase(uvm_phase phase);super.build_phase(phase);comp_A = component_A #(32)::type_id::create("comp_A", this);comp_B = component_B #(16)::type_id::create("comp_B", this);uvm_resource_db #(bit)::set("*", "control", 1, this);endfunctionfunction void end_of_elaboration_phase(uvm_phase phase);super.end_of_elaboration_phase(phase);uvm_top.print_topology();endfunctiontask run_phase(uvm_phase phase);super.run_phase(phase);void'(comp_A.display());void'(comp_B.display());endtask
endclassmodule tb_top;initial beginrun_test("my_test");end
endmodule

Output:

UVM_INFO /xcelium20.09/tools//methodology/UVM/CDNS-1.2/sv/src/base/uvm_root.svh(605) @ 0: reporter [UVMTOP] UVM testbench topology:
----------------------------------------
Name          Type           Size  Value
----------------------------------------
uvm_test_top  my_test        -     @1809comp_A      uvm_component  -     @1876comp_B      uvm_component  -     @1907my_comp   uvm_component  -     @1954
----------------------------------------UVM_INFO testbench.sv(14) @ 0: uvm_test_top.comp_A [uvm_component] inside component_A: id = 1
UVM_INFO testbench.sv(52) @ 0: uvm_test_top.comp_B [uvm_component] inside component_B: id = 3, ctrl = 1
UVM_INFO testbench.sv(28) @ 0: uvm_test_top.comp_B.my_comp [uvm_component] inside mycomponent: id = 2