動(dòng)態(tài)數(shù)組是一個(gè)unpacked數(shù)組，其大小可以在運(yùn)行時(shí)更改。

需要使用" new "操作符實(shí)例化一個(gè)動(dòng)態(tài)數(shù)組，使用[]表示。在實(shí)例化過程中，會(huì)設(shè)置動(dòng)態(tài)數(shù)組的大小。動(dòng)態(tài)數(shù)組聲明的語法如下：

data_type array_name [ ];

下面是簡單的動(dòng)態(tài)數(shù)組示例：

module darray;
 integer da [ ]; //dynamic array ‘da’ of type integer
 initial
 begin
    da = new[4]; //construct and allocate a size of 4 elements
    $display($stime,,, "da size = %0d",da.size);
    da.delete( ); //delete elements of an array
    $display($stime,,, "da size = %0d",da.size);
    da = '{1,2,3,4}; //array initialization
    $display($stime,,, "da = ",da);
 end
 endmodule

仿真log:

0 da size = 4
0 da size = 0
0 da = '{1, 2, 3, 4}
V C S S i m u l a t i o n R e p o r t

上面的module聲明了一個(gè)名為“da[]”的動(dòng)態(tài)數(shù)組，其中數(shù)據(jù)項(xiàng)的類型為integer。

Dynamic Arrays– Resizing

下面的示例展示了SystemVerilog動(dòng)態(tài)數(shù)組的大小更改。

module darray;
 bit [7:0] d_array1[ ];
 initial begin
    //memory allocation
    d_array1 = new[2];
    $display($stime,,, "d_array1 size = %0d",d_array1.size);
    $display("
");
    //array assignment - changes the size of the array
    d_array1 = {2,3,4}; //add 1 more element to the array
    $display($stime,,, "d_array1 size = %0d",d_array1.size);
    $display($stime,,, "d_array1=",d_array1);
    $display("
");
 d_array1[2]=5;
    $display($stime,,, "d_array1[0]=",d_array1[0]);
    $display($stime,,, "d_array1[1]=",d_array1[1]);
    $display($stime,,, "d_array1[2]=",d_array1[2]);
    $display($stime,,, "d_array1=",d_array1);
    $display("
");
    d_array1[3]=6; //will not change the size of the array or
    //add a new element - Warning
    $display($stime,,, "d_array1 size = %0d",d_array1.size);
    $display($stime,,, "d_array1=",d_array1);
    $display("
");
    d_array1 = {2,3,4,6};
    $display($stime,,, "d_array1 size = %0d",d_array1.size);
    $display($stime,,, "d_array1=",d_array1);
    $display("
");
    //increase the size of d_array1
    d_array1 = new [d_array1.size( ) + 1] (d_array1) ;
    $display($stime,,, "d_array1 size = %0d",d_array1.size);
$display($stime,,,"d_array1=",d_array1);
 end
 endmodule

仿真log:

 0 d_array1 size = 2
 0 d_array1 size = 3
 0 d_array1='{'h2, 'h3, 'h4}
 
 0 d_array1[0]= 2
 0 d_array1[1]= 3
 0 d_array1[2]= 5
 0 d_array1='{'h2, 'h3, 'h5}
 0 d_array1 size = 3
 0 d_array1='{'h2, 'h3, 'h5}
 0 d_array1 size = 4
 0 d_array1='{'h2, 'h3, 'h4, 'h6}
 0 d_array1 size = 5
0 d_array1='{'h2, 'h3, 'h4, 'h6, 'h0}
 V C S S i m u l a t i o n R e p o r t

聲明一個(gè)動(dòng)態(tài)數(shù)組d_array1.

分配2個(gè)數(shù)據(jù)項(xiàng)大小

 d_array1 = new[2];
 $display($stime,,, "d_array1 size = %0d",d_array1.size);
 
 0 d_array1 size = 2

初始化數(shù)組，增加了一個(gè)數(shù)據(jù)項(xiàng)，表明動(dòng)態(tài)數(shù)組的數(shù)據(jù)項(xiàng)是可以動(dòng)態(tài)更改的:

//array assignment - changes the size of the array
 d_array1 = {2,3,4}; //add 1 more element to the array
 $display($stime,,, "d_array1 size = %0d",d_array1.size);
 $display($stime,,, "d_array1=",d_array1);

仿真log打印:

 0 d_array1 size = 3
 0 d_array1='{'h2, 'h3, 'h4}

改變第2個(gè)數(shù)據(jù)項(xiàng)的值，然后打印所有的動(dòng)態(tài)數(shù)組值。

 d_array1[2]=5; //Change the value of 2nd  element
 $display($stime,,, "d_array1[0]=",d_array1[0]);
 $display($stime,,, "d_array1[1]=",d_array1[1]);
 $display($stime,,, "d_array1[2]=",d_array1[2]);
 $display($stime,,, "d_array1=",d_array1);

仿真log打印:

 0 d_array1[0]= 2
 0 d_array1[1]= 3
 0 d_array1[2]= 5
 0 d_array1='{'h2, 'h3, 'h5}

給不存在的index 3數(shù)據(jù)項(xiàng)賦值，結(jié)果是什么都不會(huì)發(fā)生，下面的賦值會(huì)被忽略：

 d_array1[3]=6; //will not change the size of the array –//Warning
 
 $display($stime,,, "d_array1 size = %0d",d_array1.size);
 $display($stime,,, "d_array1=",d_array1);

仿真log會(huì)打?。?/p>

 0 d_array1 size = 3
 0 d_array1='{'h2, 'h3, 'h5}

結(jié)果是什么都不會(huì)發(fā)生，上面的賦值會(huì)被忽略。

總結(jié)來說動(dòng)態(tài)數(shù)組的大小只能通過重新初始化來更改。

d_array1 = {2,3,4,6};
 $display($stime,,, "d_array1 size = %0d",d_array1.size);
 $display($stime,,, "d_array1=",d_array1);
-------------------------
 0 d_array1 size = 4
 0 d_array1='{'h2, 'h3, 'h4, 'h6}

以及

d_array1 = new [d_array1.size( ) + 1] (d_array1);
 //increase the size of d_array1
 $display($stime,,, "d_array1 size = %0d",d_array1.size);
 $display($stime,,, "d_array1=",d_array1);
---------------------------
0 d_array1 size = 5
0 d_array1='{'h2, 'h3, 'h4, 'h6, 'h0}

Copying ofDynamic Arrays

可以將一個(gè)動(dòng)態(tài)數(shù)組復(fù)制到另一個(gè)動(dòng)態(tài)數(shù)組。

module darray; //copying of arrays
 int oarray [ ];
 int carray [ ];
 initial begin
 // Allocate 5 memory locations to "oarray" and
 // initialize with values
 oarray = new [5];
 oarray = '{1, 2, 3, 4, 5};
 carray = oarray; // copy "oarray" to "carray"
 $display ("carray = %p", carray);
 // Grow size by 1 and copy existing elements to the 
"carray"
 carray = new [carray.size( ) + 1] (carray);
 $display("carray size = %0d",carray.size);
 // Assign value 6 to the newly added location [index 5]
 carray [carray.size( ) - 1] = 6;
 $display("carray[5]=%0d",carray[5]);
 // Display contents of new "carray"
 $display ("carray = %p", carray);
 oarray = carray; //copy carray to oarray
 $display ("oarray = %p", oarray);
 // Display size of both arrays
 $display ("oarray.size( ) = %0d, carray.size( ) = %0d", 
oarray.size( ), carray.size( ));
 end
 endmodule

我們聲明了兩個(gè)動(dòng)態(tài)數(shù)組，即“oarray”和“carray”。我們初始化“oarray”，然后復(fù)制到“carray”。然后我們增加carray的大小，將它復(fù)制回“oarray”中。

仿真log:

carray = '{1, 2, 3, 4, 5}
carray size = 6
carray[5]=6
carray = '{1, 2, 3, 4, 5, 6}
oarray = '{1, 2, 3, 4, 5, 6}
oarray.size( ) = 6, carray.size( ) = 6
 V C S S i m u l a t i o n R e p o r t

初始化數(shù)組oarray并初始化大小為5。然后復(fù)制
“oarray”到“carray。”

carray = '{1, 2, 3, 4, 5}

重新初始化“carray”，動(dòng)態(tài)數(shù)組大小增加1。所以，現(xiàn)在新創(chuàng)建的carray的大小將是6:

carray size = 6

然后我們給第6個(gè)數(shù)據(jù)項(xiàng)賦值6，然后打印整個(gè)數(shù)組:

carray [5] = 6
carray = '{1,2,3,4,5,6}

現(xiàn)在，復(fù)制“carray”回“oarray”并打印整個(gè)數(shù)組“oarray”。

oarray = '{1,2,3,4,5,6}

最后，我們顯示原始的“oarray”和復(fù)制的“carray”的大小。它們應(yīng)該是一樣的。

oarray.size( ) = 6, carray.size( ) = 6

總結(jié)來說，oarray和carray操作的實(shí)際上是同一個(gè)數(shù)組，只是通過不同的指針而已。

Dynamic Array ofArrays

動(dòng)態(tài)數(shù)組也可以多維，即動(dòng)態(tài)數(shù)組中每一個(gè)數(shù)據(jù)項(xiàng)都是一個(gè)另外的動(dòng)態(tài)數(shù)組。

module darray;
 int abc[ ][ ]; //array of arrays
 initial begin
 abc = new[3]; //sub array still not created
 $display("abc = ",abc);
 //Create sub-arrays
 foreach (abc[i]) begin
    abc[i] = new[4];
    $display("abc[%0d] = %p", i, abc[i]);
 end
    $display("abc = ",abc);
    //assign values to array and sub-array
 foreach(abc[i , j]) begin
    abc[i][j] = (j+1)+i;
 end
 //display
 foreach (abc[i , j]) begin
    $display("abc[%0d][%0d] = %0d", i, j, abc[i][j]);
 end
 $display("abc = ",abc);
 end
 endmodule

仿真log:

abc = '{'{}, '{}, '{}}
abc[0] = '{0, 0, 0, 0}
abc[1] = '{0, 0, 0, 0}
abc[2] = '{0, 0, 0, 0}
abc = '{'{0, 0, 0, 0} , '{0, 0, 0, 0} , '{0, 0, 0, 0} }
abc[0][0] = 1
abc[0][1] = 2
abc[0][2] = 3
abc[0][3] = 4
abc[1][0] = 2
abc[1][1] = 3
abc[1][2] = 4
abc[1][3] = 5
abc[2][0] = 3
abc[2][1] = 4
abc[2][2] = 5
abc[2][3] = 6
abc = '{'{1, 2, 3, 4} , '{2, 3, 4, 5} , '{3, 4, 5, 6} }
 V C S S i m u l a t i o n R e p o r t

我們聲明一個(gè)名為“abc”的二維動(dòng)態(tài)數(shù)組。然后我們分配內(nèi)存，讓它有三個(gè)元素(abc = new[3])。注意，此時(shí)只有第一維動(dòng)態(tài)數(shù)組完成了初始化，第二維動(dòng)態(tài)數(shù)組仍然沒有進(jìn)行初始化，所以都為空數(shù)組。

abc = '{'{}, '{}, '{}}

接下來，使用for循環(huán)為每個(gè)第二維數(shù)組初始化（int類型的默認(rèn)值為0）

abc[0] = '{0, 0, 0, 0}
abc[1] = '{0, 0, 0, 0}
abc[2] = '{0, 0, 0, 0}

然后就可以再次使用foreach語法遍歷賦值和打印每個(gè)數(shù)據(jù)項(xiàng)了。注意所使用的語法。

foreach(abc[i , j])

abc[0][0] = 1
abc[0][1] = 2
abc[0][2] = 3
abc[0][3] = 4
abc[1][0] = 2
abc[1][1] = 3
abc[1][2] = 4
abc[1][3] = 5
abc[2][0] = 3
abc[2][1] = 4
abc[2][2] = 5
abc[2][3] = 6

abc = '{'{1, 2, 3, 4} , '{2, 3, 4, 5} , '{3, 4, 5, 6} }

審核編輯：劉清