ch2-String

2019-10-24

How are strings represented in Verilog ?

​ A single ASCII character requires 8-bits (1 byte) and to store a string we would need as many bytes as there are number of characters in the string.

Click here to learn about Verilog Arrays

reg  [16*8-1:0]   my_string;           // Can store 16 characters
 
my_string = "How are you";             // 5 zeros are padded from MSB, and 11 char are stored
my_string = "How are you doing?"       // 19 characters; my_string will get " are you doing?"
 

Basic String Methods

​ SystemVerilog also includes a number of special methods to work with strings, which use built-in method notation.

Usage	Definition	Comments
str.len()	function int len()	Returns the number of characters in the string
str.putc()	function void putc (int i, byte c);	Replaces the ith character in the string with the given character
str.getc()	function byte getc (int i);	Returns the ASCII code of the ith character in str
str.tolower()	function string tolower();	Returns a string with characters in str converted to lowercase
str.compare(s)	function int compare (string s);	Compares str and s, as in the ANSI C stcmp function
str.icompare(s)	function int icompare (string s);	Compares str and s, like the ANSI C strcmp function
str.substr (i, j)	function string substr (int i, int j);	Returns a new string that is a substring formed by characters in position i through j of str

String Conversion Methods

(先存下，万一用上了呢)

str.atoi()	function integer atoi();	Returns the integer corresponding to the ASCII decimal representation in str
str.atohex()	function integer atohex();	Interprets the string as hexadecimal
str.atooct()	function integer atooct();	Interprets the string as octal
str.atobin()	function integer atobin();	Interprets the string as binary
str.atoreal()	function real atoreal();	Returns the real number corresponding to the ASCII decimal representation in str
str.itoa(i)	function void itoa (integer i);	Stores the ASCII decimal representation of i into str
str.hextoa(i)	function void hextoa (integer i);	Stores the ASCII hexadecimal representation of i into str
str.octtoa(i)	function void octtoa (integer i);	Stores the ASCII octal representation of i into str
str.bintoa(i)	function void bintoa (integer i);	Stores the ASCII binary representation of i into str
str.realtoa(r)	function void realtoa (real r);	Stores the ASCII real representation of r into str