The uvm_packer class provides a policy object for packing and unpacking uvm_objects. The policies determine how packing and unpacking should be done. Packing an object causes the object to be placed into a bit (byte or int) array. If the `uvm_field_* macro are used to implement pack and unpack, by default no metadata information is stored for the packing of dynamic objects (strings, arrays, class objects).
uvm_packer | |
The uvm_packer class provides a policy object for packing and unpacking uvm_objects. | |
Packing | |
pack_field | Packs an integral value (less than or equal to 4096 bits) into the packed array. |
pack_field_int | Packs the integral value (less than or equal to 64 bits) into the pack array. |
pack_string | Packs a string value into the pack array. |
pack_time | Packs a time value as 64 bits into the pack array. |
pack_real | Packs a real value as 64 bits into the pack array. |
pack_object | Packs an object value into the pack array. |
Unpacking | |
is_null | This method is used during unpack operations to peek at the next 4-bit chunk of the pack data and determine if it is 0. |
unpack_field_int | Unpacks bits from the pack array and returns the bit-stream that was unpacked. |
unpack_field | Unpacks bits from the pack array and returns the bit-stream that was unpacked. |
unpack_string | Unpacks a string. |
unpack_time | Unpacks the next 64 bits of the pack array and places them into a time variable. |
unpack_real | Unpacks the next 64 bits of the pack array and places them into a real variable. |
unpack_object | Unpacks an object and stores the result into value. |
get_packed_size | Returns the number of bits that were packed. |
Variables | |
physical | This bit provides a filtering mechanism for fields. |
abstract | This bit provides a filtering mechanism for fields. |
use_metadata | This flag indicates whether to encode metadata when packing dynamic data, or to decode metadata when unpacking. |
big_endian | This bit determines the order that integral data is packed (using pack_field, pack_field_int, pack_time, or pack_real) and how the data is unpacked from the pack array (using unpack_field, unpack_field_int, unpack_time, or unpack_real). |
virtual function void pack_field ( uvm_bitstream_t value, int size )
Packs an integral value (less than or equal to 4096 bits) into the packed array. size is the number of bits of value to pack.
virtual function void pack_field_int ( logic[63:0] value, int size )
Packs the integral value (less than or equal to 64 bits) into the pack array. The size is the number of bits to pack, usually obtained by $bits. This optimized version of pack_field is useful for sizes up to 64 bits.
virtual function void pack_string ( string value )
Packs a string value into the pack array.
When the metadata flag is set, the packed string is terminated by a null character to mark the end of the string.
This is useful for mixed language communication where unpacking may occur outside of SystemVerilog UVM.
virtual function void pack_time ( time value )
Packs a time value as 64 bits into the pack array.
virtual function void pack_real ( real value )
Packs a real value as 64 bits into the pack array.
The real value is converted to a 6-bit scalar value using the function $real2bits before it is packed into the array.
virtual function void pack_object ( uvm_object value )
Packs an object value into the pack array.
A 4-bit header is inserted ahead of the string to indicate the number of bits that was packed. If a null object was packed, then this header will be 0.
This is useful for mixed-language communication where unpacking may occur outside of SystemVerilog UVM.
virtual function bit is_null ()
This method is used during unpack operations to peek at the next 4-bit chunk of the pack data and determine if it is 0.
If the next four bits are all 0, then the return value is a 1; otherwise it is 0.
This is useful when unpacking objects, to decide whether a new object needs to be allocated or not.
virtual function logic[63:0] unpack_field_int ( int size )
Unpacks bits from the pack array and returns the bit-stream that was unpacked.
size is the number of bits to unpack; the maximum is 64 bits. This is a more efficient variant than unpack_field when unpacking into smaller vectors.
virtual function uvm_bitstream_t unpack_field ( int size )
Unpacks bits from the pack array and returns the bit-stream that was unpacked. size is the number of bits to unpack; the maximum is 4096 bits.
virtual function string unpack_string ( int num_chars = -1 )
Unpacks a string.
num_chars bytes are unpacked into a string. If num_chars is -1 then unpacking stops on at the first null character that is encountered.
virtual function time unpack_time ()
Unpacks the next 64 bits of the pack array and places them into a time variable.
virtual function real unpack_real ()
Unpacks the next 64 bits of the pack array and places them into a real variable.
The 64 bits of packed data are converted to a real using the $bits2real system function.
virtual function void unpack_object ( uvm_object value )
Unpacks an object and stores the result into value.
value must be an allocated object that has enough space for the data being unpacked. The first four bits of packed data are used to determine if a null object was packed into the array.
The is_null function can be used to peek at the next four bits in the pack array before calling this method.
bit physical = 1
This bit provides a filtering mechanism for fields.
The abstract and physical settings allow an object to distinguish between two different classes of fields. It is up to you, in the uvm_object::do_pack and uvm_object::do_unpack methods, to test the setting of this field if you want to use it as a filter.
bit abstract = 0
This bit provides a filtering mechanism for fields.
The abstract and physical settings allow an object to distinguish between two different classes of fields. It is up to you, in the uvm_object::do_pack and uvm_object::do_unpack routines, to test the setting of this field if you want to use it as a filter.
bit use_metadata = 0
This flag indicates whether to encode metadata when packing dynamic data, or to decode metadata when unpacking. Implementations of uvm_object::do_pack and uvm_object::do_unpack should regard this bit when performing their respective operation. When set, metadata should be encoded as follows:
bit big_endian = 1
This bit determines the order that integral data is packed (using pack_field, pack_field_int, pack_time, or pack_real) and how the data is unpacked from the pack array (using unpack_field, unpack_field_int, unpack_time, or unpack_real). When the bit is set, data is associated msb to lsb; otherwise, it is associated lsb to msb.
The following code illustrates how data can be associated msb to lsb and lsb to msb:
class mydata extends uvm_object; logic[15:0] value = 'h1234; function void do_pack (uvm_packer packer); packer.pack_field_int(value, 16); endfunction function void do_unpack (uvm_packer packer); value = packer.unpack_field_int(16); endfunction endclass mydata d = new; bit bits[]; initial begin d.pack(bits); // 'b0001001000110100 uvm_default_packer.big_endian = 0; d.pack(bits); // 'b0010110001001000 end
Packs an integral value (less than or equal to 4096 bits) into the packed array.
virtual function void pack_field ( uvm_bitstream_t value, int size )
Packs the integral value (less than or equal to 64 bits) into the pack array.
virtual function void pack_field_int ( logic[63:0] value, int size )
Packs a string value into the pack array.
virtual function void pack_string ( string value )
Packs a time value as 64 bits into the pack array.
virtual function void pack_time ( time value )
Packs a real value as 64 bits into the pack array.
virtual function void pack_real ( real value )
Packs an object value into the pack array.
virtual function void pack_object ( uvm_object value )
This method is used during unpack operations to peek at the next 4-bit chunk of the pack data and determine if it is 0.
virtual function bit is_null ()
Unpacks bits from the pack array and returns the bit-stream that was unpacked.
virtual function logic[63:0] unpack_field_int ( int size )
Unpacks bits from the pack array and returns the bit-stream that was unpacked.
virtual function uvm_bitstream_t unpack_field ( int size )
Unpacks a string.
virtual function string unpack_string ( int num_chars = -1 )
Unpacks the next 64 bits of the pack array and places them into a time variable.
virtual function time unpack_time ()
Unpacks the next 64 bits of the pack array and places them into a real variable.
virtual function real unpack_real ()
Unpacks an object and stores the result into value.
virtual function void unpack_object ( uvm_object value )
Returns the number of bits that were packed.
virtual function int get_packed_size()
This bit provides a filtering mechanism for fields.
bit physical = 1
This bit provides a filtering mechanism for fields.
bit abstract = 0
This flag indicates whether to encode metadata when packing dynamic data, or to decode metadata when unpacking.
bit use_metadata = 0
This bit determines the order that integral data is packed (using pack_field, pack_field_int, pack_time, or pack_real) and how the data is unpacked from the pack array (using unpack_field, unpack_field_int, unpack_time, or unpack_real).
bit big_endian = 1
The do_pack method is the user-definable hook called by the pack methods.
virtual function void do_pack ( uvm_packer packer )
The do_unpack method is the user-definable hook called by the unpack method.
virtual function void do_unpack ( uvm_packer packer )