uvm_packer

Implementation of P1800.2 16.5.3.1

The LRM specifies the set_packed_* methods as being signed, whereas the uvm_object::unpack methods are specified as unsigned.  This is being tracked in Mantis 6423.

The reference implementation has implemented these methods as unsigned so as to remain consistent.

virtual function void set_packed_bits( ref bit unsigned stream[] );
virtual function void set_packed_bytes( ref byte unsigned stream[] );
virtual function void set_packed_ints( ref int unsigned stream[] );
virtual function void set_packed_longints( ref longint unsigned stream[] );

Implementation of P1800.2 16.5.3.2

The LRM specifies the get_packed_* methods as being signed, whereas the uvm_object::pack methods are specified as unsigned.  This is being tracked in Mantis 6423.

The reference implementation has implemented these methods as unsigned so as to remain consistent.

virtual function void get_packed_bits( ref bit unsigned stream[] );
virtual function void get_packed_bytes( ref byte unsigned stream[] );
virtual function void get_packed_ints( ref int unsigned stream[] );
virtual function void get_packed_longints( ref longint unsigned stream[] );

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.

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.

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.

Packs a time value as 64 bits into the pack array.

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.

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.

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.

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.

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.

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.

Unpacks the next 64 bits of the pack array and places them into a time variable.

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.

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.

Returns the number of bits that were packed.

Packs obj into the packer data stream, such that it can be unpacked via an associated unpack_object_with_meta call.

Unlike pack_object, the pack_object_with_meta method keeps track of what objects have already been packed in this call chain.  The first time an object is passed to pack_object_with_meta after a call to <flush>, the object is assigned a unique id.  Subsequent calls to pack_object_with_meta will only add the unique id to the stream.  This allows structural information to be maintained through pack/unpack operations.

Unpacks an object which was packed into the packer data stream using pack_object_with_meta.

Unlike unpack_object, the unpack_object_with_meta method keeps track of what objects have already been unpacked in this call chain.  If the packed object was null, then value is set to null.  Otherwise, if this is the first time the object’s unique id has been encountered since a call to <flush>, then unpack_object_with_meta checks value to determine if it is the correct type.  If it is not the correct type, or if value is null, then the packer shall create a new object instance for the unpack operation, using the data provided by pack_object_with_meta.  If value is of the correct type, then it is used as the object instance for the unpack operation.  Subsequent calls to unpack_object_with_meta for this unique id shall simply set value to this object instance.