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116 lines
3.1 KiB
116 lines
3.1 KiB
library ieee;
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use ieee.std_logic_1164.all;
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--+ including vhdl 2008 libraries
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--+ These lines can be commented out when using
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--+ a simulator with built-in VHDL 2008 support
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--library ieee_proposed;
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-- use ieee_proposed.standard_additions.all;
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-- use ieee_proposed.std_logic_1164_additions.all;
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package StackP is
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-- linked list stack interface
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type t_stack is protected
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procedure push (data : in std_logic_vector);
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procedure pop (data : inout std_logic_vector);
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procedure init (logging : in boolean := false);
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impure function is_empty return boolean;
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impure function fillstate return natural;
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end protected t_stack;
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end package StackP;
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package body StackP is
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-- linked list stack implementation
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type t_stack is protected body
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type t_entry;
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type t_entry_ptr is access t_entry;
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type t_data_ptr is access std_logic_vector;
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type t_entry is record
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data : t_data_ptr;
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last_entry : t_entry_ptr;
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next_entry : t_entry_ptr;
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end record t_entry;
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variable v_head : t_entry_ptr := null;
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variable v_tail : t_entry_ptr := null;
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variable v_count : natural := 0;
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variable v_logging : boolean := false;
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-- write one entry into queue by
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-- creating new entry at head of list
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procedure push (data : in std_logic_vector) is
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variable v_entry : t_entry_ptr;
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begin
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if (v_count /= 0) then
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v_entry := new t_entry;
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v_entry.data := new std_logic_vector'(data);
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v_entry.last_entry := v_head;
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v_entry.next_entry := null;
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v_head := v_entry;
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v_head.last_entry.next_entry := v_head;
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else
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v_head := new t_entry;
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v_head.data := new std_logic_vector'(data);
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v_head.last_entry := null;
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v_head.next_entry := null;
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v_tail := v_head;
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end if;
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v_count := v_count + 1;
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if v_logging then
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report t_stack'instance_name & " pushed 0x" & to_hstring(data) & " on stack";
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end if;
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end procedure push;
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-- read one entry from queue at tail of list and
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-- delete that entry from list after read
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procedure pop (data : inout std_logic_vector) is
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variable v_entry : t_entry_ptr := v_head;
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begin
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assert not(is_empty)
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report "pop from empty queue -> discarded"
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severity failure;
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data := v_head.data.all;
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v_head := v_head.last_entry;
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deallocate(v_entry.data);
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deallocate(v_entry);
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v_count := v_count - 1;
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if v_logging then
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report t_stack'instance_name & " popped 0x" & to_hstring(data) & " from stack";
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end if;
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end procedure pop;
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procedure init (logging : in boolean := false) is
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begin
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v_logging := logging;
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end procedure init;
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-- returns true if queue is empty, false otherwise
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impure function is_empty return boolean is
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begin
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return v_head = null;
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end function is_empty;
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-- returns number of filled slots in queue
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impure function fillstate return natural is
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begin
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return v_count;
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end function fillstate;
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end protected body t_stack;
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end package body StackP;
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