integer_class.bdy

6端口寄存器IP内核VHDL源代码

-- +------------------------------------
-- | Library: VFP
-- | Designer: Tim Pagden
-- | Opened: 28 Dec 1997
-- +------------------------------------

package body integer_class is
  
  -- extensions to std.standard.integer
  -- integer defined in std.standard
  
  -- arithmetic operators
  -- defined in std.standard

  -- general purpose functions

  function integer_wordlength (
    a: integer        
  ) return integer is           
    variable wordlength: integer;    
  begin
    if (a >= -2) and (a <= 1) then
      wordlength := 2;
    elsif (a >= -4) and (a <= 3) then  
      wordlength := 3;
    elsif (a >= -8) and (a <= 7) then  
      wordlength := 4;
    elsif (a >= -16) and (a <= 15) then  
      wordlength := 5;
    elsif (a >= -32) and (a <= 31) then  
      wordlength := 6;
    elsif (a >= -64) and (a <= 63) then  
      wordlength := 7;
    elsif (a >= -128) and (a <= 127) then  
      wordlength := 8;
    elsif (a >= -256) and (a <= 255) then  
      wordlength := 9;
    elsif (a >= -512) and (a <= 511) then  
      wordlength := 10;
    elsif (a >= -1024) and (a <= 1023) then  
      wordlength := 11;
    elsif (a >= -2048) and (a <= 2047) then  
      wordlength := 12;
    elsif (a >= -4096) and (a <= 4095) then  
      wordlength := 13;
    elsif (a >= -8192) and (a <= 8191) then  
      wordlength := 14;
    elsif (a >= -16384) and (a <= 16383) then  
      wordlength := 15;
    elsif (a >= -32768) and (a <= 32767) then  
      wordlength := 16;
    elsif (a >= -65536) and (a <= 65535) then  
      wordlength := 17;
    elsif (a >= -131072) and (a <= 131071) then  
      wordlength := 18;
    elsif (a >= -262144) and (a <= 262143) then  
      wordlength := 19;
    elsif (a >= -524288) and (a <= 524287) then  
      wordlength := 20;
    elsif (a >= -1048576) and (a <= 1048575) then  
      wordlength := 21;
    elsif (a >= -2097152) and (a <= 2097151) then  
      wordlength := 22;
    elsif (a >= -4194304) and (a <= 4194303) then  
      wordlength := 23;
    elsif (a >= -8388608) and (a <= 8388607) then  
      wordlength := 24;
    elsif (a >= -16777216) and (a <= 16777215) then  
      wordlength := 25;
    elsif (a >= -33554432) and (a <= 33554431) then  
      wordlength := 26;
    elsif (a >= -67108864) and (a <= 67108863) then  
      wordlength := 27;
    elsif (a >= -134217728) and (a <= 134217727) then  
      wordlength := 28;
    elsif (a >= -268435456) and (a <= 268435455) then  
      wordlength := 29;
    elsif (a >= -536870912) and (a <= 536870911) then  
      wordlength := 30;
    elsif (a >= -1073741824) and (a <= 1073741823) then  
      wordlength := 31;
    elsif (a >= integer'low) and (a <= integer'high) then  -- i'low = -2147483647
      wordlength := 32;                                    -- or -2147483648
    end if;                                                -- depending upon implementation
    return wordlength;
  end integer_wordlength;
  
  function integer_charlength (   -- 29.12.97
    a: integer
  ) return integer is
    variable a_natural : natural;
    variable num_chars : integer := 0;
  begin
    a_natural := abs(a);
    case a_natural is
      when 0 to 9 =>
        num_chars := 1;
      when 10 to 99 =>
        num_chars := 2;
      when 100 to 999 =>
        num_chars := 3;
      when 1000 to 9999 =>
        num_chars := 4;
      when 10_000 to 99_999 =>
        num_chars := 5;
      when 100_000 to 999_999 =>
        num_chars := 6;
      when 1_000_000 to 9_999_999 =>
        num_chars := 7;
      when 10_000_000 to 99_999_999 =>
        num_chars := 8;
      when 100_000_000 to 999_999_999 =>
        num_chars := 9;
      when 1_000_000_000 to integer'high =>
        num_chars := 10;
    end case;
    if a < 0 then
      num_chars := num_chars+1;
    end if;
    return num_chars;
  end integer_charlength;

  -- ancillary function required in order to 
  -- enable the integer -> ? functions in generic_conversions 
  -- to be completed with only the required number of
  -- bits of precision in the length of the vectors.
  
  function next_greater_binary_power_minus_1 (
    a: integer        
  ) return integer is           
    variable power_minus_1: integer;    
  begin
    if (a >= -2) and (a <= 1) then
      power_minus_1 := 1;
    elsif (a >= -4) and (a <= 3) then  
      power_minus_1 := 3;
    elsif (a >= -8) and (a <= 7) then  
      power_minus_1 := 7;
    elsif (a >= -16) and (a <= 15) then  
      power_minus_1 := 15;
    elsif (a >= -32) and (a <= 31) then  
      power_minus_1 := 31;
    elsif (a >= -64) and (a <= 63) then  
      power_minus_1 := 63;
    elsif (a >= -128) and (a <= 127) then  
      power_minus_1 := 127;
    elsif (a >= -256) and (a <= 255) then  
      power_minus_1 := 255;
    elsif (a >= -512) and (a <= 511) then  
      power_minus_1 := 511;
    elsif (a >= -1024) and (a <= 1023) then  
      power_minus_1 := 1023;
    elsif (a >= -2048) and (a <= 2047) then  
      power_minus_1 := 2047;
    elsif (a >= -4096) and (a <= 4095) then  
      power_minus_1 := 4095;
    elsif (a >= -8192) and (a <= 8191) then  
      power_minus_1 := 8191;
    elsif (a >= -16384) and (a <= 16383) then  
      power_minus_1 := 16383;
    elsif (a >= -32768) and (a <= 32767) then  
      power_minus_1 := 32767;
    elsif (a >= -65536) and (a <= 65535) then  
      power_minus_1 := 65535;
    elsif (a >= -131072) and (a <= 131071) then  
      power_minus_1 := 131071;
    elsif (a >= -262144) and (a <= 262143) then  
      power_minus_1 := 262143;
    elsif (a >= -524288) and (a <= 524287) then  
      power_minus_1 := 524287;
    elsif (a >= -1048576) and (a <= 1048575) then  
      power_minus_1 := 1048575;
    elsif (a >= -2097152) and (a <= 2097151) then  
      power_minus_1 := 2097151;
    elsif (a >= -4194304) and (a <= 4194303) then  
      power_minus_1 := 4194303;
    elsif (a >= -8388608) and (a <= 8388607) then  
      power_minus_1 := 8388607;
    elsif (a >= -16777216) and (a <= 16777215) then  
      power_minus_1 := 16777215;
    elsif (a >= -33554432) and (a <= 33554431) then  
      power_minus_1 := 33554431;
    elsif (a >= -67108864) and (a <= 67108863) then  
      power_minus_1 := 67108863;
    elsif (a >= -134217728) and (a <= 134217727) then  
      power_minus_1 := 134217727;
    elsif (a >= -268435456) and (a <= 268435455) then  
      power_minus_1 := 268435455;
    elsif (a >= -536870912) and (a <= 536870911) then  
      power_minus_1 := 536870911;
    elsif (a >= -1073741824) and (a <= 1073741823) then  
      power_minus_1 := 1073741823;
    elsif (a >= integer'low) and (a <= integer'high) then  -- i'low = -2147483647
      power_minus_1 := 2147483647;                                    -- or -2147483648
    end if;                                                -- depending upon implementation
    return power_minus_1;
  end next_greater_binary_power_minus_1;

  -- hardware functions
  -- none yet defined

  -- mathematical functions

  function is_factor_of_32 (a: integer) return boolean is       -- 15.11.95
  begin
    case a is
      when 1 | 2 | 4 | 8 | 16 | 32 =>
        return TRUE;
      when others =>
        return FALSE;
    end case;
  end is_factor_of_32;
  
  function is_power_of_2 (a: integer) return boolean is       -- 15.11.95
  begin
    case a is
      when 1 | 2 | 4 | 8 | 16 | 32 | 64 | 128 | 256 | 512 | 1024 | 2048 |
           4096 | 8192 | 16384 | 32768 | 65536 | 131072 | 262144 | 524288 |
           1048576 | 2097152 | 4194304 | 8388608 | 16777216 | 33554432 |
           67108864 | 134217728 | 268435456 | 536870912 | 1073741824 =>
        return TRUE;
      when others =>
        return FALSE;
    end case;
  end is_power_of_2;
  
  function log_2 (a: integer) return integer is       -- 15.11.95
    variable remainder : integer;
    variable log_2 : integer;
  begin
    if a > 0  then
      return integer_wordlength(a) - 2;
    else
      assert FALSE
        report "log_2(a) returns an out-of-range value"
        severity warning;
      return integer'low; -- a stupid value => a 2**32-bit vector 
                          -- with an LSB of 1 !!!
    end if;
  end log_2;

end integer_class;