converts.~pa

ART OF Assembly Language Programming, 很不错

unit Converts;
interface

uses
  SysUtils, WinTypes, WinProcs, Messages, Classes, Graphics, Controls,
  Forms, Dialogs, StdCtrls, ExtCtrls;

function CheckHex(const hex:string):boolean;
function CheckDec(const dec:string):boolean;
function CheckUnsigned(const dec:string):boolean;
function CheckBin(const bin:string):boolean;
function BinToInt(const bin:string):integer;
function IntToBin(Value:LongInt; Digits:cardinal):TCaption;
function IntToHex(Value:LongInt; Digits:cardinal):TCaption;
function HexToInt(const hex:string):integer;




implementation
{ The following function returns true if the string parameter contains }
{ a legal representation of a 16-bit hexadecimal value.                }
{ Keep in mind that "Result" is where Delphi functions return their    }
{ function result.                                                     }

function CheckHex(const hex:string):boolean;
const
     HexVals = ['0'..'9', 'A'..'F', 'a'..'f'];
var
     index:integer;
     len:  integer;
begin

     len := length(hex);
     Result := (len <> 0) and (len <= 4);
     for index := 1 to len do begin

         Result := Result and (hex[index] in HexVals);

     end;
end;





{ The following function checks its parameter to see if it is a string }
{ that properly represents a signed decimal value.                     }

function CheckDec(const dec:string):boolean;
const
     DecVals = ['0'..'9'];
var
     index:integer;
     len:  integer;
     Start:integer;
begin

     len := length(dec);

     { First, check for total bail-out conditions; this would be any value }
     { greater than +32767 or less than -32768; a string that is just too  }
     { long, a zero length string, or a string containing only the '-'.    }

     Result := false;
     Start := 1;
     if (len = 0) then exit;
     if (dec[1] = '-') then begin

        if (len = 1) then exit;
        if (len > 6) then exit;
        if (len = 6) and (dec > '-32768') then exit;

        Start := 2;  { Skip over '-' when testing characters }

     end
     else begin

          if (len >= 6) then exit;
          if (len = 5) and (dec > '32767') then exit;

     end;



     { Okay, if the length is five or six, it is not a numeric value that  }
     { is out of range.  However, the string could still contain illegal   }
     { characters.  We'll check for that down here.                        }

     Result := true;
     for index := Start to len do
         Result := Result and (dec[index] in DecVals);
end;




{ CheckUnsigned is the same operation as CheckDec except it does not have  }
{ to worry about negative numbers.                                         }

function CheckUnsigned(const dec:string):boolean;
const
     DecVals = ['0'..'9'];
var
     index:integer;
     len:  integer;
begin

     len := length(dec);

     { Check for totally illegal values here }

     Result := false;
     if (len = 0) then exit;
     if (len >= 6) then exit;
     if (len = 5) and (dec > '65535') then exit;


     { If the tests above succeeded, check the individual characters here. }

     Result := true;
     for index := 1 to len do
         Result := Result and (dec[index] in DecVals);
end;




{ CheckBin checks the "bin" string to see if it is a valid binary number.  }
{ This particular function allows spaces in binary numbers;  this lets the }
{ use separate nibbles in a long binary string for readability.  Note that }
{ this function allows spaces to occur in arbitrary places in the string,  }
{ it simply ignores the spaces.                                            }

function CheckBin(const bin:string):boolean;
const
     BinVals = ['0','1',' '];
var
     index:integer;
     len:  integer;
     Bits: integer;
begin

     len := length(bin);

     { if the string's length is zero or greater than 19 (16 digits plus   }
     { three spaces to separate the nibbles) then immediately return an    }
     { error.                                                              }

     Result := (len <> 0) and (len <= 19);
     if (not Result) then exit;

     { If the length of the string is okay, then check each character in   }
     { the string to make sure it is a zero, one, or a space.              }

     Bits := 0;
     for index := 1 to len do begin

         Result := Result and (bin[index] in BinVals);
         Bits := Bits + ord(bin[index] = '0' or bin[index] = '1');

     end;
     Result := Result and (Bits <=16) and (Bits > 0);
end;






{ IntToBin-                                                           }
{                                                                     }
{    This function converts an integer value to a string of zeros and }
{    ones -- the binary representation of that integer.  The integer  }
{    to convert is the first parameter passed to this function.  The  }
{    second parameter specifies the number of digits to place in the  }
{    output string (maximum 16);  If the Digits value is less than    }
{    the number of bits actually present in the first parameter, this }
{    function outputs the L.O. 'Digits' bits.  Note that this routine }
{    inserts space between each group of four digits in order to make }
{    the output more readable.                                        }

function IntToBin(
                    Value:LongInt;
                    Digits:cardinal
                 ):TCaption;
var
   Mask: cardinal;
   Count:integer;
begin


     { Result will hold the string this function produces }

     Result := '';

     { Create a mask value with a single bit in the H.O. bit position }
     { so we can use it to see if the current value contains a zero   }
     { or one in its H.O. bit.                                        }

     Mask := $8000;

     { Eliminate the bits we're not interested in outputting.  This   }
     { adjusts the value so the first bit we want to test is located  }
     { in bit #15 of Value.                                           }

     Value := Value shl (16-Digits);

     { For each of the bits we want in the output string, test the    }
     { current value to see if it's H.O. bit is zero or one.  Append  }
     { the corresponding character to the end of the result string.   }
     { If the bit position is an even multiple of four, append a      }
     { a space as well, although this code will not append a space to }
     { the end of the string.                                         }

     Count := 16-Digits;        {# of bits we're going to test.       }

     While (true) do begin      {Really a loop..endloop construct.    }

         if ((Value and Mask) <> 0) then
              AppendStr(Result, '1')
         else AppendStr(Result,'0');

         inc(Count);
         if (Count > 15) then break;

         { After bits 3, 7, and 11, append a space to the string.     }

         if (Count mod 4) = 0 then AppendStr(Result,' ');

         { Adjust the Mask for the next loop iteration.  This moves   }
         { the single one bit in Mask one position to the right so it }
         { tests the next lower bit in Value.                         }

         Mask := Mask shr 1;

     end;
end;





{ IntToHex-                                                           }
{                                                                     }
{    This function converts an integer value to a string of hex       }
{    characters.  The integer to convert is the first parameter.      }
{    The second parameter specifies the number of digits to place in  }
{    the output string (maximum 4);  If the Digits value is less than }
{    the number of bits actually present in the first parameter, this }
{    function outputs the L.O. digits.                                }

function IntToHex(Value:LongInt; Digits:cardinal):TCaption;
const
     HexChars:array [0..$f] of char =
                            ('0','1','2','3','4','5','6','7','8','9',
                             'A','B','C','D','E','F');
var
   Count:integer;
begin


     { Result will hold the string this function produces }

     Result := '';


     { For each of the nibbles we want to output, append the corres-   }
     { ponding hex digit.                                              }

     for Count := Digits-1 downto 0 do begin

         AppendStr(Result, HexChars[ (Value shr (Count*4)) and $f]);

     end;
end;





{ HexToInt-                                                           }
{                                                                     }
{ This routine converts a string of characters that represent a hexa- }
{ decimal value into the corresponding integer value.  This routine   }
{ assumes that the string is a valid representation of a hexadecimal  }
{ value.  One should call "CheckHex" prior to this routine if not     }
{ absolutely sure that the string is valid.                           }

function HexToInt(const hex:string):integer;
var
   index:integer;
begin

     Result := StrToInt('$'+hex);

end;



{ BinToInt-                                                           }
{                                                                     }
{ The following routine converts a string containing a sequence of    }
{ ones and zeros (i.e., a binary number representation) into an inte- }
{ ger value.  Note that this routine ignores any spaces appearing in  }
{ the binary string;  this allows the user to place spaces in the     }
{ binary number to make it more readable.                             }

function BinToInt(const bin:string):integer;
var
   index:integer;
begin

     Result := 0;
     for index := 1 to length(bin) do
         if bin[index] <> ' ' then
            Result := (Result shl 1) + (ord(bin[index]) and $1);

end;








end.