LINT: Large Integer Object Library

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Introduction

Lint is a signed large integer data type class library that supports all mathematical operators available to other intrinsic integer data types. The precision is not arbitrary as in other available libraries. Rather, the number of bits that make up a lint variable is dependent on the value of a #define directive declared in the header file.

Background

So why yet another large integer library?  Several reasons, among which:

• I wanted a class that supported all possible overloaded operators so that I could use a lint just exactly like I might use an intrinsic data type such as an int or long. None of the free implementations I could find seemed to support ALL overloadable operators.
• I wanted a class that was specifically created with Visual C++ and IA-32 based PC architecture in mind. I didn't want a library that sacrificed execution speed for the sake of cross-compiler and cross-platform compatibility.  I wanted a library that I could optimize with in-line assembly code.
• I wanted a class whose methods were as fast and efficient as possible. Arbitrary-precision logic and floating point logic bring with them a performance hit. This library is efficient because precision is not arbitrary and all operations are strictly integer based. In this way, I could write highly optimized assembly routines given a known data type and size.

Using the Code

Once you include the header file in your source, using a lint is similar to using any other numeric data type in C++. The few notable exceptions are in declaration, assignment, and output.

#include "lint.h"
#include <stdio.h>

int main() {
    lint a = 1234;          // value assignment of a literal
    lint b = -5678;         // a lint is a signed integer data type
    lint c = a;             // assignment to another lint value
    lint d = "457639857304951675093650987359087";   	// use a string for those 
						// really BIG numbers
    lint e = "-563857365015613047563";	     // this works for negative values too
    
    lint x, y, z;
    x = d*e+a*b;            // math shouldn't be a problem.
    y = x/(e*e);
    
    // assignment to zero is the only ambiguous operation 
    // that you need to be specific on.
    z = (signed long)0;                                

    // the class allocates its own buffer to print a 
    // character representation of its value.
    // By default, it prints in base 10
    printf( "y base 10 = %s\n", z.value() );
    
    // You can print in another radix though - anything from 2 to 36
    printf( "y base 16 = %s\n", z.value(16) );
    printf( "y base 2 = %s\n", z.value(2) );
    
    // Internally, the memory for a lint is laid out going from 
    // MSB to LSB in an array of 32-bit DWORDs.
    // [2047th bit ... 1024th bit ... 0th bit]
    
    // If you need more or less than 2048 bit numbers, open lint.h
    // and redefine LINT_LENGTH
    
    // Lastly, the function call operator allows direct referential 
    // access to the DWORDs that comprise
    // a lint value.
    y(0) = 0x12345678;                  	// This sets the Most Significant 
					// DWORD to 0x12345678
    long my_bit_field = y(LAST_DWORD);  	// LAST_DWORD is a constant defined 
					// in the header file
    
    return 0;
}

Points of Interest

Implementing the conditional testing was a real bugger. My implementation works, but I think there must be a better way to do it.  There are additional things I'd like to do to the library as well.

• Possibly implement faster multiplication and division algorithms using FFT, Barrett, or whatever.
• Add capability to assign a value using a string in any radix from 2 to 36, not just base 10.
• Make use of MMX and XMM registers for even faster inline assembly.

History

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)