c语言中的大数运算模块

  随着计算机系统的快速发展，经常需要对海量数据和信息做处理，在处理这些数据时经常会遇到很大的数字，无法用int或者long等类型来存储，经常看到有人自己在写或者讨论大数相关的问题，本文描述从开源库polarssl中提取的大数bignum模块，独立出来集成到应用程序中的方法，该模块支持的大数位数不限制。

  摘取出来的模块仅仅包含：bignum.c、bignum.h、bn_mul.h三个文件，简单易用。

  相关代码和测试代码如下：

 /Files/youyou/bignum.rar

 1 #include <string.h>
 2 #include <stdio.h>
 3 
 4 #include "bignum.h"
 5 
 6 void test_add_mul()
 7 {
 8 /*
 9 //test result:
10     A = 123456789012345678901234567890
11     B = 123456789012345678901234567890
12     X = A + B
13     X = 246913578024691357802469135780
14 
15     A = 123456789012345678901234567890
16     B = 123456789012345678901234567890
17     X = A * B
18     X = 15241578753238836750495351562536198787501905199875019052100
19   
20     press any key to contiue ...
21 */
22     int ret, temp;
23     mpi A, B, X;
24     size_t n;
25     char a[ 2 * POLARSSL_MPI_MAX_SIZE + 2 ];
26     char b[ 2 * POLARSSL_MPI_MAX_SIZE + 2 ];
27     char x[ 2 * POLARSSL_MPI_MAX_SIZE + 2 ];
28 
29     n = sizeof(a);
30     temp = n - 2;    
31         
32     mpi_init( &A ); mpi_init( &B ); mpi_init( &X );
33     
34     MPI_CHK( mpi_read_string( &A, 10,
35         "123456789012345678901234567890") );
36     
37     MPI_CHK( mpi_read_string( &B, 10,
38         "123456789012345678901234567890") );
39     
40     MPI_CHK( mpi_add_mpi( &X, &A, &B ) );
41 
42     memset( a, 0, sizeof(a) );
43     memset( b, 0, sizeof(b) );
44     memset( x, 0, sizeof(x) );
45     n = temp;
46     MPI_CHK( mpi_write_string( &A, 10, a, (size_t *) &n ) );    
47     n = temp;
48     MPI_CHK( mpi_write_string( &B, 10, b, (size_t *) &n ) );    
49     n = temp;
50     MPI_CHK( mpi_write_string( &X, 10, x, (size_t *) &n ) );    
51     printf("A = %s\n", a);
52     printf("B = %s\n", b);
53     printf("X = A + B\n");
54     printf("X = %s\n", x);
55     printf("\n");
56 
57     MPI_CHK( mpi_mul_mpi( &X, &A, &B ) );
58     
59     memset( a, 0, sizeof(a) );
60     memset( b, 0, sizeof(b) );
61     memset( x, 0, sizeof(x) );
62     n = temp;
63     MPI_CHK( mpi_write_string( &A, 10, a, (size_t *) &n ) );    
64     n = temp;
65     MPI_CHK( mpi_write_string( &B, 10, b, (size_t *) &n ) );    
66     n = temp;
67     MPI_CHK( mpi_write_string( &X, 10, x, (size_t *) &n ) );    
68     printf("A = %s\n", a);
69     printf("B = %s\n", b);
70     printf("X = A * B\n");
71     printf("X = %s\n", x);
72     printf("\n");
73         
74 cleanup:
75     
76     mpi_free( &A ); mpi_free( &B ); mpi_free( &X );
77 }
78 
79 void my_pause()
80 {
81     printf("press any key to contiue ...");
82     getchar();
83 }
84 
85 int main( int argc, char *argv[] )
86 {
87 
88     test_add_mul();
89 
90     my_pause();
91 
92     return 0;

93 }