C语言编写大整数
本人写的大整数是256进制的，每一个字节里面的每一位都是有用的，因此比较节省空间。前面我用宏定义定义了大整数最大为128字节，也就是1024位，当然你可以改变SIZE的大小来改变大整数的位数。
大整数结构如下：
typedef struct BigNum //大整数结构
{
UCHAR data[SIZE]; //空间为(SIZE * sizeof(UCHAR))，就是SIZE个字节
}BigNum;
以下是头文件BigNum.h
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
#ifndef _BIGNUM_H_
#define _BIGNUM_H_
#define SIZE 128 //一个大整数用个字节保存，最多表示位大整数
#define SIZE_10 2 * SIZE
typedef unsigned char UCHAR;
typedef unsigned short USHORT;
UCHAR atox(char ch); //将一个十六进制的字符(4位)转位数字，转换失败返回xff
typedef struct BigNum //大整数结构
{
UCHAR data[SIZE]; //空间为(SIZE * sizeof(UCHAR))，就是SIZE个字节
}BigNum;
BigNum Init(char* str); //初始化大整数，str为十六进制字符串
int GetByte(BigNum bignum); //判断有多少个字节不为
BigNum MovByteLetf(BigNum bignum, int n); //左移n个字节
BigNum MovByteRight(BigNum bignum, int n); //右移n个字节
int Cmp(BigNum bignum_a, BigNum bignum_b); //大整数比较大小，>返回，<返回-1，==返回
BigNum Add(BigNum bignum_a, BigNum bignum_b); //大整数加法
BigNum Sub(BigNum bignum_a, BigNum bignum_b); //大整数减法
//BigNum Mul(BigNum bignum_a, UCHAR uchar); //大整数乘法UCHAR
BigNum Mul(BigNum bignum_a, BigNum bignum_b); //大整数乘法
BigNum Div(BigNum bignum_a, BigNum bignum_b); //大整数除法
BigNum Mod(BigNum bignum_a, BigNum bignum_b); //大整数模运算
BigNum Pow(BigNum bignum, int n); //大整数乘方运算
void Print_16(BigNum bignum); //打印十六进制大整数
void Print_10(BigNum bignum); //打印十进制大整数
#endif
//////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
以下是C文件BigNum.c
//////////////////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////
// BigNum.c : 定义控制台应用程序的入口点。
//
#include #include #include \"BigNum.h\" UCHAR atox(char ch) //将一个十六进制的字符(4位)转位数字，转换失败返回xff { UCHAR res; if (ch >= '0' && ch <= '9') { res = ch - '0'; } else if (ch >= 'a' && ch <= 'f') { res = ch - 'a' + 10; } else if (ch >= 'A' && ch <= 'F') { res = ch - 'A' + 10; } else { printf(\"change error!\\n\"); return 0xff; } return res; } int GetByte(BigNum bignum) //判断有多少个字节不为 { int ByteOfBigNum = SIZE; while ((bignum.data[ByteOfBigNum - 1] == 0) && (ByteOfBigNum > 0)) { ByteOfBigNum--; } return ByteOfBigNum; } BigNum MovByteLetf(BigNum bignum, int n) //左移n个字节 { int i; int bignum_len = GetByte(bignum); for (i = bignum_len - 1; i >= 0; i--) { if (i + n >= SIZE) { continue; } bignum.data[i + n] = bignum.data[i]; } for (i = n - 1; i >= 0; i--) { bignum.data[i] = 0; } return bignum; } BigNum MovByteRight(BigNum bignum, int n) { int i; int bignum_len = GetByte(bignum); for (i = 0; i < bignum_len; i++) { if (i + n >= SIZE) { bignum.data[i] = 0; continue; //右移n个字节 } bignum.data[i] = bignum.data[i + n]; } return bignum; } BigNum Init(char* str) //初始化大整数，str为十六进制字符串 { BigNum bignum; int len = (int)strlen(str); int i; int j = 0; if (len > 2 * SIZE) { len = 2 * SIZE; } for (i = len - 1; i > 0; i -= 2) { bignum.data[j] = atox(str[i]) + atox(str[i - 1]) * 16; j++; } if (i == 0) { bignum.data[j] = atox(str[i]); j++; } while (j < SIZE) { bignum.data[j] = 0; j++; } return bignum; } int Cmp(BigNum bignum_a, BigNum bignum_b) //大整数比较大小，>返回，<返回-1，==返回 { int bignum_a_len = GetByte(bignum_a); int bignum_b_len = GetByte(bignum_b); int max = bignum_a_len > bignum_b_len ? bignum_a_len : bignum_b_len; int i; for (i = max - 1; i >= 0; i--) { if (bignum_a.data[i] > bignum_b.data[i]) { return 1; } if (bignum_a.data[i] < bignum_b.data[i]) { return -1; } } return 0; } BigNum Add(BigNum bignum_a, BigNum bignum_b) //大整数加法 { BigNum bignum_c; USHORT temp; UCHAR carry = 0; int i; for (i = 0; i < SIZE; i++) { temp = bignum_a.data[i] + bignum_b.data[i] + carry; bignum_c.data[i] = temp & 0x00ff; carry = (temp >> 8) & 0xff; } return bignum_c; } BigNum Sub(BigNum bignum_a, BigNum bignum_b) //大整数减法 { BigNum bignum_c; USHORT temp; UCHAR carry = 0; int i; for (i = 0; i < SIZE; i++) { temp = bignum_a.data[i] - bignum_b.data[i] - carry; bignum_c.data[i] = temp & 0x00ff; carry = (temp >> 15) & 0x01; } return bignum_c; } BigNum Mul(BigNum bignum_a, BigNum bignum_b) //大整数乘法 { BigNum bignum_c = Init(\"0\"); USHORT temp; UCHAR carry; int i, j; for (i = 0; i < SIZE; i++) { carry = 0; for (j = 0; j < SIZE; j++) { temp = bignum_a.data[i] * bignum_b.data[j] + bignum_c.data[j + i] + carry; bignum_c.data[j + i] = temp & 0x00ff; carry = (temp >> 8) & 0xff; } } return bignum_c; } BigNum Div(BigNum bignum_a, BigNum bignum_b) { BigNum bignum_c = Init(\"0\"); BigNum B; int bignum_a_len; int bignum_b_len; int bignum_c_len; //大整数除法 if (Cmp(bignum_b, bignum_c) == 0) { printf(\"错误！除数为\\n\"); return bignum_c; } bignum_a_len = GetByte(bignum_a); bignum_b_len = GetByte(bignum_b); bignum_c_len = bignum_a_len - bignum_b_len; while (bignum_c_len >= 0) { B = MovByteLetf(bignum_b, bignum_c_len); while (Cmp(bignum_a, B) != -1) { bignum_a = Sub(bignum_a, B); bignum_c.data[bignum_c_len]++; } bignum_c_len--; } return bignum_c; } BigNum Mod(BigNum bignum_a, BigNum bignum_b) { BigNum bignum_c = Init(\"0\"); BigNum B; int bignum_a_len; int bignum_b_len; //大整数模运算 int bignum_c_len; if (Cmp(bignum_b, bignum_c) == 0) { printf(\"错误！除数为\\n\"); return bignum_c; } bignum_a_len = GetByte(bignum_a); bignum_b_len = GetByte(bignum_b); bignum_c_len = bignum_a_len - bignum_b_len; while (bignum_c_len >= 0) { B = MovByteLetf(bignum_b, bignum_c_len); while (Cmp(bignum_a, B) != -1) { bignum_a = Sub(bignum_a, B); } bignum_c_len--; } return bignum_a; } BigNum Pow(BigNum bignum, int n) { int i; BigNum bignum_res = Init(\"1\"); for (i = 0; i < n; i++) { //大整数乘方运算 bignum_res = Mul(bignum_res, bignum); } return bignum_res; } void Print_16(BigNum bignum) //打印十六进制大整数 { int i; int nFlag = 0; for (i = SIZE - 1; i >= 0; i--) { if (nFlag == 0 && bignum.data[i] == 0) //前面是的不打印 { continue; } else { nFlag++; if (nFlag == 1) //首位的不打印，如x01，只打印 { printf(\"%x\", bignum.data[i]); } else //后面的要打印 { printf(\"%02x\", bignum.data[i]); } } } if (nFlag == 0) { printf(\"0\"); } printf(\"\\n\"); } void Print_10(BigNum bignum) //打印十进制大整数 { int data_10[SIZE_10]; int i = 0; int j; while (Cmp(bignum, Init(\"0\")) == 1) { data_10[i] = (Mod(bignum, Init(\"a\"))).data[0]; bignum = (Div(bignum, Init(\"a\"))); i++; } for (j = i - 1; j >= 0; j--) { printf(\"%d\", data_10[j]); } printf(\"\\n\"); } ////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////////// 虽然本人的方法不是最好的，但能够基本实现1024位甚至更大的数的运算，只需要 改变SIZE的大小就可以了。 因篇幅问题不能全部显示，请点此查看更多更全内容