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| #include <stdio.h>
//functions prototype declearation
void checkShift();
void inplaceReverseArray();
void reverse_array(int a[], size_t cnt);
int gVar;
int main()
{
int x1 = 23, y1 = 0xAA;
//pinter test
int B = -12345;
int *p;
int i;
p = &B; //pass the address of B to p
*p = 56789;
char *pc;
pc = (char *)&B;
//check pointer addressed value
printf("%d = %8.8x\n", p[0], p[0]);
printf("%d = %x\n", (char)pc[0], pc[0] & 0xFF);
//check local address & endian
for (i = 0; i < sizeof(B); i++)
{
printf("localVar @ %p:%2.2x\n", pc + i, (unsigned char)*(pc + i));
}
//check global address & endian
pc = (char *)&gVar;
gVar = 0x12345678;
for (i = 0; i < sizeof(B); i++)
{
printf("gVar @ %p:%2.2x\n", pc + i, (unsigned char)*(pc + i));
}
//check code address
printf("main @ %p\n", main);
//check lib code address
printf("printf @ %p\n", printf);
//check inplace swap
x1 = 0x23;
y1 = 0xAA;
printf("before swap: %x,%x\n", x1, y1);
inpswap(&x1, &y1);
printf("after swap: %x,%x\n", x1, y1);
printf("%d,%d\n", x1, y1);
//check Logical/arithmetic shift
checkShift();
//use inplace swap reverse array element
inplaceReverseArray();
}
//check shift bits>=variable size
//learn shift
void checkShift()
{
unsigned uBig = 0x00123456;
int varBig = (0x00123456 >> 32);
//signed constant shift by compiler
printf("signed constant shift by compiler\n");
varBig = (0x87123456 >> 32);
printf("0x87123456 >> 32: %d\n", varBig);
varBig = (0x87123456 >> 40);
printf("0x87123456 >> 40: %d\n", varBig);
varBig = (0x87123456 << 32);
printf("0x87123456 << 32: %d\n", varBig);
varBig = (0x87123456 << 40);
printf("0x87123456 << 40: %d\n", varBig);
//signed varable shift by CPU
printf("signed varible shift by CPU\n");
varBig = (0x87123456);
varBig <<= 32;
printf("0x87123456 << 32: %d\n", varBig);
varBig = (0x87123456);
varBig <<= 40;
printf("0x87123456 << 40: %d\n", varBig);
varBig = (0x87123456);
varBig >>= 32;
printf("0x87123456 >> 32: %d\n", varBig);
varBig = (0x87123456);
varBig >>= 40;
printf("0x87123456 >> 40: %d\n", varBig);
//unsigned shift by variable
printf("unsigned shift by variable\n");
uBig = 0x87654321;
uBig <<= 40;
printf("0x87654321 << 40: %d\n", uBig);
uBig = 0x87654321;
uBig <<= 32;
printf("0x87654321 << 32: %d\n", uBig);
uBig = 0x87654321;
uBig >>= 40;
printf("0x87654321 >> 40: %d\n", uBig);
uBig = 0x87654321;
uBig >>= 32;
printf("0x87654321 >> 32: %d\n", uBig);
unsigned int varBig2 = (0x123456 << 40); //compiler =>0
printf("%d\n", varBig);
}
//you can not use other array as intermidiate buffer
//参考 中文ebook p38练习题2.11，完善代码，找出BUG
//ref English Book p91 Practice Problem 2.11 complete the code & find bugs
void inplaceReverseArray()
{
int table1[] = {1, 2, 3, 4, 5};
int table2[] = {1, 2, 3, 4};
// table1
for (int i = 0; i < sizeof(table1) / sizeof(int); i++)
printf("%d\n", table1[i]);
reverse_array(table1, sizeof(table1) / sizeof(int));
for (int i = 0; i < sizeof(table1) / sizeof(int); i++)
printf("%d\n", table1[i]);
// table2
for (int i = 0; i < sizeof(table2) / sizeof(int); i++)
printf("%d\n", table2[i]);
reverse_array(table2, sizeof(table2) / sizeof(int));
for (int i = 0; i < sizeof(table2) / sizeof(int); i++)
printf("%d\n", table2[i]);
}
//reverseArray without buffer
void reverse_array(int a[], size_t cnt)
{
size_t first, last;
for (first = 0, last = cnt - 1; first < last; first++, last--)
{
inpswap(&a[first], &a[last]);
}
}
//swap without buffer
void inpswap(int *x, int *y)
{
*x = *x ^ *y;
*y = *x ^ *y;
*x = *x ^ *y;
}
|