/* show-bytes - prints byte representation of data */
/* $begin show-bytes */
#include <stdio.h>
/* $end show-bytes */
#include <stdlib.h>
#include <string.h>
/* $begin show-bytes */
typedef unsigned char *byte_pointer; /*unsigned char char和int由于有符 号，无符号和字节长短区别会有扩展*/
//typedef char *byte_pointer;
//typedef int *byte_pointer;
void show_bytes(byte_pointer start, size_t len)
{
size_t i;
for (i = 0; i < len; i++)//历遍字符
printf("%p\t0x%.2x\n", &start[i], start[i]); //得到存储地址及该存储地址里的字符
printf("\n");
}
void show_int(int x)//显示int型整数的存储方式
{
show_bytes((byte_pointer) &x, sizeof(int));
}
void show_float(float x)//显示float型浮点数的存储方式
{
show_bytes((byte_pointer) &x, sizeof(float));
}
void show_pointer(void *x)
{
show_bytes((byte_pointer) &x, sizeof(void *));
}
/* $end show-bytes */
/* $begin test-show-bytes */
void test_show_bytes(int val)
{
int ival = val;
//float fval = (float) ival; //将ival从int型转化为float
double fval = (double) ival; //将ival从int型转化为double
int *pval = &ival;
printf("Stack variable ival = %d\n", ival); //输出转换后ival的值
printf("(int)ival:\n");
show_int(ival); //显示int型ival的存储方式
printf("(float)ival:\n");
show_float(fval); //显示float型ival的存储方式
printf("&ival:\n");
show_pointer(pval); //显示ival的地址
}
/* $end test-show-bytes */
//可判断机器是大端存储还是小端存储
void simple_show_a()
{
/* $begin simple-show-a */
int val = 0x87654321;
byte_pointer valp = (byte_pointer) &val;
show_bytes(valp, 1); /* A. */
show_bytes(valp, 2); /* B. */
show_bytes(valp, 3); /* C. */
/* $end simple-show-a */
}
void simple_show_b()
{
/* $begin simple-show-b */
int val = 0x12345678;
byte_pointer valp = (byte_pointer) &val;
show_bytes(valp, 1); /* A. */
show_bytes(valp, 2); /* B. */
show_bytes(valp, 3); /* C. */
/* $end simple-show-b */
}
void float_eg()
{
int x = 3490593;
float f = (float) x; //将int型转化为float型
printf("For x = %d\n", x); //输出转化后的数值
show_int(x); //输出该数据为int型时的存储方式
show_float(f); //输出该数据为float型时的存储方式
x = 3510593;
f = (float) x;
printf("For x = %d\n", x);
show_int(x);
show_float(f);
}
void string_ueg() //大写字母在计算机中的存储方式
{
/* $begin show-ustring */
const char *s = "ABCDEF"; //定义为const常量使之不允许被改变
show_bytes((byte_pointer) s, strlen(s));
/* $end show-ustring */
}
void string_leg() //小写字母在计算机中的存储方式
{
/* $begin show-lstring */
const char *s = "abcdef";
show_bytes((byte_pointer) s, strlen(s));
/* $end show-lstring */
}
void show_twocomp() //求一个数的补码
{
/* $begin show-twocomp */
short x = 12345;
short mx = -x;
show_bytes((byte_pointer) &x, sizeof(short));
show_bytes((byte_pointer) &mx, sizeof(short));
/* $end show-twocomp */
}
int main(int argc, char *argv[])
{
int val = 12345;
if (argc > 1) //输入测试数据
{
val = strtol(argv[1], NULL, 0);
printf("calling test_show_bytes\n");
test_show_bytes(val);
}
else //未输入测试数据
{
printf("calling show_twocomp\n");
show_twocomp();
printf("Calling simple_show_a\n");
simple_show_a();
printf("Calling simple_show_b\n");
simple_show_b();
printf("Calling float_eg\n");
float_eg();
printf("Calling string_ueg\n");
string_ueg();
printf("Calling string_leg\n");
string_leg();
}
return 0;
}
/*不带参数的运行结果
calling show_twocomp
0xbfa18b4c 0x39
0xbfa18b4d 0x30
0xbfa18b4e 0xc7
0xbfa18b4f 0xcf
Calling simple_show_a
0xbfa18b48 0x21
0xbfa18b48 0x21
0xbfa18b49 0x43
0xbfa18b48 0x21
0xbfa18b49 0x43
0xbfa18b4a 0x65
Calling simple_show_b
0xbfa18b48 0x78
0xbfa18b48 0x78
0xbfa18b49 0x56
0xbfa18b48 0x78
0xbfa18b49 0x56
0xbfa18b4a 0x34
Calling float_eg
For x = 3490593
0xbfa18b30 0x21
0xbfa18b31 0x43
0xbfa18b32 0x35
0xbfa18b33 0x00
0xbfa18b30 0x84
0xbfa18b31 0x0c
0xbfa18b32 0x55
0xbfa18b33 0x4a
For x = 3510593
0xbfa18b30 0x41
0xbfa18b31 0x91
0xbfa18b32 0x35
0xbfa18b33 0x00
0xbfa18b30 0x04
0xbfa18b31 0x45
0xbfa18b32 0x56
0xbfa18b33 0x4a
Calling string_ueg
0x8048940 0x41
0x8048941 0x42
0x8048942 0x43
0x8048943 0x44
0x8048944 0x45
0x8048945 0x46
Calling string_leg
0x8048947 0x61
0x8048948 0x62
0x8048949 0x63
0x804894a 0x64
0x804894b 0x65
0x804894c 0x66
gec@ubuntu:/mnt/hgfs/share/csapp_code$ ./a.out 1073741824
calling test_show_bytes
Stack variable ival = 1073741824
(int)ival:
0xbfd40020 0x00
0xbfd40021 0x00
0xbfd40022 0x00
0xbfd40023 0x40
(float)ival:
0xbfd40020 0x00
0xbfd40021 0x00
0xbfd40022 0x80
0xbfd40023 0x4e
&ival:
0xbfd40020 0x34
0xbfd40021 0x00
0xbfd40022 0xd4
0xbfd40023 0xbf
*/
/*改为：typedef int *byte_pointer的结果
gec@ubuntu:/mnt/hgfs/share/csapp_code$ ./a.out 1073741824
calling test_show_bytes
Stack variable ival = 1073741824
(int)ival:
0xbfae9b90 0x40000000
0xbfae9b94 0x40000000
0xbfae9b98 0x40000000
0xbfae9b9c 0xb7521940
(float)ival:
0xbfae9b90 0x4e800000
0xbfae9b94 0x40000000
0xbfae9b98 0x40000000
0xbfae9b9c 0x4e800000
&ival:
0xbfae9b90 0xbfae9ba0
0xbfae9b94 0x40000000
0xbfae9b98 0x40000000
0xbfae9b9c 0x4e800000
改为：typedef char *byte_pointer的结果
gec@ubuntu:/mnt/hgfs/share/csapp_code$ ./a.out 1073741824
calling test_show_bytes
Stack variable ival = 1073741824
(int)ival:
0xbfbe3150 0x00
0xbfbe3151 0x00
0xbfbe3152 0x00
0xbfbe3153 0x40
(float)ival:
0xbfbe3150 0x00
0xbfbe3151 0x00
0xbfbe3152 0xffffff80
0xbfbe3153 0x4e
&ival:
0xbfbe3150 0x60
0xbfbe3151 0x31
0xbfbe3152 0xffffffbe
0xbfbe3153 0xffffffbf
*/
/*calling test_show_bytes
Stack variable ival = 15213
(int)ival:
0x7fff2b9ed9cc 0x6d
0x7fff2b9ed9cd 0x3b
0x7fff2b9ed9ce 0x00
0x7fff2b9ed9cf 0x00
(float)ival:
0x7fff2b9ed9cc 0x00
0x7fff2b9ed9cd 0xb4
0x7fff2b9ed9ce 0x6d
0x7fff2b9ed9cf 0x46
&ival:
0x7fff2b9ed9c8 0xfc
0x7fff2b9ed9c9 0xd9
0x7fff2b9ed9ca 0x9e
0x7fff2b9ed9cb 0x2b
0x7fff2b9ed9cc 0xff
0x7fff2b9ed9cd 0x7f
0x7fff2b9ed9ce 0x00
0x7fff2b9ed9cf 0x00
*/
