struct tag {char a;short b;int c;}*p;p=0x100000 p+0x100=?
时间: 2024-05-26 12:16:11 浏览: 15
这段代码定义了一个名为 `tag` 的结构体,包含三个成员变量:`a`(类型为 `char`)、`b`(类型为 `short`)和 `c`(类型为 `int`)。接下来定义了一个指向 `tag` 结构体的指针变量 `p`,并将其初始化为 `0x100000`。最后输出 `p+0x100` 的值。
由于 `p` 的类型为 `tag*`,指针加上一个整数,会根据指针所指向的类型进行加法运算,因此 `p+0x100` 表示将 `p` 指向的地址增加 `0x100*sizeof(tag)`(即 `0x100*7`)个字节,即 `p+0x700`。因此,输出的结果是 `0x100700`。
相关问题
unsigned long datapack(void *inBuf, unsigned long len, void *outBuf) { WORD16 *hdr; BYTE *in = (BYTE *)inBuf; BYTE *out = (BYTE *)outBuf; BYTE *pscrc; BYTE *ptr = out; unsigned long i; unsigned long fcs = ~(crc32_le(~0, in, len)); *ptr++ = 0x55; *ptr++ = 0xAA; hdr = (WORD16 *)ptr; ptr += 2; *ptr++ = 0x7e; *ptr++ = 0x7e; for (i = 0; i < len; i++) { switch (in[i]) { case 0x7d: *ptr++ = 0x7d; *ptr++ = 0x5d; break; case 0x7e: *ptr++ = 0x7d; *ptr++ = 0x5e; break; default: *ptr++ = in[i]; break; } } pscrc = (BYTE *)&fcs; for (i = 0; i < 4; i++, pscrc++) { switch (*pscrc) { case 0x7d: *ptr++ = 0x7d; *ptr++ = 0x5d; break; case 0x7e: *ptr++ = 0x7d; *ptr++ = 0x5e; break; default: *ptr++ = *pscrc; break; } } *ptr++ = 0x7e; *ptr++ = 0x7e; *hdr = ptr - out - 4; return ptr - out; } 转化为python程序
Here's the Python equivalent of the given C function:
```
import struct
import binascii
def datapack(inBuf, length, outBuf):
inBytes = struct.unpack(str(length)+'B', inBuf)
fcs = binascii.crc32(bytes(inBytes)) ^ 0xffffffff
outBytes = bytearray()
outBytes.append(0x55)
outBytes.append(0xAA)
outBytes.extend(struct.pack('<H', length))
outBytes.append(0x7e)
outBytes.append(0x7e)
for b in inBytes:
if b == 0x7d:
outBytes.extend([0x7d, 0x5d])
elif b == 0x7e:
outBytes.extend([0x7d, 0x5e])
else:
outBytes.append(b)
for i in range(4):
pscrc = (fcs >> (i * 8)) & 0xff
if pscrc == 0x7d:
outBytes.extend([0x7d, 0x5d])
elif pscrc == 0x7e:
outBytes.extend([0x7d, 0x5e])
else:
outBytes.append(pscrc)
outBytes.append(0x7e)
outBytes.append(0x7e)
struct.pack_into('<H', outBytes, 2, len(outBytes) - 6)
outBuf[:len(outBytes)] = outBytes
return len(outBytes)
```
Note: This implementation assumes that `inBuf`, `len`, and `outBuf` are already byte arrays in Python. If they are not, you may need to modify the code accordingly.
char *p = (char *)0x1000; memcpy(p, &person, sizeof(struct Person));
这段代码的作用是将结构体变量person的值拷贝到内存地址0x1000处。其中,p是指向内存地址0x1000的指针,memcpy函数将person的值按照其大小(即sizeof(struct Person))拷贝到p指向的内存地址处。需要注意的是,这段代码中的内存地址0x1000是一个示例,实际使用时需要根据具体情况进行修改。同时,如果0x1000处的内存已经被占用或者没有权限访问,那么这段代码就会导致程序崩溃。
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