*(unsigned char*)0x0 = 0xdead;
时间: 2024-08-16 21:04:59 浏览: 23
这行代码是一个C语言表达式,它将无符号字符类型的指针`unsigned char*`指向地址0x0,并将其值设置为0xdead。在内存模型中,`0x0`通常表示空指针,但这里赋值为`0xdead`可能是为了示例目的或者是用来测试或者填充特定内存位置。
`unsigned char*`是一个指针变量,可以指向8位无符号数据。`= 0xdead`则是给这个指针赋予了内存地址0xdead所对应的值,`0xdead`转换成十进制是45973,不过通常来说,直接给空指针赋值这种做法并不常见,因为它可能会导致未定义的行为,尤其是在没有初始化内存区域的情况下。
相关问题
帮我分析下面这段代码 *( ( unsigned long * ) 0x40022000 ) = 0x02;
这段代码的作用是将地址为x40022000的内存空间中的值设置为x02。这里使用了类型转换,将x40022000强制转换为unsigned long类型的指针,然后通过解引用操作符*来访问该指针指向的内存空间,并将其赋值为x02。
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.