帮我分析下面这段代码 *( ( unsigned long * ) 0x40022000 ) = 0x02;
时间: 2023-04-01 10:03:12 浏览: 101
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。
相关问题
32位操作系统 unsigned char*p1=(unsigned char *)0x801000; unsigned int* p2=(unsigned long*)0x810000; P1+5=? P2+5=? Class A{},sizeof(A)= ?
在32位操作系统中,指针的大小为4个字节。
对于问题一:`unsigned char *p1 = (unsigned char *)0x801000;` 表示将地址 `0x801000` 强制转换为 `unsigned char*` 类型的指针 `p1`。而 `P1+5` 的结果是 `0x801005`,因为 `unsigned char` 类型的指针每次偏移1个字节。
对于问题二:`unsigned int *p2 = (unsigned long *)0x810000;` 表示将地址 `0x810000` 强制转换为 `unsigned int*` 类型的指针 `p2`。而 `P2+5` 的结果是 `0x810014`,因为 `unsigned int` 类型的指针每次偏移4个字节。
对于问题三:`sizeof(A)` 表示类 `A` 的大小。这取决于类的成员变量和对齐方式。通常情况下,类的大小是其成员变量大小的总和,并且可能会根据编译器和特定系统的对齐要求进行调整。您可以使用 `sizeof(A)` 来获取类 `A` 的大小。
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.