反转一个字节 [英] reversing a byte
问题描述
大家好，你能告诉最有效的方法来反转
byte.Function应该返回一个反转的字节。
" Ajay < AJ *********** @ gmail.com>写道：大家好，你能告诉最有效的方法来反转一个
byte.Function应该返回一个反转的字节。
通过编写一个函数来完成它。对于这个任务，C将是一个很好的语言选择
。
祝你好运。
如果你想要别人为你做这件事，我相信你能找到一个愿意讨论咨询费率的人。如果这是作业，
请给我们您的教师的电子邮件地址，以便我们直接提交我们的
解决方案。
并期待您的下一次跟进，请阅读
< http://cfaj.freeshell.org/google/>。
-
Keith Thompson（The_Other_Keith） ks***@mib.org < http：// www.ghoti.net/~kst>
圣地亚哥超级计算机中心< *> < http://users.sdsc.edu/~kst>
我们必须做点什么。这是事情。因此，我们必须这样做。
Ajay写道：大家好，你能告诉最有效的方法来反转 byte.Function应该返回一个反转的字节。
使用查找表（下面未经测试的生成代码）：
static unsigned char
reverse_byte（unsigned char b）
{
static const unsigned char b_tbl [] = {
0xff，0xfe，0xfd，0xfc，0xfb，0xfa，0xf9,0xf8，
0xf7,0xf6,0xf5,0xf4,0xf3,0xf2,0xf1,0xf0，
0xef，0xee，0xed，0xec，0xeb，0xea，0xe9,0xe8，
0xe7,0xe6,0xe5,0xe4,0xe3,0xe2,0xe1,0xe0，
0xdf ，0xde，0xdd，0xdc，0xdb，0xda，0xd9,0xd8，
0xd7,0xd6,0xd5,0xd4,0xd3,0xd2,0xd1,0xd0，
0xcf，0xce ，0xcd，0xcc，0xcb，0xca，0xc9,0xc8，
0xc7,0xc6,0xc5,0xc4,0xc3,0xc2,0xc1,0xc0，
0xbf，0xbe，0xbd ，0xbc，0xbb，0xba，0xb9,0xb8，
0xb7,0xb6,0xb5,0xb4,0xb3,0xb2,0xb1,0xb0，
0xaf，0xae，0xad，0xac，0xab，0xaa，0xa9,0xa8，
0xa7， 0xa6,0xa5,0xa4,0xa3,0xa2,0xa1,0xa0，
0x9f，0x9e，0x9d，0x9c，0x9b，0x9a，0x99,0x98，
0x97,0x96， 0x95,0x94,0x93,0x92,0x91,0x90，
0x8f，0x8e，0x8d，0x8c，0x8b，0x8a，0x89,0x88，
0x87,0x86,0x85， 0x84,0x83,0x82,0x81,0x80，
0x7f，0x7e，0x7d，0x7c，0x7b，0x7a，0x79,0x78，
0x77,0x76,0x75,0x74， 0x73,0x72,0x71,0x70，
0x6f，0x6e，0x6d，0x6c，0x6b，0x6a，0x69,0x68，
0x67,0x66,0x65,0x64,0x63， 0x62,0x61,0x60，
0x5f，0x5e，0x5d，0x5c，0x5b，0x5a，0x59,0x58，
0x57,0x56,0x55,0x54,0x53,0x52， 0x51,0x50，
0x4f，0x4e，0x4d，0x4c，0x4b，0x4a，0x49,0x48，
0x47,0x46,0x45,0x44,0x43,0x42,0x41， 0x40，
0x3f，0x3e，0x3d，0x3c，0x3b，0x3a，0x39,0x38，
0x37,0x36,0x35,0x34,0x33,0x32,0x31,0x30，
0x2f，0x2e，0x2d，0x2c，0x2b，0x2a，0x29,0x28，
0x27,0x26,0x25,0x24,0x23,0x22,0x21,0x20，
0x1f，0x1e，0x1d，0x1c，0x1b，0x1a，0x19,0x18，
0x17,0x16,0x15,0x14,0x13,0x12,0x11,0x10，
0xf ，0xe，0xd，0xc，0xb，0xa，0x9,0x8，
0x7,0x6,0x5,0x4,0x3,0x2,0x1,0x0
};
返回b_tbl [b];
}
-Charlie
Charles Mills写道：Ajay写道：大家好，你能告诉最有效的方法来扭转一个
byte.Function应返回一个反转的字节。
使用查找表（下面未经测试的生成代码）：
static unsigned char
reverse_byte（unsigned char b） ）
{const const unsigned char b_tbl [] = {
--- 8< ----完全错误的查找表--- 8< ----};
返回b_tbl [b];
}
-Charlie
可能需要这样的东西：
static const unsigned char b_tbl [] = {
0x0,0x80,0x40,0xc0,0x20,0xa0,0x60,0xe0，
0x10,0x90,0x50,0xd0,0x30,0xb0,0x70,0xf0，
......，
0xf，0x8f，0x4f，0xcf，0x2f，0xaf，0x6f，0xef，
0x1f，0x9f，0x5f，0xdf，0x3f，0xbf，0x7f， 0xff
};
你可以填空。
-Charlie
Hi all,can you please tell the most efficient method to reverse a
byte.Function should return a byte that is reversed.
"Ajay" <aj***********@gmail.com> writes:Hi all,can you please tell the most efficient method to reverse a
byte.Function should return a byte that is reversed.
By writing a function to do it. C would be a good choice of language
for this task.
Good luck.
If you want somebody else to do it for you, I''m sure you can find
someone willing to discuss consulting rates. If this is homework,
please give us your instructor''s e-mail address so we can submit our
solutions directly.
And in anticipation of your next followup, please read
<http://cfaj.freeshell.org/google/>.
--
Keith Thompson (The_Other_Keith) ks***@mib.org <http://www.ghoti.net/~kst>
San Diego Supercomputer Center <*> <http://users.sdsc.edu/~kst>
We must do something. This is something. Therefore, we must do this.
Ajay wrote:Hi all,can you please tell the most efficient method to reverse a
byte.Function should return a byte that is reversed.
Use a look up table (untested generated code below):
static unsigned char
reverse_byte(unsigned char b)
{
static const unsigned char b_tbl[] = {
0xff, 0xfe, 0xfd, 0xfc, 0xfb, 0xfa, 0xf9, 0xf8,
0xf7, 0xf6, 0xf5, 0xf4, 0xf3, 0xf2, 0xf1, 0xf0,
0xef, 0xee, 0xed, 0xec, 0xeb, 0xea, 0xe9, 0xe8,
0xe7, 0xe6, 0xe5, 0xe4, 0xe3, 0xe2, 0xe1, 0xe0,
0xdf, 0xde, 0xdd, 0xdc, 0xdb, 0xda, 0xd9, 0xd8,
0xd7, 0xd6, 0xd5, 0xd4, 0xd3, 0xd2, 0xd1, 0xd0,
0xcf, 0xce, 0xcd, 0xcc, 0xcb, 0xca, 0xc9, 0xc8,
0xc7, 0xc6, 0xc5, 0xc4, 0xc3, 0xc2, 0xc1, 0xc0,
0xbf, 0xbe, 0xbd, 0xbc, 0xbb, 0xba, 0xb9, 0xb8,
0xb7, 0xb6, 0xb5, 0xb4, 0xb3, 0xb2, 0xb1, 0xb0,
0xaf, 0xae, 0xad, 0xac, 0xab, 0xaa, 0xa9, 0xa8,
0xa7, 0xa6, 0xa5, 0xa4, 0xa3, 0xa2, 0xa1, 0xa0,
0x9f, 0x9e, 0x9d, 0x9c, 0x9b, 0x9a, 0x99, 0x98,
0x97, 0x96, 0x95, 0x94, 0x93, 0x92, 0x91, 0x90,
0x8f, 0x8e, 0x8d, 0x8c, 0x8b, 0x8a, 0x89, 0x88,
0x87, 0x86, 0x85, 0x84, 0x83, 0x82, 0x81, 0x80,
0x7f, 0x7e, 0x7d, 0x7c, 0x7b, 0x7a, 0x79, 0x78,
0x77, 0x76, 0x75, 0x74, 0x73, 0x72, 0x71, 0x70,
0x6f, 0x6e, 0x6d, 0x6c, 0x6b, 0x6a, 0x69, 0x68,
0x67, 0x66, 0x65, 0x64, 0x63, 0x62, 0x61, 0x60,
0x5f, 0x5e, 0x5d, 0x5c, 0x5b, 0x5a, 0x59, 0x58,
0x57, 0x56, 0x55, 0x54, 0x53, 0x52, 0x51, 0x50,
0x4f, 0x4e, 0x4d, 0x4c, 0x4b, 0x4a, 0x49, 0x48,
0x47, 0x46, 0x45, 0x44, 0x43, 0x42, 0x41, 0x40,
0x3f, 0x3e, 0x3d, 0x3c, 0x3b, 0x3a, 0x39, 0x38,
0x37, 0x36, 0x35, 0x34, 0x33, 0x32, 0x31, 0x30,
0x2f, 0x2e, 0x2d, 0x2c, 0x2b, 0x2a, 0x29, 0x28,
0x27, 0x26, 0x25, 0x24, 0x23, 0x22, 0x21, 0x20,
0x1f, 0x1e, 0x1d, 0x1c, 0x1b, 0x1a, 0x19, 0x18,
0x17, 0x16, 0x15, 0x14, 0x13, 0x12, 0x11, 0x10,
0xf, 0xe, 0xd, 0xc, 0xb, 0xa, 0x9, 0x8,
0x7, 0x6, 0x5, 0x4, 0x3, 0x2, 0x1, 0x0
};
return b_tbl[b];
}
-Charlie
Charles Mills wrote:Ajay wrote:Hi all,can you please tell the most efficient method to reverse a
byte.Function should return a byte that is reversed.
Use a look up table (untested generated code below):
static unsigned char
reverse_byte(unsigned char b)
{
static const unsigned char b_tbl[] = {
---8<---- sniped totally wrong lookup table ---8<---- };
return b_tbl[b];
}
-Charlie
probably want something like this:
static const unsigned char b_tbl[] = {
0x0, 0x80, 0x40, 0xc0, 0x20, 0xa0, 0x60, 0xe0,
0x10, 0x90, 0x50, 0xd0, 0x30, 0xb0, 0x70, 0xf0,
...,
0xf, 0x8f, 0x4f, 0xcf, 0x2f, 0xaf, 0x6f, 0xef,
0x1f, 0x9f, 0x5f, 0xdf, 0x3f, 0xbf, 0x7f, 0xff
};
you can fill in the blanks.
-Charlie
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