比较两个strcasecmp（stricmp）实现 [英] comparing two strcasecmp (stricmp) implementations
问题描述
我目前正在评估两个不区分大小写的实现
字符串比较函数来替换非ANSI stricmp（）。两个以下的实现似乎都运行正常，但我想知道一个是否比另一个更好或者是否有某种混合的 b br />
这将是优越的。
实施1：
#ifndef HAVE_STRCASECMP
#define ccmp（ a，b）（（a）==（b）？0：（（a）>（b）？1：-1））
int strcasecmp（unsigned char * s1，unsigned char * s2）
{
unsigned char c1，c2;
for（;;）
{
if（* s1 ==''\'''|| * s2 ==''\'''）
返回ccmp（* s1，* s2） ;
c1 =（isascii（* s1）&& isupper（* s1））？ （unsigned char）tolower（* s1）：
* s1;
c2 =（isascii（* s2）&& isupper（* s2））？ （unsigned char）tolower（* s2）：
* s2;
if（c1！= c2）
返回ccmp（c1，c2） ）;
s1 ++;
s2 ++;
}
}
#undef ccmp
#endif
实施2：
int strcasecmp（const char * s1，const char * s2）
{
unsigned char c1，c2;
do {
c1 = * s1 ++;
c2 = * s2 ++;
c1 =（unsigned char）tolower（（unsigned char）c1）;
c2 =（unsigned char）tolower（（unsigned char）c2 ）;
}
while（（c1 == c2）&&（c1！=''\'''））;
return（int）c1-c2;
}
I''m currently evaluating two implementations of a case insensitive
string comparison function to replace the non-ANSI stricmp(). Both of
the implementations below seem to work fine but I''m wondering if one is
better than the other or if there is some sort of hybrid of the two
that would be superior.
IMPLEMENTATION 1:
#ifndef HAVE_STRCASECMP
#define ccmp(a,b) ((a) == (b) ? 0 : ((a) > (b) ? 1 : -1))
int strcasecmp(unsigned char *s1, unsigned char *s2)
{
unsigned char c1, c2;
for ( ; ; )
{
if (*s1 == ''\0'' || *s2 == ''\0'')
return ccmp(*s1,*s2);
c1= (isascii(*s1) && isupper(*s1)) ? (unsigned char) tolower(*s1) :
*s1;
c2= (isascii(*s2) && isupper(*s2)) ? (unsigned char) tolower(*s2) :
*s2;
if (c1 != c2)
return ccmp(c1,c2);
s1++;
s2++;
}
}
#undef ccmp
#endif
IMPLEMENTATION 2:
int strcasecmp(const char *s1, const char *s2)
{
unsigned char c1,c2;
do {
c1 = *s1++;
c2 = *s2++;
c1 = (unsigned char) tolower( (unsigned char) c1);
c2 = (unsigned char) tolower( (unsigned char) c2);
}
while((c1 == c2) && (c1 != ''\0''));
return (int) c1-c2;
}
推荐答案
William Krick写道：
William Krick wrote:
我正在评估两个不区分大小写的字符串比较函数的实现来替换非ANSI stricmp（）。以下两种实现似乎都运行良好，但我想知道一个人是否比另一个更好，或者是否存在某种优于两者的混合物。
实施1：
#ifndef HAVE_STRCASECMP
#define ccmp（a，b）（（a）==（b）？0：（（a） >（b）？1：-1））
int strcasecmp（unsigned char * s1，unsigned char * s2）
{
unsigned char c1，c2;
for（ ;;）
{
if（* s1 ==''\'''|| * s2 ==''\'''）
返回ccmp（* s1，* s2）;
c1 =（isascii（* s1）&& isupper（* s1））？ （unsigned char）tolower（* s1）：
* s1;
c2 =（isascii（* s2）&& isupper（* s2））？ （unsigned char）tolower（* s2）：
* s2;
if（c1！= c2）
返回ccmp（c1，c2）;
s1 ++;
s2 ++;
}
}
#undef ccmp
#endif
实施2：
int strcasecmp（const char * s1，const char * s2）
{
unsigned char c1，c2;
do {
c1 = * s1 ++;
c2 = * s2 ++;
c1 =（unsigned char）tolower（（unsigned char）c1）;
c2 =（unsigned char）tolower（（unsigned char）c2）;
}
while（（c1 == c2 ）&&（c1！=''\'''））;
return（int）c1-c2;
}
I''m currently evaluating two implementations of a case insensitive
string comparison function to replace the non-ANSI stricmp(). Both of
the implementations below seem to work fine but I''m wondering if one is
better than the other or if there is some sort of hybrid of the two
that would be superior.
IMPLEMENTATION 1:
#ifndef HAVE_STRCASECMP
#define ccmp(a,b) ((a) == (b) ? 0 : ((a) > (b) ? 1 : -1))
int strcasecmp(unsigned char *s1, unsigned char *s2)
{
unsigned char c1, c2;
for ( ; ; )
{
if (*s1 == ''\0'' || *s2 == ''\0'')
return ccmp(*s1,*s2);
c1= (isascii(*s1) && isupper(*s1)) ? (unsigned char) tolower(*s1) :
*s1;
c2= (isascii(*s2) && isupper(*s2)) ? (unsigned char) tolower(*s2) :
*s2;
if (c1 != c2)
return ccmp(c1,c2);
s1++;
s2++;
}
}
#undef ccmp
#endif
IMPLEMENTATION 2:
int strcasecmp(const char *s1, const char *s2)
{
unsigned char c1,c2;
do {
c1 = *s1++;
c2 = *s2++;
c1 = (unsigned char) tolower( (unsigned char) c1);
c2 = (unsigned char) tolower( (unsigned char) c2);
}
while((c1 == c2) && (c1 != ''\0''));
return (int) c1-c2;
}
怎么样 ：
int strcasecmp（const char * s1，const char * s2）
{
while（1）
{
int c1 = tolower（（unsigned char）* s1 ++）;
int c2 = tolower （（unsigned char）* s2 ++）;
如果（c1 == 0 || c1！= c2）返回c1 - c2;
}
}
不重复使用变量，没有iffy强制转换，略短。
我错过了什么？
-
Chris" one-track" Dollin
功能并不意味着必要。
How about:
int strcasecmp( const char *s1, const char *s2 )
{
while (1)
{
int c1 = tolower( (unsigned char) *s1++ );
int c2 = tolower( (unsigned char) *s2++ );
if (c1 == 0 || c1 != c2) return c1 - c2;
}
}
Doesn''t reuse variables, doesn''t have iffy casts, slightly shorter.
What have I missed?
--
Chris "one-track" Dollin
Capability does not imply necessity.
为了使代码与旧的C编译器兼容，我不得不移动
c1& b的声明c2到顶部。我也将它从while（1）
改为for（;;），因为while正在发出警告。然而，虽然
这个代码在大多数情况下工作得很好，但它不会处理NULL字符串并且
只会爆炸。
int strcasecmp（const char * s1，const char * s2）
{
int c1，c2;
for（;;）
{
c1 = tolower（（unsigned char）* s1 ++）;
c2 = tolower（（unsigned char）* s2 ++）;
if（c1 == 0 || c1！= c2）
返回c1 - c2;
}
}
To make the code compatible with older C compilers, I had to move the
declaration of c1 & c2 up to the top. I also changed it from while(1)
to for(;;) because the while was throwing a warning. However, while
this code works great in most cases, it doesn''t handle NULL strings and
just blows up.
int strcasecmp( const char *s1, const char *s2 )
{
int c1, c2;
for(;;)
{
c1 = tolower( (unsigned char) *s1++ );
c2 = tolower( (unsigned char) *s2++ );
if (c1 == 0 || c1 != c2)
return c1 - c2;
}
}
文章< 11 ********************** @ o13g2000cwo。 googlegroups .com>，
William Krick< wk **** @ gmail.com>写道：
In article <11**********************@o13g2000cwo.googlegroups .com>,
William Krick <wk****@gmail.com> wrote:
为了使代码与旧的C编译器兼容，我不得不移动c1&的
声明。 c2到顶部。
真的吗？这些C编译器是什么？
我也将它从while（1）
改为for（;;）因为while正在发出警告。
绝对是新编译器的时间了！
但是，虽然这段代码在大多数情况下工作得很好，但它并没有处理NULL字符串只是爆炸了。
To make the code compatible with older C compilers, I had to move the
declaration of c1 & c2 up to the top.
Really? What C compilers are these?
I also changed it from while(1)
to for(;;) because the while was throwing a warning.
Definitely time for a new compiler!
However, while
this code works great in most cases, it doesn''t handle NULL strings and
just blows up.
从什么时候str *函数应该处理NULL？
- - 理查德
Since when were the str* functions supposed to handle NULL?
-- Richard
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