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Simplify search in ioctl table

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text	   data	    bss	    dec	    hex	filename
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 236929	    704	  18944	 256577	  3ea41	strace

* ioctl.c (compare): Simplify generation of compare result.
(ioctl_lookup): Pass key directly, not as part of dummy struct.
(ioctl_next_match): More readable code. No logic changes.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2012-03-20 10:57:41 +01:00
parent 8cf2c261ea
commit 1c2e912cc3
1 changed files with 31 additions and 10 deletions
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41
ioctl.c
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@ -29,30 +29,50 @@
*/
#include "defs.h"
#include <limits.h>
#include <asm/ioctl.h>
static int
compare(const void *a, const void *b)
{
unsigned long code1 = ((struct ioctlent *) a)->code;
unsigned long code1 = (long) a;
unsigned long code2 = ((struct ioctlent *) b)->code;
return (code1 > code2) ? 1 : (code1 < code2) ? -1 : 0;
/* Simply returning (code1 - code2) may be wrong.
* Exmaple: 0xffffffff - 0 = 0xffffffff = -1.
* Need to shift both values down until they both fit
* in positive int.
*/
while ((code1|code2) > INT_MAX) {
#if INT_MAX == LONG_MAX
/* this case is easy */
code1 >>= 1;
code2 >>= 1;
break;
#else
/* Remove INT_MAX worth of bits, then check again */
code1 >>= sizeof(int) * 8 - 1;
code2 >>= sizeof(int) * 8 - 1;
#endif
}
return (int)code1 - (int)code2;
}
const struct ioctlent *
ioctl_lookup(long code)
{
struct ioctlent *iop, ioent;
struct ioctlent *iop;
ioent.code = code;
ioent.code &= (_IOC_NRMASK<<_IOC_NRSHIFT) | (_IOC_TYPEMASK<<_IOC_TYPESHIFT);
iop = (struct ioctlent *) bsearch((char *) &ioent, (char *) ioctlent,
nioctlents, sizeof(struct ioctlent), compare);
while (iop > ioctlent)
if ((--iop)->code != ioent.code) {
code &= (_IOC_NRMASK<<_IOC_NRSHIFT) | (_IOC_TYPEMASK<<_IOC_TYPESHIFT);
iop = bsearch((void*)code, ioctlent,
nioctlents, sizeof(ioctlent[0]), compare);
while (iop > ioctlent) {
iop--;
if (iop->code != code) {
iop++;
break;
}
}
return iop;
}
@ -61,7 +81,8 @@ ioctl_next_match(const struct ioctlent *iop)
{
long code;
code = (iop++)->code;
code = iop->code;
iop++;
if (iop < ioctlent + nioctlents && iop->code == code)
return iop;
return NULL;