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Reworked strlen and strnlen to follow style guide.

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Fix problems pointed out by Marcus.
This commit is contained in:
Fredrik Holmqvist 2011-12-25 17:00:31 +01:00
parent 753a02c156
commit 11048d3619
2 changed files with 38 additions and 40 deletions
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37
src/system/libroot/posix/string/strlen.c
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@ -6,30 +6,29 @@
#include <string.h>
#include <SupportDefs.h>
// From Bit twiddling hacks: http://graphics.stanford.edu/~seander/bithacks.html
#define hasZeroByte(value) (value - 0x01010101) & ~value & 0x80808080
/* From Bit twiddling hacks:
http://graphics.stanford.edu/~seander/bithacks.html */
#define HasZeroByte(value) ((value - 0x01010101) & ~value & 0x80808080)
size_t
strlen(char const *s)
strlen(const char* s)
{
size_t i = 0;
uint32 *value;
size_t length = 0;
uint32* valuePointer;
//Make sure we use aligned access
while (((uint32) s + i) & 3) {
if (!s[i]) return i;
i++;
}
/* Align access for four byte reads */
for (; (((addr_t) s + length) & 3) != 0; length++)
if (s[length] == '\0')
return length;
//Check four bytes at once
value = (uint32 *) (s + i);
while (!(hasZeroByte(*value)))
value++;
/* Check four bytes for zero char */
for (valuePointer = (uint32*) (s + length); !HasZeroByte(*valuePointer);
valuePointer++);
//Find the exact length
i = ((char *) value) - s;
while (s[i])
i++;
/* Find the exact length */
for (length = ((char*) valuePointer) - s; s[length] != '\0'; length++);
return i;
return length;
}

41
src/system/libroot/posix/string/strnlen.c
View File

@ -7,32 +7,31 @@
#include <SupportDefs.h>
// From Bit twiddling hacks: http://graphics.stanford.edu/~seander/bithacks.html
#define hasZeroByte(value) (value - 0x01010101) & ~value & 0x80808080
/* From Bit twiddling hacks:
http://graphics.stanford.edu/~seander/bithacks.html */
#define HasZeroByte(value) ((value - 0x01010101) & ~value & 0x80808080)
size_t
strnlen(char const *s, size_t count)
strnlen(const char* s, size_t count)
{
size_t i = 0;
uint32 *value;
size_t length = 0;
uint32* valuePointer;
uint32* maxScanPosition;
//Make sure we use aligned access
while (((uint32) s + i) & 3) {
if (i == count || !s[i]) return i;
i++;
}
/* Align access for four byte reads */
for (; (((addr_t) s + length) & 3) != 0; length++)
if (length == count || s[length] == '\0')
return length;
/* Check four bytes for zero char */
maxScanPosition = (uint32*) (s + count - 4);
for (valuePointer = (uint32*) (s + length); valuePointer <= maxScanPosition
&& !HasZeroByte(*valuePointer); valuePointer++);
const uint32 * end = (uint32 *) s + count;
//Check four bytes at once
value = (uint32 *) (s + i);
while (value < end && !(hasZeroByte(*value)) )
value++;
/* Find the exact length */
for (length = ((char*) valuePointer) - s; length < count
&& s[length] != '\0'; length++);
//Find the exact length
i = ((char *) value) - s;
while (s[i] && i < count )
i++;
return i;
return length;
}