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Optimize kmod_elf_get_strings() by reducing calls to memcpy

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Copy the entire string only once and then scan it, setting up the
pointers of the vector.
This commit is contained in:
Lucas De Marchi 2011-12-20 03:25:23 -02:00
parent b20dc17068
commit f8fa525c7f
1 changed files with 14 additions and 27 deletions
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41
libkmod/libkmod-elf.c
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@ -395,11 +395,11 @@ static int kmod_elf_get_section(const struct kmod_elf *elf, const char *section,
/* array will be allocated with strings in a single malloc, just free *array */
int kmod_elf_get_strings(const struct kmod_elf *elf, const char *section, char ***array)
{
uint64_t i, last, size;
size_t i, j, size, count;
const void *buf;
const char *strings;
char *itr, **a;
int count, err;
char *s, **a;
int err;
*array = NULL;
@ -434,33 +434,20 @@ int kmod_elf_get_strings(const struct kmod_elf *elf, const char *section, char *
if (*array == NULL)
return -errno;
s = (char *)(a + count + 1);
memcpy(s, strings, size);
/* make sure the last string is NULL-terminated */
s[size] = '\0';
a[count] = NULL;
itr = (char *)(a + count);
last = 0;
a[0] = s;
for (i = 0, count = 0; i < size; i++) {
if (strings[i] == '\0') {
size_t slen = i - last;
if (last == i) {
last = i + 1;
continue;
}
a[count] = itr;
memcpy(itr, strings + last, slen);
itr[slen] = '\0';
itr += slen + 1;
count++;
last = i + 1;
}
}
for (i = 0, j = 1; j < count && i < size; i++) {
if (s[i] != '\0')
continue;
if (strings[i - 1] != '\0') {
size_t slen = i - last;
a[count] = itr;
memcpy(itr, strings + last, slen);
itr[slen] = '\0';
itr += slen + 1;
count++;
a[j] = &s[i + 1];
j++;
}
return count;