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LibC: bsearch fix for large arrays (#3138)

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Implement unsigned arithmetic to compute middle without causing overflow.
And without mixed signed/unsigned operations.
This commit is contained in:
Muhammad Zahalqa 2020-08-15 01:18:52 +03:00 • committed by GitHub
parent bba2da66e7
commit cdae3f53f1
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1 changed files with 9 additions and 10 deletions
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19
Libraries/LibC/stdlib.cpp
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@ -745,18 +745,17 @@ char* mkdtemp(char* pattern)
void* bsearch(const void* key, const void* base, size_t nmemb, size_t size, int (*compar)(const void*, const void*))
{
int low = 0;
int high = nmemb - 1;
while (low <= high) {
int middle = (low + high) / 2;
void* middle_memb = const_cast<char*>((const char*)base + middle * size);
char* start = static_cast<char*>(const_cast<void*>(base));
while (nmemb > 0) {
char* middle_memb = start + (nmemb / 2) * size;
int comparison = compar(key, middle_memb);
if (comparison < 0)
high = middle - 1;
else if (comparison > 0)
low = middle + 1;
else
if (comparison == 0)
return middle_memb;
else if (comparison > 0) {
start = middle_memb + size;
--nmemb;
}
nmemb /= 2;
}
return NULL;