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Ext2FS: allocate_blocks allocates contiguous blocks (#1095)

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This implementation uses the new helper method of Bitmap called
find_longest_range_of_unset_bits. This method looks for the biggest 
range of contiguous bits unset in the bitmap and returns the start of
the range back to the caller.
This commit is contained in:
Marios Prokopakis 2020-01-26 10:48:24 +02:00 • committed by Andreas Kling
parent d847368c88
commit da296f5865
2 changed files with 81 additions and 5 deletions
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41
AK/Bitmap.h
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@ -157,6 +157,46 @@ public:
return -1;
}
int find_longest_range_of_unset_bits(int max_length, int& found_range_size) const
{
int first_index = find_first_unset();
if (first_index == -1)
return -1;
int free_region_start = first_index;
int free_region_size = 1;
int max_region_start = free_region_start;
int max_region_size = free_region_size;
// Let's try and find the best fit possible
for (int j = first_index + 1; j < m_size && free_region_size < max_length; j++) {
if (!get(j)) {
if (free_region_size == 0)
free_region_start = j;
free_region_size++;
} else {
if (max_region_size < free_region_size) {
max_region_size = free_region_size;
max_region_start = free_region_start;
}
free_region_start = 0;
free_region_size = 0;
}
}
if (max_region_size < free_region_size) {
max_region_size = free_region_size;
max_region_start = free_region_start;
}
found_range_size = max_region_size;
if (max_region_size > 1)
return max_region_start;
// if the max free region size is one, then return the earliest one found
return first_index;
}
explicit Bitmap()
: m_size(0)
, m_owned(true)
@ -181,7 +221,6 @@ public:
}
private:
int size_in_bytes() const { return ceil_div(m_size, 8); }
u8* m_data { nullptr };