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Expand the memcpy fast path in flate.CircularBuffer.writeMatch to allow for overlapping regions.

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IntegratedQuantum 2024-02-27 21:55:24 +01:00 committed by Andrew Kelley
parent 62ce753814
commit 6e078883ee
1 changed files with 12 additions and 6 deletions
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18
lib/std/compress/flate/CircularBuffer.zig
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@ -50,19 +50,25 @@ pub fn writeMatch(self: *Self, length: u16, distance: u16) !void {
} }
assert(self.wp - self.rp < mask); assert(self.wp - self.rp < mask);
var from: usize = self.wp - distance; var from: usize = self.wp - distance & mask;
const from_end: usize = from + length; const from_end: usize = from + length;
var to: usize = self.wp; var to: usize = self.wp & mask;
const to_end: usize = to + length; const to_end: usize = to + length;
self.wp += length; self.wp += length;
// Fast path using memcpy // Fast path using memcpy
if (length <= distance and // no overlapping buffers if (from_end < buffer_len and to_end < buffer_len) // start and end at the same circle
(from >> 16 == from_end >> 16) and // start and and at the same circle
(to >> 16 == to_end >> 16))
{ {
@memcpy(self.buffer[to & mask .. to_end & mask], self.buffer[from & mask .. from_end & mask]); var cur_len = distance;
var remaining_len = length;
while (cur_len < remaining_len) {
@memcpy(self.buffer[to..][0..cur_len], self.buffer[from..][0..cur_len]);
to += cur_len;
remaining_len -= cur_len;
cur_len = cur_len * 2;
}
@memcpy(self.buffer[to..][0..remaining_len], self.buffer[from..][0..remaining_len]);
return; return;
} }