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terminal: bitmapallocator handles perfectly divisble chunk size

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This commit is contained in:
Mitchell Hashimoto
2024-03-22 12:07:00 -07:00
parent cd30534808
commit 8818e4da05
1 changed files with 36 additions and 9 deletions
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45
src/terminal/bitmap_allocator.zig
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@ -203,22 +203,30 @@ fn findFreeChunks(bitmaps: []u64, n: usize) ?usize {
// then add one and continue, we're still accumulating blanks.
if (seq != div) {
seq += 1;
continue;
if (seq != div or mod > 0) continue;
}
// We've reached the seq count see if this has mod starting empty
// blanks.
const final = @as(u64, std.math.maxInt(u64)) >> @intCast(64 - mod);
if (bitmap.* & final == 0) {
// No blanks, reset.
seq = 0;
continue;
if (mod > 0) {
const final = @as(u64, std.math.maxInt(u64)) >> @intCast(64 - mod);
if (bitmap.* & final == 0) {
// No blanks, reset.
seq = 0;
continue;
}
bitmap.* ^= final;
}
// Found! Set all in our sequence to full and mask our final.
const start_idx = idx - seq;
for (start_idx..idx) |i| bitmaps[i] = 0;
bitmap.* ^= final;
// The "zero_mod" modifier below handles the case where we have
// a perfectly divisible number of chunks so we don't have to
// mark the trailing bitmap.
const zero_mod = @intFromBool(mod == 0);
const start_idx = idx - (seq - zero_mod);
const end_idx = idx + zero_mod;
for (start_idx..end_idx) |i| bitmaps[i] = 0;
return (start_idx * 64);
}
@ -344,6 +352,25 @@ test "findFreeChunks larger than 64 chunks not at beginning" {
try testing.expectEqual(@as(usize, 64), idx);
}
test "findFreeChunks larger than 64 chunks exact" {
const testing = std.testing;
var bitmaps = [_]u64{
0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111,
0b11111111_11111111_11111111_11111111_11111111_11111111_11111111_11111111,
};
const idx = findFreeChunks(&bitmaps, 128).?;
try testing.expectEqual(
0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000,
bitmaps[0],
);
try testing.expectEqual(
0b00000000_00000000_00000000_00000000_00000000_00000000_00000000_00000000,
bitmaps[1],
);
try testing.expectEqual(@as(usize, 0), idx);
}
test "BitmapAllocator layout" {
const Alloc = BitmapAllocator(4);
const cap = 64 * 4;