Commit a21f9b6d8b9b027e64795dcdec40494bad76675e | zig

author	Igor Anić <igor.anic@gmail.com> 2024-03-13 18:22:08+01:00
committer	Igor Anić <igor.anic@gmail.com> 2024-03-13 18:22:08+01:00
log	a21f9b6d8b9b027e64795dcdec40494bad76675e
tree	7e4e28e59005ba7b09e4e9ba5a3935f1e1a1dc70
parent	b9cca3b63dbcedadbda1c884e5b3333c8458b30d

compress.xz: remove copyForwards from tight loop

In the example from the issue #19052 to_read holds 213_315_584
uncompressed bytes. Calling read with small output results in many
shifts of that big buffer.
This removes need to shift to_read after each read.

1 files changed, 10 insertions(+), 5 deletions(-)

lib
- std
  - compress
    xz
    block.zig

lib/std/compress/xz/block.zig+10-5

...	...	@@ -34,6 +34,7 @@ pub fn Decoder(comptime ReaderType: type) type {
34	34	check: xz.Check,
35	35	err: ?Error,
36	36	to_read: ArrayListUnmanaged(u8),
	37	read_pos: usize,
37	38	block_count: usize,
38	39
39	40	fn init(allocator: Allocator, in_reader: ReaderType, check: xz.Check) !Self {
...	...	@@ -43,6 +44,7 @@ pub fn Decoder(comptime ReaderType: type) type {
43	44	.check = check,
44	45	.err = null,
45	46	.to_read = .{},
	47	.read_pos = 0,
46	48	.block_count = 0,
47	49	};
48	50	}
...	...	@@ -57,13 +59,12 @@ pub fn Decoder(comptime ReaderType: type) type {
57	59
58	60	pub fn read(self: *Self, output: []u8) Error!usize {
59	61	while (true) {
60		if (self.to_read.items.len > 0) {
61		const input = self.to_read.items;
	62	const input = self.to_read.items[self.read_pos..];
	63	if (input.len > 0) {
62	64	const n = @min(input.len, output.len);
63	65	@memcpy(output[0..n], input[0..n]);
64		std.mem.copyForwards(u8, input, input[n..]);
65		self.to_read.shrinkRetainingCapacity(input.len - n);
66		if (self.to_read.items.len == 0 and self.err != null) {
	66	self.read_pos += n;
	67	if (self.read_pos == self.to_read.items.len and self.err != null) {
67	68	if (self.err.? == DecodeError.EndOfStreamWithNoError) {
68	69	return n;
69	70	}
...	...	@@ -77,6 +78,10 @@ pub fn Decoder(comptime ReaderType: type) type {
77	78	}
78	79	return self.err.?;
79	80	}
	81	if (self.read_pos > 0) {
	82	self.to_read.shrinkRetainingCapacity(0);
	83	self.read_pos = 0;
	84	}
80	85	self.readBlock() catch \|e\| {
81	86	self.err = e;
82	87	};