Previously, index out-of-bounds could occur when copying match_length bytes while decoding whatever sequence happened to overflow `dest`. Now, each sequence checks that there is enough room for the full sequence_length (literal_length + match_length) before doing any copying.
Fixes the failing inputs found here: https://github.com/ziglang/zig/issues/24817#issuecomment-3192927715
* std.Io.Reader: appendRemaining no longer supports alignment and has
different rules about how exceeding limit. Fixed bug where it would
return success instead of error.StreamTooLong like it was supposed to.
* std.Io.Reader: simplify appendRemaining and appendRemainingUnlimited
to be implemented based on std.Io.Writer.Allocating
* std.Io.Writer: introduce unreachableRebase
* std.Io.Writer: remove minimum_unused_capacity from Allocating. maybe
that flexibility could have been handy, but let's see if anyone
actually needs it. The field is redundant with the superlinear growth
of ArrayList capacity.
* std.Io.Writer: growingRebase also ensures total capacity on the
preserve parameter, making it no longer necessary to do
ensureTotalCapacity at the usage site of decompression streams.
* std.compress.flate.Decompress: fix rebase not taking into account seek
* std.compress.zstd.Decompress: split into "direct" and "indirect" usage
patterns depending on whether a buffer is provided to init, matching
how flate works. Remove some overzealous asserts that prevented buffer
expansion from within rebase implementation.
* std.zig: fix readSourceFileToAlloc returning an overaligned slice
which was difficult to free correctly.
fixes#24608
The previous code assumed that `initFrame` during the `new_frame` state would always result in the `in_frame` state, but that's not always the case. `initFrame` can also result in the `skippable_frame` state, which would lead to access of union field 'in_frame' while field 'skipping_frame' is active.
Now, the switch is re-entered with the updated state so either case is handled appropriately.
Fixes the crashes from https://github.com/ziglang/zig/issues/24817
Previously, the "allow EndOfStream" part of this logic was too permissive. If there are a few dangling bytes at the end of the stream, that should be treated as a bad magic number. The only case where EndOfStream is allowed is when the stream is truly at the end, with exactly zero bytes available.
This eliminates a footgun and special case handling with fixed buffers,
as well as allowing decompression streams to keep a window in the output
buffer.
This passes tests but it doesn't provide as big a window size as is
required to decompress larger streams.
The next commit in this branch will work towards that, without
introducing an additional buffer.
