The class was an inner class of `BrotliDecompressionStream`, let's move
it outside the `Stream` object in order to ease the access to user only
interested in this part.
These routines:
- read_prefix_code
- read_simple_prefix_code
- read_complex_prefix_code
were methods of `BrotliDecompressionStream` taking a `CanonicalCode` as
an out parameter. This patch puts them in `CanonicalCode` as static
methods.
Similar to POSIX read, the basic read and write functions of AK::Stream
do not have a lower limit of how much data they read or write (apart
from "none at all").
Rename the functions to "read some [data]" and "write some [data]" (with
"data" being omitted, since everything here is reading and writing data)
to make them sufficiently distinct from the functions that ensure to
use the entire buffer (which should be the go-to function for most
usages).
No functional changes, just a lot of new FIXMEs.
This allows us to either pass a reference, which keeps compatibility
with old code, or to pass a NonnullOwnPtr, which allows us to
comfortably chain streams as usual.
The relevant RFC section from
https://www.rfc-editor.org/rfc/rfc7932#section-9.2
MSKIPBYTES * 8 bits: MSKIPLEN - 1, where MSKIPLEN is
the number of metadata bytes; this field is
only present if MSKIPBYTES is positive;
otherwise, MSKIPLEN is 0 (if MSKIPBYTES is
greater than 1, and the last byte is all
zeros, then the stream should be rejected as
invalid)
So when skip_bytes is zero we need to break and
re-align bytes.
Added the relevant test case that demonstrates this from:
https://github.com/google/brotli/blob/master/tests/testdata/x.compressed
The test-case is heavily inspired by:
https://github.com/google/brotli/blob/master/tests/testdata/x.compressed.01
Or in words: A metadata meta-block containing `Y` (which should be
ignored), and then the actual data (a single `Z`). The bug used to skip
one metadata byte too few, and thus read garbage.
