This generic stream wrapper performs checksum calculations on all data
passed through it for reading or writing, and is therefore convenient
for calculating checksums while performing normal data input/output, as
well as computing streaming checksums on non-seekable streams.
The implementation of this is naive enough so it can handle all 8-bit
CRC polynomials, of which there are quite a few. The table generation
and update procedure is MSB first, which is backwards from the LSB first
method of CRC32.
This implements Intel's slicing-by-8 algorithm for CRC checksums (only
little endian CPUs for now, as I don't have a way to test big endian).
The original paper for this algorithm seems to have disappeared, but
Intel's source code is still available as a reference:
https://sourceforge.net/projects/slicing-by-8/
As well as other implementations for reference:
https://docs.rs/slice-by-8/latest/src/slice_by_8/algorithm.rs.html
Using the "enwik8" file as a test (100MB uncompressed, commonly used in
benchmarks: https://www.mattmahoney.net/dc/enwik8.zip), decompression
time decreases from:
4.89s to 3.52s on Serenity (cold)
1.72s to 1.32s on Serenity (warm)
1.06s to 0.92s on Linux
CRC32 table is generated at compile-time and put into a static
variable in the header file. This can be moved to be a function
instead of a class, be moved to the `.cpp` file` and generated as an
array instead of a class which only implements `operator[]`.
This option is already enabled when building Lagom, so let's enable it
for the main build too. We will no longer be surprised by Lagom Clang
CI builds failing while everything compiles locally.
Furthermore, the stronger `-Wsuggest-override` warning is enabled in
this commit, which enforces the use of the `override` keyword in all
classes, not just those which already have some methods marked as
`override`. This works with both GCC and Clang.
We had some inconsistencies before:
- Sometimes "The", sometimes "the"
- Sometimes trailing ".", sometimes no trailing "."
I picked the most common one (lowecase "the", trailing ".") and applied
it to all copyright headers.
By using the exact same string everywhere we can ensure nothing gets
missed during a global search (and replace), and that these
inconsistencies are not spread any further (as copyright headers are
commonly copied to new files).
SPDX License Identifiers are a more compact / standardized
way of representing file license information.
See: https://spdx.dev/resources/use/#identifiers
This was done with the `ambr` search and replace tool.
ambr --no-parent-ignore --key-from-file --rep-from-file key.txt rep.txt *
This flag warns on classes which have `virtual` functions but do not
have a `virtual` destructor.
This patch adds both the flag and missing destructors. The access level
of the destructors was determined by a two rules of thumb:
1. A destructor should have a similar or lower access level to that of a
constructor.
2. Having a `private` destructor implicitly deletes the default
constructor, which is probably undesirable for "interface" types
(classes with only virtual functions and no data).
In short, most of the added destructors are `protected`, unless the
compiler complained about access.
