This class is the only reason we have to support krealloc() in the
kernel heap, something which adds a lot of complexity.
Let's move towards a simpler path and do malloc+memset in the
ByteBuffer code (where we know the sizes anyway.)
Other software might not expect these to be defined and behave
differently if they _are_ defined, e.g. scummvm which checks if
the TODO macro is defined and fails to build if it is.
This allows us to mark the slow part (i.e. where we copy the buffer) as
NEVER_INLINE because this should almost never get called and therefore
should also not get inlined into callers.
Previously ByteBuffer::grow() behaved like Vector<T>::resize().
However the function name was somewhat ambiguous - and so this patch
updates ByteBuffer to behave more like Vector<T> by replacing grow()
with resize() and adding an ensure_capacity() method.
This also lets the user change the buffer's capacity without affecting
the size which was not previously possible.
Additionally this patch makes the capacity() method public (again).
Previously GCC came to the conclusion that we were reading
m_outline_capacity via ByteBuffer(ByteBuffer const&) -> grow()
-> capacity() even though that could never be the case because
m_size is 0 at that point which means we have an inline buffer
and capacity() would return inline_capacity in that case without
reading m_outline_capacity.
This makes GCC inline parts of the grow() function into the
ByteBuffer copy constructor which seems sufficient for GCC to
realize that m_outline_capacity isn't actually being read.
When compiling the Kernel with Og, the compiler complains that
m_outline_capacity might be uninitialized when calling capacity()
Note that this fix is not really what we want. Ideally only outline
buffer and outline capacity would need initialized, not the entire
inline buffer. However, clang considers the class to not be
default-constructible if we make that change, while gcc accepts it.
Previously ByteBuffer would internally hold a RefPtr to the byte
buffer and would behave like a reference type, i.e. copying a
ByteBuffer would not create a duplicate byte buffer, but rather
two objects which refer to the same internal buffer.
This also changes ByteBuffer so that it has some internal capacity
much like the Vector<T> type. Unlike Vector<T> however a byte
buffer's data may be uninitialized.
With this commit ByteBuffer makes use of the kmalloc_good_size()
API to pick an optimal allocation size for its internal buffer.
Creating a ByteBuffer involves two allocations:
-One for the ByteBufferImpl object
-Another one for the actual byte buffer
This changes the ByteBuffer and ByteBufferImpl classes
so only one allocation is necessary.
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 *
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
In the interest memory safety and of removing as many
of foot guns as possible (like raw memset's which are
notorious for typo's), a zeroing method seems like a
useful utility to have on a buffer class.
Arbitrarily split up to make git bisect easier.
These unnecessary #include's were found by combining an automated tool (which
determined likely candidates) and some brain power (which decided whether
the #include is also semantically superfluous).
Problem:
- Many constructors are defined as `{}` rather than using the ` =
default` compiler-provided constructor.
- Some types provide an implicit conversion operator from `nullptr_t`
instead of requiring the caller to default construct. This violates
the C++ Core Guidelines suggestion to declare single-argument
constructors explicit
(https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#c46-by-default-declare-single-argument-constructors-explicit).
Solution:
- Change default constructors to use the compiler-provided default
constructor.
- Remove implicit conversion operators from `nullptr_t` and change
usage to enforce type consistency without conversion.
ByteBuffer previously had a flag that determined whether it owned the
bytes inside it or not (m_owned.) Owned ByteBuffers would free() on
destruction and non-owned ones would not.
This was a huge source of confusion and made it hard to reason about
lifetimes since there were no compile-time clues about whether a buffer
was owned or non-owned.
The adopt mode was used at some point to take over ownership of a
random malloc'ed buffer, but nothing was using it so this patch removes
that as well.
When a process crashes, we generate a coredump file and write it in
/tmp/coredumps/.
The coredump file is an ELF file of type ET_CORE.
It contains a segment for every userspace memory region of the process,
and an additional PT_NOTE segment that contains the registers state for
each thread, and a additional data about memory regions
(e.g their name).
Thankfully, this hasn't happened in any other code yet, but it happened
while I was trying something out. Using '==' on two ByteBuffers to check
whether they're equal seemed straight-forward, so I ran into the trap.
I originally defined the bytes() method for the String class, because it
made it obvious that it's a span of bytes instead of span of characters.
This commit makes this more consistent by defining a bytes() method when
the type of the span is known to be u8.
Additionaly, the cast operator to Bytes is overloaded for ByteBuffer and
such.
This function did a const_cast internally which made the call side look
"safe". This method is removed completely and call sites are replaced
with ByteBuffer::wrap(const_cast<void*>(data), size) which makes the
behaviour obvious.
Prior to this, we wrote to the log every time the << operator
was used, which meant that only these parts of the log statement
were serialized. If the thread was preempted, or especially with
multiple CPUs the debug output was hard to decipher. Instead, we
buffer up the log statements. To avoid allocations we'll attempt
to use stack space, which covers most log statements.
Since ByteBuffer is a Buffer, it should allow us to overwrite parts of
it that we have allocated.
This comes in useful in handling unsequenced writes like handling
fragmented ip packets :^)
We can use __builtin_memset() without including <string.h>.
This is pretty neat, as it will allow us to reduce the header deps
of AK templates a bit, if applied consistently.
Note that this is an enabling change for an upcoming #include removal.
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
So we already have ByteBuffer::wrap() which is like a StringView for random
data. This might not be the best abstraction actually, but this will be
immediately useful so let's add it.
