Note that js_rope_string() has been folded into this, the old name was
misleading - it would not always create a rope string, only if both
sides are not empty strings. Use a three-argument create() overload
instead.
Three standalone Cell creation functions remain in the JS namespace:
- js_bigint()
- js_string()
- js_symbol()
All of them are leftovers from early iterations when LibJS still took
inspiration from JSC, which itself has jsString(). Nowadays, we pretty
much exclusively use static create() functions to construct types
allocated on the JS heap, and there's no reason to not do the same for
these.
Also change the return type from BigInt* to NonnullGCPtr<BigInt> while
we're here.
This is patch 1/3, replacement of js_string() and js_symbol() follow.
The sql REPL had the created/updated rows swapped by mistake. Also make
sure SQLServer fills in the correct value depending on the executed
command, and that the DELETE command indicates the rows it deleted.
We've been sending the values converted to a string, but now that the
Value type is transferrable over IPC, send the values themselves. Any
client that wants the value as a string may do so easily, whereas this
will allow less trivial clients to avoid string parsing.
If a statement is executed multiple times in quick succession, we may
overwrite the results of a previous execution. Instead of storing the
result, pass it around as it is sent to the client.
Currently, when clients connect to SQL server, we inform them of any
errors opening the database via an asynchronous IPC. But we already know
about these errors before returning from the connect() IPC, so this
roundabout propagation is a bit unnecessary. Now if we fail to open the
database, we will simply not send back a valid connection ID.
Disconnect has a similar story. Rather than disconnecting and invoking
an asynchronous IPC to inform the client of the disconnect, make the
disconnect() IPC synchronous (because all it does is remove the database
from the map of open databases). Further, the only user of this command
is the SQL REPL when it wants to connect to a different database, so it
makes sense to block it. This did require moving a bit of logic around
in the REPL to accommodate this change.
In order to execute a prepared statement multiple times, and track each
execution's results, clients will need to be provided an execution ID.
This will create a monotonically increasing ID each time a prepared
statement is executed for this purpose.
When storing IDs and sending values over IPC, this changes SQLServer to:
1. Stop using -1 as a nominal "bad" ID. Store the IDs as unsigned, and
use Optional in the one place that the IPC needs to indicate an ID
was not allocated.
2. Let LibIPC encode/decode enumerations (SQLErrorCode) on our behalf.
3. Use size_t for array sizes.
One of the benefits of prepared statements is that the SQL string is
parsed just once and re-used. This updates SQLStatement to do just that
and store the parsed result.
This partially implements SQLite's bind-parameter expression to support
indicating placeholder values in a SQL statement. For example:
INSERT INTO table VALUES (42, ?);
In the above statement, the '?' identifier is a placeholder. This will
allow clients to compile statements a single time while running those
statements any number of times with different placeholder values.
Further, this will help mitigate SQL injection attacks.
Gfx::Color is always 4 bytes (it's just a wrapper over u32) it's less
work just to pass the color directly.
This also updates IPCCompiler to prevent from generating
Gfx::Color const &, which makes replacement easier.
This allows us to pass the new String type to functions that take a
StringView directly, having to call bytes_as_string_view() every time
gets old quickly.
This makes more sense as an Object method rather than living within the
VM class for no good reason. Most of the other 7.3.xx AOs already work
the same way.
Also add spec comments while we're here.
DeprecatedString (formerly String) has been with us since the start,
and it has served us well. However, it has a number of shortcomings
that I'd like to address.
Some of these issues are hard if not impossible to solve incrementally
inside of DeprecatedString, so instead of doing that, let's build a new
String class and then incrementally move over to it instead.
Problems in DeprecatedString:
- It assumes string allocation never fails. This makes it impossible
to use in allocation-sensitive contexts, and is the reason we had to
ban DeprecatedString from the kernel entirely.
- The awkward null state. DeprecatedString can be null. It's different
from the empty state, although null strings are considered empty.
All code is immediately nicer when using Optional<DeprecatedString>
but DeprecatedString came before Optional, which is how we ended up
like this.
- The encoding of the underlying data is ambiguous. For the most part,
we use it as if it's always UTF-8, but there have been cases where
we pass around strings in other encodings (e.g ISO8859-1)
- operator[] and length() are used to iterate over DeprecatedString one
byte at a time. This is done all over the codebase, and will *not*
give the right results unless the string is all ASCII.
How we solve these issues in the new String:
- Functions that may allocate now return ErrorOr<String> so that ENOMEM
errors can be passed to the caller.
- String has no null state. Use Optional<String> when needed.
- String is always UTF-8. This is validated when constructing a String.
We may need to add a bypass for this in the future, for cases where
you have a known-good string, but for now: validate all the things!
- There is no operator[] or length(). You can get the underlying data
with bytes(), but for iterating over code points, you should be using
an UTF-8 iterator.
Furthermore, it has two nifty new features:
- String implements a small string optimization (SSO) for strings that
can fit entirely within a pointer. This means up to 3 bytes on 32-bit
platforms, and 7 bytes on 64-bit platforms. Such small strings will
not be heap-allocated.
- String can create substrings without making a deep copy of the
substring. Instead, the superstring gets +1 refcount from the
substring, and it acts like a view into the superstring. To make
substrings like this, use the substring_with_shared_superstring() API.
One caveat:
- String does not guarantee that the underlying data is null-terminated
like DeprecatedString does today. While this was nifty in a handful of
places where we were calling C functions, it did stand in the way of
shared-superstring substrings.
This is still not perfect, as we now actually crash in the
`try-finally-continue` tests, while we now succeed all
`try-catch-finally-*` tests.
Note that we do not yet go through the finally block when exiting the
unwind context through a break or continue.
We are already doing this in a good manner via the generated code,
doing so in the execution loop as well will cause us to pop contexts
multiple times, which is not very good.
