Hi rust enthusiasts,
With this patch I propose to add a "streaming" API to the existing json parser in libserialize.
By "streaming" I mean a parser that let you act on JsonEvents that are generated as while parsing happens, as opposed to parsing the entire source, generating a big data structure and working with this data structure. I think both approaches have their pros and cons so this pull request adds the streaming API, preserving the existing one.
The streaming API is simple: It consist into an Iterator<JsonEvent> that consumes an Iterator<char>. JsonEvent is an enum with values such as NumberValue(f64), BeginList, EndList, BeginObject, etc.
The user would ideally use the API as follows:
```
for evt in StreamingParser::new(src) {
match evt {
BeginList => {
// ...
}
// ...
}
}
```
The iterator provides a stack() method returning a slice of StackNodes which represent "where we currently are" in the logical structure of the json stream (for instance at "foo.bar[3].x" you get [ Key("foo"), Key("bar"), Index(3), Key("x") ].)
I wrote "ideally" above because the current way rust expands for loops, you can't call the stack() method because the iterator is already borrowed. So for know you need to manually advance the iterator in the loop. I hope this is something we can cope with, until for loops are better integrated with the compiler.
Streaming parsers are useful when you want to read from a json stream, generate a custom data structure and you know how the json is going to be structured. For example, imagine you have to parse a 3D mesh file represented in the json format. In this case you probably expect to have large arrays of vertices and using the generic parser will be very inefficient because it will create a big list of all these vertices, which you will copy into a contiguous array afterwards (so you end up doing a lot of small allocations, parsing the json once and parsing the data structure afterwards). With a streaming parser, you can add the vertices to a contiguous array as they come in without paying the cost of creating the intermediate Json data structure. You have much fewer allocations since you write directly in the final data structure and you can be smart in how you will pre-allocate it.
I added added this directly into serialize::json rather than in its own library because it turns out I can reuse most of the existing code whereas maintaining a separate library (which I did originally) forces me to duplicate this code.
I wrote this trying to minimize the size of the patch so there may be places where the code could be nicer at the expenses of more changes (let me know what you prefer).
This is my first (potential) contribution to rust, so please let me know if I am doing something wrong (maybe I should have first introduced this proposition in the mailing list, or opened a github issue, etc.?). I work a few meters away from @pknfelix so I am not too hard to find :)
This addresses the ICE from #13763, but it does not allow the test to compile,
due to #13768. An alternate test was checked in in the meantime.
Closes#13763
This addresses the ICE from #13763, but it does not allow the test to compile,
due to #13768. An alternate test was checked in in the meantime.
Closes#13763
It didn't work because it tried to call itself but symbols are not
exported as default in executables.
Note that `fun5` is not internal anymore since it is in library.
Second commit removes/updates some old tests.
It didn't work because it tried to call itself but symbols are not
exported as default in executables.
Note that `fun5` is not internal anymore since it is in library.
This patch removes the special auto-rooting for `@` from the borrow checker. With `@` moving into a library, it doesn't make sense to keep this code around anymore. It also simplifies `trans` by removing root checking from there
@nikomatsakis
Closes: #11586
This is really only useful for #[cfg()]. For example:
```rust
enum Foo {
Bar,
Baz,
#[cfg(blob)]
Blob
}
fn match_foos(f: &Foo) {
match *f {
Bar => {}
Baz => {}
#[cfg(blob)]
Blob => {}
}
}
```
This is a kind of weird place to allow attributes, so it should probably
be discussed before merging.
The constructor for `TaskBuilder` is being changed to an associated
function called `new` for consistency with the rest of the standard
library.
Closes#13666
[breaking-change]
The constructor for `TaskBuilder` is being changed to an associated
function called `new` for consistency with the rest of the standard
library.
Closes#13666
[breaking-change]
This alters the borrow checker's requirements on invoking closures from
requiring an immutable borrow to requiring a unique immutable borrow. This means
that it is illegal to invoke a closure through a `&` pointer because there is no
guarantee that is not aliased. This does not mean that a closure is required to
be in a mutable location, but rather a location which can be proven to be
unique (often through a mutable pointer).
For example, the following code is unsound and is no longer allowed:
type Fn<'a> = ||:'a;
fn call(f: |Fn|) {
f(|| {
f(|| {})
});
}
fn main() {
call(|a| {
a();
});
}
There is no replacement for this pattern. For all closures which are stored in
structures, it was previously allowed to invoke the closure through `&self` but
it now requires invocation through `&mut self`.
The standard library has a good number of violations of this new rule, but the
fixes will be separated into multiple breaking change commits.
Closes#12224
The BSD builders are failing with a different error that is not a timeout error
(Connection reset by peer), so this test isn't really all that useful on
freebsd. Due to a lack of a better idea of how to test a connect timeout, this
test is going to just be ignored for now.
The BSD builders are failing with a different error that is not a timeout error
(Connection reset by peer), so this test isn't really all that useful on
freebsd. Due to a lack of a better idea of how to test a connect timeout, this
test is going to just be ignored for now.
Now with proper checking of enums and allows unsized fields as the last field in a struct or variant. This PR only checks passing of unsized types and distinguishing them from sized ones. To be safe we also need to control storage.
Closes issues #12969 and #13121, supersedes #13375 (all the discussion there is valid here too).
This currently requires linking against a library like libquadmath (or
libgcc), because compiler-rt barely has any support for this and most
hardware does not yet have 128-bit precision floating point. For this
reason, it's currently hidden behind a feature gate.
When compiler-rt is updated to trunk, some tests can be added for
constant evaluation since there will be support for the comparison
operators.
Closes#13381
This adds a `TcpStream::connect_timeout` function in order to assist opening
connections with a timeout (cc #13523). There isn't really much design space for
this specific operation (unlike timing out normal blocking reads/writes), so I
am fairly confident that this is the correct interface for this function.
The function is marked #[experimental] because it takes a u64 timeout argument,
and the u64 type is likely to change in the future.
This adds a `TcpStream::connect_timeout` function in order to assist opening
connections with a timeout (cc #13523). There isn't really much design space for
this specific operation (unlike timing out normal blocking reads/writes), so I
am fairly confident that this is the correct interface for this function.
The function is marked #[experimental] because it takes a u64 timeout argument,
and the u64 type is likely to change in the future.
When instantiating trait default methods for certain implementation,
`typeck` correctly combined type parameters from trait bound with those
from method bound, but didn't do so for lifetime parameters. Applies
the same logic to lifetime parameters.
Closes#13204
