Tage Johansson
2023-Jul-19 09:09 UTC
[Libguestfs] [libnbd PATCH 04/10] generator: Add information about the lifetime of closures
Add a new field `cbkind` to the `closure` type in generator/API.ml*.
It tells how many times the closure may be invoked and for how long time
it might be used. More specifically, it can take any of these values:
- `CBOnceCommand`: The closure may only be called once and shall not
be called after the command is retired.
- `CBManyCommand`: The closure may be called any number of times but
not after the command is retired.
- `CBManyHandle`: The closure may be called any number of times before
the handle is destructed.
This information is needed in the Rust bindings for:
a) Knowing if the closure trait should be `FnMut` or `FnOnce`
(see <https://doc.rust-lang.org/std/ops/trait.FnOnce.html>).
b) Knowing for what lifetime the closure should be valid. A closure that
may be called after the function invokation has returned must live
for the `'static` lifetime. But static closures are inconveniant for
the user since they can't effectively borrow any local data. So it is
good if this restriction is relaxed when it is not needed.
---
generator/API.ml | 11 +++++++++++
generator/API.mli | 13 +++++++++++++
2 files changed, 24 insertions(+)
diff --git a/generator/API.ml b/generator/API.ml
index f90a6fa..086b2f9 100644
--- a/generator/API.ml
+++ b/generator/API.ml
@@ -77,6 +77,7 @@ and ret and closure = {
cbname : string;
cbargs : cbarg list;
+ cbkind : cbkind;
}
and cbarg | CBArrayAndLen of arg * string
@@ -87,6 +88,10 @@ and cbarg | CBString of string
| CBUInt of string
| CBUInt64 of string
+and cbkind +| CBOnceCommand
+| CBManyCommand
+| CBManyHandle
and enum = {
enum_prefix : string;
enums : (string * int) list
@@ -141,20 +146,24 @@ the handle from the NBD protocol handshake."
(* Closures. *)
let chunk_closure = {
cbname = "chunk";
+ cbkind = CBManyCommand;
cbargs = [ CBBytesIn ("subbuf", "count");
CBUInt64 "offset"; CBUInt "status";
CBMutable (Int "error") ]
}
let completion_closure = {
cbname = "completion";
+ cbkind = CBOnceCommand;
cbargs = [ CBMutable (Int "error") ]
}
let debug_closure = {
cbname = "debug";
+ cbkind = CBManyHandle;
cbargs = [ CBString "context"; CBString "msg" ]
}
let extent_closure = {
cbname = "extent";
+ cbkind = CBManyCommand;
cbargs = [ CBString "metacontext";
CBUInt64 "offset";
CBArrayAndLen (UInt32 "entries",
@@ -163,10 +172,12 @@ let extent_closure = {
}
let list_closure = {
cbname = "list";
+ cbkind = CBManyCommand;
cbargs = [ CBString "name"; CBString "description" ]
}
let context_closure = {
cbname = "context";
+ cbkind = CBManyCommand;
cbargs = [ CBString "name" ]
}
let all_closures = [ chunk_closure; completion_closure;
diff --git a/generator/API.mli b/generator/API.mli
index 361132d..73dc40a 100644
--- a/generator/API.mli
+++ b/generator/API.mli
@@ -94,6 +94,10 @@ and ret and closure = {
cbname : string; (** name of callback function *)
cbargs : cbarg list; (** all closures return int for now *)
+ (** Wether the closure should be used once or many times and wether it might
+ be used only until the command is completed or until the handle is
+ destructed. *)
+ cbkind : cbkind;
}
and cbarg | CBArrayAndLen of arg * string (** array + number of entries *)
@@ -104,6 +108,15 @@ and cbarg | CBString of string (** like String *)
| CBUInt of string (** like UInt *)
| CBUInt64 of string (** like UInt64 *)
+and cbkind +| CBOnceCommand (** The closure will be used 0 or 1 time if the
aio_* call
+ returned a error and exactly once if the call succeeded.
+ The closure may only be called before the command
+ is retired. (E.g., completion callback.) *)
+| CBManyCommand (** The closure may be used any number of times but only
+ before the command is retired. (E.g., list callback.) *)
+| CBManyHandle (** The closure may be used any number of times for as long
+ as the handle exists. (E.g., debug callback.) *)
and enum = {
enum_prefix : string; (** prefix of each enum variant *)
enums : (string * int) list (** enum names and their values in C *)
--
2.41.0
Richard W.M. Jones
2023-Jul-19 14:35 UTC
[Libguestfs] [libnbd PATCH 04/10] generator: Add information about the lifetime of closures
On Wed, Jul 19, 2023 at 09:09:48AM +0000, Tage Johansson wrote:> Add a new field `cbkind` to the `closure` type in generator/API.ml*. > It tells how many times the closure may be invoked and for how long time > it might be used. More specifically, it can take any of these values: > - `CBOnceCommand`: The closure may only be called once and shall not > be called after the command is retired. > - `CBManyCommand`: The closure may be called any number of times but > not after the command is retired. > - `CBManyHandle`: The closure may be called any number of times before > the handle is destructed. > This information is needed in the Rust bindings for: > a) Knowing if the closure trait should be `FnMut` or `FnOnce` > (see <https://doc.rust-lang.org/std/ops/trait.FnOnce.html>). > b) Knowing for what lifetime the closure should be valid. A closure that > may be called after the function invokation has returned must live > for the `'static` lifetime. But static closures are inconveniant for > the user since they can't effectively borrow any local data. So it is > good if this restriction is relaxed when it is not needed. > --- > generator/API.ml | 11 +++++++++++ > generator/API.mli | 13 +++++++++++++ > 2 files changed, 24 insertions(+) > > diff --git a/generator/API.ml b/generator/API.ml > index f90a6fa..086b2f9 100644 > --- a/generator/API.ml > +++ b/generator/API.ml > @@ -77,6 +77,7 @@ and ret > and closure = { > cbname : string; > cbargs : cbarg list; > + cbkind : cbkind;I'm dubious about the premise of this patch, but let's at least call it "cblifetime" since that's what it is expressing.> } > and cbarg > | CBArrayAndLen of arg * string > @@ -87,6 +88,10 @@ and cbarg > | CBString of string > | CBUInt of string > | CBUInt64 of string > +and cbkind > +| CBOnceCommand > +| CBManyCommand > +| CBManyHandle > and enum = { > enum_prefix : string; > enums : (string * int) list > @@ -141,20 +146,24 @@ the handle from the NBD protocol handshake." > (* Closures. *) > let chunk_closure = { > cbname = "chunk"; > + cbkind = CBManyCommand; > cbargs = [ CBBytesIn ("subbuf", "count"); > CBUInt64 "offset"; CBUInt "status"; > CBMutable (Int "error") ] > } > let completion_closure = { > cbname = "completion"; > + cbkind = CBOnceCommand; > cbargs = [ CBMutable (Int "error") ] > } > let debug_closure = { > cbname = "debug"; > + cbkind = CBManyHandle; > cbargs = [ CBString "context"; CBString "msg" ] > } > let extent_closure = { > cbname = "extent"; > + cbkind = CBManyCommand; > cbargs = [ CBString "metacontext"; > CBUInt64 "offset"; > CBArrayAndLen (UInt32 "entries", > @@ -163,10 +172,12 @@ let extent_closure = { > } > let list_closure = { > cbname = "list"; > + cbkind = CBManyCommand; > cbargs = [ CBString "name"; CBString "description" ] > } > let context_closure = { > cbname = "context"; > + cbkind = CBManyCommand; > cbargs = [ CBString "name" ] > } > let all_closures = [ chunk_closure; completion_closure; > diff --git a/generator/API.mli b/generator/API.mli > index 361132d..73dc40a 100644 > --- a/generator/API.mli > +++ b/generator/API.mli > @@ -94,6 +94,10 @@ and ret > and closure = { > cbname : string; (** name of callback function *) > cbargs : cbarg list; (** all closures return int for now *) > + (** Wether the closure should be used once or many times and wether it mightwether -> whether Rich.> + be used only until the command is completed or until the handle is > + destructed. *) > + cbkind : cbkind; > } > and cbarg > | CBArrayAndLen of arg * string (** array + number of entries *) > @@ -104,6 +108,15 @@ and cbarg > | CBString of string (** like String *) > | CBUInt of string (** like UInt *) > | CBUInt64 of string (** like UInt64 *) > +and cbkind > +| CBOnceCommand (** The closure will be used 0 or 1 time if the aio_* call > + returned a error and exactly once if the call succeeded. > + The closure may only be called before the command > + is retired. (E.g., completion callback.) *) > +| CBManyCommand (** The closure may be used any number of times but only > + before the command is retired. (E.g., list callback.) *) > +| CBManyHandle (** The closure may be used any number of times for as long > + as the handle exists. (E.g., debug callback.) *) > and enum = { > enum_prefix : string; (** prefix of each enum variant *) > enums : (string * int) list (** enum names and their values in C *) > -- > 2.41.0 > > _______________________________________________ > Libguestfs mailing list > Libguestfs at redhat.com > https://listman.redhat.com/mailman/listinfo/libguestfs-- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html