class Availability

Defined at line 213 of file ../../tools/fidl/fidlc/src/versioning_types.h

An availability represents the versions when a FIDL element was added (A),

deprecated (D), removed (R), and re-added as legacy (L) in a platform. These

versions break the platform's timeline into the following regions:

Present -- [A, R) and [L, +inf) if L is set

Available -- [A, D or R)

Deprecated -- [D, R) if D is set

Legacy -- [L, +inf) if L is set

Absent -- (-inf, A) and [R, L or +inf)

Here is what the timeline looks like for finite versions A, D, R:

-inf A-1 A D-1 D R-1 R +inf

o--- ... ---o---o--- ....... ---o---o--- ....... ---o---o--- ... ---o

|-- Absent -| |-------------- Present ------------| |-- Absent -|

Here is what the timeline looks like for a legacy element (L = LEGACY):

-inf A-1 A R-1 R L-1 L +inf

o--- ... ---o---o--- ....... ---o---o--- ... ---o----o---- ... ---o

|-- Absent -| |--- Present ---| |-- Absent -| |-- Present -|

Here is what the timeline looks like for Availability::Unbounded():

-inf +inf

o-------------------------------------------------------------------o

|---------------------------- Available ----------------------------|

|----------------------------- Present -----------------------------|

Public Methods

void Availability ()

Defined at line 215 of file ../../tools/fidl/fidlc/src/versioning_types.h

Availability Unbounded ()

Returns an availability that exists forever. This only exists as the base

case for calling `Inherit`. It never occurs as a final result.

Defined at line 219 of file ../../tools/fidl/fidlc/src/versioning_types.h

std::set<Version> points ()

Returns the points demarcating the availability: `added`, `removed`,

`deprecated` (if deprecated), and LEGACY and +inf (if Legacy::kYes).

Must be in the kInherited or kNarrowed state.

VersionSet set ()

Returns the presence set: [added, removed) and possibly [LEGACY, +inf).

Must be in the kInherited or kNarrowed state.

VersionRange range ()

Returns the presence range: [added, removed). Must be in the kNarrowed state.

bool is_deprecated ()

Returns true if the whole range is deprecated, and false if none of it is.

Must be in the kNarrowed state (where deprecation is all-or-nothing).

void Fail ()

Explicitly mark the availability as failed. Must not have called Init yet.

bool Init (InitArgs args)

Must be called first. Initializes the availability from

fields.

Returns false if they do not satisfy `added

= deprecated

removed`.

InheritResult Inherit (const Availability & parent)

Must be called second. Inherits unset fields from `parent`.

void SetLegacy ()

Optionally call this after Inherit to mark the availability as legacy=true.

TODO(https://fxbug.dev/42085274): This is temporary for the transition from

the LEGACY model to the RFC-0232 model. It will be removed.

void Narrow (VersionRange range)

Must be called third. Narrows the availability to the given range, which

must be a subset of range().

std::string Debug ()

Returns a string representation of the availability for debugging, of the

form "<added> <deprecated> <removed> <legacy>", using "_" for null values.

State state ()

Defined at line 245 of file ../../tools/fidl/fidlc/src/versioning_types.h

Ending ending ()

Returns the availability's ending. Must be in the kNarrowed state.

Defined at line 293 of file ../../tools/fidl/fidlc/src/versioning_types.h

Enumerations

enum class State : uint8_t

Name	Value	Comments
kUnset	0	1. Default constructed. All fields are null.
kInitialized	1	2. `Init` succeeded. Some fields might be set, and they are in order.
kInherited	2	3. `Inherit` succeeded. Now `added`, `removed`, `ending`, and `legacy` are always set.
kNarrowed	3	4. `Narrow` succeeded. Now `deprecated` is unset or equal to `added`, and `legacy` is either kNotApplicable or kNo.
kFailed	4	One of the steps failed.

An availability advances through four states. All reach kNarrowed on

success, except for library availabilities, which stay at kInherited

because libraries do not get decomposed.

Defined at line 231 of file ../../tools/fidl/fidlc/src/versioning_types.h

enum class Legacy : uint8_t

Name	Value	Comments
kNotApplicable	0	Not applicable because [added, removed) already includes LEGACY, i.e. `removed` is +inf.
kNo	1	No legacy support: do not re-add at LEGACY.
kYes	2	Legacy support: re-add at LEGACY.

Represents whether an availability includes legacy support.

Defined at line 267 of file ../../tools/fidl/fidlc/src/versioning_types.h

enum class Ending : uint8_t

Name	Value	Comments
kNone	0	This availability never ends, i.e. `removed` is +inf.
kRemoved	1	Directly marked removed=N. Validate that there IS NOT an added=N replacement.
kReplaced	2	Directly marked replaced=N. Validate that there IS an added=N replacement.
kInherited	3	The availability ends because an ancestor was kRemoved or kReplaced.
kSplit	4	During decomposition, only the last piece keeps the original ending. All the others get the kSplit ending.

Meaning of the `removed` version, how this availability ends.

Defined at line 278 of file ../../tools/fidl/fidlc/src/versioning_types.h