capnproto

schema.capnp (18724B)

---

 # Copyright (c) 2013-2014 Sandstorm Development Group, Inc. and contributors
 # Licensed under the MIT License:
 #
 # Permission is hereby granted, free of charge, to any person obtaining a copy
 # of this software and associated documentation files (the "Software"), to deal
 # in the Software without restriction, including without limitation the rights
 # to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 # copies of the Software, and to permit persons to whom the Software is
 # furnished to do so, subject to the following conditions:
 #
 # The above copyright notice and this permission notice shall be included in
 # all copies or substantial portions of the Software.
 #
 # THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 # IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 # FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 # AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 # LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 # OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 # THE SOFTWARE.
 
 using Cxx = import "/capnp/c++.capnp";
 
 @0xa93fc509624c72d9;
 $Cxx.namespace("capnp::schema");
 
 using Id = UInt64;
 # The globally-unique ID of a file, type, or annotation.
 
 struct Node {
   id @0 :Id;
 
   displayName @1 :Text;
   # Name to present to humans to identify this Node.  You should not attempt to parse this.  Its
   # format could change.  It is not guaranteed to be unique.
   #
   # (On Zooko's triangle, this is the node's nickname.)
 
   displayNamePrefixLength @2 :UInt32;
   # If you want a shorter version of `displayName` (just naming this node, without its surrounding
   # scope), chop off this many characters from the beginning of `displayName`.
 
   scopeId @3 :Id;
   # ID of the lexical parent node.  Typically, the scope node will have a NestedNode pointing back
   # at this node, but robust code should avoid relying on this (and, in fact, group nodes are not
   # listed in the outer struct's nestedNodes, since they are listed in the fields).  `scopeId` is
   # zero if the node has no parent, which is normally only the case with files, but should be
   # allowed for any kind of node (in order to make runtime type generation easier).
 
   parameters @32 :List(Parameter);
   # If this node is parameterized (generic), the list of parameters. Empty for non-generic types.
 
   isGeneric @33 :Bool;
   # True if this node is generic, meaning that it or one of its parent scopes has a non-empty
   # `parameters`.
 
   struct Parameter {
     # Information about one of the node's parameters.
 
     name @0 :Text;
   }
 
   nestedNodes @4 :List(NestedNode);
   # List of nodes nested within this node, along with the names under which they were declared.
 
   struct NestedNode {
     name @0 :Text;
     # Unqualified symbol name.  Unlike Node.displayName, this *can* be used programmatically.
     #
     # (On Zooko's triangle, this is the node's petname according to its parent scope.)
 
     id @1 :Id;
     # ID of the nested node.  Typically, the target node's scopeId points back to this node, but
     # robust code should avoid relying on this.
   }
 
   annotations @5 :List(Annotation);
   # Annotations applied to this node.
 
   union {
     # Info specific to each kind of node.
 
     file @6 :Void;
 
     struct :group {
       dataWordCount @7 :UInt16;
       # Size of the data section, in words.
 
       pointerCount @8 :UInt16;
       # Size of the pointer section, in pointers (which are one word each).
 
       preferredListEncoding @9 :ElementSize;
       # The preferred element size to use when encoding a list of this struct.  If this is anything
       # other than `inlineComposite` then the struct is one word or less in size and is a candidate
       # for list packing optimization.
 
       isGroup @10 :Bool;
       # If true, then this "struct" node is actually not an independent node, but merely represents
       # some named union or group within a particular parent struct.  This node's scopeId refers
       # to the parent struct, which may itself be a union/group in yet another struct.
       #
       # All group nodes share the same dataWordCount and pointerCount as the top-level
       # struct, and their fields live in the same ordinal and offset spaces as all other fields in
       # the struct.
       #
       # Note that a named union is considered a special kind of group -- in fact, a named union
       # is exactly equivalent to a group that contains nothing but an unnamed union.
 
       discriminantCount @11 :UInt16;
       # Number of fields in this struct which are members of an anonymous union, and thus may
       # overlap.  If this is non-zero, then a 16-bit discriminant is present indicating which
       # of the overlapping fields is active.  This can never be 1 -- if it is non-zero, it must be
       # two or more.
       #
       # Note that the fields of an unnamed union are considered fields of the scope containing the
       # union -- an unnamed union is not its own group.  So, a top-level struct may contain a
       # non-zero discriminant count.  Named unions, on the other hand, are equivalent to groups
       # containing unnamed unions.  So, a named union has its own independent schema node, with
       # `isGroup` = true.
 
       discriminantOffset @12 :UInt32;
       # If `discriminantCount` is non-zero, this is the offset of the union discriminant, in
       # multiples of 16 bits.
 
       fields @13 :List(Field);
       # Fields defined within this scope (either the struct's top-level fields, or the fields of
       # a particular group; see `isGroup`).
       #
       # The fields are sorted by ordinal number, but note that because groups share the same
       # ordinal space, the field's index in this list is not necessarily exactly its ordinal.
       # On the other hand, the field's position in this list does remain the same even as the
       # protocol evolves, since it is not possible to insert or remove an earlier ordinal.
       # Therefore, for most use cases, if you want to identify a field by number, it may make the
       # most sense to use the field's index in this list rather than its ordinal.
     }
 
     enum :group {
       enumerants@14 :List(Enumerant);
       # Enumerants ordered by numeric value (ordinal).
     }
 
     interface :group {
       methods @15 :List(Method);
       # Methods ordered by ordinal.
 
       superclasses @31 :List(Superclass);
       # Superclasses of this interface.
     }
 
     const :group {
       type @16 :Type;
       value @17 :Value;
     }
 
     annotation :group {
       type @18 :Type;
 
       targetsFile @19 :Bool;
       targetsConst @20 :Bool;
       targetsEnum @21 :Bool;
       targetsEnumerant @22 :Bool;
       targetsStruct @23 :Bool;
       targetsField @24 :Bool;
       targetsUnion @25 :Bool;
       targetsGroup @26 :Bool;
       targetsInterface @27 :Bool;
       targetsMethod @28 :Bool;
       targetsParam @29 :Bool;
       targetsAnnotation @30 :Bool;
     }
   }
 
   struct SourceInfo {
     # Additional information about a node which is not needed at runtime, but may be useful for
     # documentation or debugging purposes. This is kept in a separate struct to make sure it
     # doesn't accidentally get included in contexts where it is not needed. The
     # `CodeGeneratorRequest` includes this information in a separate array.
 
     id @0 :Id;
     # ID of the Node which this info describes.
 
     docComment @1 :Text;
     # The top-level doc comment for the Node.
 
     members @2 :List(Member);
     # Information about each member -- i.e. fields (for structs), enumerants (for enums), or
     # methods (for interfaces).
     #
     # This list is the same length and order as the corresponding list in the Node, i.e.
     # Node.struct.fields, Node.enum.enumerants, or Node.interface.methods.
 
     struct Member {
       docComment @0 :Text;
       # Doc comment on the member.
     }
 
     # TODO(someday): Record location of the declaration in the original source code.
   }
 }
 
 struct Field {
   # Schema for a field of a struct.
 
   name @0 :Text;
 
   codeOrder @1 :UInt16;
   # Indicates where this member appeared in the code, relative to other members.
   # Code ordering may have semantic relevance -- programmers tend to place related fields
   # together.  So, using code ordering makes sense in human-readable formats where ordering is
   # otherwise irrelevant, like JSON.  The values of codeOrder are tightly-packed, so the maximum
   # value is count(members) - 1.  Fields that are members of a union are only ordered relative to
   # the other members of that union, so the maximum value there is count(union.members).
 
   annotations @2 :List(Annotation);
 
   const noDiscriminant :UInt16 = 0xffff;
 
   discriminantValue @3 :UInt16 = Field.noDiscriminant;
   # If the field is in a union, this is the value which the union's discriminant should take when
   # the field is active.  If the field is not in a union, this is 0xffff.
 
   union {
     slot :group {
       # A regular, non-group, non-fixed-list field.
 
       offset @4 :UInt32;
       # Offset, in units of the field's size, from the beginning of the section in which the field
       # resides.  E.g. for a UInt32 field, multiply this by 4 to get the byte offset from the
       # beginning of the data section.
 
       type @5 :Type;
       defaultValue @6 :Value;
 
       hadExplicitDefault @10 :Bool;
       # Whether the default value was specified explicitly.  Non-explicit default values are always
       # zero or empty values.  Usually, whether the default value was explicit shouldn't matter.
       # The main use case for this flag is for structs representing method parameters:
       # explicitly-defaulted parameters may be allowed to be omitted when calling the method.
     }
 
     group :group {
       # A group.
 
       typeId @7 :Id;
       # The ID of the group's node.
     }
   }
 
   ordinal :union {
     implicit @8 :Void;
     explicit @9 :UInt16;
     # The original ordinal number given to the field.  You probably should NOT use this; if you need
     # a numeric identifier for a field, use its position within the field array for its scope.
     # The ordinal is given here mainly just so that the original schema text can be reproduced given
     # the compiled version -- i.e. so that `capnp compile -ocapnp` can do its job.
   }
 }
 
 struct Enumerant {
   # Schema for member of an enum.
 
   name @0 :Text;
 
   codeOrder @1 :UInt16;
   # Specifies order in which the enumerants were declared in the code.
   # Like Struct.Field.codeOrder.
 
   annotations @2 :List(Annotation);
 }
 
 struct Superclass {
   id @0 :Id;
   brand @1 :Brand;
 }
 
 struct Method {
   # Schema for method of an interface.
 
   name @0 :Text;
 
   codeOrder @1 :UInt16;
   # Specifies order in which the methods were declared in the code.
   # Like Struct.Field.codeOrder.
 
   implicitParameters @7 :List(Node.Parameter);
   # The parameters listed in [] (typically, type / generic parameters), whose bindings are intended
   # to be inferred rather than specified explicitly, although not all languages support this.
 
   paramStructType @2 :Id;
   # ID of the parameter struct type.  If a named parameter list was specified in the method
   # declaration (rather than a single struct parameter type) then a corresponding struct type is
   # auto-generated.  Such an auto-generated type will not be listed in the interface's
   # `nestedNodes` and its `scopeId` will be zero -- it is completely detached from the namespace.
   # (Awkwardly, it does of course inherit generic parameters from the method's scope, which makes
   # this a situation where you can't just climb the scope chain to find where a particular
   # generic parameter was introduced. Making the `scopeId` zero was a mistake.)
 
   paramBrand @5 :Brand;
   # Brand of param struct type.
 
   resultStructType @3 :Id;
   # ID of the return struct type; similar to `paramStructType`.
 
   resultBrand @6 :Brand;
   # Brand of result struct type.
 
   annotations @4 :List(Annotation);
 }
 
 struct Type {
   # Represents a type expression.
 
   union {
     # The ordinals intentionally match those of Value.
 
     void @0 :Void;
     bool @1 :Void;
     int8 @2 :Void;
     int16 @3 :Void;
     int32 @4 :Void;
     int64 @5 :Void;
     uint8 @6 :Void;
     uint16 @7 :Void;
     uint32 @8 :Void;
     uint64 @9 :Void;
     float32 @10 :Void;
     float64 @11 :Void;
     text @12 :Void;
     data @13 :Void;
 
     list :group {
       elementType @14 :Type;
     }
 
     enum :group {
       typeId @15 :Id;
       brand @21 :Brand;
     }
     struct :group {
       typeId @16 :Id;
       brand @22 :Brand;
     }
     interface :group {
       typeId @17 :Id;
       brand @23 :Brand;
     }
 
     anyPointer :union {
       unconstrained :union {
         # A regular AnyPointer.
         #
         # The name "unconstrained" means as opposed to constraining it to match a type parameter.
         # In retrospect this name is probably a poor choice given that it may still be constrained
         # to be a struct, list, or capability.
 
         anyKind @18 :Void;       # truly AnyPointer
         struct @25 :Void;        # AnyStruct
         list @26 :Void;          # AnyList
         capability @27 :Void;    # Capability
       }
 
       parameter :group {
         # This is actually a reference to a type parameter defined within this scope.
 
         scopeId @19 :Id;
         # ID of the generic type whose parameter we're referencing. This should be a parent of the
         # current scope.
 
         parameterIndex @20 :UInt16;
         # Index of the parameter within the generic type's parameter list.
       }
 
       implicitMethodParameter :group {
         # This is actually a reference to an implicit (generic) parameter of a method. The only
         # legal context for this type to appear is inside Method.paramBrand or Method.resultBrand.
 
         parameterIndex @24 :UInt16;
       }
     }
   }
 }
 
 struct Brand {
   # Specifies bindings for parameters of generics. Since these bindings turn a generic into a
   # non-generic, we call it the "brand".
 
   scopes @0 :List(Scope);
   # For each of the target type and each of its parent scopes, a parameterization may be included
   # in this list. If no parameterization is included for a particular relevant scope, then either
   # that scope has no parameters or all parameters should be considered to be `AnyPointer`.
 
   struct Scope {
     scopeId @0 :Id;
     # ID of the scope to which these params apply.
 
     union {
       bind @1 :List(Binding);
       # List of parameter bindings.
 
       inherit @2 :Void;
       # The place where the Brand appears is within this scope or a sub-scope, and bindings
       # for this scope are deferred to later Brand applications. This is equivalent to a
       # pass-through binding list, where each of this scope's parameters is bound to itself.
       # For example:
       #
       #   struct Outer(T) {
       #     struct Inner {
       #       value @0 :T;
       #     }
       #     innerInherit @0 :Inner;            # Outer Brand.Scope is `inherit`.
       #     innerBindSelf @1 :Outer(T).Inner;  # Outer Brand.Scope explicitly binds T to T.
       #   }
       #
       # The innerInherit and innerBindSelf fields have equivalent types, but different Brand
       # styles.
     }
   }
 
   struct Binding {
     union {
       unbound @0 :Void;
       type @1 :Type;
 
       # TODO(someday): Allow non-type parameters? Unsure if useful.
     }
   }
 }
 
 struct Value {
   # Represents a value, e.g. a field default value, constant value, or annotation value.
 
   union {
     # The ordinals intentionally match those of Type.
 
     void @0 :Void;
     bool @1 :Bool;
     int8 @2 :Int8;
     int16 @3 :Int16;
     int32 @4 :Int32;
     int64 @5 :Int64;
     uint8 @6 :UInt8;
     uint16 @7 :UInt16;
     uint32 @8 :UInt32;
     uint64 @9 :UInt64;
     float32 @10 :Float32;
     float64 @11 :Float64;
     text @12 :Text;
     data @13 :Data;
 
     list @14 :AnyPointer;
 
     enum @15 :UInt16;
     struct @16 :AnyPointer;
 
     interface @17 :Void;
     # The only interface value that can be represented statically is "null", whose methods always
     # throw exceptions.
 
     anyPointer @18 :AnyPointer;
   }
 }
 
 struct Annotation {
   # Describes an annotation applied to a declaration.  Note AnnotationNode describes the
   # annotation's declaration, while this describes a use of the annotation.
 
   id @0 :Id;
   # ID of the annotation node.
 
   brand @2 :Brand;
   # Brand of the annotation.
   #
   # Note that the annotation itself is not allowed to be parameterized, but its scope might be.
 
   value @1 :Value;
 }
 
 enum ElementSize {
   # Possible element sizes for encoded lists.  These correspond exactly to the possible values of
   # the 3-bit element size component of a list pointer.
 
   empty @0;    # aka "void", but that's a keyword.
   bit @1;
   byte @2;
   twoBytes @3;
   fourBytes @4;
   eightBytes @5;
   pointer @6;
   inlineComposite @7;
 }
 
 struct CapnpVersion {
   major @0 :UInt16;
   minor @1 :UInt8;
   micro @2 :UInt8;
 }
 
 struct CodeGeneratorRequest {
   capnpVersion @2 :CapnpVersion;
   # Version of the `capnp` executable. Generally, code generators should ignore this, but the code
   # generators that ship with `capnp` itself will print a warning if this mismatches since that
   # probably indicates something is misconfigured.
   #
   # The first version of 'capnp' to set this was 0.6.0. So, if it's missing, the compiler version
   # is older than that.
 
   nodes @0 :List(Node);
   # All nodes parsed by the compiler, including for the files on the command line and their
   # imports.
 
   sourceInfo @3 :List(Node.SourceInfo);
   # Information about the original source code for each node, where available. This array may be
   # omitted or may be missing some nodes if no info is available for them.
 
   requestedFiles @1 :List(RequestedFile);
   # Files which were listed on the command line.
 
   struct RequestedFile {
     id @0 :Id;
     # ID of the file.
 
     filename @1 :Text;
     # Name of the file as it appeared on the command-line (minus the src-prefix).  You may use
     # this to decide where to write the output.
 
     imports @2 :List(Import);
     # List of all imported paths seen in this file.
 
     struct Import {
       id @0 :Id;
       # ID of the imported file.
 
       name @1 :Text;
       # Name which *this* file used to refer to the foreign file.  This may be a relative name.
       # This information is provided because it might be useful for code generation, e.g. to
       # generate #include directives in C++.  We don't put this in Node.file because this
       # information is only meaningful at compile time anyway.
       #
       # (On Zooko's triangle, this is the import's petname according to the importing file.)
     }
   }
 }