Module move_binary_format::file_format
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Binary format for transactions and modules.
This module provides a simple Rust abstraction over the binary format. That is the format of modules stored on chain or the format of the code section of a transaction.
file_format_common.rs provides the constant values for entities in the binary format.
(The binary format is evolving so please come back here in time to check evolutions.)
Overall the binary format is structured in a number of sections:
- Header: this must start at offset 0 in the binary. It contains a blob that starts every Diem binary, followed by the version of the VM used to compile the code, and last is the number of tables present in this binary.
- Table Specification: it’s a number of tuple of the form
(table type, starting_offset, byte_count). The number of entries is specified in the header (last entry in header). There can only be a single entry per table type. Thestarting offsetis from the beginning of the binary. Tables must cover the entire size of the binary blob and cannot overlap. - Table Content: the serialized form of the specific entries in the table. Those roughly map to the structs defined in this module. Entries in each table must be unique.
We have two formats: one for modules here represented by CompiledModule, another
for transaction scripts which is CompiledScript. Building those tables and passing them
to the serializer (serializer.rs) generates a binary of the form described. Vectors in
those structs translate to tables and table specifications.
Structs
A set of Abilitys
Index into the AddressIdentifier table.
A CodeUnit is the body of a function. It has the function header and the instruction stream.
A CompiledModule defines the structure of a module which is the unit of published code.
Contains the main function to execute and its dependencies.
A Constant is a serialized value along with its type. That type will be deserialized by the
loader/evauluator
Index into the ConstantPool table.
A FieldDefinition is the definition of a field: its name and the field type.
A field access info (owner type and offset)
Index into the FieldHandle table.
A complete or partial instantiation of a field (or the type of it).
Index into the FieldInstantiation table.
A FunctionDefinition is the implementation of a function. It defines
the prototype of the function and the function body.
Index into the FunctionDefinition table.
A FunctionHandle is a reference to a function. It is composed by a
ModuleHandle and the name and signature of that function within the module.
Index into the FunctionHandle table.
A complete or partial instantiation of a function
Index into the FunctionInstantiation table.
A FunctionSignature in internally used to create a unique representation of the overall
signature as need. Consider deprecated…
Index into the Identifier table.
A ModuleHandle is a reference to a MOVE module. It is composed by an address and a name.
Index into the ModuleHandle table.
A Signature is the list of locals used by a function.
Index into the Signature table.
An iterator to help traverse the SignatureToken in a non-recursive fashion to avoid
overflowing the stack.
Alternative preorder traversal iterator for SignatureToken that also returns the depth at each node.
A complete or partial instantiation of a generic struct
Index into the StructInstantiation table.
A StructDefinition is a type definition. It either indicates it is native or defines all the
user-specified fields declared on the type.
Index into the StructDefinition table.
A StructHandle is a reference to a user defined type. It is composed by a ModuleHandle
and the name of the type within that module.
Index into the StructHandle table.
A type parameter used in the declaration of a struct.
A type definition. SignatureToken allows the definition of the set of known types and their
composition.
Enums
An Ability classifies what operations are permitted for a given type
Bytecode is a VM instruction of variable size. The type of the bytecode (opcode) defines
the size of the bytecode.
A SignatureToken is a type declaration for a location.
StructFieldInformation indicates whether a struct is native or has user-specified fields
Visibility restricts the accessibility of the associated entity.
Constants
Index 0 into the LocalsSignaturePool, which is guaranteed to be an empty list. Used to represent function/struct instantiation with no type arguments – effectively non-generic functions and structs.
Functions
Create the following module which is convenient in tests:
// module
Return the simplest module that will pass the bounds checker
Return a simple script that contains only a return in the main()
Type Definitions
The pool of address identifiers (addresses used in ModuleHandles/ModuleIds).
Does not include runtime values. Those are placed in the ConstantPool
Index into the code stream for a jump. The offset is relative to the beginning of the instruction stream.
The pool of Constant values
The pool of identifiers.
Index of a local variable in a function.
Max number of fields in a StructDefinition.
The pool of Signature instances. Every function definition must define the set of
locals used and their types.
Generic index into one of the tables in the binary format.
Type parameters are encoded as indices. This index can also be used to lookup the kind of a
type parameter in the FunctionHandle and StructHandle.
The pool of TypeSignature instances. Those are system and user types used and
their composition (e.g. &U64).