wasmi/src/imports.rs

use std::collections::HashMap;
use global::GlobalRef;
use memory::MemoryRef;
use func::FuncRef;
use table::TableRef;
use module::ModuleRef;
use types::{GlobalDescriptor, TableDescriptor, MemoryDescriptor};
use {Error, Signature};


/// Resolver of a module's dependencies.
///
/// A module have dependencies in a form of a list of imports (i.e.
/// tuple of a (`module_name`, `field_name`, `descriptor`)).
///
/// The job of implementations of this trait is to provide on each
/// import a corresponding concrete reference.
///
/// For simple use-cases you can use [`ImportsBuilder`].
///
/// [`ImportsBuilder`]: struct.ImportsBuilder.html
pub trait ImportResolver {

	/// Resolve a function.
	///
	/// Returned function should match given `signature`, i.e. all parameter types and return value should have exact match.
	/// Otherwise, link-time error will occur.
	fn resolve_func(
		&self,
		_module_name: &str,
		field_name: &str,
		_signature: &Signature,
	) -> Result<FuncRef, Error>;

	/// Resolve a global variable.
	///
	/// Returned global should match given `descriptor`, i.e. type and mutability
	/// should match. Otherwise, link-time error will occur.
	fn resolve_global(
		&self,
		module_name: &str,
		field_name: &str,
		descriptor: &GlobalDescriptor,
	) -> Result<GlobalRef, Error>;

	/// Resolve a memory.
	///
	/// Returned memory should match requested memory (described by the `descriptor`),
	/// i.e. initial size of a returned memory should be equal or larger than requested memory.
	/// Furthermore, if requested memory have maximum size, returned memory either should have
	/// equal or larger maximum size or have no maximum size at all.
	/// If returned memory doesn't match the requested then link-time error will occur.
	fn resolve_memory(
		&self,
		module_name: &str,
		field_name: &str,
		descriptor: &MemoryDescriptor,
	) -> Result<MemoryRef, Error>;

	/// Resolve a table.
	///
	/// Returned table should match requested table (described by the `descriptor`),
	/// i.e. initial size of a returned table should be equal or larger than requested table.
	/// Furthermore, if requested memory have maximum size, returned memory either should have
	/// equal or larger maximum size or have no maximum size at all.
	/// If returned table doesn't match the requested then link-time error will occur.
	fn resolve_table(
		&self,
		module_name: &str,
		field_name: &str,
		descriptor: &TableDescriptor,
	) -> Result<TableRef, Error>;
}

/// Convenience builder of [`ImportResolver`].
///
/// With help of this builder, you can easily create [`ImportResolver`], just by
/// adding needed [resolvers][`ModuleImportResolver`] by names.
///
/// # Examples
///
/// ```rust
/// use wasmi::{ModuleInstance, ImportsBuilder};
/// #
/// # struct EnvModuleResolver;
/// # impl ::wasmi::ModuleImportResolver for EnvModuleResolver { }
/// # fn func() -> Result<(), ::wasmi::Error> {
/// # let module = wasmi::Module::from_buffer(&[0x00, 0x61, 0x73, 0x6d, 0x01, 0x00, 0x00, 0x00]).unwrap();
/// # let other_instance = ModuleInstance::new(&module, &ImportsBuilder::default())?.assert_no_start();
///
/// let imports = ImportsBuilder::new()
///     .with_resolver("env", &EnvModuleResolver)
///     // Note, that ModuleInstance can be a resolver too.
///     .with_resolver("other_instance", &other_instance);
/// let instance = ModuleInstance::new(&module, &imports)?.assert_no_start();
///
/// # Ok(())
/// # }
/// ```
///
/// [`ImportResolver`]: trait.ImportResolver.html
/// [`ModuleImportResolver`]: trait.ModuleImportResolver.html
pub struct ImportsBuilder<'a> {
	modules: HashMap<String, &'a ModuleImportResolver>,
}

impl<'a> Default for ImportsBuilder<'a> {
	fn default() -> Self {
		Self::new()
	}
}

impl<'a> ImportsBuilder<'a> {
	/// Create an empty `ImportsBuilder`.
	pub fn new() -> ImportsBuilder<'a> {
		ImportsBuilder { modules: HashMap::new() }
	}

	/// Register an resolver by a name.
	pub fn with_resolver<N: Into<String>>(
		mut self,
		name: N,
		resolver: &'a ModuleImportResolver,
	) -> Self {
		self.modules.insert(name.into(), resolver);
		self
	}

	/// Register an resolver by a name.
	pub fn push_resolver<N: Into<String>>(&mut self, name: N, resolver: &'a ModuleImportResolver) {
		self.modules.insert(name.into(), resolver);
	}

	fn resolver(&self, name: &str) -> Option<&ModuleImportResolver> {
		self.modules.get(name).cloned()
	}
}

impl<'a> ImportResolver for ImportsBuilder<'a> {
	fn resolve_func(
		&self,
		module_name: &str,
		field_name: &str,
		signature: &Signature,
	) -> Result<FuncRef, Error> {
		self.resolver(module_name).ok_or_else(||
			Error::Instantiation(format!("Module {} not found", module_name))
		)?.resolve_func(field_name, signature)
	}

	fn resolve_global(
		&self,
		module_name: &str,
		field_name: &str,
		global_type: &GlobalDescriptor,
	) -> Result<GlobalRef, Error> {
		self.resolver(module_name).ok_or_else(||
			Error::Instantiation(format!("Module {} not found", module_name))
		)?.resolve_global(field_name, global_type)
	}

	fn resolve_memory(
		&self,
		module_name: &str,
		field_name: &str,
		memory_type: &MemoryDescriptor,
	) -> Result<MemoryRef, Error> {
		self.resolver(module_name).ok_or_else(||
			Error::Instantiation(format!("Module {} not found", module_name))
		)?.resolve_memory(field_name, memory_type)
	}

	fn resolve_table(
		&self,
		module_name: &str,
		field_name: &str,
		table_type: &TableDescriptor,
	) -> Result<TableRef, Error> {
		self.resolver(module_name).ok_or_else(||
			Error::Instantiation(format!("Module {} not found", module_name))
		)?.resolve_table(field_name, table_type)
	}
}

/// Version of [`ImportResolver`] specialized for a single module.
///
/// [`ImportResolver`]: trait.ImportResolver.html
pub trait ModuleImportResolver {
	/// Resolve a function.
	///
	/// See [`ImportResolver::resolve_func`] for details.
	///
	/// [`ImportResolver::resolve_func`]: trait.ImportResolver.html#tymethod.resolve_func
	fn resolve_func(
		&self,
		field_name: &str,
		_signature: &Signature,
	) -> Result<FuncRef, Error> {
		Err(Error::Instantiation(
			format!("Export {} not found", field_name),
		))
	}

	/// Resolve a global variable.
	///
	/// See [`ImportResolver::resolve_global`] for details.
	///
	/// [`ImportResolver::resolve_global`]: trait.ImportResolver.html#tymethod.resolve_global
	fn resolve_global(
		&self,
		field_name: &str,
		_global_type: &GlobalDescriptor,
	) -> Result<GlobalRef, Error> {
		Err(Error::Instantiation(
			format!("Export {} not found", field_name),
		))
	}

	/// Resolve a memory.
	///
	/// See [`ImportResolver::resolve_memory`] for details.
	///
	/// [`ImportResolver::resolve_memory`]: trait.ImportResolver.html#tymethod.resolve_memory
	fn resolve_memory(
		&self,
		field_name: &str,
		_memory_type: &MemoryDescriptor,
	) -> Result<MemoryRef, Error> {
		Err(Error::Instantiation(
			format!("Export {} not found", field_name),
		))
	}

	/// Resolve a table.
	///
	/// See [`ImportResolver::resolve_table`] for details.
	///
	/// [`ImportResolver::resolve_table`]: trait.ImportResolver.html#tymethod.resolve_table
	fn resolve_table(
		&self,
		field_name: &str,
		_table_type: &TableDescriptor,
	) -> Result<TableRef, Error> {
		Err(Error::Instantiation(
			format!("Export {} not found", field_name),
		))
	}
}

impl ModuleImportResolver for ModuleRef {
	fn resolve_func(
		&self,
		field_name: &str,
		_signature: &Signature,
	) -> Result<FuncRef, Error> {
		Ok(self.export_by_name(field_name)
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} not found", field_name))
			})?
			.as_func()
			.cloned()
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} is not a function", field_name))
			})?)
	}

	fn resolve_global(
		&self,
		field_name: &str,
		_global_type: &GlobalDescriptor,
	) -> Result<GlobalRef, Error> {
		Ok(self.export_by_name(field_name)
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} not found", field_name))
			})?
			.as_global()
			.cloned()
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} is not a global", field_name))
			})?)
	}

	fn resolve_memory(
		&self,
		field_name: &str,
		_memory_type: &MemoryDescriptor,
	) -> Result<MemoryRef, Error> {
		Ok(self.export_by_name(field_name)
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} not found", field_name))
			})?
			.as_memory()
			.cloned()
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} is not a memory", field_name))
			})?)
	}

	fn resolve_table(
		&self,
		field_name: &str,
		_table_type: &TableDescriptor,
	) -> Result<TableRef, Error> {
		Ok(self.export_by_name(field_name)
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} not found", field_name))
			})?
			.as_table()
			.cloned()
			.ok_or_else(|| {
				Error::Instantiation(format!("Export {} is not a table", field_name))
			})?)
	}
}