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    use crate::rust::string::String;
    use crate::io;
    use super::{
    	Deserialize, Serialize, Error, VarUint7, VarInt7, VarUint32, VarUint1, Uint8,
    	ValueType, TableElementType
    };

    const FLAG_HAS_MAX: u8 = 0x01;
    #[cfg(feature="atomics")]
    const FLAG_SHARED: u8 = 0x02;

    /// Global definition struct
    #[derive(Debug, Copy, Clone, PartialEq)]
    pub struct GlobalType {
    	content_type: ValueType,
    	is_mutable: bool,
    }

    impl GlobalType {
    	/// New global type
    	pub fn new(content_type: ValueType, is_mutable: bool) -> Self {
    		GlobalType {
    			content_type: content_type,
    			is_mutable: is_mutable,
    		}
    	}

    	/// Type of the global entry
    	pub fn content_type(&self) -> ValueType { self.content_type }

    	/// Is global entry is declared as mutable
    	pub fn is_mutable(&self) -> bool { self.is_mutable }
    }

    impl Deserialize for GlobalType {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		let content_type = ValueType::deserialize(reader)?;
    		let is_mutable = VarUint1::deserialize(reader)?;
    		Ok(GlobalType {
    			content_type: content_type,
    			is_mutable: is_mutable.into(),
    		})
    	}
    }

    impl Serialize for GlobalType {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		self.content_type.serialize(writer)?;
    		VarUint1::from(self.is_mutable).serialize(writer)?;
    		Ok(())
    	}
    }

    /// Table entry
    #[derive(Debug, Copy, Clone, PartialEq)]
    pub struct TableType {
    	elem_type: TableElementType,
    	limits: ResizableLimits,
    }

    impl TableType {
    	/// New table definition
    	pub fn new(min: u32, max: Option<u32>) -> Self {
    		TableType {
    			elem_type: TableElementType::AnyFunc,
    			limits: ResizableLimits::new(min, max),
    		}
    	}

    	/// Table memory specification
    	pub fn limits(&self) -> &ResizableLimits { &self.limits }

    	/// Table element type
    	pub fn elem_type(&self) -> TableElementType { self.elem_type }
    }

    impl Deserialize for TableType {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		let elem_type = TableElementType::deserialize(reader)?;
    		let limits = ResizableLimits::deserialize(reader)?;
    		Ok(TableType {
    			elem_type: elem_type,
    			limits: limits,
    		})
    	}
    }

    impl Serialize for TableType {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		self.elem_type.serialize(writer)?;
    		self.limits.serialize(writer)
    	}
    }

    /// Memory and table limits.
    #[derive(Debug, Copy, Clone, PartialEq)]
    pub struct ResizableLimits {
    	initial: u32,
    	maximum: Option<u32>,
    	#[cfg(feature = "atomics")]
    	shared: bool,
    }

    impl ResizableLimits {
    	/// New memory limits definition.
    	pub fn new(min: u32, max: Option<u32>) -> Self {
    		ResizableLimits {
    			initial: min,
    			maximum: max,
    			#[cfg(feature = "atomics")]
    			shared: false,
    		}
    	}
    	/// Initial size.
    	pub fn initial(&self) -> u32 { self.initial }
    	/// Maximum size.
    	pub fn maximum(&self) -> Option<u32> { self.maximum }

    	#[cfg(feature = "atomics")]
    	/// Whether or not this is a shared array buffer.
    	pub fn shared(&self) -> bool { self.shared }
    }

    impl Deserialize for ResizableLimits {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		let flags: u8 = Uint8::deserialize(reader)?.into();
    		match flags {
    			// Default flags are always supported. This is simply: FLAG_HAS_MAX={true, false}.
    			0x00 | 0x01 => {},

    			// Atomics proposal introduce FLAG_SHARED (0x02). Shared memories can be used only
    			// together with FLAG_HAS_MAX (0x01), hence 0x03.
    			#[cfg(feature="atomics")]
    			0x03 => {},

    			_ => return Err(Error::InvalidLimitsFlags(flags)),
    		}

    		let initial = VarUint32::deserialize(reader)?;
    		let maximum = if flags & FLAG_HAS_MAX != 0 {
    			Some(VarUint32::deserialize(reader)?.into())
    		} else {
    			None
    		};

    		Ok(ResizableLimits {
    			initial: initial.into(),
    			maximum: maximum,

    			#[cfg(feature="atomics")]
    			shared: flags & FLAG_SHARED != 0,
    		})
    	}
    }

    impl Serialize for ResizableLimits {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		let mut flags: u8 = 0;
    		if self.maximum.is_some() {
    			flags |= FLAG_HAS_MAX;
    		}

    		#[cfg(feature="atomics")]
    		{
    			// If the atomics feature is enabled and if the shared flag is set, add logically
    			// it to the flags.
    			if self.shared {
    				flags |= FLAG_SHARED;
    			}
    		}
    		Uint8::from(flags).serialize(writer)?;
    		VarUint32::from(self.initial).serialize(writer)?;
    		if let Some(max) = self.maximum {
    			VarUint32::from(max).serialize(writer)?;
    		}
    		Ok(())
    	}
    }

    /// Memory entry.
    #[derive(Debug, Copy, Clone, PartialEq)]
    pub struct MemoryType(ResizableLimits);

    impl MemoryType {
    	/// New memory definition
    	pub fn new(min: u32, max: Option<u32>) -> Self {
    		let r = ResizableLimits::new(min, max);
    		MemoryType(r)
    	}

    	/// Set the `shared` flag that denotes a memory that can be shared between threads.
    	///
    	/// `false` by default. This is only available if the `atomics` feature is enabled.
    	#[cfg(feature = "atomics")]
    	pub fn set_shared(&mut self, shared: bool) {
    		self.0.shared = shared;
    	}

    	/// Limits of the memory entry.
    	pub fn limits(&self) -> &ResizableLimits {
    		&self.0
    	}
    }

    impl Deserialize for MemoryType {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		Ok(MemoryType(ResizableLimits::deserialize(reader)?))
    	}
    }

    impl Serialize for MemoryType {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		self.0.serialize(writer)
    	}
    }

    /// External to local binding.
    #[derive(Debug, Copy, Clone, PartialEq)]
    pub enum External {
    	/// Binds to a function whose type is associated with the given index in the
    	/// type section.
    	Function(u32),
    	/// Describes local table definition to be imported as.
    	Table(TableType),
    	/// Describes local memory definition to be imported as.
    	Memory(MemoryType),
    	/// Describes local global entry to be imported as.
    	Global(GlobalType),
    }

    impl Deserialize for External {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		let kind = VarUint7::deserialize(reader)?;
    		match kind.into() {
    			0x00 => Ok(External::Function(VarUint32::deserialize(reader)?.into())),
    			0x01 => Ok(External::Table(TableType::deserialize(reader)?)),
    			0x02 => Ok(External::Memory(MemoryType::deserialize(reader)?)),
    			0x03 => Ok(External::Global(GlobalType::deserialize(reader)?)),
    			_ => Err(Error::UnknownExternalKind(kind.into())),
    		}
    	}
    }

    impl Serialize for External {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		use self::External::*;

    		match self {
    			Function(index) => {
    				VarUint7::from(0x00).serialize(writer)?;
    				VarUint32::from(index).serialize(writer)?;
    			},
    			Table(tt) => {
    				VarInt7::from(0x01).serialize(writer)?;
    				tt.serialize(writer)?;
    			},
    			Memory(mt) => {
    				VarInt7::from(0x02).serialize(writer)?;
    				mt.serialize(writer)?;
    			},
    			Global(gt) => {
    				VarInt7::from(0x03).serialize(writer)?;
    				gt.serialize(writer)?;
    			},
    		}

    		Ok(())
    	}
    }

    /// Import entry.
    #[derive(Debug, Clone, PartialEq)]
    pub struct ImportEntry {
    	module_str: String,
    	field_str: String,
    	external: External,
    }

    impl ImportEntry {
    	/// New import entry.
    	pub fn new(module_str: String, field_str: String, external: External) -> Self {
    		ImportEntry {
    			module_str: module_str,
    			field_str: field_str,
    			external: external,
    		}
    	}

    	/// Module reference of the import entry.
    	pub fn module(&self) -> &str { &self.module_str }

    	/// Module reference of the import entry (mutable).
    	pub fn module_mut(&mut self) -> &mut String {
    		&mut self.module_str
    	}

    	/// Field reference of the import entry.
    	pub fn field(&self) -> &str { &self.field_str }

    	/// Field reference of the import entry (mutable)
    	pub fn field_mut(&mut self) -> &mut String {
    		&mut self.field_str
    	}

    	/// Local binidng of the import entry.
    	pub fn external(&self) -> &External { &self.external }

    	/// Local binidng of the import entry (mutable)
    	pub fn external_mut(&mut self) -> &mut External { &mut self.external }
    }

    impl Deserialize for ImportEntry {
    	type Error = Error;

    	fn deserialize<R: io::Read>(reader: &mut R) -> Result<Self, Self::Error> {
    		let module_str = String::deserialize(reader)?;
    		let field_str = String::deserialize(reader)?;
    		let external = External::deserialize(reader)?;

    		Ok(ImportEntry {
    			module_str: module_str,
    			field_str: field_str,
    			external: external,
    		})
    	}
    }

    impl Serialize for ImportEntry {
    	type Error = Error;

    	fn serialize<W: io::Write>(self, writer: &mut W) -> Result<(), Self::Error> {
    		self.module_str.serialize(writer)?;
    		self.field_str.serialize(writer)?;
    		self.external.serialize(writer)
    	}
    }

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