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//! This module deals with serializing rust types into raw SPA pods.
//!
//! A raw pod can be serialized by passing a implementor of the [`PodSerialize`] trait
//! to [`PodSerializer::serialize`].
//!
//! The crate provides a number of implementors of this trait either directly,
//! or through [`FixedSizedPod`](`super::FixedSizedPod`).
//!
//! You can also implement the [`PodSerialize`] trait on another type yourself. See the traits documentation for more
//! information on how to do that.
use std::{
convert::TryInto,
ffi::CString,
io::{Seek, SeekFrom, Write},
marker::PhantomData,
};
pub use cookie_factory::GenError;
use cookie_factory::{
bytes::{ne_u32, ne_u64, ne_u8},
combinator::slice,
gen,
multi::all,
sequence::{pair, tuple},
SerializeFn,
};
use crate::{
pod::ChoiceValue,
utils::{Choice, ChoiceEnum},
};
use super::{CanonicalFixedSizedPod, FixedSizedPod, PropertyFlags, Value, ValueArray};
/// Implementors of this trait are able to serialize themselves into a SPA pod by using a [`PodSerializer`].
///
/// Their [`serialize`](`PodSerialize::serialize`) method should invoke exactly one of the `serialize_*()` methods
/// of the provided [`PodSerializer`] that fits the type that will be serialized.
///
/// If you want to serialize into a pod that always has the same size, implement [`FixedSizedPod`] instead
/// and this trait will be implemented for you automatically.
///
/// # Examples
/// Make a type serialize into a `String` pod.
/// ```rust
/// use std::io;
/// use libspa::pod::serialize::{GenError, PodSerialize, PodSerializer, SerializeSuccess};
///
/// struct StringNewtype(String);
///
/// impl PodSerialize for StringNewtype {
/// fn serialize<O: io::Write + io::Seek>(
/// &self,
/// serializer: PodSerializer<O>,
/// ) -> Result<SerializeSuccess<O>, GenError> {
/// serializer.serialize_string(self.0.as_str())
/// }
/// }
/// ```
/// `Bytes` pods are created in the same way, but with the `serialize_bytes` method.
///
/// Make a type serialize into a `Array` pod with `Int` pod elements:
/// ```rust
/// use std::io;
/// use libspa::pod::serialize::{GenError, PodSerialize, PodSerializer, SerializeSuccess};
///
/// struct Numbers(Vec<i32>);
///
/// impl PodSerialize for Numbers {
/// fn serialize<O: io::Write + io::Seek>(
/// &self,
/// serializer: PodSerializer<O>,
/// ) -> Result<SerializeSuccess<O>, GenError> {
/// let mut array_serializer = serializer.serialize_array(self.0.len() as u32)?;
/// for element in self.0.iter() {
/// array_serializer.serialize_element(element)?;
/// }
/// array_serializer.end()
/// }
/// }
/// ```
///
/// Make a struct serialize into a `Struct` pod:
/// ```rust
/// use std::io;
/// use libspa::pod::serialize::{GenError, PodSerialize, PodSerializer, SerializeSuccess};
///
/// struct Animal {
/// name: String,
/// feet: u8,
/// can_fly: bool,
/// }
///
/// impl PodSerialize for Animal {
/// fn serialize<O: io::Write + io::Seek>(
/// &self,
/// serializer: PodSerializer<O>,
/// ) -> Result<SerializeSuccess<O>, GenError> {
/// let mut struct_serializer = serializer.serialize_struct()?;
/// struct_serializer.serialize_field(self.name.as_str())?;
/// // No pod exists for u8, we need to use an `Int` type pod by casting to `i32`.
/// struct_serializer.serialize_field(&(self.feet as i32))?;
/// struct_serializer.serialize_field(&self.can_fly)?;
/// struct_serializer.end()
/// }
/// }
/// ```
pub trait PodSerialize {
/// Serialize the type by using the provided [`PodSerializer`]
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError>;
}
// Serialize into a `String` pod.
impl PodSerialize for str {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
serializer.serialize_string(self)
}
}
// Serialize into a `Bytes` pod.
impl PodSerialize for [u8] {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
serializer.serialize_bytes(self)
}
}
// Serialize into the kind of pod represented by the value.
impl PodSerialize for Value {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
/// Helper function that fully serializes an array containing FixedSizedPod elements.
fn serialize_array<E: FixedSizedPod, O: Write + Seek>(
array: &[E],
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
let mut arr_serializer = serializer.serialize_array(array.len() as u32)?;
for e in array.iter() {
arr_serializer.serialize_element(e)?;
}
arr_serializer.end()
}
match self {
Value::None => serializer.serialized_fixed_sized_pod(&()),
Value::Bool(b) => serializer.serialized_fixed_sized_pod(b),
Value::Id(id) => serializer.serialized_fixed_sized_pod(id),
Value::Int(i) => serializer.serialized_fixed_sized_pod(i),
Value::Long(l) => serializer.serialized_fixed_sized_pod(l),
Value::Float(f) => serializer.serialized_fixed_sized_pod(f),
Value::Double(d) => serializer.serialized_fixed_sized_pod(d),
Value::String(s) => serializer.serialize_string(s.as_str()),
Value::Bytes(b) => serializer.serialize_bytes(b.as_slice()),
Value::Rectangle(rect) => serializer.serialized_fixed_sized_pod(rect),
Value::Fraction(frac) => serializer.serialized_fixed_sized_pod(frac),
Value::Fd(fd) => serializer.serialized_fixed_sized_pod(fd),
Value::ValueArray(array) => match array {
ValueArray::None(arr) => serialize_array(arr, serializer),
ValueArray::Bool(arr) => serialize_array(arr, serializer),
ValueArray::Id(arr) => serialize_array(arr, serializer),
ValueArray::Int(arr) => serialize_array(arr, serializer),
ValueArray::Long(arr) => serialize_array(arr, serializer),
ValueArray::Float(arr) => serialize_array(arr, serializer),
ValueArray::Double(arr) => serialize_array(arr, serializer),
ValueArray::Rectangle(arr) => serialize_array(arr, serializer),
ValueArray::Fraction(arr) => serialize_array(arr, serializer),
ValueArray::Fd(arr) => serialize_array(arr, serializer),
},
Value::Struct(array) => {
let mut struct_serializer = serializer.serialize_struct()?;
for elem in array.iter() {
struct_serializer.serialize_field(elem)?;
}
struct_serializer.end()
}
Value::Object(object) => {
let mut object_serializer = serializer.serialize_object(object.type_, object.id)?;
for prop in object.properties.iter() {
object_serializer.serialize_property(prop.key, &prop.value, prop.flags)?;
}
object_serializer.end()
}
Value::Choice(choice) => match choice {
ChoiceValue::Bool(choice) => serializer.serialize_choice(choice),
ChoiceValue::Int(choice) => serializer.serialize_choice(choice),
ChoiceValue::Long(choice) => serializer.serialize_choice(choice),
ChoiceValue::Float(choice) => serializer.serialize_choice(choice),
ChoiceValue::Double(choice) => serializer.serialize_choice(choice),
ChoiceValue::Id(choice) => serializer.serialize_choice(choice),
ChoiceValue::Rectangle(choice) => serializer.serialize_choice(choice),
ChoiceValue::Fraction(choice) => serializer.serialize_choice(choice),
ChoiceValue::Fd(choice) => serializer.serialize_choice(choice),
},
Value::Pointer(type_, pointer) => serializer.serialize_pointer(*type_, *pointer),
}
}
}
impl<P: FixedSizedPod> PodSerialize for [P] {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
let mut arr_serializer = serializer.serialize_array(
self.len()
.try_into()
.expect("Array length does not fit in a u32"),
)?;
for element in self.iter() {
arr_serializer.serialize_element(element)?;
}
arr_serializer.end()
}
}
impl<T> PodSerialize for (u32, *const T) {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
serializer.serialize_pointer(self.0, self.1)
}
}
/// This struct is returned by [`PodSerialize`] implementors on serialization success.
///
/// Because this can only be constructed by the [`PodSerializer`], [`PodSerialize`] implementors are forced
/// to finish serialization of their pod instead of stopping after serializing only part of a pod.
pub struct SerializeSuccess<O: Write + Seek> {
/// Because [`PodSerialize`] implementors get ownership of the serializer,
/// it is returned back to the caller in this struct.
serializer: PodSerializer<O>,
/// The number of bytes written by the serialization operation that returns this struct.
len: u64,
}
/// This struct is responsible for serializing a [`PodSerialize`] implementor into the raw POD format.
pub struct PodSerializer<O: Write + Seek> {
/// The writer is saved in an option, but can be expected to always be a `Some` when a `serialize_*` function
/// is called.
/// The function should then `take()` the writer, use it to serialize the item,
/// and must then put the writer back inside.
/// The [`Self::gen`] function can be used to do this.
out: Option<O>,
}
impl<O: Write + Seek> PodSerializer<O> {
/// Serialize the provided POD into the raw pod format, writing it into `out`.
///
/// When serializing into an in-memory-buffer such as [`Vec`], you might have to wrap it into a [`std::io::Cursor`]
/// to provide the [`Seek`] trait.
///
/// The function returns back the `out` writer and the number of bytes written,
/// or a generation error if serialization failed.
pub fn serialize<P>(out: O, pod: &P) -> Result<(O, u64), GenError>
where
P: PodSerialize + ?Sized,
{
let serializer = Self { out: Some(out) };
pod.serialize(serializer).map(|success| {
(
success
.serializer
.out
.expect("Serializer does not contain a writer"),
success.len,
)
})
}
/// Helper serialization method for serializing the Pod header.
///
/// # Parameters
/// - size: The size of the pod body
/// - type: The type of the pod, e.g. `spa_sys::SPA_TYPE_Int` for a `spa_pod_int`
fn header(size: usize, ty: u32) -> impl SerializeFn<O> {
pair(ne_u32(size as u32), ne_u32(ty))
}
/// Helper serialization function for adding padding to a pod..
///
/// Pad output with 0x00 bytes so that it is aligned to 8 bytes.
fn padding(len: usize) -> impl SerializeFn<O> {
let zeroes = std::iter::repeat(0u8);
all(zeroes.take(len).map(ne_u8))
}
/// Use the provided serialization function to write into the writer contained in self.
fn gen(&mut self, f: impl SerializeFn<O>) -> Result<u64, GenError> {
gen(
f,
self.out
.take()
.expect("PodSerializer does not contain a writer"),
)
.map(|(writer, len)| {
self.out = Some(writer);
len
})
}
/// Write out a full pod (header, body, padding), with the body computed using the provided serialization function.
fn write_pod(
mut self,
size: usize,
type_: u32,
f: impl SerializeFn<O>,
) -> Result<SerializeSuccess<O>, GenError> {
let padding = if size % 8 == 0 { 0 } else { 8 - (size % 8) };
let written = self.gen(tuple((
Self::header(size, type_),
f,
Self::padding(padding),
)))?;
Ok(SerializeSuccess {
serializer: self,
len: written,
})
}
// Implementation note:
// Each `serialize_*` function must serialize the _full_ pod, meaning header, body, and padding.
// The `write_pod` method may be used to help with this.
/// Serialize any fixed size pod.
///
/// The type of the serialized pod will depend on the [`FixedSizedPod::CanonicalType`] that the passed type has.
pub fn serialized_fixed_sized_pod<P>(self, pod: &P) -> Result<SerializeSuccess<O>, GenError>
where
P: FixedSizedPod + ?Sized,
{
self.write_pod(
P::CanonicalType::SIZE as usize,
P::CanonicalType::TYPE,
|out| pod.as_canonical_type().serialize_body(out),
)
}
/// Serialize a `String` pod.
pub fn serialize_string(self, string: &str) -> Result<SerializeSuccess<O>, GenError> {
let cstr = CString::new(string)
.expect("Pod::String contains string with '\0' byte")
.into_bytes_with_nul();
self.write_pod(cstr.len(), spa_sys::SPA_TYPE_String, slice(cstr))
}
/// Serialize a `Bytes` pod.
pub fn serialize_bytes(self, bytes: &[u8]) -> Result<SerializeSuccess<O>, GenError> {
self.write_pod(bytes.len(), spa_sys::SPA_TYPE_Bytes, slice(bytes))
}
/// Begin serializing an `Array` pod with exactly `length` elements.
pub fn serialize_array<P: FixedSizedPod>(
mut self,
length: u32,
) -> Result<ArrayPodSerializer<O, P>, GenError> {
self.gen(pair(
Self::header(
(8 + length * P::CanonicalType::SIZE) as usize,
spa_sys::SPA_TYPE_Array,
),
Self::header(P::CanonicalType::SIZE as usize, P::CanonicalType::TYPE),
))?;
Ok(ArrayPodSerializer {
serializer: self,
length,
written: 0,
_phantom: PhantomData,
})
}
/// Begin serializing a `Struct` pod.
pub fn serialize_struct(mut self) -> Result<StructPodSerializer<O>, GenError> {
let header_position = self
.out
.as_mut()
.expect("PodSerializer does not contain a writer")
.stream_position()
.expect("Could not get current position in writer");
// Write a size of 0 for now, this will be updated when calling `StructPodSerializer.end()`.
self.gen(Self::header(0, spa_sys::SPA_TYPE_Struct))?;
Ok(StructPodSerializer {
serializer: Some(self),
header_position,
written: 0,
})
}
/// Begin serializing an `Object` pod.
pub fn serialize_object(
mut self,
object_type: u32,
object_id: u32,
) -> Result<ObjectPodSerializer<O>, GenError> {
let header_position = self
.out
.as_mut()
.expect("PodSerializer does not contain a writer")
.stream_position()
.expect("Could not get current position in writer");
// Write a size of 0 for now, this will be updated when calling `ObjectPodSerializer.end()`.
self.gen(Self::header(0, spa_sys::SPA_TYPE_Object))?;
self.gen(pair(ne_u32(object_type), ne_u32(object_id)))?;
Ok(ObjectPodSerializer {
serializer: Some(self),
header_position,
written: 0,
})
}
/// Serialize a `Choice` pod.
pub fn serialize_choice<T: CanonicalFixedSizedPod>(
mut self,
choice: &Choice<T>,
) -> Result<SerializeSuccess<O>, GenError> {
let flags = choice.0;
let (choice_type, values) = match &choice.1 {
ChoiceEnum::None(value) => (spa_sys::SPA_CHOICE_None, vec![value]),
ChoiceEnum::Range { default, min, max } => {
(spa_sys::SPA_CHOICE_Range, vec![default, min, max])
}
ChoiceEnum::Step {
default,
min,
max,
step,
} => (spa_sys::SPA_CHOICE_Step, vec![default, min, max, step]),
ChoiceEnum::Enum {
default,
alternatives,
} => {
let mut values = vec![default];
values.extend(alternatives);
(spa_sys::SPA_CHOICE_Enum, values)
}
ChoiceEnum::Flags { default, flags } => {
let mut values = vec![default];
values.extend(flags);
(spa_sys::SPA_CHOICE_Flags, values)
}
};
let len: usize = 2 * 8 + values.len() * (T::SIZE as usize);
self.gen(Self::header(len, spa_sys::SPA_TYPE_Choice))?;
self.gen(pair(ne_u32(choice_type), ne_u32(flags.bits())))?;
self.gen(pair(ne_u32(T::SIZE), ne_u32(T::TYPE)))?;
for v in values {
self.gen(|out| v.serialize_body(out))?;
}
let padding = if len % 8 == 0 { 0 } else { 8 - (len % 8) };
// Add padding to the pod.
let pad_bytes = self.gen(PodSerializer::padding(padding))?;
Ok(SerializeSuccess {
serializer: self,
// pod header + choice body + padding
len: 8 + len as u64 + pad_bytes,
})
}
/// Serialize a pointer pod.
pub fn serialize_pointer<T>(
mut self,
type_: u32,
ptr: *const T,
) -> Result<SerializeSuccess<O>, GenError> {
let ptr_size = std::mem::size_of::<usize>();
let len = 8 + ptr_size;
let mut written = self.gen(Self::header(len, spa_sys::SPA_TYPE_Pointer))?;
written += self.gen(pair(ne_u32(type_), ne_u32(0)))?;
written += match ptr_size {
4 => self.gen(ne_u32(ptr as u32))?,
8 => self.gen(ne_u64(ptr as u64))?,
_ => panic!("unsupported pointer size {}", ptr_size),
};
Ok(SerializeSuccess {
serializer: self,
len: written,
})
}
}
/// This struct handles serializing arrays.
///
/// It can be obtained by calling [`PodSerializer::serialize_array`].
///
/// The exact number of elements that was specified during that call must be written into it
/// using its [`serialize_element`](`Self::serialize_element`) function,
/// followed by calling its [`end`](`Self::end`) function to finish serialization of the array.
pub struct ArrayPodSerializer<O: Write + Seek, P: FixedSizedPod> {
serializer: PodSerializer<O>,
/// The total length the array should have
length: u32,
/// The number of elements that have been written already
written: u32,
/// The struct has the type parameter P to ensure all serialized elements are the same type,
/// but doesn't actually own any P, so we need the `PhantomData<P>` instead.
_phantom: PhantomData<P>,
}
impl<O: Write + Seek, P: FixedSizedPod> ArrayPodSerializer<O, P> {
/// Serialize a single element.
///
/// Returns the amount of bytes written for this field.
pub fn serialize_element(&mut self, elem: &P) -> Result<u64, GenError> {
if !self.written < self.length {
panic!("More elements than specified were serialized into the array POD");
}
let result = self
.serializer
.gen(|out| elem.as_canonical_type().serialize_body(out));
self.written += 1;
result
}
/// Finish serializing the array.
pub fn end(mut self) -> Result<SerializeSuccess<O>, GenError> {
assert_eq!(
self.length, self.written,
"Array POD was not serialized with the specified amount of elements"
);
let bytes_written = self.written * P::CanonicalType::SIZE;
let padding = if bytes_written % 8 == 0 {
0
} else {
8 - (bytes_written as usize % 8)
};
// Add padding to the pod.
let pad_bytes = self.serializer.gen(PodSerializer::padding(padding))?;
Ok(SerializeSuccess {
serializer: self.serializer,
// Number of bytes written for the pod is two headers + body length + padding
len: 16 + u64::from(self.written * P::CanonicalType::SIZE) + pad_bytes,
})
}
}
/// This struct handles serializing structs.
///
/// It can be obtained by calling [`PodSerializer::serialize_struct`].
///
/// Its [`serialize_field`](`Self::serialize_field`) method can be repeatedly called to serialize one field each.
/// To finalize the struct, its [`end`](`Self::end`) method must be called.
pub struct StructPodSerializer<O: Write + Seek> {
/// The serializer is saved in an option, but can be expected to always be a `Some`
/// when `serialize_field()` or `end()` is called.
///
/// `serialize_field()` `take()`s the serializer, uses it to serialize the field,
/// and then puts the serializer back inside.
serializer: Option<PodSerializer<O>>,
/// The position to seek to when modifying header.
header_position: u64,
written: usize,
}
impl<O: Write + Seek> StructPodSerializer<O> {
/// Serialize a single field of the struct.
///
/// Returns the amount of bytes written for this field.
pub fn serialize_field<P>(&mut self, field: &P) -> Result<u64, GenError>
where
P: PodSerialize + ?Sized,
{
let success = field.serialize(
self.serializer
.take()
.expect("StructSerializer does not contain a serializer"),
)?;
self.written += success.len as usize;
self.serializer = Some(success.serializer);
Ok(success.len)
}
/// Finish serialization of the pod.
pub fn end(self) -> Result<SerializeSuccess<O>, GenError> {
let mut serializer = self
.serializer
.expect("StructSerializer does not contain a serializer");
// Seek to header position, write header with updates size, seek back.
serializer
.out
.as_mut()
.expect("Serializer does not contain a writer")
.seek(SeekFrom::Start(self.header_position))
.expect("Failed to seek to header position");
serializer.gen(PodSerializer::header(
self.written,
spa_sys::SPA_TYPE_Struct,
))?;
serializer
.out
.as_mut()
.expect("Serializer does not contain a writer")
.seek(SeekFrom::End(0))
.expect("Failed to seek to end");
// No padding needed: Last field will already end aligned.
// Return full length of written pod.
Ok(SerializeSuccess {
serializer,
len: self.written as u64 + 8,
})
}
}
/// This struct handles serializing objects.
///
/// It can be obtained by calling [`PodSerializer::serialize_object`].
///
/// Its [`serialize_property`](`Self::serialize_property`) method can be repeatedly called to serialize each property.
/// To finalize the object, its [`end`](`Self::end`) method must be called.
pub struct ObjectPodSerializer<O: Write + Seek> {
/// The serializer is saved in an option, but can be expected to always be a `Some`
/// when `serialize_field()` or `end()` is called.
///
/// `serialize_property()` `take()`s the serializer, uses it to serialize the property,
/// and then puts the serializer back inside.
serializer: Option<PodSerializer<O>>,
/// The position to seek to when modifying header.
header_position: u64,
written: usize,
}
impl<O: Write + Seek> ObjectPodSerializer<O> {
/// Serialize a single property of the object.
///
/// Returns the amount of bytes written for this field.
pub fn serialize_property<P>(
&mut self,
key: u32,
value: &P,
flags: PropertyFlags,
) -> Result<u64, GenError>
where
P: PodSerialize + ?Sized,
{
let mut serializer = self
.serializer
.take()
.expect("ObjectPodSerializer does not contain a serializer");
serializer.gen(pair(ne_u32(key), ne_u32(flags.bits())))?;
let mut success = value.serialize(serializer)?;
success.len += 8; // add the key and flags len
self.written += success.len as usize;
self.serializer = Some(success.serializer);
Ok(success.len)
}
/// Finish serialization of the pod.
pub fn end(self) -> Result<SerializeSuccess<O>, GenError> {
let mut serializer = self
.serializer
.expect("ObjectSerializer does not contain a serializer");
// Seek to header position, write header with updates size, seek back.
serializer
.out
.as_mut()
.expect("Serializer does not contain a writer")
.seek(SeekFrom::Start(self.header_position))
.expect("Failed to seek to header position");
// size of properties + object type + object id
let written = self.written + 8;
serializer.gen(PodSerializer::header(written, spa_sys::SPA_TYPE_Object))?;
serializer
.out
.as_mut()
.expect("Serializer does not contain a writer")
.seek(SeekFrom::End(0))
.expect("Failed to seek to end");
// No padding needed: Last field will already end aligned.
// Return full length of written pod.
Ok(SerializeSuccess {
serializer,
// pod header + object body
len: 8 + written as u64,
})
}
}
impl<T: CanonicalFixedSizedPod + FixedSizedPod> PodSerialize for Choice<T> {
fn serialize<O: Write + Seek>(
&self,
serializer: PodSerializer<O>,
) -> Result<SerializeSuccess<O>, GenError> {
serializer.serialize_choice(self)
}
}