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Use a trait for representing attribute values #166

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Use a trait for representing attribute values #166

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4b46386
Use a trait for representing attribute values
lulf Dec 7, 2020
21ea16e
Use trait objects (dyn AttrValue)
lulf Dec 8, 2020
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51 changes: 37 additions & 14 deletions rubble/src/att/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -35,47 +35,69 @@ mod server;
mod uuid;

use self::{handle::*, pdus::*};
use crate::{utils::HexSlice, Error};
use crate::Error;

pub use self::handle::{Handle, HandleRange};
pub use self::server::{AttributeServer, AttributeServerTx};
pub use self::uuid::AttUuid;

/// An attribute value that can be represented as a byte slice.
pub trait AttrValue {
fn as_slice(&self) -> &[u8];
}

impl AttrValue for &[u8] {
fn as_slice(&self) -> &[u8] {
self
}
}

impl AttrValue for () {
fn as_slice(&self) -> &[u8] {
&[]
}
}

/// An ATT server attribute
pub struct Attribute<'a> {
pub struct Attribute<T>
where
T: AttrValue,
{
/// The type of the attribute as a UUID16, EG "Primary Service" or "Anaerobic Heart Rate Lower Limit"
pub att_type: AttUuid,
/// Unique server-side identifer for attribute
pub handle: Handle,
/// Attribute values can be any fixed length or variable length octet array, which if too large
/// can be sent across multiple PDUs
pub value: HexSlice<&'a [u8]>,
pub value: T,
}

impl<'a> Attribute<'a> {
impl<T: AttrValue> Attribute<T> {
/// Creates a new attribute.
pub fn new(att_type: AttUuid, handle: Handle, value: &'a [u8]) -> Self {
pub fn new(att_type: AttUuid, handle: Handle, value: T) -> Self {
assert_ne!(handle, Handle::NULL);
Attribute {
att_type,
handle,
value: HexSlice(value),
value: value,
}
}

/// Retrieves the attribute's value as a slice.
pub fn value(&self) -> &'a [u8] {
self.value.as_ref()
pub fn value(&self) -> &[u8] {
self.value.as_slice()
}

/// Overrides the previously set attribute's value.
pub fn set_value(&mut self, value: &'a [u8]) {
self.value = HexSlice(value)
pub fn set_value(&mut self, value: T) {
self.value = value;
}
}

/// Trait for attribute sets that can be hosted by an `AttributeServer`.
pub trait AttributeProvider {
type ValueType: AttrValue;
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/// Calls a closure `f` with every attribute whose handle is inside `range`, ascending.
///
/// If `f` returns an error, this function will stop calling `f` and propagate the error
Expand All @@ -87,7 +109,7 @@ pub trait AttributeProvider {
fn for_attrs_in_range(
&mut self,
range: HandleRange,
f: impl FnMut(&Self, Attribute<'_>) -> Result<(), Error>,
f: impl FnMut(&Self, &Attribute<Self::ValueType>) -> Result<(), Error>,
) -> Result<(), Error>;

/// Returns whether `uuid` is a valid grouping attribute type that can be used in *Read By
Expand All @@ -109,7 +131,7 @@ pub trait AttributeProvider {
/// last attribute contained within that service.
///
/// TODO: document what the BLE spec has to say about grouping for characteristics.
fn group_end(&self, handle: Handle) -> Option<&Attribute<'_>>;
fn group_end(&self, handle: Handle) -> Option<&Attribute<Self::ValueType>>;
}

/// An empty attribute set.
Expand All @@ -118,10 +140,11 @@ pub trait AttributeProvider {
pub struct NoAttributes;

impl AttributeProvider for NoAttributes {
type ValueType = ();
fn for_attrs_in_range(
&mut self,
_range: HandleRange,
_f: impl FnMut(&Self, Attribute<'_>) -> Result<(), Error>,
_f: impl FnMut(&Self, &Attribute<Self::ValueType>) -> Result<(), Error>,
) -> Result<(), Error> {
Ok(())
}
Expand All @@ -130,7 +153,7 @@ impl AttributeProvider for NoAttributes {
false
}

fn group_end(&self, _handle: Handle) -> Option<&Attribute<'_>> {
fn group_end(&self, _handle: Handle) -> Option<&Attribute<Self::ValueType>> {
None
}
}
12 changes: 6 additions & 6 deletions rubble/src/att/server.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,7 +2,7 @@

use super::{
pdus::{AttPdu, ByGroupAttData, ByTypeAttData, ErrorCode, Opcode},
AttError, AttributeProvider, Handle, HandleRange,
AttError, AttrValue, AttributeProvider, Handle, HandleRange,
};
use crate::bytes::{ByteReader, FromBytes, ToBytes};
use crate::l2cap::{Protocol, ProtocolObj, Sender};
Expand Down Expand Up @@ -99,7 +99,7 @@ impl<A: AttributeProvider> AttributeServer<A> {
.for_attrs_in_range(range, |_provider, attr| {
if attr.att_type == *attribute_type {
let data =
ByTypeAttData::new(att_mtu, attr.handle, attr.value.as_ref());
ByTypeAttData::new(att_mtu, attr.handle, attr.value.as_slice());
if size == Some(data.encoded_size()) || size.is_none() {
// Can try to encode `data`. If we run out of space, end the list.
data.to_bytes(writer)?;
Expand Down Expand Up @@ -156,7 +156,7 @@ impl<A: AttributeProvider> AttributeServer<A> {
att_mtu,
attr.handle,
provider.group_end(attr.handle).unwrap().handle,
attr.value.as_ref(),
attr.value.as_slice(),
);
if size == Some(data.encoded_size()) || size.is_none() {
// Can try to encode `data`. If we run out of space, end the list.
Expand Down Expand Up @@ -197,10 +197,10 @@ impl<A: AttributeProvider> AttributeServer<A> {
self.attrs.for_attrs_in_range(
HandleRange::new(*handle, *handle),
|_provider, attr| {
let value = if writer.space_left() < attr.value.as_ref().len() {
&attr.value.as_ref()[..writer.space_left()]
let value = if writer.space_left() < attr.value.as_slice().len() {
&attr.value.as_slice()[..writer.space_left()]
} else {
attr.value.as_ref()
attr.value.as_slice()
};
writer.write_slice(value)
},
Expand Down
50 changes: 11 additions & 39 deletions rubble/src/gatt/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -8,11 +8,11 @@ pub mod characteristic;
use crate::att::{AttUuid, Attribute, AttributeProvider, Handle, HandleRange};
use crate::uuid::{Uuid128, Uuid16};
use crate::Error;
use core::{cmp, slice};
use core::cmp;

/// A demo `AttributeProvider` that will enumerate as a *Battery Service*.
pub struct BatteryServiceAttrs {
attributes: [Attribute<'static>; 3],
attributes: [Attribute<&'static [u8]>; 3],
}

impl BatteryServiceAttrs {
Expand Down Expand Up @@ -45,10 +45,11 @@ impl BatteryServiceAttrs {
}

impl AttributeProvider for BatteryServiceAttrs {
type ValueType = &'static [u8];
fn for_attrs_in_range(
&mut self,
range: HandleRange,
mut f: impl FnMut(&Self, Attribute<'_>) -> Result<(), Error>,
mut f: impl FnMut(&Self, &Attribute<Self::ValueType>) -> Result<(), Error>,
) -> Result<(), Error> {
let count = self.attributes.len();
let start = usize::from(range.start().as_u16() - 1); // handles start at 1, not 0
Expand All @@ -62,14 +63,7 @@ impl AttributeProvider for BatteryServiceAttrs {
};

for attr in attrs {
f(
self,
Attribute {
att_type: attr.att_type,
handle: attr.handle,
value: attr.value,
},
)?;
f(self, attr)?;
}
Ok(())
}
Expand All @@ -78,7 +72,7 @@ impl AttributeProvider for BatteryServiceAttrs {
uuid == Uuid16(0x2800) // FIXME not characteristics?
}

fn group_end(&self, handle: Handle) -> Option<&Attribute<'_>> {
fn group_end(&self, handle: Handle) -> Option<&Attribute<Self::ValueType>> {
match handle.as_u16() {
0x0001 => Some(&self.attributes[2]),
0x0002 => Some(&self.attributes[2]),
Expand All @@ -87,27 +81,11 @@ impl AttributeProvider for BatteryServiceAttrs {
}
}

pub struct Attributes<'a> {
to_yield: slice::Iter<'a, Attribute<'a>>,
}

impl<'a> Iterator for Attributes<'a> {
type Item = Attribute<'a>;

fn next(&mut self) -> Option<Attribute<'a>> {
self.to_yield.next().map(|attr| Attribute {
att_type: attr.att_type,
handle: attr.handle,
value: attr.value,
})
}
}

/// A demo `AttributeProvider` that will enumerate as a *Midi Service*.
///
/// Also refer to https://www.midi.org/specifications-old/item/bluetooth-le-midi
pub struct MidiServiceAttrs {
attributes: [Attribute<'static>; 4],
attributes: [Attribute<&'static [u8]>; 4],
}

// MIDI Service (UUID: 03B80E5A-EDE8-4B33-A751-6CE34EC4C700)
Expand Down Expand Up @@ -178,10 +156,11 @@ impl MidiServiceAttrs {
}

impl AttributeProvider for MidiServiceAttrs {
type ValueType = &'static [u8];
fn for_attrs_in_range(
&mut self,
range: HandleRange,
mut f: impl FnMut(&Self, Attribute<'_>) -> Result<(), Error>,
mut f: impl FnMut(&Self, &Attribute<Self::ValueType>) -> Result<(), Error>,
) -> Result<(), Error> {
let count = self.attributes.len();
let start = usize::from(range.start().as_u16() - 1); // handles start at 1, not 0
Expand All @@ -195,14 +174,7 @@ impl AttributeProvider for MidiServiceAttrs {
};

for attr in attrs {
f(
self,
Attribute {
att_type: attr.att_type,
handle: attr.handle,
value: attr.value,
},
)?;
f(self, attr)?;
}
Ok(())
}
Expand All @@ -211,7 +183,7 @@ impl AttributeProvider for MidiServiceAttrs {
uuid == Uuid16(0x2800) // FIXME not characteristics?
}

fn group_end(&self, handle: Handle) -> Option<&Attribute<'_>> {
fn group_end(&self, handle: Handle) -> Option<&Attribute<Self::ValueType>> {
match handle.as_u16() {
0x0001 => Some(&self.attributes[3]),
0x0002 => Some(&self.attributes[3]),
Expand Down