refactor(core/rust): improve BinaryData

* add direct reference to a Gc<[u8]> slice, so that we are not forced
  to create a Python bytes object for allocated data
* add From implementations

core/embed/rust/src/io.rs

@@ -1,4 +1,4 @@
-use crate::error::Error;
+use crate::{error::Error, micropython::gc::Gc};
 
 #[cfg(feature = "micropython")]
 use crate::micropython::{buffer::get_buffer, obj::Obj};
@@ -78,23 +78,11 @@ pub enum BinaryData<'a> {
     Slice(&'a [u8]),
     #[cfg(feature = "micropython")]
     Object(Obj),
+    #[cfg(feature = "micropython")]
+    AllocatedSlice(Gc<[u8]>),
 }
 
 impl<'a> BinaryData<'a> {
-    /// Creates a new `BinaryData` from a slice of binary data.
-    pub fn from_slice(data: &'a [u8]) -> Self {
-        Self::Slice(data)
-    }
-
-    /// Creates a new `BinaryData` from a micropython `bytes` object.
-    #[cfg(feature = "micropython")]
-    pub fn from_object(obj: Obj) -> Result<Self, Error> {
-        if !obj.is_bytes() {
-            return Err(Error::TypeError);
-        }
-        Ok(Self::Object(obj))
-    }
-
     /// Returns `true` if the binary data is empty.
     pub fn is_empty(&self) -> bool {
         self.len() == 0
@@ -114,17 +102,15 @@ impl<'a> BinaryData<'a> {
             // note above.
             #[cfg(feature = "micropython")]
             Self::Object(obj) => unsafe { unwrap!(get_buffer(*obj)) },
+            #[cfg(feature = "micropython")]
+            Self::AllocatedSlice(data) => data,
         }
     }
 
     /// Returns the length of the binary data in bytes.
     pub fn len(&self) -> usize {
-        match self {
-            Self::Slice(data) => data.len(),
-            #[cfg(feature = "micropython")]
-            // SAFETY: We expect no existing mutable reference.
-            Self::Object(obj) => unsafe { unwrap!(get_buffer(*obj)).len() },
-        }
+        // SAFETY: reference is discarded immediately
+        unsafe { self.data().len() }
     }
 
     /// Reads binary data from the source into the buffer.
@@ -150,6 +136,14 @@ impl<'a> BinaryData<'a> {
                 buff[..size].copy_from_slice(&data[ofs..ofs + size]);
                 size
             }
+
+            #[cfg(feature = "micropython")]
+            Self::AllocatedSlice(data) => {
+                let remaining = data.len().saturating_sub(ofs);
+                let size = buff.len().min(remaining);
+                buff[..size].copy_from_slice(&data[ofs..ofs + size]);
+                size
+            }
         }
     }
 }
@@ -165,3 +159,26 @@ impl<'a> PartialEq for BinaryData<'a> {
         }
     }
 }
+
+impl From<Gc<[u8]>> for BinaryData<'static> {
+    fn from(data: Gc<[u8]>) -> Self {
+        Self::AllocatedSlice(data)
+    }
+}
+
+impl TryFrom<Obj> for BinaryData<'static> {
+    type Error = Error;
+
+    fn try_from(obj: Obj) -> Result<Self, Self::Error> {
+        if !obj.is_bytes() {
+            return Err(Error::TypeError);
+        }
+        Ok(Self::Object(obj))
+    }
+}
+
+impl<'a> From<&'a [u8]> for BinaryData<'a> {
+    fn from(data: &'a [u8]) -> Self {
+        Self::Slice(data)
+    }
+}

core/embed/rust/src/ui/layout/util.rs

@@ -181,8 +181,5 @@ pub fn get_user_custom_image() -> Result<BinaryData<'static>, Error> {
     let mut data = Gc::<[u8]>::new_slice(len)?;
     // SAFETY: buffer is freshly allocated so nobody else has it.
     load_avatar(unsafe { Gc::<[u8]>::as_mut(&mut data) })?;
-    // Convert to mp_obj_bytes
-    let bytes = Obj::try_from(data.as_ref())?;
-    // Convert to BinaryData
-    BinaryData::from_object(bytes)
+    Ok(data.into())
 }

core/embed/rust/src/ui/model_tr/layout.rs

@@ -4,7 +4,6 @@ use heapless::Vec;
 
 use crate::{
     error::Error,
-    io::BinaryData,
     maybe_trace::MaybeTrace,
     micropython::{
         buffer::StrBuffer, gc::Gc, iter::IterBuf, list::List, map::Map, module::Module, obj::Obj,
@@ -392,10 +391,7 @@ extern "C" fn new_confirm_homescreen(n_args: usize, args: *const Obj, kwargs: *m
     let block = move |_args: &[Obj], kwargs: &Map| {
         let title: TString = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
         let image: Obj = kwargs.get(Qstr::MP_QSTR_image)?;
-        let obj = LayoutObj::new(ConfirmHomescreen::new(
-            title,
-            BinaryData::from_object(image)?,
-        ))?;
+        let obj = LayoutObj::new(ConfirmHomescreen::new(title, image.try_into()?))?;
         Ok(obj.into())
     };
 
@@ -1600,7 +1596,7 @@ extern "C" fn new_confirm_firmware_update(
 
 pub extern "C" fn upy_check_homescreen_format(data: Obj) -> Obj {
     let block = || {
-        let image = BinaryData::from_object(data)?;
+        let image = data.try_into()?;
         Ok(check_homescreen_format(image).into())
     };
 

core/embed/rust/src/ui/model_tt/component/homescreen/mod.rs

@@ -568,7 +568,7 @@ fn get_homescreen_image() -> BinaryData<'static> {
             return image;
         }
     }
-    BinaryData::from_slice(IMAGE_HOMESCREEN)
+    IMAGE_HOMESCREEN.into()
 }
 
 #[cfg(feature = "ui_debug")]

core/embed/rust/src/ui/model_tt/layout.rs

@@ -615,12 +615,12 @@ extern "C" fn new_confirm_homescreen(n_args: usize, args: *const Obj, kwargs: *m
         let title: TString = kwargs.get(Qstr::MP_QSTR_title)?.try_into()?;
         let image: Obj = kwargs.get(Qstr::MP_QSTR_image)?;
 
-        let mut jpeg = BinaryData::from_object(image)?;
+        let mut jpeg: BinaryData = image.try_into()?;
 
         if jpeg.is_empty() {
             // Incoming data may be empty, meaning we should
             // display default homescreen image.
-            jpeg = BinaryData::from_slice(theme::IMAGE_HOMESCREEN);
+            jpeg = theme::IMAGE_HOMESCREEN.into();
         }
 
         if !check_homescreen_format(jpeg, false) {
@@ -1573,7 +1573,7 @@ extern "C" fn new_show_lockscreen(n_args: usize, args: *const Obj, kwargs: *mut
 
 pub extern "C" fn upy_check_homescreen_format(data: Obj) -> Obj {
     let block = || {
-        let buffer = BinaryData::from_object(data)?;
+        let buffer = data.try_into()?;
         Ok(check_homescreen_format(buffer, false).into())
     };
 

core/embed/rust/src/ui/shape/jpeg.rs

@@ -46,7 +46,7 @@ impl<'a> JpegImage<'a> {
     }
 
     pub fn new(pos: Point, jpeg: &'a [u8]) -> Self {
-        Self::new_image(pos, BinaryData::from_slice(jpeg))
+        Self::new_image(pos, jpeg.into())
     }
 
     pub fn with_align(self, align: Alignment2D) -> Self {

core/embed/rust/src/ui/shape/toif.rs

@@ -42,7 +42,7 @@ impl<'a> ToifImage<'a> {
         Self {
             pos,
             align: Alignment2D::TOP_LEFT,
-            toif: BinaryData::from_slice(toif.original_data()),
+            toif: toif.original_data().into(),
             fg_color: Color::white(),
             bg_color: None,
             size: Offset::zero(),