Simplify string conversion code

ctru-rs/src/applets/swkbd.rs

@@ -5,10 +5,10 @@
 
 use crate::services::{apt::Apt, gfx::Gfx};
 use ctru_sys::{
-    self, aptLaunchLibraryApplet, aptSetMessageCallback, envGetAptAppId, svcBreak, svcCloseHandle,
+    self, aptLaunchLibraryApplet, aptSetMessageCallback, envGetAptAppId, svcCloseHandle,
     svcCreateMemoryBlock, APT_SendParameter, SwkbdButton, SwkbdDictWord, SwkbdExtra,
     SwkbdLearningData, SwkbdState, SwkbdStatusData, APPID_SOFTWARE_KEYBOARD, APTCMD_MESSAGE,
-    NS_APPID, SWKBD_CALLBACK_OK, USERBREAK_PANIC,
+    NS_APPID, SWKBD_CALLBACK_OK,
 };
 
 use bitflags::bitflags;
@@ -281,7 +281,7 @@ impl SoftwareKeyboard {
                 (self as *mut Self).cast(),
             );
 
-            match Self::swkbd_input_text(self.state.as_mut(), output.as_mut_vec()) {
+            match Self::swkbd_input_text(self.state.as_mut(), &mut output) {
                 ctru_sys::SWKBD_BUTTON_NONE => Err(self.state.result.into()),
                 ctru_sys::SWKBD_BUTTON_LEFT => Ok((output, Button::Left)),
                 ctru_sys::SWKBD_BUTTON_MIDDLE => Ok((output, Button::Middle)),
@@ -631,7 +631,7 @@ impl SoftwareKeyboard {
     // A reimplementation of `swkbdInputText` from `libctru/source/applets/swkbd.c`. Allows us to
     // get text from the software keyboard and put it directly into a `String` without requiring
     // an intermediate fixed-size buffer
-    fn swkbd_input_text(swkbd: &mut SwkbdState, buf: &mut Vec<u8>) -> SwkbdButton {
+    fn swkbd_input_text(swkbd: &mut SwkbdState, output: &mut String) -> SwkbdButton {
         use ctru_sys::{
             MEMPERM_READ, MEMPERM_WRITE, R_FAILED, SWKBD_BUTTON_LEFT, SWKBD_BUTTON_MIDDLE,
             SWKBD_BUTTON_NONE, SWKBD_BUTTON_RIGHT, SWKBD_D0_CLICK, SWKBD_D1_CLICK0,
@@ -715,11 +715,11 @@ impl SoftwareKeyboard {
             swkbd.initial_text_offset = 0;
 
             unsafe {
-                let utf16_iter = CStr::from_ptr(extra.initial_text)
-                    .to_str()
-                    .unwrap()
-                    .encode_utf16()
-                    .chain(once(0));
+                let utf16_iter =
+                    str::from_utf8_unchecked(CStr::from_ptr(extra.initial_text).to_bytes())
+                        .encode_utf16()
+                        .take(swkbd.max_text_len as _)
+                        .chain(once(0));
 
                 let mut initial_text_cursor = SWKBD_SHARED_MEM.cast::<u16>();
 
@@ -803,17 +803,16 @@ impl SoftwareKeyboard {
 
         let text16 = if swkbd.text_length > 0 {
             unsafe {
-                widestring::Utf16Str::from_slice(std::slice::from_raw_parts(
+                widestring::Utf16Str::from_slice_unchecked(std::slice::from_raw_parts(
                     SWKBD_SHARED_MEM.add(swkbd.text_offset as _).cast::<u16>(),
                     swkbd.text_length as usize,
                 ))
-                .unwrap()
             }
         } else {
             widestring::utf16str!("")
         };
 
-        buf.extend(text16.encode_utf8());
+        *output = text16.to_string();
 
         if swkbd.save_state_flags & (1 << 0) != 0 {
             unsafe {
@@ -860,20 +859,13 @@ impl SoftwareKeyboard {
         }
 
         let text16 = unsafe {
-            widestring::Utf16Str::from_slice(std::slice::from_raw_parts(
+            widestring::Utf16Str::from_slice_unchecked(std::slice::from_raw_parts(
                 SWKBD_SHARED_MEM.add(swkbd.text_offset as _).cast::<u16>(),
                 swkbd.text_length as usize + 1,
             ))
-            .unwrap()
         };
 
-        let text8 = match String::from_utf8(text16.encode_utf8().collect()) {
-            Ok(s) => s,
-            Err(_) => {
-                svcBreak(USERBREAK_PANIC);
-                unreachable!();
-            }
-        };
+        let text8 = text16.to_string();
 
         let mut retmsg = std::ptr::null();