Replace AllocStringWriter with CVec

src/platform/mod.rs

@@ -104,45 +104,6 @@ impl Read for FileReader {
     }
 }
 
-pub struct AllocStringWriter(pub *mut u8, pub usize);
-impl Write for AllocStringWriter {
-    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
-        let ptr = unsafe { realloc(self.0 as *mut c_void, self.1 + buf.len() + 1) as *mut u8 };
-        if ptr.is_null() {
-            return Err(io::Error::new(
-                io::ErrorKind::Other,
-                "AllocStringWriter::write failed to allocate",
-            ));
-        }
-        self.0 = ptr;
-
-        unsafe {
-            ptr::copy_nonoverlapping(buf.as_ptr(), self.0.add(self.1), buf.len());
-            self.1 += buf.len();
-            *self.0.add(self.1) = 0;
-        }
-
-        Ok(buf.len())
-    }
-    fn flush(&mut self) -> io::Result<()> {
-        Ok(())
-    }
-}
-impl fmt::Write for AllocStringWriter {
-    fn write_str(&mut self, s: &str) -> fmt::Result {
-        // can't fail
-        self.write(s.as_bytes()).unwrap();
-        Ok(())
-    }
-}
-impl WriteByte for AllocStringWriter {
-    fn write_u8(&mut self, byte: u8) -> fmt::Result {
-        // can't fail
-        self.write(&[byte]).unwrap();
-        Ok(())
-    }
-}
-
 pub struct StringWriter(pub *mut u8, pub usize);
 impl Write for StringWriter {
     fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
@@ -155,11 +116,14 @@ impl Write for StringWriter {
                 self.0 = self.0.add(copy_size);
                 *self.0 = 0;
             }
-
-            Ok(copy_size)
-        } else {
-            Ok(0)
         }
+
+        // Pretend the entire slice was written. This is because many functions
+        // (like snprintf) expects a return value that reflects how many bytes
+        // *would have* been written. So keeping track of this information is
+        // good, and then if we want the *actual* written size we can just go
+        // `cmp::min(written, maxlen)`.
+        Ok(buf.len())
     }
     fn flush(&mut self) -> io::Result<()> {
         Ok(())