fix binary slice lifetimes (#181)

Author: davidcole1340

src/binary_slice.rs

@@ -6,16 +6,11 @@
 
 use crate::ffi::zend_string;
 
-use std::{convert::TryFrom, ops::Deref, slice::from_raw_parts};
+use std::{ops::Deref, slice::from_raw_parts};
 
-use crate::{
-    convert::FromZval,
-    error::{Error, Result},
-    flags::DataType,
-    types::Zval,
-};
+use crate::{convert::FromZval, flags::DataType, types::Zval};
 
-/// Acts as a wrapper around [`&[T]`] where `T` implements [`PackSlice`].
+/// Acts as a wrapper around `&[T]` where `T` implements [`PackSlice`].
 /// Primarily used for passing read-only binary data into Rust functions.
 #[derive(Debug)]
 pub struct BinarySlice<'a, T>(&'a [T])
@@ -47,28 +42,17 @@ where
     }
 }
 
-impl<T> FromZval<'_> for BinarySlice<'_, T>
+impl<'a, T> FromZval<'a> for BinarySlice<'a, T>
 where
     T: PackSlice,
 {
     const TYPE: DataType = DataType::String;
 
-    fn from_zval(zval: &Zval) -> Option<Self> {
+    fn from_zval(zval: &'a Zval) -> Option<Self> {
         zval.binary_slice().map(BinarySlice)
     }
 }
 
-impl<T> TryFrom<Zval> for BinarySlice<'_, T>
-where
-    T: PackSlice,
-{
-    type Error = Error;
-
-    fn try_from(value: Zval) -> Result<Self> {
-        Self::from_zval(&value).ok_or_else(|| Error::ZvalConversion(value.get_type()))
-    }
-}
-
 impl<'a, T> From<BinarySlice<'a, T>> for &'a [T]
 where
     T: PackSlice,
@@ -117,7 +101,7 @@ pub unsafe trait PackSlice: Clone {
     /// * `s` - The Zend string containing the binary data.
     ///
     /// [`pack`]: https://www.php.net/manual/en/function.pack.php
-    fn unpack_into<'a>(s: &zend_string) -> &'a [Self];
+    fn unpack_into(s: &zend_string) -> &[Self];
 }
 
 /// Implements the [`PackSlice`] trait for a given type.
@@ -128,7 +112,7 @@ macro_rules! pack_slice_impl {
 
     ($t: ty, $d: expr) => {
         unsafe impl PackSlice for $t {
-            fn unpack_into<'a>(s: &zend_string) -> &'a [Self] {
+            fn unpack_into(s: &zend_string) -> &[Self] {
                 let bytes = ($d / 8) as usize;
                 let len = (s.len as usize) / bytes;
                 let ptr = s.val.as_ptr() as *const $t;

src/types/zval.rs

@@ -130,21 +130,26 @@ impl Zval {
     ///
     /// [`pack`]: https://www.php.net/manual/en/function.pack.php
     pub fn binary<T: Pack>(&self) -> Option<Vec<T>> {
-        if self.is_string() {
-            // SAFETY: Type is string therefore we are able to take a reference.
-            Some(T::unpack_into(unsafe { self.value.str_.as_ref() }?))
-        } else {
-            None
-        }
+        self.zend_str().map(T::unpack_into)
     }
 
-    pub fn binary_slice<'a, T: PackSlice>(&self) -> Option<&'a [T]> {
-        if self.is_string() {
-            // SAFETY: Type is string therefore we are able to take a reference.
-            Some(T::unpack_into(unsafe { self.value.str_.as_ref() }?))
-        } else {
-            None
-        }
+    /// Returns the value of the zval if it is a string and can be unpacked into
+    /// a slice of a given type. Similar to the [`unpack`](https://www.php.net/manual/en/function.unpack.php)
+    /// in PHP, except you can only unpack one type.
+    ///
+    /// This function is similar to [`Zval::binary`] except that a slice is
+    /// returned instead of a vector, meaning the contents of the string is
+    /// not copied.
+    ///
+    /// # Safety
+    ///
+    /// There is no way to tell if the data stored in the string is actually of
+    /// the given type. The results of this function can also differ from
+    /// platform-to-platform due to the different representation of some
+    /// types on different platforms. Consult the [`pack`] function
+    /// documentation for more details.
+    pub fn binary_slice<T: PackSlice>(&self) -> Option<&[T]> {
+        self.zend_str().map(T::unpack_into)
     }
 
     /// Returns the value of the zval if it is a resource.