Fix INSData::from_vec on GNUStep

NSData initWithBytesNoCopy:length:deallocator: is broken in GNUStep, see gnustep/libs-base#213

Author: madsmtm

objc2_foundation/Cargo.toml

@@ -16,6 +16,8 @@ repository = "https://github.com/madsmtm/objc2"
 documentation = "https://docs.rs/objc2_foundation/"
 license = "MIT"
 
+build = "build.rs"
+
 [features]
 default = ["block"]
 # Provided as a way to cut down on dependencies
@@ -24,3 +26,4 @@ block = ["objc2_block"]
 [dependencies]
 objc2_block = { path = "../objc2_block", optional = true }
 objc2 = { path = "../objc2" }
+objc2_sys = { path = "../objc2_sys" }

objc2_foundation/build.rs

@@ -0,0 +1,9 @@
+use std::env;
+
+fn main() {
+    // The script doesn't depend on our code
+    println!("cargo:rerun-if-changed=build.rs");
+
+    let runtime = env::var("DEP_OBJC_RUNTIME").unwrap();
+    println!("cargo:rustc-cfg={}", runtime);
+}

objc2_foundation/src/data.rs

@@ -7,8 +7,6 @@ use core::{ffi::c_void, ptr::NonNull};
 use super::{INSCopying, INSMutableCopying, INSObject, NSRange};
 use objc2::msg_send;
 use objc2::rc::{Id, Owned};
-#[cfg(feature = "block")]
-use objc2_block::{Block, ConcreteBlock};
 
 pub trait INSData: INSObject {
     fn len(&self) -> usize {
@@ -22,12 +20,11 @@ pub trait INSData: INSObject {
     fn bytes(&self) -> &[u8] {
         let ptr: *const c_void = unsafe { msg_send![self, bytes] };
         // The bytes pointer may be null for length zero
-        let (ptr, len) = if ptr.is_null() {
-            (0x1 as *const u8, 0)
+        if ptr.is_null() {
+            &[]
         } else {
-            (ptr as *const u8, self.len())
-        };
-        unsafe { slice::from_raw_parts(ptr, len) }
+            unsafe { slice::from_raw_parts(ptr as *const u8, self.len()) }
+        }
     }
 
     fn with_bytes(bytes: &[u8]) -> Id<Self, Owned> {
@@ -46,6 +43,8 @@ pub trait INSData: INSObject {
 
     #[cfg(feature = "block")]
     fn from_vec(bytes: Vec<u8>) -> Id<Self, Owned> {
+        use objc2_block::{Block, ConcreteBlock};
+
         let capacity = bytes.capacity();
         let dealloc = ConcreteBlock::new(move |bytes: *mut c_void, len: usize| unsafe {
             // Recreate the Vec and let it drop
@@ -56,6 +55,22 @@ pub trait INSData: INSObject {
 
         let mut bytes = bytes;
         let bytes_ptr = bytes.as_mut_ptr() as *mut c_void;
+
+        // GNUStep's NSData `initWithBytesNoCopy:length:deallocator:` has a
+        // bug; it forgets to assign the input buffer and length to the
+        // instance before it swizzles to NSDataWithDeallocatorBlock.
+        // See https://github.com/gnustep/libs-base/pull/213
+        // So we just use NSDataWithDeallocatorBlock directly.
+        #[cfg(gnustep)]
+        let cls = {
+            let cls = Self::class();
+            if cls == objc2::class!(NSData) {
+                objc2::class!(NSDataWithDeallocatorBlock)
+            } else {
+                cls
+            }
+        };
+        #[cfg(not(gnustep))]
         let cls = Self::class();
         unsafe {
             let obj: *mut Self = msg_send![cls, alloc];
@@ -216,6 +231,6 @@ mod tests {
         let bytes_ptr = bytes.as_ptr();
 
         let data = NSData::from_vec(bytes);
-        assert!(data.bytes().as_ptr() == bytes_ptr);
+        assert_eq!(data.bytes().as_ptr(), bytes_ptr);
     }
 }