Fixes and content modification

blogs/hands_on_with_mojo_24_5/generic_safe_buffer.mojo

@@ -36,14 +36,13 @@ struct SafeBuffer[T: CollectionElement]:
     fn __del__(owned self):
         self._data.free()
 
-    fn _get_ref(ref [_]self: Self, index: Int) -> Reference[Optional[T], __lifetime_of(self)]:
-        return Reference[Optional[T], __lifetime_of(self)](self._data[index])
-
     fn write(inout self, index: Int, value: Optional[T]):
-        self._get_ref(index)[] = value
+        debug_assert(0 <= index < self.size, "index must be within the buffer")
+        self._data[index] = value
 
     fn read(self, index: Int) -> Optional[T]:
-        return self._get_ref(index)[]
+        debug_assert(0 <= index < self.size, "index must be within the buffer")
+        return self._data[index]
 
     fn __str__[U: StringableFormattableCollectionElement](self: SafeBuffer[U]) -> String:
         ret = String()
@@ -73,6 +72,7 @@ struct SafeBuffer[T: CollectionElement]:
     fn take(inout self, index: Int) -> Optional[T] as output:
         output = self.read(index)
         self.write(index, Optional[T](None))
+        return
 
 
 fn process_buffers[T: CollectionElement](buffer1: SafeBuffer[T], inout buffer2: SafeBuffer[T]):
@@ -82,9 +82,14 @@ fn process_buffers[T: CollectionElement](buffer1: SafeBuffer[T], inout buffer2:
 
 
 struct NotStringableNorFormattable(CollectionElement):
-    fn __init__(inout self): ...
-    fn __copyinit__(inout self, existing: Self): ...
-    fn __moveinit__(inout self, owned existing: Self): ...
+    fn __init__(inout self):
+        ...
+
+    fn __copyinit__(inout self, existing: Self):
+        ...
+
+    fn __moveinit__(inout self, owned existing: Self):
+        ...
 
 
 def main():

blogs/hands_on_with_mojo_24_5/safe_buffer.mojo

@@ -22,14 +22,13 @@ struct SafeBuffer(Stringable, Formattable):
     fn __del__(owned self):
         self._data.free()
 
-    fn _get_ref(ref [_]self: Self, index: Int) -> Reference[UInt8, __lifetime_of(self)]:
-        return Reference[UInt8, __lifetime_of(self)](self._data[index])
-
     fn write(inout self, index: Int, value: UInt8):
-        self._get_ref(index)[] = value
+        debug_assert(0 <= index < self.size, "index must be within the buffer")
+        self._data[index] = value
 
     fn read(self, index: Int) -> UInt8:
-        return self._get_ref(index)[]
+        debug_assert(0 <= index < self.size, "index must be within the buffer")
+        return self._data[index]
 
     fn __str__(self) -> String:
         return String.format_sequence(self)
@@ -53,14 +52,11 @@ fn process_buffers(buffer1: SafeBuffer, inout buffer2: SafeBuffer):
 def main():
     sb = SafeBuffer(10)
     sb.write(0, 255)
-    sb.write(1, 128)
-    print("safe buffer outputs:")
+    print("value at index 0 after getting set to 255:")
     print(sb.read(0))
-    print(sb.read(1))
 
     buffer1 = SafeBuffer.initialize_with_value(size=10, value=128)
     buffer2 = SafeBuffer(10)
     # process_buffers(buffer1, buffer1) # <-- argument exclusivity detects such errors at compile time
     process_buffers(buffer1, buffer2)
-    print("buffer2:")
-    print(buffer2)
+    print("buffer2:", buffer2)

blogs/hands_on_with_mojo_24_5/test_generic_safe_buffer.mojo

@@ -2,6 +2,7 @@ from testing import assert_equal
 
 from generic_safe_buffer import SafeBuffer
 
+
 def test_buffer():
     buffer = SafeBuffer[String].initialize_with_value(size=5, value=String("hi"))
     val = buffer.take(2).value()

blogs/hands_on_with_mojo_24_5/unsafe_buffer.mojo

@@ -1,28 +1,23 @@
+from memory import memset_zero
+
+
 struct UnsafeBuffer:
     var data: UnsafePointer[UInt8]
     var size: Int
 
     fn __init__(inout self, size: Int):
         self.data = UnsafePointer[UInt8].alloc(size)
+        memset_zero(self.data, size)
         self.size = size
 
-    fn write(inout self, index: Int, value: UInt8):
-        # note `self.data` is uninitialized so we have to use `init_pointee_copy/move`
-        # methods to safely initialize the allocated memory
-        self.data.init_pointee_copy(value)
-
-    fn read(self, index: Int) -> UInt8:
-        return self.data[index]
-
     fn __del__(owned self):
         self.data.free()
 
 
 def main():
     ub = UnsafeBuffer(10)
-    ub.write(0, 255)
-    ub.write(1, 128)
-    print("unsafe buffer outputs:")
-    print(ub.read(0))
-    print("the data of the unsafe buffer is freed here bc there's no lifetime associate with it")
-    print(ub.read(1))
+    print("initial value at index 0:")
+    print(ub.data[0])
+    ub.data[0] = 255
+    print("value at index 0 after getting set to 255:")
+    print(ub.data[0])