Direct assignment for some types in arrays and readme

README.md

@@ -76,49 +76,40 @@ NOTE: Some compilers may optimize away unused debug types. For example, with `gc
 
 # 🛠️ Quick Start
 
-## 1️⃣ CFFI-style `cdef`
+## Load an ISF (Linux/ELF DWARF)
 
 ```python
 from dwarffi import DFFI
 
-ffi = DFFI()
-ffi.cdef("""
-    struct sensor_data {
-        uint32_t timestamp;
-        int16_t  readings[3];
-        uint8_t  status;
-    };
-""")
-
-sensor = ffi.new("struct sensor_data", {
-    "timestamp": 1234567,
-    "readings": [10, -5, 20],
-    "status": 0x01
-})
-
-print(f"Bytes: {ffi.to_bytes(sensor).hex()}")
-print(f"Reading[1]: {sensor.readings[1]}")  # -5
-```
+# Accepts .json or .json.xz
+ffi = DFFI("ubuntu:5.4.0-26-generic:64.json.xz")
 
----
 
-## 2️⃣ Load an ISF (Linux/ELF DWARF)
+list_head_type = ffi.typeof("list_head")
+print("list_head sizeof:", ffi.sizeof(list_head_type))
+print(list_head_type)
 
-```python
-from dwarffi import DFFI
+''' prints out:
+struct list_head (size: 16 bytes) {
+  [+0  ] pointer next;
+  [+8  ] pointer prev;
+}
+'''
 
-# Accepts .json or .json.xz
-ffi = DFFI("vmlinux_isf.json.xz")
+# make a new complex type
+proc = ffi.new("struct task_struct", init={"pid": 1234, "comm": b"my_process"})
 
-task = ffi.typeof("struct task_struct")
-print("task_struct sizeof:", ffi.sizeof(task))
 
-ffi.inspect_layout("struct task_struct")
+print(proc.pid)              # 1234
+print(bytes(proc.comm))      # b'my_process\x00\x00\x00\x00\x00\x00'
+print(ffi.string(proc.comm)) # b'my_process'
 ```
 
+Download this example .json.xz [here](https://panda.re/volatility3_profiles/ubuntu:5.4.0-26-generic:64.json.xz).
+
 ---
 
-## 3️⃣ Load an ISF (Windows PDB-derived / Volatility-style)
+## Load an ISF (Windows PDB-derived / Volatility-style)
 
 ```python
 from dwarffi import DFFI
@@ -141,6 +132,34 @@ ffi.inspect_layout("struct _UNICODE_STRING")
 
 ---
 
+## CFFI-style `cdef`
+
+We do support inline C definitions that compile down to DWARF and ISF on the fly. This is ideal for quick prototyping or when you have a small struct definition that isn't already in your ISF.
+
+```python
+from dwarffi import DFFI
+
+ffi = DFFI()
+ffi.cdef("""
+    struct sensor_data {
+        uint32_t timestamp;
+        int16_t  readings[3];
+        uint8_t  status;
+    };
+""")
+
+sensor = ffi.new("struct sensor_data", {
+    "timestamp": 1234567,
+    "readings": [10, -5, 20],
+    "status": 0x01
+})
+
+print(f"Bytes: {ffi.to_bytes(sensor).hex()}")
+print(f"Reading[1]: {sensor.readings[1]}")  # -5
+```
+---
+
+
 # 🧩 Advanced Usage
 
 ## Anonymous Unions

src/dwarffi/instances.py

@@ -724,9 +724,52 @@ def __setattr__(self, name: str, new_value: Any) -> None:
             _, field_offset, resolved_info, resolved_obj = flat_fields[name]
 
             if resolved_info["kind"] == "array":
-                raise NotImplementedError(
-                    f"Direct assignment to array field '{name}' is not supported."
-                )
+                # Allow direct assignment only for byte/char arrays
+                if isinstance(new_value, str):
+                    data = new_value.encode("utf-8")
+                elif isinstance(new_value, (bytes, bytearray, memoryview)):
+                    data = bytes(new_value)
+                else:
+                    raise NotImplementedError(
+                        f"Direct assignment to array field '{name}' is not supported."
+                    )
+
+                # Resolve element type and ensure it's 1 byte
+                subtype_info = resolved_info.get("subtype")
+                if subtype_info is None:
+                    raise ValueError(f"Array field '{name}' missing subtype info.")
+
+                elem_size = self._instance_vtype_accessor.get_type_size(subtype_info)
+                if elem_size != 1:
+                    raise NotImplementedError(
+                        f"Direct assignment to non-byte array field '{name}' is not supported."
+                    )
+
+                count = resolved_info.get("count", 0)
+                if count <= 0:
+                    return
+
+                # Compute array start in underlying buffer
+                start = self._instance_offset + field_offset
+                end = start + count
+
+                # Write like a C string: truncate, NUL-terminate, zero-fill
+                buf = self._instance_buffer
+                mv = memoryview(buf)
+
+                # zero-fill
+                mv[start:end] = b"\x00" * count
+
+                # copy payload
+                payload = data[: max(0, count - 1)]
+                mv[start : start + len(payload)] = payload
+
+                # Invalidate cache for this field if present
+                try:
+                    del self._instance_cache[name]
+                except KeyError:
+                    pass
+                return
             self._write_data(resolved_info, resolved_obj, field_offset, new_value, name)
 
             # Try/except is faster than checking 'in' for cache invalidation