acpi_tables: aml: Add support for generating AML name paths

Root ("\"), single, dual and multi-part names are supported. "^" is not
supported (not widely used.)

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

acpi_tables/src/aml.rs

@@ -0,0 +1,88 @@
+// Copyright © 2019 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+
+pub trait Aml {
+    fn to_bytes(&self) -> Vec<u8>;
+}
+
+pub struct Path {
+    root: bool,
+    name_parts: Vec<[u8; 4]>,
+}
+
+impl Aml for Path {
+    fn to_bytes(&self) -> Vec<u8> {
+        let mut bytes = Vec::new();
+
+        if self.root {
+            bytes.push(b'\\');
+        }
+
+        match self.name_parts.len() {
+            0 => panic!("Name cannot be empty"),
+            1 => {}
+            2 => {
+                bytes.push(0x2e); /* DualNamePrefix */
+            }
+            n => {
+                bytes.push(0x2f); /* MultiNamePrefix */
+                bytes.push(n as u8);
+            }
+        };
+
+        for part in self.name_parts.clone().iter_mut() {
+            bytes.append(&mut part.to_vec());
+        }
+
+        bytes
+    }
+}
+
+impl Path {
+    pub fn new(name: &str) -> Self {
+        let root = name.starts_with('\\');
+        let offset = root as usize;
+        let mut name_parts = Vec::new();
+        for part in name[offset..].split('.') {
+            assert_eq!(part.len(), 4);
+            let mut name_part = [0u8; 4];
+            name_part.copy_from_slice(part.as_bytes());
+            name_parts.push(name_part);
+        }
+
+        Path { root, name_parts }
+    }
+}
+
+impl From<&str> for Path {
+    fn from(s: &str) -> Self {
+        Path::new(s)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_name_path() {
+        assert_eq!(
+            (&"_SB_".into() as &Path).to_bytes(),
+            [0x5Fu8, 0x53, 0x42, 0x5F]
+        );
+        assert_eq!(
+            (&"\\_SB_".into() as &Path).to_bytes(),
+            [0x5C, 0x5F, 0x53, 0x42, 0x5F]
+        );
+        assert_eq!(
+            (&"_SB_.COM1".into() as &Path).to_bytes(),
+            [0x2E, 0x5F, 0x53, 0x42, 0x5F, 0x43, 0x4F, 0x4D, 0x31]
+        );
+        assert_eq!(
+            (&"_SB_.PCI0._HID".into() as &Path).to_bytes(),
+            [0x2F, 0x03, 0x5F, 0x53, 0x42, 0x5F, 0x50, 0x43, 0x49, 0x30, 0x5F, 0x48, 0x49, 0x44]
+        );
+    }
+}

acpi_tables/src/lib.rs

@@ -3,6 +3,7 @@
 // SPDX-License-Identifier: Apache-2.0
 //
 
+pub mod aml;
 pub mod rsdp;
 pub mod sdt;