Add macro support for register arrays

I'm experimenting with a RAL code generator that collapses contiguous
register arrays. The generated code would resemble

    pub struct RegisterBlock {
        pub MY_ARRAY: [RWRegister<u32>; 3],
    }

and an individual register would be addressed like

    ral::read_reg!(ral::my_mod, my_inst, MY_ARRAY[1]);

This commit extends the four macros so that we can specify an array
offset. We simply need to match zero or more `[N]` patterns, where `N`
is some expression that produces an array offset. The included test case
shows that the approach should support multi-dimensional arrays.

1 files changed, 70 insertions, 0 deletions

diff --git a/tests/pathological.rs b/tests/pathological.rs
new file mode 100644
index 0000000..d463e29
--- /dev/null
+++ b/tests/pathological.rs
@@ -0,0 +1,70 @@
+//! Testing corner cases.
+
+#![allow(non_upper_case_globals, non_snake_case)] // Macro conventions.
+
+use ral_registers as ral;
+
+mod periph {
+    #[repr(C)]
+    pub struct RegisterBlock {
+        /// Multi-dimensional arrays.
+        #[allow(clippy::type_complexity)] // Intentionally complex type.
+        pub DEEP_LEARNING: [[[[[[[[ral_registers::RWRegister<u32>; 1]; 2]; 3]; 4]; 5]; 6]; 7]; 8],
+    }
+
+    pub mod DEEP_LEARNING {
+        pub mod GRADIENT {
+            pub const offset: u32 = 3;
+            pub const mask: u32 = 0x1F << offset;
+            pub mod R {}
+            pub mod W {}
+            pub mod RW {}
+        }
+    }
+
+    pub struct ResetValues {
+        pub DEEP_LEARNING: u32,
+    }
+
+    pub mod INST {
+        pub const reset: super::ResetValues = super::ResetValues { DEEP_LEARNING: 42 };
+    }
+}
+
+fn register_block() -> periph::RegisterBlock {
+    // Safety: bitpattern of zero is fine.
+    use std::mem::MaybeUninit;
+    unsafe { MaybeUninit::zeroed().assume_init() }
+}
+
+#[test]
+fn read_deep_array() {
+    let rb = register_block();
+    rb.DEEP_LEARNING[7][6][5][4][3][2][1][0].write(u32::MAX);
+    let gradient = ral::read_reg!(periph, &rb, DEEP_LEARNING[7][6][5][4][3][2][1][0], GRADIENT);
+    assert_eq!(gradient, 0x1F);
+}
+
+#[test]
+fn write_deep_array() {
+    let rb = register_block();
+    ral::write_reg!(periph, &rb, DEEP_LEARNING[7][6][5][4][3][2][1][0], 23);
+    assert_eq!(rb.DEEP_LEARNING[7][6][5][4][3][2][1][0].read(), 23);
+}
+
+#[test]
+fn modify_deep_array() {
+    let rb = register_block();
+    ral::modify_reg!(periph, &rb, DEEP_LEARNING[7][6][5][4][3][2][1][0], GRADIENT: 42);
+    assert_eq!(
+        rb.DEEP_LEARNING[7][6][5][4][3][2][1][0].read(),
+        (42 & 0x1F) << 3
+    );
+}
+
+#[test]
+fn reset_deep_array() {
+    let rb = register_block();
+    ral::reset_reg!(periph, &rb, INST, DEEP_LEARNING[7][6][5][4][3][2][1][0]);
+    assert_eq!(rb.DEEP_LEARNING[7][6][5][4][3][2][1][0].read(), 42);
+}