Add Projection associated type to BitField (#130)

Updates the `BitField` associated type to require a `Projection` associated type which conforms to `BitFieldProjectable`. Renames existing `insert` and `extract` methods to `insertBits` and `extractBits` respectively. Adds new typed variants of `insert` and `extract` which operate on `Projection`. The result of this change is that `preconditionMatchingBitWidth` can be hidden from the MMIO module's public API and the macro expansion code is simpler.
apple · Oct 8, 2024 · c24e034 · c24e034
1 parent 1f84beb
commit c24e034
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Showing 5 changed files with 124 additions and 101 deletions.
diff --git a/Sources/MMIO/BitField.swift b/Sources/MMIO/BitField.swift
@@ -99,10 +99,53 @@ extension FixedWidthInteger {
 
 public protocol BitField {
   associatedtype Storage: FixedWidthInteger & UnsignedInteger
+  associatedtype Projection: BitFieldProjectable
+
   static var bitWidth: Int { get }
 
-  static func insert(_ value: Storage, into storage: inout Storage)
-  static func extract(from storage: Storage) -> Storage
+  static func insertBits(_ value: Storage, into storage: inout Storage)
+  static func extractBits(from storage: Storage) -> Storage
+
+  static func insert(_ value: Projection, into storage: inout Storage)
+  static func extract(from storage: Storage) -> Projection
+}
+
+extension BitField {
+  @inlinable @inline(__always)
+  static func preconditionMatchingBitWidth(
+    file: StaticString = #file,
+    line: UInt = #line
+  ) {
+    #if hasFeature(Embedded)
+    // FIXME: Embedded doesn't have static interpolated strings yet
+    precondition(
+      Self.bitWidth == Projection.bitWidth,
+      "Illegal projection of bit-field as type of differing bit-width",
+      file: file,
+      line: line)
+    #else
+    precondition(
+      Self.bitWidth == Projection.bitWidth,
+      """
+      Illegal projection of \(Self.bitWidth) bit bit-field '\(Self.self)' \
+      as \(Projection.bitWidth) bit type '\(Projection.self)'
+      """,
+      file: file,
+      line: line)
+    #endif
+  }
+
+  @inlinable @inline(__always)
+  public static func insert(_ value: Projection, into storage: inout Storage) {
+    Self.preconditionMatchingBitWidth()
+    Self.insertBits(value.storage(Storage.self), into: &storage)
+  }
+
+  @inlinable @inline(__always)
+  public static func extract(from storage: Self.Storage) -> Projection {
+    Self.preconditionMatchingBitWidth()
+    return Projection(storage: Self.extractBits(from: storage))
+  }
 }
 
 public protocol ContiguousBitField: BitField {
@@ -125,12 +168,12 @@ extension ContiguousBitField {
 
   // FIXME: value.bitWidth <= Self.bitWidth <= Storage.bitWidth
   @inlinable @inline(__always)
-  public static func insert(_ value: Storage, into storage: inout Storage) {
+  public static func insertBits(_ value: Storage, into storage: inout Storage) {
     storage[bits: Self.bitRange] = value
   }
 
   @inlinable @inline(__always)
-  public static func extract(from storage: Storage) -> Storage {
+  public static func extractBits(from storage: Storage) -> Storage {
     storage[bits: Self.bitRange]
   }
 }
@@ -152,12 +195,12 @@ extension DiscontiguousBitField {
   }
 
   @inlinable @inline(__always)
-  public static func insert(_ value: Storage, into storage: inout Storage) {
+  public static func insertBits(_ value: Storage, into storage: inout Storage) {
     storage[bits: Self.bitRanges] = value
   }
 
   @inlinable @inline(__always)
-  public static func extract(from storage: Storage) -> Storage {
+  public static func extractBits(from storage: Storage) -> Storage {
     storage[bits: Self.bitRanges]
   }
 }
diff --git a/Sources/MMIO/BitFieldProjectable.swift b/Sources/MMIO/BitFieldProjectable.swift
@@ -186,29 +186,3 @@ where Self: RawRepresentable, RawValue: FixedWidthInteger {
     return Storage(rawValue)
   }
 }
-
-@inlinable @inline(__always)
-public func preconditionMatchingBitWidth(
-  _ fieldType: (some BitField).Type,
-  _ projectedType: (some BitFieldProjectable).Type,
-  file: StaticString = #file,
-  line: UInt = #line
-) {
-  #if hasFeature(Embedded)
-  // FIXME: Embedded doesn't have static interpolated strings yet
-  precondition(
-    fieldType.bitWidth == projectedType.bitWidth,
-    "Illegal projection of bit-field as type of differing bit-width",
-    file: file,
-    line: line)
-  #else
-  precondition(
-    fieldType.bitWidth == projectedType.bitWidth,
-    """
-    Illegal projection of \(fieldType.bitWidth) bit bit-field '\(fieldType)' \
-    as \(projectedType.bitWidth) bit type '\(projectedType)'
-    """,
-    file: file,
-    line: line)
-  #endif
-}
diff --git a/Sources/MMIOMacros/Macros/Descriptions/BitFieldDescription.swift b/Sources/MMIOMacros/Macros/Descriptions/BitFieldDescription.swift
@@ -59,6 +59,7 @@ extension BitFieldDescription {
         """
         \(self.accessLevel)enum \(self.fieldType): ContiguousBitField {
           \(self.accessLevel)typealias Storage = \(self.storageType())
+          \(self.accessLevel)typealias Projection = \(self.projectedType ?? "Never")
           \(self.accessLevel)static let bitRange = \(bitRangeExpression)
         }
         """
@@ -71,6 +72,7 @@ extension BitFieldDescription {
         """
         \(self.accessLevel)enum \(self.fieldType): DiscontiguousBitField {
           \(self.accessLevel)typealias Storage = \(self.storageType())
+          \(self.accessLevel)typealias Projection = \(self.projectedType ?? "Never")
           \(self.accessLevel)static let bitRanges = \(ArrayExprSyntax(expressions: bitRangeExpressions))
         }
         """
@@ -84,10 +86,10 @@ extension BitFieldDescription {
     """
     \(self.accessLevel)var \(self.fieldName): \(self.storageType()) {
       @inlinable @inline(__always) get {
-        \(self.fieldType).extract(from: self.storage)
+        \(self.fieldType).extractBits(from: self.storage)
       }
       @inlinable @inline(__always) set {
-        \(self.fieldType).insert(newValue, into: &self.storage)
+        \(self.fieldType).insertBits(newValue, into: &self.storage)
       }
     }
     """
@@ -105,12 +107,10 @@ extension BitFieldDescription {
     return """
       \(self.accessLevel)var \(self.fieldName): \(projectedType) {
         @inlinable @inline(__always) get {
-          preconditionMatchingBitWidth(\(self.fieldType).self, \(projectedType).self)
-          return \(projectedType)(storage: self.raw.\(self.fieldName))
+          \(self.fieldType).extract(from: self.storage)
         }
         @inlinable @inline(__always) set {
-          preconditionMatchingBitWidth(\(self.fieldType).self, \(projectedType).self)
-          self.raw.\(self.fieldName) = newValue.storage(Self.Value.Raw.Storage.self)
+          \(self.fieldType).insert(newValue, into: &self.storage)
         }
       }
       """
@@ -127,8 +127,7 @@ extension BitFieldDescription {
     return """
       \(self.accessLevel)var \(self.fieldName): \(projectedType) {
         @inlinable @inline(__always) get {
-          preconditionMatchingBitWidth(\(self.fieldType).self, \(projectedType).self)
-          return \(projectedType)(storage: self.raw.\(self.fieldName))
+          \(self.fieldType).extract(from: self.storage)
         }
       }
       """
@@ -149,12 +148,10 @@ extension BitFieldDescription {
       \(self.accessLevel)var \(self.fieldName): \(projectedType) {
         @available(*, deprecated, message: "API misuse; read from write view returns the value to be written, not the value initially read.")
         @inlinable @inline(__always) get {
-          preconditionMatchingBitWidth(\(self.fieldType).self, \(projectedType).self)
-          return \(projectedType)(storage: self.raw.\(self.fieldName))
+          \(self.fieldType).extract(from: self.storage)
         }
         @inlinable @inline(__always) set {
-          preconditionMatchingBitWidth(\(self.fieldType).self, \(projectedType).self)
-          self.raw.\(self.fieldName) = newValue.storage(Self.Value.Raw.Storage.self)
+          \(self.fieldType).insert(newValue, into: &self.storage)
         }
       }
       """

diff --git a/Tests/MMIOFileCheckTests/MMIOFileCheckTestCase.swift b/Tests/MMIOFileCheckTests/MMIOFileCheckTestCase.swift
@@ -91,13 +91,18 @@ final class MMIOFileCheckTests: XCTestCase, @unchecked Sendable {
       print("TOOLCHAINS not set.")
       #if os(macOS)
       print("Searching for swift-latest toolchain")
-      toolchainID = try sh(
-        """
-        plutil \
-          -extract CFBundleIdentifier raw \
-          -o - \
-          /Library/Developer/Toolchains/swift-latest.xctoolchain/Info.plist
-        """)
+      do {
+        toolchainID = try sh(
+          """
+          plutil \
+            -extract CFBundleIdentifier raw \
+            -o - \
+            /Library/Developer/Toolchains/swift-latest.xctoolchain/Info.plist
+          """)
+      } catch {
+        print("Failed to locate toolchain by plist: \(error)")
+        toolchainID = ""
+      }
       #else
       toolchainID = ""
       #endif