Merge pull request #236 from p-x9/feature/string-at-offset

Add method to retrieve a string at a specified offset from string table

Author: p-x9

Sources/MachOKit/MachOFile+Strings.swift

@@ -49,7 +49,8 @@ extension MachOFile {
 }
 
 extension MachOFile.UnicodeStrings {
-    init(
+    @_spi(Support)
+    public init(
         machO: MachOFile,
         offset: Int,
         size: Int,
@@ -74,6 +75,18 @@ extension MachOFile.UnicodeStrings {
     }
 }
 
+extension MachOFile.UnicodeStrings {
+    public func string(at offset: Int) -> Element? {
+        guard 0 <= offset, offset < fileSlice.size else { return nil }
+        let string = String(
+            cString: fileSlice.ptr
+                .advanced(by: offset)
+                .assumingMemoryBound(to: CChar.self)
+        )
+        return .init(string: string, offset: offset)
+    }
+}
+
 extension MachOFile.UnicodeStrings {
     public struct Iterator: IteratorProtocol {
         public typealias Element = StringTableEntry

Sources/MachOKit/MachOImage+Strings.swift

@@ -16,7 +16,8 @@ extension MachOImage {
         public let basePointer: UnsafePointer<Encoding.CodeUnit>
         public let tableSize: Int
 
-        init(
+        @_spi(Support)
+        public init(
             basePointer: UnsafePointer<Encoding.CodeUnit>,
             tableSize: Int
         ) {
@@ -63,6 +64,18 @@ extension MachOImage.UnicodeStrings {
     }
 }
 
+extension MachOImage.UnicodeStrings {
+    public func string(at offset: Int) -> Element? {
+        guard 0 <= offset, offset < tableSize else { return nil }
+        let string = String(
+            cString: UnsafeRawPointer(basePointer)
+                .advanced(by: offset)
+                .assumingMemoryBound(to: CChar.self)
+        )
+        return .init(string: string, offset: offset)
+    }
+}
+
 extension MachOImage.UnicodeStrings {
     public struct Iterator: IteratorProtocol {
         public typealias Element = StringTableEntry

Sources/MachOKit/Protocol/StringTable.swift

@@ -8,4 +8,11 @@
 
 public protocol StringTable<Encoding>: Sequence<StringTableEntry> {
     associatedtype Encoding: _UnicodeEncoding
+
+    /// Returns the string entry located at the specified offset within the string table.
+    ///
+    /// - Parameter offset: The byte offset from the start of the string table.
+    /// - Returns: A `StringTableEntry` containing the string and its offset,
+    ///            or `nil` if the offset is out of bounds or invalid.
+    func string(at offset: Int) -> Element?
 }