vfs: expand support for NCA reading

src/common/alignment.h

@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include <bit>
 #include <cstddef>
 #include <new>
 #include <type_traits>
@@ -10,7 +11,7 @@
 namespace Common {
 
 template <typename T>
-    requires std::is_unsigned_v<T>
+    requires std::is_integral_v<T>
 [[nodiscard]] constexpr T AlignUp(T value, size_t size) {
     auto mod{static_cast<T>(value % size)};
     value -= mod;
@@ -24,7 +25,7 @@ template <typename T>
 }
 
 template <typename T>
-    requires std::is_unsigned_v<T>
+    requires std::is_integral_v<T>
 [[nodiscard]] constexpr T AlignDown(T value, size_t size) {
     return static_cast<T>(value - value % size);
 }
@@ -55,6 +56,30 @@ template <typename T, typename U>
     return (x + (y - 1)) / y;
 }
 
+template <typename T>
+    requires std::is_integral_v<T>
+[[nodiscard]] constexpr T LeastSignificantOneBit(T x) {
+    return x & ~(x - 1);
+}
+
+template <typename T>
+    requires std::is_integral_v<T>
+[[nodiscard]] constexpr T ResetLeastSignificantOneBit(T x) {
+    return x & (x - 1);
+}
+
+template <typename T>
+    requires std::is_integral_v<T>
+[[nodiscard]] constexpr bool IsPowerOfTwo(T x) {
+    return x > 0 && ResetLeastSignificantOneBit(x) == 0;
+}
+
+template <typename T>
+    requires std::is_integral_v<T>
+[[nodiscard]] constexpr T FloorPowerOfTwo(T x) {
+    return T{1} << (sizeof(T) * 8 - std::countl_zero(x) - 1);
+}
+
 template <typename T, size_t Align = 16>
 class AlignmentAllocator {
 public:

src/common/lz4_compression.cpp

@@ -71,4 +71,10 @@ std::vector<u8> DecompressDataLZ4(std::span<const u8> compressed, std::size_t un
     return uncompressed;
 }
 
+int DecompressLZ4(void* dst, size_t dst_size, const void* src, size_t src_size) {
+    // This is just a thin wrapper around LZ4.
+    return LZ4_decompress_safe(reinterpret_cast<const char*>(src), reinterpret_cast<char*>(dst),
+                               static_cast<int>(src_size), static_cast<int>(dst_size));
+}
+
 } // namespace Common::Compression

src/common/lz4_compression.h

@@ -56,4 +56,6 @@ namespace Common::Compression {
 [[nodiscard]] std::vector<u8> DecompressDataLZ4(std::span<const u8> compressed,
                                                 std::size_t uncompressed_size);
 
+int DecompressLZ4(void* dst, size_t dst_size, const void* src, size_t src_size);
+
 } // namespace Common::Compression