HLE: Revamp error handling throrough the HLE code

All service calls in the CTR OS return result codes indicating the
success or failure of the call. Previous to this commit, Citra's HLE
emulation of services and the kernel universally either ignored errors
or returned dummy -1 error codes.

This commit makes an initial effort to provide an infrastructure for
error reporting and propagation which can be use going forward to make
HLE calls accurately return errors as the original system. A few parts
of the code have been updated to use the new system where applicable.

One part of this effort is the definition of the `ResultCode` type,
which provides facilities for constructing and parsing error codes in
the structured format used by the CTR.

The `ResultVal` type builds on `ResultCode` by providing a container for
values returned by function that can report errors. It enforces that
correct error checking will be done on function returns by preventing
the use of the return value if the function returned an error code.

Currently this change is mostly internal since errors are still
suppressed on the ARM<->HLE border, as a temporary compatibility hack.
As functionality is implemented and tested this hack can be eventually
removed.

1 files changed, 400 insertions, 0 deletions

diff --git a/src/core/hle/result.h b/src/core/hle/result.h
new file mode 100644
index 00000000..15c4a267
--- /dev/null
+++ b/src/core/hle/result.h
@@ -0,0 +1,400 @@
+// Copyright 2014 Citra Emulator Project
+// Licensed under GPLv2
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <cassert>
+#include <cstddef>
+#include <type_traits>
+#include <utility>
+
+#include "common/common_types.h"
+#include "common/bit_field.h"
+
+// All the constants in this file come from http://3dbrew.org/wiki/Error_codes
+
+/// Detailed description of the error. This listing is likely incomplete.
+enum class ErrorDescription : u32 {
+    Success = 0,
+    InvalidSection = 1000,
+    TooLarge = 1001,
+    NotAuthorized = 1002,
+    AlreadyDone = 1003,
+    InvalidSize = 1004,
+    InvalidEnumValue = 1005,
+    InvalidCombination = 1006,
+    NoData = 1007,
+    Busy = 1008,
+    MisalignedAddress = 1009,
+    MisalignedSize = 1010,
+    OutOfMemory = 1011,
+    NotImplemented = 1012,
+    InvalidAddress = 1013,
+    InvalidPointer = 1014,
+    InvalidHandle = 1015,
+    NotInitialized = 1016,
+    AlreadyInitialized = 1017,
+    NotFound = 1018,
+    CancelRequested = 1019,
+    AlreadyExists = 1020,
+    OutOfRange = 1021,
+    Timeout = 1022,
+    InvalidResultValue = 1023,
+};
+
+/**
+ * Identifies the module which caused the error. Error codes can be propagated through a call
+ * chain, meaning that this doesn't always correspond to the module where the API call made is
+ * contained.
+ */
+enum class ErrorModule : u32 {
+    Common = 0,
+    Kernel = 1,
+    Util = 2,
+    FileServer = 3,
+    LoaderServer = 4,
+    TCB = 5,
+    OS = 6,
+    DBG = 7,
+    DMNT = 8,
+    PDN = 9,
+    GX = 10,
+    I2C = 11,
+    GPIO = 12,
+    DD = 13,
+    CODEC = 14,
+    SPI = 15,
+    PXI = 16,
+    FS = 17,
+    DI = 18,
+    HID = 19,
+    CAM = 20,
+    PI = 21,
+    PM = 22,
+    PM_LOW = 23,
+    FSI = 24,
+    SRV = 25,
+    NDM = 26,
+    NWM = 27,
+    SOC = 28,
+    LDR = 29,
+    ACC = 30,
+    RomFS = 31,
+    AM = 32,
+    HIO = 33,
+    Updater = 34,
+    MIC = 35,
+    FND = 36,
+    MP = 37,
+    MPWL = 38,
+    AC = 39,
+    HTTP = 40,
+    DSP = 41,
+    SND = 42,
+    DLP = 43,
+    HIO_LOW = 44,
+    CSND = 45,
+    SSL = 46,
+    AM_LOW = 47,
+    NEX = 48,
+    Friends = 49,
+    RDT = 50,
+    Applet = 51,
+    NIM = 52,
+    PTM = 53,
+    MIDI = 54,
+    MC = 55,
+    SWC = 56,
+    FatFS = 57,
+    NGC = 58,
+    CARD = 59,
+    CARDNOR = 60,
+    SDMC = 61,
+    BOSS = 62,
+    DBM = 63,
+    Config = 64,
+    PS = 65,
+    CEC = 66,
+    IR = 67,
+    UDS = 68,
+    PL = 69,
+    CUP = 70,
+    Gyroscope = 71,
+    MCU = 72,
+    NS = 73,
+    News = 74,
+    RO_1 = 75,
+    GD = 76,
+    CardSPI = 77,
+    EC = 78,
+    RO_2 = 79,
+    WebBrowser = 80,
+    Test = 81,
+    ENC = 82,
+    PIA = 83,
+
+    Application = 254,
+    InvalidResult = 255
+};
+
+/// A less specific error cause.
+enum class ErrorSummary : u32 {
+    Success = 0,
+    NothingHappened = 1,
+    WouldBlock = 2,
+    OutOfResource = 3,      ///< There are no more kernel resources (memory, table slots) to
+                            ///< execute the operation.
+    NotFound = 4,           ///< A file or resource was not found.
+    InvalidState = 5,
+    NotSupported = 6,       ///< The operation is not supported or not implemented.
+    InvalidArgument = 7,    ///< Returned when a passed argument is invalid in the current runtime
+                            ///< context. (Invalid handle, out-of-bounds pointer or size, etc.)
+    WrongArgument = 8,      ///< Returned when a passed argument is in an incorrect format for use
+                            ///< with the function. (E.g. Invalid enum value)
+    Canceled = 9,
+    StatusChanged = 10,
+    Internal = 11,
+
+    InvalidResult = 63
+};
+
+/// The severity of the error.
+enum class ErrorLevel : u32 {
+    Success = 0,
+    Info = 1,
+
+    Status = 25,
+    Temporary = 26,
+    Permanent = 27,
+    Usage = 28,
+    Reinitialize = 29,
+    Reset = 30,
+    Fatal = 31
+};
+
+/// Encapsulates a CTR-OS error code, allowing it to be separated into its constituent fields.
+union ResultCode {
+    u32 raw;
+
+    BitField<0, 10, ErrorDescription> description;
+    BitField<10, 8, ErrorModule> module;
+
+    BitField<21, 6, ErrorSummary> summary;
+    BitField<27, 5, ErrorLevel> level;
+
+    // The last bit of `level` is checked by apps and the kernel to determine if a result code is an error
+    BitField<31, 1, u32> is_error;
+
+    explicit ResultCode(u32 raw) : raw(raw) {}
+    ResultCode(ErrorDescription description_, ErrorModule module_,
+            ErrorSummary summary_, ErrorLevel level_) : raw(0) {
+        description = description_;
+        module = module_;
+        summary = summary_;
+        level = level_;
+    }
+
+    ResultCode& operator=(const ResultCode& o) { raw = o.raw; return *this; }
+
+    bool IsSuccess() const {
+        return is_error == 0;
+    }
+
+    bool IsError() const {
+        return is_error == 1;
+    }
+};
+
+inline bool operator==(const ResultCode a, const ResultCode b) {
+    return a.raw == b.raw;
+}
+
+inline bool operator!=(const ResultCode a, const ResultCode b) {
+    return a.raw != b.raw;
+}
+
+// Convenience functions for creating some common kinds of errors:
+
+/// The default success `ResultCode`.
+const ResultCode RESULT_SUCCESS(0);
+
+/// Might be returned instead of a dummy success for unimplemented APIs.
+inline ResultCode UnimplementedFunction(ErrorModule module) {
+    return ResultCode(ErrorDescription::NotImplemented, module,
+            ErrorSummary::NotSupported, ErrorLevel::Permanent);
+}
+/// Returned when a function is passed an invalid handle.
+inline ResultCode InvalidHandle(ErrorModule module) {
+    return ResultCode(ErrorDescription::InvalidHandle, module,
+            ErrorSummary::InvalidArgument, ErrorLevel::Permanent);
+}
+
+/**
+ * This is an optional value type. It holds a `ResultCode` and, if that code is a success code,
+ * also holds a result of type `T`. If the code is an error code then trying to access the inner
+ * value fails, thus ensuring that the ResultCode of functions is always checked properly before
+ * their return value is used.  It is similar in concept to the `std::optional` type
+ * (http://en.cppreference.com/w/cpp/experimental/optional) originally proposed for inclusion in
+ * C++14, or the `Result` type in Rust (http://doc.rust-lang.org/std/result/index.html).
+ *
+ * An example of how it could be used:
+ * \code
+ * ResultVal<int> Frobnicate(float strength) {
+ *     if (strength < 0.f || strength > 1.0f) {
+ *         // Can't frobnicate too weakly or too strongly
+ *         return ResultCode(ErrorDescription::OutOfRange, ErrorModule::Common,
+ *             ErrorSummary::InvalidArgument, ErrorLevel::Permanent);
+ *     } else {
+ *         // Frobnicated! Give caller a cookie
+ *         return MakeResult<int>(42);
+ *     }
+ * }
+ * \endcode
+ *
+ * \code
+ * ResultVal<int> frob_result = Frobnicate(0.75f);
+ * if (frob_result) {
+ *     // Frobbed ok
+ *     printf("My cookie is %d\n", *frob_result);
+ * } else {
+ *     printf("Guess I overdid it. :( Error code: %ux\n", frob_result.code().hex);
+ * }
+ * \endcode
+ */
+template <typename T>
+class ResultVal {
+public:
+    /// Constructs an empty `ResultVal` with the given error code. The code must not be a success code.
+    ResultVal(ResultCode error_code = ResultCode(-1))
+        : result_code(error_code)
+    {
+        assert(error_code.IsError());
+        UpdateDebugPtr();
+    }
+
+    /**
+     * Similar to the non-member function `MakeResult`, with the exception that you can manually
+     * specify the success code. `success_code` must not be an error code.
+     */
+    template <typename... Args>
+    static ResultVal WithCode(ResultCode success_code, Args&&... args) {
+        ResultVal<T> result;
+        result.emplace(success_code, std::forward<Args>(args)...);
+        return result;
+    }
+
+    ResultVal(const ResultVal& o)
+        : result_code(o.result_code)
+    {
+        if (!o.empty()) {
+            new (&storage) T(*o.GetPointer());
+        }
+        UpdateDebugPtr();
+    }
+
+    ResultVal(ResultVal&& o)
+        : result_code(o.result_code)
+    {
+        if (!o.empty()) {
+            new (&storage) T(std::move(*o.GetPointer()));
+        }
+        UpdateDebugPtr();
+    }
+
+    ~ResultVal() {
+        if (!empty()) {
+            GetPointer()->~T();
+        }
+    }
+
+    ResultVal& operator=(const ResultVal& o) {
+        if (*this) {
+            if (o) {
+                *GetPointer() = *o.GetPointer();
+            } else {
+                GetPointer()->~T();
+            }
+        } else {
+            if (o) {
+                new (&storage) T(*o.GetPointer());
+            }
+        }
+        result_code = o.result_code;
+        UpdateDebugPtr();
+
+        return *this;
+    }
+
+    /**
+     * Replaces the current result with a new constructed result value in-place. The code must not
+     * be an error code.
+     */
+    template <typename... Args>
+    void emplace(ResultCode success_code, Args&&... args) {
+        assert(success_code.IsSuccess());
+        if (!empty()) {
+            GetPointer()->~T();
+        }
+        new (&storage) T(std::forward<Args>(args)...);
+        result_code = success_code;
+        UpdateDebugPtr();
+    }
+
+    /// Returns true if the `ResultVal` contains an error code and no value.
+    bool empty() const { return result_code.IsError(); }
+
+    /// Returns true if the `ResultVal` contains a return value.
+    bool Succeeded() const { return result_code.IsSuccess(); }
+    /// Returns true if the `ResultVal` contains an error code and no value.
+    bool Failed() const { return empty(); }
+
+    ResultCode Code() const { return result_code; }
+
+    const T& operator* () const { return *GetPointer(); }
+          T& operator* ()       { return *GetPointer(); }
+    const T* operator->() const { return  GetPointer(); }
+          T* operator->()       { return  GetPointer(); }
+
+    /// Returns the value contained in this `ResultVal`, or the supplied default if it is missing.
+    template <typename U>
+    T ValueOr(U&& value) const {
+        return !empty() ? *GetPointer() : std::move(value);
+    }
+
+private:
+    typedef typename std::aligned_storage<sizeof(T), std::alignment_of<T>::value>::type StorageType;
+
+    StorageType storage;
+    ResultCode result_code;
+#if _DEBUG
+    // The purpose of this pointer is to aid inspecting the type with a debugger, eliminating the
+    // need to cast `storage` to a pointer or pay attention to `result_code`.
+    const T* debug_ptr;
+#endif
+
+    void UpdateDebugPtr() {
+#if _DEBUG
+        debug_ptr = empty() ? nullptr : static_cast<const T*>(static_cast<const void*>(&storage));
+#endif
+    }
+
+    const T* GetPointer() const {
+        assert(!empty());
+        return static_cast<const T*>(static_cast<const void*>(&storage));
+    }
+
+    T* GetPointer() {
+        assert(!empty());
+        return static_cast<T*>(static_cast<void*>(&storage));
+    }
+};
+
+/**
+ * This function is a helper used to construct `ResultVal`s. It receives the arguments to construct
+ * `T` with and creates a success `ResultVal` contained the constructed value.
+ */
+template <typename T, typename... Args>
+ResultVal<T> MakeResult(Args&&... args) {
+    return ResultVal<T>::WithCode(RESULT_SUCCESS, std::forward<Args>(args)...);
+}