service/set: Correct and simplify behavior related to copying language codes

This corrects cases where it was possible to write more entries into the
write buffer than were requested. Now, we check the size of the buffer
before actually writing into them.

We were also returning the wrong value for
GetAvailableLanguageCodeCount2(). This was previously returning 64, but
only 17 should have been returned. 64 entries is the size of the static
array used in MakeLanguageCode() within the service binary itself, but
isn't the actual total number of language codes present.

src/core/hle/service/set/set.cpp

@@ -2,16 +2,15 @@
 // Licensed under GPLv2 or any later version
 // Refer to the license.txt file included.
 
+#include <algorithm>
 #include <chrono>
 #include "common/logging/log.h"
 #include "core/hle/ipc_helpers.h"
-#include "core/hle/kernel/client_port.h"
-#include "core/hle/kernel/client_session.h"
 #include "core/hle/service/set/set.h"
 #include "core/settings.h"
 
 namespace Service::Set {
-
+namespace {
 constexpr std::array<LanguageCode, 17> available_language_codes = {{
     LanguageCode::JA,
     LanguageCode::EN_US,
@@ -32,41 +31,35 @@ constexpr std::array<LanguageCode, 17> available_language_codes = {{
     LanguageCode::ZH_HANT,
 }};
 
-constexpr std::size_t pre4_0_0_max_entries = 0xF;
-constexpr std::size_t post4_0_0_max_entries = 0x40;
+constexpr std::size_t pre4_0_0_max_entries = 15;
+constexpr std::size_t post4_0_0_max_entries = 17;
 
 constexpr ResultCode ERR_INVALID_LANGUAGE{ErrorModule::Settings, 625};
 
-LanguageCode GetLanguageCodeFromIndex(std::size_t index) {
-    return available_language_codes.at(index);
+void PushResponseLanguageCode(Kernel::HLERequestContext& ctx, std::size_t num_language_codes) {
+    IPC::ResponseBuilder rb{ctx, 3};
+    rb.Push(RESULT_SUCCESS);
+    rb.Push(static_cast<u32>(num_language_codes));
 }
 
-template <std::size_t size>
-static std::array<LanguageCode, size> MakeLanguageCodeSubset() {
-    std::array<LanguageCode, size> arr;
-    std::copy_n(available_language_codes.begin(), size, arr.begin());
-    return arr;
+void GetAvailableLanguageCodesImpl(Kernel::HLERequestContext& ctx, std::size_t max_size) {
+    const std::size_t requested_amount = ctx.GetWriteBufferSize() / sizeof(LanguageCode);
+    const std::size_t copy_amount = std::min(requested_amount, max_size);
+    const std::size_t copy_size = copy_amount * sizeof(LanguageCode);
+
+    ctx.WriteBuffer(available_language_codes.data(), copy_size);
+    PushResponseLanguageCode(ctx, copy_amount);
 }
+} // Anonymous namespace
 
-static void PushResponseLanguageCode(Kernel::HLERequestContext& ctx, std::size_t max_size) {
-    IPC::ResponseBuilder rb{ctx, 3};
-    rb.Push(RESULT_SUCCESS);
-    if (available_language_codes.size() > max_size) {
-        rb.Push(static_cast<u32>(max_size));
-    } else {
-        rb.Push(static_cast<u32>(available_language_codes.size()));
-    }
+LanguageCode GetLanguageCodeFromIndex(std::size_t index) {
+    return available_language_codes.at(index);
 }
 
 void SET::GetAvailableLanguageCodes(Kernel::HLERequestContext& ctx) {
     LOG_DEBUG(Service_SET, "called");
 
-    if (available_language_codes.size() > pre4_0_0_max_entries) {
-        ctx.WriteBuffer(MakeLanguageCodeSubset<pre4_0_0_max_entries>());
-    } else {
-        ctx.WriteBuffer(available_language_codes);
-    }
-    PushResponseLanguageCode(ctx, pre4_0_0_max_entries);
+    GetAvailableLanguageCodesImpl(ctx, pre4_0_0_max_entries);
 }
 
 void SET::MakeLanguageCode(Kernel::HLERequestContext& ctx) {
@@ -87,12 +80,7 @@ void SET::MakeLanguageCode(Kernel::HLERequestContext& ctx) {
 void SET::GetAvailableLanguageCodes2(Kernel::HLERequestContext& ctx) {
     LOG_DEBUG(Service_SET, "called");
 
-    if (available_language_codes.size() > post4_0_0_max_entries) {
-        ctx.WriteBuffer(MakeLanguageCodeSubset<post4_0_0_max_entries>());
-    } else {
-        ctx.WriteBuffer(available_language_codes);
-    }
-    PushResponseLanguageCode(ctx, post4_0_0_max_entries);
+    GetAvailableLanguageCodesImpl(ctx, post4_0_0_max_entries);
 }
 
 void SET::GetAvailableLanguageCodeCount(Kernel::HLERequestContext& ctx) {
@@ -102,9 +90,9 @@ void SET::GetAvailableLanguageCodeCount(Kernel::HLERequestContext& ctx) {
 }
 
 void SET::GetAvailableLanguageCodeCount2(Kernel::HLERequestContext& ctx) {
-    PushResponseLanguageCode(ctx, post4_0_0_max_entries);
-
     LOG_DEBUG(Service_SET, "called");
+
+    PushResponseLanguageCode(ctx, post4_0_0_max_entries);
 }
 
 void SET::GetLanguageCode(Kernel::HLERequestContext& ctx) {