language.cpp: Load whole translations file if MPQ

Fixes very slow translation loading from MPQs.

Compressed MPQs files are very slow to seek in.
If the RWops is and MPQ, load the whole file first.

Source/utils/language.cpp

@@ -13,6 +13,10 @@
 #include "utils/paths.h"
 #include "utils/stdcompat/string_view.hpp"
 
+#ifdef USE_SDL1
+#include "utils/sdl2_to_1_2_backports.h"
+#endif
+
 #define MO_MAGIC 0x950412de
 
 namespace {
@@ -264,6 +268,22 @@ bool ReadEntry(AssetHandle &handle, const MoEntry &e, char *result)
 	return handle.read(result, e.length);
 }
 
+bool CopyData(void *dst, const byte *data, size_t dataSize, size_t offset, size_t length)
+{
+	if (offset + length > dataSize)
+		return false;
+	memcpy(dst, data + offset, length);
+	return true;
+}
+
+bool ReadEntry(const byte *data, size_t dataSize, const MoEntry &e, char *result)
+{
+	if (!CopyData(result, data, dataSize, e.offset, e.length))
+		return false;
+	result[e.length] = '\0';
+	return true;
+}
+
 } // namespace
 
 string_view LanguageParticularTranslate(string_view context, string_view message)
@@ -346,12 +366,13 @@ void LanguageInitialize()
 	const std::string lang(*sgOptions.Language.code);
 
 	AssetHandle handle;
-	uint32_t loadTranslationsStart = SDL_GetTicks();
+	const uint32_t loadTranslationsStart = SDL_GetTicks();
 
 	std::string translationsPath;
+	size_t fileSize;
 	for (const char *ext : Extensions) {
 		translationsPath = lang + ext;
-		handle = OpenAsset(translationsPath.c_str());
+		handle = OpenAsset(translationsPath.c_str(), fileSize);
 		if (handle.ok())
 			break;
 	}
@@ -360,9 +381,27 @@ void LanguageInitialize()
 		return;
 	}
 
+#ifdef UNPACKED_MPQS
+	const bool readWholeFile = false;
+#else
+	// If reading from an MPQ, it is much faster to
+	// load the whole file instead of seeking.
+	const bool readWholeFile = handle.handle->type == SDL_RWOPS_UNKNOWN;
+#endif
+
+	std::unique_ptr<byte[]> data;
+	if (readWholeFile) {
+		data.reset(new byte[fileSize]);
+		if (!handle.read(data.get(), fileSize))
+			return;
+		handle = {};
+	}
+
 	// Read header and do sanity checks
 	MoHead head;
-	if (!handle.read(&head, sizeof(MoHead))) {
+	if (readWholeFile
+	        ? !CopyData(&head, data.get(), fileSize, 0, sizeof(MoHead))
+	        : !handle.read(&head, sizeof(MoHead))) {
 		return;
 	}
 	SwapLE(head);
@@ -377,10 +416,9 @@ void LanguageInitialize()
 
 	// Read entries of source strings
 	std::unique_ptr<MoEntry[]> src { new MoEntry[head.nbMappings] };
-	if (!handle.seek(head.srcOffset)) {
-		return;
-	}
-	if (!handle.read(src.get(), head.nbMappings * sizeof(MoEntry))) {
+	if (readWholeFile
+	        ? !CopyData(src.get(), data.get(), fileSize, head.srcOffset, head.nbMappings * sizeof(MoEntry))
+	        : !handle.seek(head.srcOffset) || !handle.read(src.get(), head.nbMappings * sizeof(MoEntry))) {
 		return;
 	}
 	for (size_t i = 0; i < head.nbMappings; ++i) {
@@ -389,10 +427,9 @@ void LanguageInitialize()
 
 	// Read entries of target strings
 	std::unique_ptr<MoEntry[]> dst { new MoEntry[head.nbMappings] };
-	if (!handle.seek(head.dstOffset)) {
-		return;
-	}
-	if (!handle.read(dst.get(), head.nbMappings * sizeof(MoEntry))) {
+	if (readWholeFile
+	        ? !CopyData(dst.get(), data.get(), fileSize, head.dstOffset, head.nbMappings * sizeof(MoEntry))
+	        : !handle.seek(head.dstOffset) || !handle.read(dst.get(), head.nbMappings * sizeof(MoEntry))) {
 		return;
 	}
 	for (size_t i = 0; i < head.nbMappings; ++i) {
@@ -405,7 +442,9 @@ void LanguageInitialize()
 	}
 	{
 		auto headerValue = std::unique_ptr<char[]> { new char[dst[0].length + 1] };
-		if (!ReadEntry(handle, dst[0], &headerValue[0])) {
+		if (readWholeFile
+		        ? !ReadEntry(data.get(), fileSize, dst[0], &headerValue[0])
+		        : !ReadEntry(handle, dst[0], &headerValue[0])) {
 			return;
 		}
 		ParseMetadata(&headerValue[0]);
@@ -428,7 +467,9 @@ void LanguageInitialize()
 	char *keyPtr = &translationKeys[0];
 	char *valuePtr = &translationValues[0];
 	for (uint32_t i = 1; i < head.nbMappings; i++) {
-		if (ReadEntry(handle, src[i], keyPtr) && ReadEntry(handle, dst[i], valuePtr)) {
+		if (readWholeFile
+		        ? ReadEntry(data.get(), fileSize, src[i], keyPtr) && ReadEntry(data.get(), fileSize, dst[i], valuePtr)
+		        : ReadEntry(handle, src[i], keyPtr) && ReadEntry(handle, dst[i], valuePtr)) {
 			// Plural keys also have a plural form but it does not participate in lookup.
 			// Plural values are \0-terminated.
 			string_view value { valuePtr, dst[i].length + 1 };

Source/utils/sdl2_to_1_2_backports.h

@@ -315,6 +315,7 @@ int SDL_BlitScaled(SDL_Surface *src, SDL_Rect *srcrect,
     SDL_Surface *dst, SDL_Rect *dstrect);
 
 //== Filesystem
+#define SDL_RWOPS_UNKNOWN 0U
 
 Sint64 SDL_RWsize(SDL_RWops *context);