Provide filepath compatibility layer

See #17

src/audio_file.cc

@@ -100,7 +100,7 @@ int audioFileOpen(const char* fname, int flags, ...)
         audioFile->soundDecoder = soundDecoderInit(audioFileSoundDecoderReadHandler, audioFile->fileHandle, &(audioFile->field_14), &(audioFile->field_10), &(audioFile->fileSize));
         audioFile->fileSize *= 2;
     } else {
-        audioFile->fileSize = std::filesystem::file_size(path);
+        audioFile->fileSize = compat_filelength(fileno(stream));
     }
 
     audioFile->position = 0;

src/dfile.cc

@@ -8,7 +8,6 @@
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <filesystem>
 
 // Reads .DAT file contents.
 //
@@ -32,7 +31,7 @@ DBase* dbaseOpen(const char* filePath)
 
     // Get file size, and reposition stream to read footer, which contains two
     // 32-bits ints.
-    int fileSize = std::filesystem::file_size(filePath);
+    int fileSize = compat_filelength(fileno(stream));
     if (fseek(stream, fileSize - sizeof(int) * 2, SEEK_SET) != 0) {
         goto err;
     }

src/platform_compat.cc

@@ -5,6 +5,13 @@
 
 #include <filesystem>
 
+#ifdef _WIN32
+#include <io.h>
+#include <stdio.h>
+#else
+#include <unistd.h>
+#endif
+
 int compat_stricmp(const char* string1, const char* string2)
 {
     return SDL_strcasecmp(string1, string2);
@@ -81,3 +88,12 @@ void compat_makepath(char* path, const char* drive, const char* dir, const char*
     strcpy(path, p.string().substr(0, COMPAT_MAX_PATH - 1).c_str());
 #endif
 }
+
+long compat_filelength(int fd)
+{
+    long originalOffset = lseek(fd, 0, SEEK_CUR);
+    lseek(fd, 0, SEEK_SET);
+    long filesize = lseek(fd, 0, SEEK_END);
+    lseek(fd, originalOffset, SEEK_SET);
+    return filesize;
+}

src/platform_compat.h

@@ -24,5 +24,6 @@ char* compat_strlwr(char* string);
 char* compat_itoa(int value, char* buffer, int radix);
 void compat_splitpath(const char* path, char* drive, char* dir, char* fname, char* ext);
 void compat_makepath(char* path, const char* drive, const char* dir, const char* fname, const char* ext);
+long compat_filelength(int fd);
 
 #endif /* PLATFORM_COMPAT_H */

src/xfile.cc

@@ -418,9 +418,7 @@ long xfileGetSize(XFile* stream)
         fileSize = 0;
         break;
     default:
-        fseek(stream->file, 0L, SEEK_END);
-        fileSize = ftell(stream->file);
-        rewind(stream->file);
+        fileSize = compat_filelength(fileno(stream->file));
         break;
     }