filesystem: Added SDL_GetCurrentDirectory().

Fixes #11531.

src/filesystem/SDL_filesystem.c

@@ -495,10 +495,13 @@ const char *SDL_GetUserFolder(SDL_Folder folder)
 
 char *SDL_GetPrefPath(const char *org, const char *app)
 {
-    char *path = SDL_SYS_GetPrefPath(org, app);
-    return path;
+    return SDL_SYS_GetPrefPath(org, app);
 }
 
+char *SDL_GetCurrentDirectory(void)
+{
+    return SDL_SYS_GetCurrentDirectory();
+}
 
 void SDL_InitFilesystem(void)
 {

src/filesystem/SDL_sysfilesystem.h

@@ -26,6 +26,7 @@
 extern char *SDL_SYS_GetBasePath(void);
 extern char *SDL_SYS_GetPrefPath(const char *org, const char *app);
 extern char *SDL_SYS_GetUserFolder(SDL_Folder folder);
+extern char *SDL_SYS_GetCurrentDirectory(void);
 
 extern bool SDL_SYS_EnumerateDirectory(const char *path, const char *dirname, SDL_EnumerateDirectoryCallback cb, void *userdata);
 extern bool SDL_SYS_RemovePath(const char *path);

src/filesystem/dummy/SDL_sysfilesystem.c

@@ -45,4 +45,10 @@ char *SDL_SYS_GetUserFolder(SDL_Folder folder)
     return NULL;
 }
 
+char *SDL_SYS_GetCurrentDirectory(void)
+{
+    SDL_Unsupported();
+    return NULL;
+}
+
 #endif // SDL_FILESYSTEM_DUMMY || SDL_FILESYSTEM_DISABLED

src/filesystem/posix/SDL_sysfsops.c

@@ -33,6 +33,7 @@
 #include <errno.h>
 #include <dirent.h>
 #include <sys/stat.h>
+#include <unistd.h>
 
 bool SDL_SYS_EnumerateDirectory(const char *path, const char *dirname, SDL_EnumerateDirectoryCallback cb, void *userdata)
 {
@@ -185,5 +186,36 @@ bool SDL_SYS_GetPathInfo(const char *path, SDL_PathInfo *info)
     return true;
 }
 
+// Note that this isn't actually part of filesystem, not fsops, but everything that uses posix fsops uses this implementation, even with separate filesystem code.
+char *SDL_SYS_GetCurrentDirectory(void)
+{
+    size_t buflen = 64;
+    char *buf = NULL;
+
+    while (true) {
+        void *ptr = SDL_realloc(buf, buflen);
+        if (!ptr) {
+            SDL_free(buf);
+            return NULL;
+        }
+        buf = (char *) ptr;
+
+        if (getcwd(buf, buflen) != NULL) {
+            break;  // we got it!
+        }
+
+        if (errno == ERANGE) {
+            buflen *= 2;  // try again with a bigger buffer.
+            continue;
+        }
+
+        SDL_free(buf);
+        SDL_SetError("getcwd failed: %s", strerror(errno));
+        return NULL;
+    }
+
+    return buf;
+}
+
 #endif // SDL_FSOPS_POSIX
 

src/filesystem/windows/SDL_sysfilesystem.c

@@ -345,4 +345,32 @@ done:
     }
     return result;
 }
+
+char *SDL_SYS_GetCurrentDirectory(void)
+{
+    WCHAR *wstr = NULL;
+    DWORD buflen = 0;
+    while (true) {
+        const DWORD bw = GetCurrentDirectoryW(buflen, wstr);
+        if (bw == 0) {
+            WIN_SetError("GetCurrentDirectoryW failed");
+            return NULL;
+        } else if (bw < buflen) {
+            break;  // we got it!
+        }
+
+        void *ptr = SDL_realloc(wstr, bw * sizeof (WCHAR));
+        if (!ptr) {
+            SDL_free(wstr);
+            return NULL;
+        }
+        wstr = (WCHAR *) ptr;
+        buflen = bw;
+    }
+
+    char *retval = WIN_StringToUTF8W(wstr);
+    SDL_free(wstr);
+    return retval;
+}
+
 #endif // SDL_FILESYSTEM_WINDOWS