FEXCore/FileUtils: Adds a way to walk a directory with callback

We need to walk a directory calling back to the DiskCache, but without
recursion.

Also fixes a function signature issue on win32.

FEXCore/Source/Utils/FileUtils.cpp

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MIT
 #include <FEXCore/fextl/fmt.h>
+#include <FEXCore/fextl/functional.h>
 #include <FEXCore/fextl/string.h>
 #include <FEXCore/Utils/CompilerDefs.h>
 #include <FEXCore/Utils/LogManager.h>
@@ -115,10 +116,87 @@ end:
 FEX_DEFAULT_VISIBILITY bool RecursiveRemoveDirectory(const fextl::string& Directory) {
   return RecursiveRemoveDirectory(AT_FDCWD, Directory.c_str()) && unlinkat(AT_FDCWD, Directory.c_str(), true);
 }
+
+FEX_DEFAULT_VISIBILITY void WalkDirectory(std::string_view Directory, fextl::move_only_function<void(std::string_view name, bool is_dir)> Callback) {
+  constexpr int DIR_FLAGS = O_RDONLY | O_DIRECTORY | O_NOFOLLOW | O_CLOEXEC;
+  int dir_fd = ::openat(AT_FDCWD, fextl::string(Directory).c_str(), DIR_FLAGS);
+  if (dir_fd == -1) {
+    if (errno == ENOENT) {
+      // Probably raced something. Non-error.
+      return;
+    }
+  }
+  // Four pages arbitrary chosen to be a balance between NFS wanting to return data in page-size granules and
+  // local filesystems returning arbitrary sizes.
+  size_t dirent_size = 4096 * 4;
+  uint8_t* dirent_buffer = reinterpret_cast<uint8_t*>(FEXCore::Allocator::malloc(dirent_size));
+
+  if (!dirent_buffer) {
+    // Ran out of memory?
+    goto end;
+  }
+
+  while (true) {
+    ssize_t read = getdents64(dir_fd, dirent_buffer, dirent_size);
+
+    if (read == -1) {
+      if (errno == EINVAL) {
+        // Buffer too small? Scale and try again.
+        dirent_size *= 2;
+        FEXCore::Allocator::free(dirent_buffer);
+        dirent_buffer = reinterpret_cast<uint8_t*>(FEXCore::Allocator::malloc(dirent_size));
+        if (!dirent_buffer) {
+          // Ran out of memory?
+          goto end;
+        }
+
+        continue;
+      }
+
+      // Anything else just exit.
+      goto end;
+    }
+
+    if (read == 0) {
+      // Done.
+      break;
+    }
+
+    for (size_t dirent_offset = 0; dirent_offset < read;) {
+      auto path_dirent = reinterpret_cast<const struct dirent*>(dirent_buffer + dirent_offset);
+      std::string_view path_name_view = path_dirent->d_name;
+
+      if (path_name_view == "." || path_name_view == "..") {
+        // Skip these two special files.
+        dirent_offset += path_dirent->d_reclen;
+        continue;
+      }
+
+      Callback(path_name_view, path_dirent->d_type == DT_DIR);
+
+      // dirent is a VLA so we need to increment by reported size.
+      dirent_offset += path_dirent->d_reclen;
+    }
+  }
+
+end:
+  if (dirent_buffer) {
+    FEXCore::Allocator::free(dirent_buffer);
+  }
+
+  close(dir_fd);
+}
+
 #else
-FEX_DEFAULT_VISIBILITY bool RecursiveRemoveDirectory(std::string_view Directory) {
+FEX_DEFAULT_VISIBILITY bool RecursiveRemoveDirectory(const fextl::string& Directory) {
   std::error_code ec;
   return std::filesystem::remove_all(Directory, ec) != ~0ULL;
 }
+
+FEX_DEFAULT_VISIBILITY void WalkDirectory(std::string_view Directory, fextl::move_only_function<void(std::string_view name, bool is_dir)> Callback) {
+  for (const auto& iter : std::filesystem::directory_iterator(Directory)) {
+    Callback(iter.path().string(), iter.is_directory());
+  }
+}
 #endif
 } // namespace FEXCore::FileUtils

FEXCore/include/FEXCore/Utils/FileUtils.h

@@ -1,6 +1,8 @@
 // SPDX-License-Identifier: MIT
 #pragma once
+#include <FEXCore/fextl/functional.h>
 #include <FEXCore/fextl/string.h>
+
 #include <FEXCore/Utils/CompilerDefs.h>
 
 namespace FEXCore::FileUtils {
@@ -10,4 +12,6 @@ namespace FEXCore::FileUtils {
  * @return True if the directory didn't exist or was deleted.
  */
 FEX_DEFAULT_VISIBILITY bool RecursiveRemoveDirectory(const fextl::string& Directory);
+
+FEX_DEFAULT_VISIBILITY void WalkDirectory(std::string_view Directory, fextl::move_only_function<void(std::string_view name, bool is_dir)> Callback);
 } // namespace FEXCore::FileUtils