[NFC][WasmFS] Reorganize source files (#16286)

 - Combine memory_file.cpp and memory_file_backend.cpp into memory_backend.cpp
 - Rename memory_file.h to memory_backend.h
 - Split path parsing out into paths.h and paths.cpp
 - Move backend implementations into a new backends directory

Author: tlively

system/lib/wasmfs/fetch_backend.cpp renamed to system/lib/wasmfs/backends/fetch_backend.cpp

@@ -2,14 +2,17 @@
 // Emscripten is available under two separate licenses, the MIT license and the
 // University of Illinois/NCSA Open Source License.  Both these licenses can be
 // found in the LICENSE file.
-// This file defines the memory file class of the new file system.
-// This should be the only backend file type defined in a header since it is the
-// default type. Current Status: Work in Progress. See
-// https://github.com/emscripten-core/emscripten/issues/15041.
 
-#include "memory_file.h"
+// This file defines the memory file backend of the new file system.
+// Current Status: Work in Progress.
+// See https://github.com/emscripten-core/emscripten/issues/15041.
+
+#include "backend.h"
+#include "memory_backend.h"
+#include "wasmfs.h"
 
 namespace wasmfs {
+
 __wasi_errno_t MemoryFile::write(const uint8_t* buf, size_t len, off_t offset) {
   if (offset + len > buffer.size()) {
     buffer.resize(offset + len);
@@ -27,4 +30,16 @@ __wasi_errno_t MemoryFile::read(uint8_t* buf, size_t len, off_t offset) {
 
   return __WASI_ERRNO_SUCCESS;
 }
+
+class MemoryFileBackend : public Backend {
+public:
+  std::shared_ptr<DataFile> createFile(mode_t mode) override {
+    return std::make_shared<MemoryFile>(mode, this);
+  }
+};
+
+backend_t createMemoryFileBackend() {
+  return wasmFS.addBackend(std::make_unique<MemoryFileBackend>());
+}
+
 } // namespace wasmfs

system/lib/wasmfs/js_file_backend.cpp renamed to system/lib/wasmfs/backends/js_file_backend.cpp

@@ -108,165 +108,4 @@ size_t Symlink::getSize() {
   return target.size();
 }
 
-//
-// Path Parsing utilities
-//
-
-ParsedPath getParsedPath(std::vector<std::string> pathParts,
-                         long& err,
-                         std::shared_ptr<File> forbiddenAncestor,
-                         std::optional<__wasi_fd_t> baseFD) {
-  std::shared_ptr<Directory> curr;
-  auto begin = pathParts.begin();
-
-  if (pathParts.empty()) {
-    err = -ENOENT;
-    return ParsedPath{{}, nullptr};
-  }
-
-  // Check if the first path element is '/', indicating an absolute path.
-  if (pathParts[0] == "/") {
-    curr = wasmFS.getRootDirectory();
-    begin++;
-    // If the pathname is the root directory, return the root as the child.
-    if (pathParts.size() == 1) {
-      return ParsedPath{curr->locked(), curr};
-    }
-  } else {
-    // This is a relative path. It is either relative to the current working
-    // directory if no base FD is given, or if the base FD is the special value
-    // indicating the CWD.
-    if (baseFD && *baseFD != AT_FDCWD) {
-      auto lockedOpenDir = wasmFS.getLockedFileTable()[*baseFD].locked();
-      auto openDir = lockedOpenDir.getFile();
-      if (!openDir->is<Directory>()) {
-        err = -EBADF;
-        return ParsedPath{{}, nullptr};
-      }
-      curr = openDir->dynCast<Directory>();
-    } else {
-      curr = wasmFS.getCWD();
-    }
-  }
-
-  for (auto pathPart = begin; pathPart != pathParts.end() - 1; ++pathPart) {
-    // Find the next entry in the current directory entry
-#ifdef WASMFS_DEBUG
-    curr->locked().printKeys();
-#endif
-    auto entry = curr->locked().getEntry(*pathPart);
-
-    if (forbiddenAncestor) {
-      if (entry == forbiddenAncestor) {
-        err = -EINVAL;
-        return ParsedPath{{}, nullptr};
-      }
-    }
-
-    // An entry is defined in the current directory's entries vector.
-    if (!entry) {
-      err = -ENOENT;
-      return ParsedPath{{}, nullptr};
-    }
-
-    curr = entry->dynCast<Directory>();
-
-    // If file is nullptr, then the file was not a Directory.
-    // TODO: Change this to accommodate symlinks
-    if (!curr) {
-      err = -ENOTDIR;
-      return ParsedPath{{}, nullptr};
-    }
-
-#ifdef WASMFS_DEBUG
-    emscripten_console_log(*pathPart->c_str());
-#endif
-  }
-
-  // Lock the parent once.
-  auto lockedCurr = curr->locked();
-  auto child = lockedCurr.getEntry(*(pathParts.end() - 1));
-  return ParsedPath{std::move(lockedCurr), child};
-}
-
-std::shared_ptr<Directory> getDir(std::vector<std::string>::iterator begin,
-                                  std::vector<std::string>::iterator end,
-                                  long& err,
-                                  std::shared_ptr<File> forbiddenAncestor) {
-
-  std::shared_ptr<File> curr;
-  // Check if the first path element is '/', indicating an absolute path.
-  if (*begin == "/") {
-    curr = wasmFS.getRootDirectory();
-    begin++;
-  } else {
-    curr = wasmFS.getCWD();
-  }
-
-  for (auto it = begin; it != end; ++it) {
-    auto directory = curr->dynCast<Directory>();
-
-    // If file is nullptr, then the file was not a Directory.
-    // TODO: Change this to accommodate symlinks
-    if (!directory) {
-      err = -ENOTDIR;
-      return nullptr;
-    }
-
-    // Find the next entry in the current directory entry
-#ifdef WASMFS_DEBUG
-    directory->locked().printKeys();
-#endif
-    curr = directory->locked().getEntry(*it);
-
-    if (forbiddenAncestor) {
-      if (curr == forbiddenAncestor) {
-        err = -EINVAL;
-        return nullptr;
-      }
-    }
-
-    // Requested entry (file or directory)
-    if (!curr) {
-      err = -ENOENT;
-      return nullptr;
-    }
-
-#ifdef WASMFS_DEBUG
-    emscripten_console_log(it->c_str());
-#endif
-  }
-
-  auto currDirectory = curr->dynCast<Directory>();
-
-  if (!currDirectory) {
-    err = -ENOTDIR;
-    return nullptr;
-  }
-
-  return currDirectory;
-}
-
-// TODO: Check for trailing slash, i.e. /foo/bar.txt/
-// Currently any trailing slash is ignored.
-std::vector<std::string> splitPath(char* pathname) {
-  std::vector<std::string> pathParts;
-  char newPathName[strlen(pathname) + 1];
-  strcpy(newPathName, pathname);
-
-  // TODO: Other path parsing edge cases.
-  char* current;
-  // Handle absolute path.
-  if (newPathName[0] == '/') {
-    pathParts.push_back("/");
-  }
-
-  current = strtok(newPathName, "/");
-  while (current != NULL) {
-    pathParts.push_back(current);
-    current = strtok(NULL, "/");
-  }
-
-  return pathParts;
-}
 } // namespace wasmfs

system/lib/wasmfs/memory_file.cpp renamed to system/lib/wasmfs/backends/memory_backend.cpp

@@ -264,37 +264,4 @@ struct ParsedPath {
   std::shared_ptr<File> child;
 };
 
-// Call getParsedPath if one needs a locked handle to a parent dir and a
-// shared_ptr to its child file, given a file path.
-// TODO: When locking the directory structure is refactored, parent should be
-// returned as a pointer, similar to child.
-// Will return an empty handle if the parent is not a directory.
-//
-// Will error if the forbiddenAncestor is encountered while processing.
-// If the forbiddenAncestor is encountered, err will be set to EINVAL and
-// an empty parent handle will be returned.
-//
-// If baseFD is provided, and the path is relative, then it will be interpreted
-// relative to the base. That is the behavior that the *at() syscalls require.
-ParsedPath getParsedPath(std::vector<std::string> pathParts,
-                         long& err,
-                         std::shared_ptr<File> forbiddenAncestor = nullptr,
-                         std::optional<__wasi_fd_t> baseFD = {});
-
-// Call getDir if one needs a parent directory of a file path.
-// TODO: Remove this when directory structure locking is refactored and use
-// getParsedPath instead. Obtains parent directory of a given pathname.
-// Will return a nullptr if the parent is not a directory. Will error if the
-// forbiddenAncestor is encountered while processing. If the forbiddenAncestor
-// is encountered, err will be set to EINVAL and nullptr will be returned.
-std::shared_ptr<Directory>
-getDir(std::vector<std::string>::iterator begin,
-       std::vector<std::string>::iterator end,
-       long& err,
-       std::shared_ptr<File> forbiddenAncestor = nullptr);
-
-// Return a vector of the '/'-delimited components of a path. The first
-// element will be "/" iff the path is an absolute path.
-std::vector<std::string> splitPath(char* pathname);
-
 } // namespace wasmfs

system/lib/wasmfs/proxied_file_backend.cpp renamed to system/lib/wasmfs/backends/proxied_file_backend.cpp

@@ -7,6 +7,7 @@
 #include <unistd.h>
 
 #include "file.h"
+#include "paths.h"
 
 using namespace wasmfs;