pw_file: FlatFileSystem service implementation
Provides an optional implementation for the FileSystem RPC service that
enumerates a list of files as a "flat" file system.
Change-Id: Icfabbec17ba9d458aba8652d22342d3697ca3a07
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/60401
Reviewed-by: Keir Mierle <keir@google.com>
Commit-Queue: Armando Montanez <amontanez@google.com>
diff --git a/pw_file/flat_file_system.cc b/pw_file/flat_file_system.cc
new file mode 100644
index 0000000..d347903
--- /dev/null
+++ b/pw_file/flat_file_system.cc
@@ -0,0 +1,175 @@
+// Copyright 2021 The Pigweed Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License"); you may not
+// use this file except in compliance with the License. You may obtain a copy of
+// the License at
+//
+// https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+// License for the specific language governing permissions and limitations under
+// the License.
+
+#define PW_LOG_MODULE_NAME "FS"
+
+#include "pw_file/flat_file_system.h"
+
+#include <cstddef>
+#include <cstdint>
+#include <span>
+#include <string_view>
+
+#include "pw_assert/check.h"
+#include "pw_bytes/span.h"
+#include "pw_file/file.pwpb.h"
+#include "pw_log/log.h"
+#include "pw_protobuf/decoder.h"
+#include "pw_protobuf/encoder.h"
+#include "pw_protobuf/serialized_size.h"
+#include "pw_rpc/raw/server_reader_writer.h"
+#include "pw_status/status.h"
+#include "pw_status/status_with_size.h"
+
+namespace pw::file {
+
+using FileSystemEntry = FlatFileSystemService::FileSystemEntry;
+
+Status FlatFileSystemService::EnumerateFile(
+ FileSystemEntry& entry,
+ pw::file::ListResponse::StreamEncoder& output_encoder) {
+ StatusWithSize sws = entry.Name(file_name_buffer_);
+ if (!sws.ok()) {
+ return sws.status();
+ }
+ {
+ pw::file::Path::StreamEncoder encoder = output_encoder.GetPathsEncoder();
+
+ encoder.WritePath(reinterpret_cast<const char*>(file_name_buffer_.data()),
+ sws.size());
+ encoder.WriteSizeBytes(entry.SizeBytes());
+ encoder.WritePermissions(entry.Permissions());
+ encoder.WriteFileId(entry.FileId());
+ }
+ return output_encoder.status();
+}
+
+void FlatFileSystemService::EnumerateAllFiles(RawServerWriter& writer) {
+ for (FileSystemEntry* entry : entries_) {
+ PW_DCHECK_NOTNULL(entry);
+ // For now, don't try to pack entries.
+ pw::file::ListResponse::MemoryEncoder encoder(writer.PayloadBuffer());
+ if (Status status = EnumerateFile(*entry, encoder); !status.ok()) {
+ PW_LOG_ERROR("Failed to enumerate file (id: %u) with status %d",
+ static_cast<unsigned>(entry->FileId()),
+ static_cast<int>(status.code()));
+ continue;
+ }
+
+ Status write_status = writer.Write(encoder);
+ if (!write_status.ok()) {
+ writer.Finish(write_status);
+ return;
+ }
+ }
+ writer.Finish(OkStatus());
+}
+
+void FlatFileSystemService::List(ServerContext&,
+ ConstByteSpan request,
+ RawServerWriter& writer) {
+ protobuf::Decoder decoder(request);
+ // If a file name was provided, try and find and enumerate the file.
+ while (decoder.Next().ok()) {
+ if (decoder.FieldNumber() !=
+ static_cast<uint32_t>(pw::file::ListRequest::Fields::PATH)) {
+ continue;
+ }
+
+ std::string_view file_name_view;
+ if (!decoder.ReadString(&file_name_view).ok() ||
+ file_name_view.length() == 0) {
+ writer.Finish(Status::DataLoss());
+ return;
+ }
+
+ // Find and enumerate the file requested.
+ Result<FileSystemEntry*> result = FindFile(file_name_view);
+ if (!result.ok()) {
+ writer.Finish(result.status());
+ return;
+ }
+
+ pw::file::ListResponse::MemoryEncoder encoder(writer.PayloadBuffer());
+ Status proto_encode_status = EnumerateFile(*result.value(), encoder);
+ if (!proto_encode_status.ok()) {
+ writer.Finish(proto_encode_status);
+ return;
+ }
+
+ writer.Finish(writer.Write(encoder));
+ return;
+ }
+
+ // If no path was provided in the ListRequest, just enumerate everything.
+ EnumerateAllFiles(writer);
+}
+
+StatusWithSize FlatFileSystemService::Delete(ServerContext&,
+ ConstByteSpan request,
+ ByteSpan) {
+ protobuf::Decoder decoder(request);
+ while (decoder.Next().ok()) {
+ if (decoder.FieldNumber() !=
+ static_cast<uint32_t>(pw::file::DeleteRequest::Fields::PATH)) {
+ continue;
+ }
+
+ std::string_view file_name_view;
+ if (!decoder.ReadString(&file_name_view).ok()) {
+ return StatusWithSize(Status::DataLoss(), 0);
+ }
+ return StatusWithSize(FindAndDeleteFile(file_name_view), 0);
+ }
+ return StatusWithSize(Status::InvalidArgument(), 0);
+}
+
+Result<FileSystemEntry*> FlatFileSystemService::FindFile(
+ std::string_view file_name) {
+ Status search_status;
+ for (FileSystemEntry* entry : entries_) {
+ PW_DCHECK_NOTNULL(entry);
+ StatusWithSize sws = entry->Name(file_name_buffer_);
+
+ // If there not an exact file name length match, don't try and check against
+ // a prefix.
+ if (!sws.ok() || file_name.length() != sws.size()) {
+ if (sws.status() != Status::NotFound()) {
+ PW_LOG_ERROR("Failed to read file name (id: %u) with status %d",
+ static_cast<unsigned>(entry->FileId()),
+ static_cast<int>(sws.status().code()));
+ }
+ continue;
+ }
+
+ if (memcmp(file_name.data(), file_name_buffer_.data(), file_name.size()) ==
+ 0) {
+ return entry;
+ }
+ }
+
+ search_status.Update(Status::NotFound());
+ return search_status;
+}
+
+Status FlatFileSystemService::FindAndDeleteFile(std::string_view file_name) {
+ Result<FileSystemEntry*> result = FindFile(file_name);
+ if (!result.ok()) {
+ return result.status();
+ }
+
+ return result.value()->Delete();
+}
+
+} // namespace pw::file