Create server side

proto/buf.gen.yaml

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+version: v2
+plugins:
+  - remote: buf.build/community/neoeinstein-prost
+    out: ../src/proto/generated
+  - remote: buf.build/community/neoeinstein-tonic
+    out: ../src/proto/generated

proto/buf.yaml

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+version: v2
+modules:
+  - path: .
+lint:
+  use:
+    - STANDARD
+breaking:
+  use:
+    - FILE

proto/musicfs.proto

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+syntax = "proto3";
+
+package musicfs;
+
+// MusicFs service exposes a server-side music library to a remote musicfs
+// FUSE mount. Three RPCs, all server-streaming so the client can pull
+// incrementally and the server can keep large bodies off the heap.
+service MusicFs {
+  // Stream every file entry in the library. The client diffs each entry's
+  // hash against its DB to decide what changed.
+  rpc GetManifest(GetManifestRequest) returns (stream ManifestEntry);
+
+  // Stream the bytes of one file. If `start` and `length` are both set on
+  // the request, only that byte range is sent; otherwise the whole file.
+  // The first chunk carries `total_size` and `offset`; subsequent chunks
+  // continue from there.
+  rpc GetFile(GetFileRequest) returns (stream FileChunk);
+
+  // Long-lived stream of filesystem change events. The client uses these as
+  // wake-ups to refetch the manifest; correctness always rests on the hash
+  // diff, never on the event payload.
+  rpc SubscribeEvents(SubscribeEventsRequest) returns (stream ChangeEvent);
+}
+
+message GetManifestRequest {}
+
+message GetFileRequest {
+  uint64 id = 1;
+  // When both are zero the server streams the entire file.
+  uint64 start = 2;
+  uint64 length = 3;
+}
+
+message SubscribeEventsRequest {}
+
+message ManifestEntry {
+  uint64 id = 1;
+  string rel_path = 2;
+  uint64 size = 3;
+  uint64 mtime = 4;
+  uint64 ctime = 5;
+  uint64 crtime = 6;
+  MusicMetadata music_metadata = 7;
+}
+
+message MusicMetadata {
+  repeated string artist = 1;
+  optional string album_artist = 2;
+  string album = 3;
+  int32 track_number = 4;
+  string track_title = 5;
+  repeated string other_tags = 6;
+  bytes header = 7;
+  repeated bytes picture_block_headers = 8;
+  repeated PictureDataRange picture_data_ranges = 9;
+  uint64 real_audio_start = 10;
+  uint64 vorbis_comment_offset = 11;
+  uint64 vorbis_comment_length = 12;
+}
+
+message PictureDataRange {
+  uint64 offset = 1;
+  uint64 length = 2;
+}
+
+message FileChunk {
+  bytes data = 1;
+  uint64 offset = 2;
+  uint64 total_size = 3;
+}
+
+message ChangeEvent {
+  // "create", "modify", or "remove".
+  string kind = 1;
+}