1	import Base
2	import bend-kit-bytes@0.3.2.0/bytes.bend as StorageBytes
3	import 0x6c54b2522c2258baf6f58d2b970c3902/files.bend as PackedFiles
4	import ./FsPolicy.bend as Policy
5	
6	# Audited host effects (spec §3.3). Thin syscall wrappers with .c + .js
7	# twins and matching intended semantics. No laws — validated empirically.
8	
9	# Read at most 1 MiB as packed words. Short reads are valid progress; zero is EOF.
10	def read_words(
11	  file: File,
12	  max: U32
13	) ->
14	  IO(File & Result<&1, &1, U32 & String, U32 & Array<U32>>):
15	  PackedFiles.read.words(file, max)
16	
17	# Write all bytes from a packed word array, retaining the file handle on errors.
18	def write_words(
19	  file: File,
20	  len: U32,
21	  words: Array<U32>
22	) ->
23	  IO(File & Result<&1, &1, U32 & String, Unit>):
24	  PackedFiles.write.words(file, len, words)
25	
26	def read_bytes.wrap(
27	  result: Result<&1, &1, U32 & String, U32 & Array<U32>>
28	) ->
29	  Result<&1, &1, U32 & String, StorageBytes.Bytes>:
30	  match result:
31	    case Fail{err}:
32	      Fail{err}
33	    case Done{(len, words)}:
34	      Done{StorageBytes.Bytes{len, words}}
35	
36	def read_bytes.pair(
37	  pair: File & Result<&1, &1, U32 & String, U32 & Array<U32>>
38	) ->
39	  File & Result<&1, &1, U32 & String, StorageBytes.Bytes>:
40	  match pair:
41	    case (handle, result):
42	      (handle, read_bytes.wrap(result))
43	
44	# Read one bounded packed chunk; nonempty short reads are not EOF.
45	def read_bytes(
46	  file: File,
47	  max: U32
48	) ->
49	  IO(File & Result<&1, &1, U32 & String, StorageBytes.Bytes>):
50	  do IO<File & Result<&1, &1, U32 & String, StorageBytes.Bytes>>:
51	    pair : File & Result<&1, &1, U32 & String, U32 & Array<U32>> <- read_words(file, max)
52	    return read_bytes.pair(pair)
53	
54	# Write the significant bytes of a packed buffer through the pinned host effect.
55	def write_bytes(
56	  file: File,
57	  bytes: StorageBytes.Bytes
58	) ->
59	  IO(File & Result<&1, &1, U32 & String, Unit>):
60	  StorageBytes.Bytes{len, buf} = bytes
61	  write_words(file, len, buf)
62	
63	# Sync file contents to stable storage.
64	def fsync(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):
65	  import "./effs/fsync.c"
66	  import "./effs/fsync.js"
67	
68	# Handle truncate in the filesystem effects.
69	def truncate(path: String, offset: Nat) -> IO(Result<&1, &1, U32 & String, Unit>):
70	  import "./effs/truncate.c"
71	  import "./effs/truncate.js"
72	
73	# Atomically rename a filesystem path.
74	def rename(old: String, new: String) -> IO(Result<&1, &1, U32 & String, Unit>):
75	  PackedFiles.rename(old, new)
76	
77	# Remove a file or empty directory.
78	def remove(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):
79	  PackedFiles.remove(path)
80	
81	# Return the number of entries available through the indexed directory API.
82	def read_dir_count(path: String) -> IO(Result<&1, &1, U32 & String, Nat>):
83	  import "./effs/read_dir.c"
84	  import "./effs/read_dir.js"
85	
86	# Fetch one directory entry by index.
87	def read_dir_at(path: String, idx: Nat) -> IO(Result<&1, &1, U32 & String, String>):
88	  import "./effs/read_dir.c"
89	  import "./effs/read_dir.js"
90	
91	# Create one directory.
92	def make_dir(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):
93	  import "./effs/make_dir.c"
94	  import "./effs/make_dir.js"
95	
96	# Set POSIX permission bits.
97	def chmod(path: String, bits: U32) -> IO(Result<&1, &1, U32 & String, Unit>):
98	  import "./effs/chmod.c"
99	  import "./effs/chmod.js"
100	
101	# Check whether a filesystem path exists.
102	def exists.result(result: Result<&1, &1, U32 & String, PackedFiles.Info>) -> Result<&1, &1, U32 & String, Bool>:
103	  match result:
104	    case Fail{(+code, message)}:
105	      Policy.missing_path_result(U32.is_eq(code, 2), code, message)
106	    case Done{_}:
107	      Done{True{}}
108	
109	# Returns whether a path exists and preserves other stat errors.
110	def exists(path: String) -> IO(Result<&1, &1, U32 & String, Bool>):
111	  do IO<Result<&1, &1, U32 & String, Bool>>:
112	    result : Result<&1, &1, U32 & String, PackedFiles.Info> <- PackedFiles.stat(path)
113	    return exists.result(result)
114	
115	# Read-only byte size for Bend-side accounting (no shell wc needed).
116	def file_size(path: String) -> IO(Result<&1, &1, U32 & String, Nat>):
117	  import "./effs/file_size.c"
118	  import "./effs/file_size.js"
119	
120	# Pure accumulator step (leaf: matches structurally, never recurses).
121	# Past-end fetches answer "" (SNil{}), which is skipped.
122	def grab_name(nm: String, acc: List<String>) -> List<String>:
123	  match nm:
124	    case SNil{}:
125	      acc
126	    case SCon{_, _}:
127	      Con{nm, acc}
128	
129	# Fuel-bounded sweep 0..count-1. Startup-only use (spec §10 below): the
130	# directory is stable during recovery, so count-then-fetch is exact.
131	def read_go(fuel: Nat, +path: String, +idx: Nat, acc: List<String>) -> IO(List<String>):
132	  match fuel:
133	    case 0n:
134	      IO.pure(List<String>, List.reverse(&1, String, acc))
135	    case 1n+f:
136	      do IO<List<String>>:
137	        nm : String <- IO.try(String, read_dir_at(path, idx))
138	        read_go(f, path, Nat.add(idx, 1n), grab_name(nm, acc))
139	
140	# List directory names using the bounded count-then-fetch host API.
141	def read_dir(+path: String) -> IO(Result<&1, &1, U32 & String, List<String>>):
142	  do IO<Result<&1, &1, U32 & String, List<String>>>:
143	    n : Nat <- IO.try(Nat, read_dir_count(path))
144	    names : List<String> <- read_go(Nat.add(n, 1n), path, 0n, Nil{})
145	    return Done{names}