src/Fs.bend source

src/Fs.bend on the hub · documented module

import Baseimport bend-kit-bytes@0.3.2.0/bytes.bend as StorageBytesimport 0x6c54b2522c2258baf6f58d2b970c3902/files.bend as PackedFiles# Audited host effects (spec §3.3). Thin syscall wrappers with .c + .js# twins and matching intended semantics. No laws — validated empirically.# Read at most 1 MiB as packed words. Short reads are valid progress; zero is EOF.def read_words(  file: File,  max: U32) ->  IO(File & Result<&1, &1, U32 & String, U32 & Array<U32>>):  PackedFiles.read.words(file, max)# Write all bytes from a packed word array, retaining the file handle on errors.def write_words(  file: File,  len: U32,  words: Array<U32>) ->  IO(File & Result<&1, &1, U32 & String, Unit>):  PackedFiles.write.words(file, len, words)def read_bytes.wrap(  result: Result<&1, &1, U32 & String, U32 & Array<U32>>) ->  Result<&1, &1, U32 & String, StorageBytes.Bytes>:  match result:    case Fail{err}:      Fail{err}    case Done{(len, words)}:      Done{StorageBytes.Bytes{len, words}}def read_bytes.pair(  pair: File & Result<&1, &1, U32 & String, U32 & Array<U32>>) ->  File & Result<&1, &1, U32 & String, StorageBytes.Bytes>:  match pair:    case (handle, result):      (handle, read_bytes.wrap(result))# Read one bounded packed chunk; nonempty short reads are not EOF.def read_bytes(  file: File,  max: U32) ->  IO(File & Result<&1, &1, U32 & String, StorageBytes.Bytes>):  do IO<File & Result<&1, &1, U32 & String, StorageBytes.Bytes>>:    pair : File & Result<&1, &1, U32 & String, U32 & Array<U32>> <- read_words(file, max)    return read_bytes.pair(pair)# Write the significant bytes of a packed buffer through the pinned host effect.def write_bytes(  file: File,  bytes: StorageBytes.Bytes) ->  IO(File & Result<&1, &1, U32 & String, Unit>):  StorageBytes.Bytes{len, buf} = bytes  write_words(file, len, buf)# Sync file contents to stable storage.def fsync(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/fsync.c"  import "./effs/fsync.js"# Handle truncate in the filesystem effects.def truncate(path: String, offset: Nat) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/truncate.c"  import "./effs/truncate.js"# Atomically rename a filesystem path.def rename(old: String, new: String) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/rename.c"  import "./effs/rename.js"# Remove a file or empty directory.def remove(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/remove.c"  import "./effs/remove.js"# Return the number of entries available through the indexed directory API.def read_dir_count(path: String) -> IO(Result<&1, &1, U32 & String, Nat>):  import "./effs/read_dir.c"  import "./effs/read_dir.js"# Fetch one directory entry by index.def read_dir_at(path: String, idx: Nat) -> IO(Result<&1, &1, U32 & String, String>):  import "./effs/read_dir.c"  import "./effs/read_dir.js"# Create one directory.def make_dir(path: String) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/make_dir.c"  import "./effs/make_dir.js"# Set POSIX permission bits.def chmod(path: String, bits: U32) -> IO(Result<&1, &1, U32 & String, Unit>):  import "./effs/chmod.c"  import "./effs/chmod.js"# Check whether a filesystem path exists.def exists(path: String) -> IO(Result<&1, &1, U32 & String, Bool>):  import "./effs/exists.c"  import "./effs/exists.js"# Read-only byte size for Bend-side accounting (no shell wc needed).def file_size(path: String) -> IO(Result<&1, &1, U32 & String, Nat>):  import "./effs/file_size.c"  import "./effs/file_size.js"# Pure accumulator step (leaf: matches structurally, never recurses).# Past-end fetches answer "" (SNil{}), which is skipped.def grab_name(nm: String, acc: List<String>) -> List<String>:  match nm:    case SNil{}:      acc    case SCon{_, _}:      Con{nm, acc}# Fuel-bounded sweep 0..count-1. Startup-only use (spec §10 below): the# directory is stable during recovery, so count-then-fetch is exact.def read_go(fuel: Nat, +path: String, +idx: Nat, acc: List<String>) -> IO(List<String>):  match fuel:    case 0n:      IO.pure(List<String>, List.reverse(&1, String, acc))    case 1n+f:      do IO<List<String>>:        nm : String <- IO.try(String, read_dir_at(path, idx))        read_go(f, path, Nat.add(idx, 1n), grab_name(nm, acc))# List directory names using the bounded count-then-fetch host API.def read_dir(+path: String) -> IO(Result<&1, &1, U32 & String, List<String>>):  do IO<Result<&1, &1, U32 & String, List<String>>>:    n : Nat <- IO.try(Nat, read_dir_count(path))    names : List<String> <- read_go(Nat.add(n, 1n), path, 0n, Nil{})    return Done{names}