src/walk/disk.bend

bolt@1.25.0.0 · 81 lines · 0 definitions

1# walk/disk: an effect (CPU event loop only): the names directly in a
2# directory, whether a path is a directory, and the working directory
3# relative paths are named from. A name that is itself a directory ends in
4# "/"; "." and ".." are never in the list, and a directory that cannot be
5# opened lists as empty. Order is the file system's; the lint planner
6# (src/lint/plan.bend) sorts what it keeps.
7#
8# It is the real file system, through a foreign effect (dir.c, dir.js) that
9# lists one directory: its names, one a line, a directory's name ending in
10# "/"; one (cwd.c, cwd.js) that names the working directory; and Base's
11# File, which tells a directory from a file.
12#
13# Trusted, not proved: the listing effect returns a directory's entries,
14# marking directories with `/`, the OS tells the truth when `is_dir` asks
15# whether a path is a folder, and the file read returns a file's text. They
16# are foreign code, and the planner takes their answers as given.
17import Base
18
19# every name directly in the directory, one a line
20def walkdir.entries(dir: String) -> IO(String):
21  import "./dir.c"
22  import "./dir.js"
23
24# the named lines: the text ends in a newline, so the last line is empty
25def named(ls: List<&2, String>) -> List<&2, String>:
26  match ls:
27    case Nil{}:
28      Nil{}
29    case Con{+l, t}:
30      +more = named(t)
31      Bool.pick(List<&2, String>, String.is_empty(l), more, l <> more)
32
33# a directory's entries, a directory marked by a `/`
34def entries(dir: String) -> IO(List<&2, String>):  # noqa: L001 disk effect
35  do IO<List<&2, String>>:
36    text : String <- walkdir.entries(dir)
37    return named(String.lines(text))
38
39# whether a first read failed as a directory's does (EISDIR, 21, in C and
40# in node alike)
41def is_dir.code(rr: Result<&1, &1, U32 & String, List<&2, U32>>) -> Bool:
42  match rr:
43    case Fail{e}:
44      (code, _msg) = e
45      U32.is_eq(code, 21)
46    case Done{_bytes}:
47      False{}
48
49# the file closed, and what its first read said
50def is_dir.got(got: File & Result<&1, &1, U32 & String, List<&2, U32>>) -> IO(Bool):
51  (file, rr) = got
52  do IO<Bool>:
53    File.close(file)
54    return is_dir.code(rr)
55
56# a path that opened: read one byte and see; one that did not is no directory
57def is_dir.opened(rr: Result<&1, &1, U32 & String, File>) -> IO(Bool):
58  match rr:
59    case Fail{_e}:
60      IO.pure(Bool, False{})
61    case Done{file}:
62      do IO<Bool>:
63        got : File & Result<&1, &1, U32 & String, List<&2, U32>> <- File.read_bytes(file, 1)
64        is_dir.got(got)
65
66# whether a path is a directory: it opens, and reading it fails as a
67# directory's read does. Base's File has no stat, and a directory opens for
68# reading on both lanes.
69def is_dir(path: String) -> IO(Bool):  # noqa: L001 disk effect
70  do IO<Bool>:
71    r : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
72    is_dir.opened(r)
73
74# the working directory, from the root; "" when it cannot be named
75def walkdir.cwd() -> IO(String):
76  import "./cwd.c"
77  import "./cwd.js"
78
79# the working directory, from the root ("" when it cannot be named)
80def cwd() -> IO(String):  # noqa: L001 disk effect
81  walkdir.cwd()