src/file.bend
snap@1.1.0.0 · 72 lines · 0 definitions
1# src/file: a file's text, read whole, or None when it cannot be opened.
2import Base
3
4# the handle closed, and whatever was gathered
5def file.slurp.end(file: File, acc: String) -> IO(String):
6 do IO<String>:
7 File.close(file)
8 return acc
9
10# an empty chunk means the end of the file
11def file.slurp.cut(chunk: String, file: File, acc: String, rest: File -> String -> IO(String)) -> IO(String):
12 match chunk:
13 case SNil{}:
14 file.slurp.end(file, acc)
15 case SCon{c, t}:
16 rest(file, acc ++ SCon{c, t})
17
18# a failed read ends the file as surely as an empty one
19def file.slurp.more(
20 res: Result<&1, &1, U32 & String, String>,
21 file: File,
22 acc: String,
23 rest: File -> String -> IO(String)
24) -> IO(String):
25 match res:
26 case Fail{_e}:
27 file.slurp.end(file, acc)
28 case Done{chunk}:
29 file.slurp.cut(chunk, file, acc, rest)
30
31# the handle comes back paired with what it read
32def file.slurp.next(
33 got: File & Result<&1, &1, U32 & String, String>,
34 acc: String,
35 rest: File -> String -> IO(String)
36) -> IO(String):
37 (file, res) = got
38 file.slurp.more(res, file, acc, rest)
39
40# the whole file, read in chunks until one is empty, or the fuel is
41def file.slurp(fuel: Nat, file: File, acc: String) -> IO(String):
42 match fuel:
43 case 0n:
44 file.slurp.end(file, acc)
45 case 1n+f:
46 do IO<String>:
47 got : File & Result<&1, &1, U32 & String, String> <- File.read(file, 65536)
48 file.slurp.next(got, acc, fl => a => file.slurp(f, fl, a))
49
50# what an opened file holds, or nothing when it would not open
51def file.read.opened(res: Result<&1, &1, U32 & String, File>) -> IO(Maybe<&2, String>):
52 match res:
53 case Fail{_e}:
54 IO.pure(Maybe<&2, String>, None{})
55 case Done{file}:
56 do IO<Maybe<&2, String>>:
57 text : String <- file.slurp(U32.to_nat(100000), file, "")
58 return Some{text}
59
60# a file's text, or None when it cannot be opened
61def file.read(path: String) -> IO(Maybe<&2, String>):
62 do IO<Maybe<&2, String>>:
63 res : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
64 file.read.opened(res)
65
66# a file's text, or "" when there is none
67def file.text_of(got: Maybe<&2, String>) -> String:
68 match got:
69 case None{}:
70 ""
71 case Some{s}:
72 s