src/io/file.bend
ezx@1.5.0.0 · 137 lines · 0 definitions
1# io/file: a whole file read or written in one call. Base gives an open handle
2# and chunked reads; this is the loop over them.
3import Base
4
5# the handle closed, and whatever was gathered
6def slurp.end(file: File, acc: String) -> IO(String):
7 do IO<String>:
8 File.close(file)
9 return acc
10
11# an empty chunk means the end of the file
12def slurp.cut(chunk: String, file: File, acc: String, rest: File -> String -> IO(String)) -> IO(String):
13 match chunk:
14 case SNil{}:
15 slurp.end(file, acc)
16 case SCon{c, t}:
17 rest(file, acc ++ SCon{c, t})
18
19# a failed read ends the file as surely as an empty one
20def slurp.more(
21 res: Result<&1, &1, U32 & String, String>,
22 file: File,
23 acc: String,
24 rest: File -> String -> IO(String)
25) -> IO(String):
26 match res:
27 case Fail{_e}:
28 slurp.end(file, acc)
29 case Done{chunk}:
30 slurp.cut(chunk, file, acc, rest)
31
32# the handle comes back paired with what it read
33def slurp.next(
34 got: File & Result<&1, &1, U32 & String, String>,
35 acc: String,
36 rest: File -> String -> IO(String)
37) -> IO(String):
38 (file, r) = got
39 slurp.more(r, file, acc, rest)
40
41# the whole file, read in chunks until one is empty, or the fuel is
42def slurp(fuel: Nat, file: File, acc: String) -> IO(String):
43 match fuel:
44 case 0n:
45 slurp.end(file, acc)
46 case 1n+f:
47 do IO<String>:
48 got : File & Result<&1, &1, U32 & String, String> <- File.read(file, 65536)
49 slurp.next(got, acc, fl => a => slurp(f, fl, a))
50
51# the reads a file with no size to go by may take: a pipe, a device or a
52# /proc file reports 0 bytes and a file past 4 GiB fails to report, so these
53# are read until they end, up to 100000 reads of 64 KiB, past any file ez reads
54def unsized() -> Nat:
55 U32.to_nat(100000)
56
57# a size of 0 is no size to go by; any other is read to
58def reads.given(none: Bool, bytes: U32) -> Nat:
59 match none:
60 case True{}:
61 unsized()
62 case False{}:
63 U32.to_nat(U32.add(U32.div(bytes, 65536), 2))
64
65# the reads a file of this many bytes takes: one for every 64 KiB, one for
66# the part past the last whole 64 KiB, and one to spare for a short read
67def reads(+bytes: U32) -> Nat:
68 reads.given(U32.is_zero(bytes), bytes)
69
70# the reads the size the host reported allows
71def reads.of(res: Result<&1, &1, U32 & String, U32>) -> Nat:
72 match res:
73 case Fail{_e}:
74 unsized()
75 case Done{bytes}:
76 reads(bytes)
77
78# a file read whole, with fuel enough for the size it reported
79def read.sized(got: File & Result<&1, &1, U32 & String, U32>) -> IO(String):
80 (file, r) = got
81 slurp(reads.of(r), file, "")
82
83# what an opened file holds, or nothing when it would not open
84def read.opened(res: Result<&1, &1, U32 & String, File>) -> IO(Maybe<&2, String>):
85 match res:
86 case Fail{_e}:
87 IO.pure(Maybe<&2, String>, None{})
88 case Done{file}:
89 do IO<Maybe<&2, String>>:
90 got : File & Result<&1, &1, U32 & String, U32> <- File.size(file)
91 text : String <- read.sized(got)
92 return Some{text}
93
94# a file's text, or None when it cannot be opened
95def read(path: String) -> IO(Maybe<&2, String>):
96 do IO<Maybe<&2, String>>:
97 r : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
98 read.opened(r)
99
100# whether a write reported success
101def write.ok(res: Result<&1, &1, U32 & String, Unit>) -> Bool:
102 match res:
103 case Fail{_e}:
104 False{}
105 case Done{_u}:
106 True{}
107
108# a write's outcome, once the handle is shut
109def write.done(written: File & Result<&1, &1, U32 & String, Unit>) -> IO(Bool):
110 (file, r) = written
111 do IO<Bool>:
112 File.close(file)
113 return write.ok(r)
114
115# the text written to an opened file
116def write.opened(res: Result<&1, &1, U32 & String, File>, text: String) -> IO(Bool):
117 match res:
118 case Fail{_e}:
119 IO.pure(Bool, False{})
120 case Done{file}:
121 do IO<Bool>:
122 w : File & Result<&1, &1, U32 & String, Unit> <- File.write(file, text)
123 write.done(w)
124
125# a file replaced with this text; False when it could not be written
126def write(path: String, text: String) -> IO(Bool):
127 do IO<Bool>:
128 r : Result<&1, &1, U32 & String, File> <- File.open(path, "w")
129 write.opened(r, text)
130
131# a file's text, or "" when there is none
132def text_of(got: Maybe<&2, String>) -> String:
133 match got:
134 case None{}:
135 ""
136 case Some{s}:
137 s