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.
3	import Base
4	
5	# the handle closed, and whatever was gathered
6	def 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
12	def 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
20	def 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
33	def 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
42	def 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
54	def unsized() -> Nat:
55	  U32.to_nat(100000)
56	
57	# a size of 0 is no size to go by; any other is read to
58	def 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
67	def reads(+bytes: U32) -> Nat:
68	  reads.given(U32.is_zero(bytes), bytes)
69	
70	# the reads the size the host reported allows
71	def 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
79	def 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
84	def 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
95	def 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
101	def 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
109	def 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
116	def 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
126	def 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
132	def text_of(got: Maybe<&2, String>) -> String:
133	  match got:
134	    case None{}:
135	      ""
136	    case Some{s}:
137	      s