1	# src/file: a file's text, read whole, or None when it cannot be opened.
2	import Base
3	
4	# the handle closed, and whatever was gathered
5	def 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
11	def 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
19	def 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
32	def 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
41	def 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	# the reads a file with no size to go by may take: a pipe, a device or a
51	# /proc file reports 0 bytes and a file past 4 GiB fails to report, so these
52	# are read until they end, up to 100000 reads of 64 KiB
53	def file.unsized() -> Nat:
54	  U32.to_nat(100000)
55	
56	# a size of 0 is no size to go by; any other is read to
57	def file.reads.given(none: Bool, bytes: U32) -> Nat:
58	  match none:
59	    case True{}:
60	      file.unsized()
61	    case False{}:
62	      U32.to_nat(U32.add(U32.div(bytes, 65536), 2))
63	
64	# the reads a file of this many bytes takes: one for every 64 KiB, one for
65	# the part past the last whole 64 KiB, and one to spare for a short read
66	def file.reads(+bytes: U32) -> Nat:
67	  file.reads.given(U32.is_zero(bytes), bytes)
68	
69	# the reads the size the host reported allows
70	def file.reads.of(res: Result<&1, &1, U32 & String, U32>) -> Nat:
71	  match res:
72	    case Fail{_e}:
73	      file.unsized()
74	    case Done{bytes}:
75	      file.reads(bytes)
76	
77	# a file read whole, with fuel enough for the size it reported
78	def file.read.sized(got: File & Result<&1, &1, U32 & String, U32>) -> IO(String):
79	  (file, res) = got
80	  file.slurp(file.reads.of(res), file, "")
81	
82	# what an opened file holds, or nothing when it would not open
83	def file.read.opened(res: Result<&1, &1, U32 & String, File>) -> IO(Maybe<&2, String>):
84	  match res:
85	    case Fail{_e}:
86	      IO.pure(Maybe<&2, String>, None{})
87	    case Done{file}:
88	      do IO<Maybe<&2, String>>:
89	        got : File & Result<&1, &1, U32 & String, U32> <- File.size(file)
90	        text : String <- file.read.sized(got)
91	        return Some{text}
92	
93	# a file's text, or None when it cannot be opened
94	def file.read(path: String) -> IO(Maybe<&2, String>):
95	  do IO<Maybe<&2, String>>:
96	    res : Result<&1, &1, U32 & String, File> <- File.open(path, "r")
97	    file.read.opened(res)
98	
99	# a file's text, or "" when there is none
100	def file.text_of(got: Maybe<&2, String>) -> String:
101	  match got:
102	    case None{}:
103	      ""
104	    case Some{s}:
105	      s