src/io/file.bend source

src/io/file.bend on the hub · documented module

# io/file: a whole file read or written in one call. Base gives an open handle# and chunked reads; this is the loop over them.import Base# the handle closed, and whatever was gathereddef slurp.end(file: File, acc: String) -> IO(String):  do IO<String>:    File.close(file)    return acc# an empty chunk means the end of the filedef slurp.cut(chunk: String, file: File, acc: String, rest: File -> String -> IO(String)) -> IO(String):  match chunk:    case SNil{}:      slurp.end(file, acc)    case SCon{c, t}:      rest(file, acc ++ SCon{c, t})# a failed read ends the file as surely as an empty onedef slurp.more(  res: Result<&1, &1, U32 & String, String>,  file: File,  acc: String,  rest: File -> String -> IO(String)) -> IO(String):  match res:    case Fail{_e}:      slurp.end(file, acc)    case Done{chunk}:      slurp.cut(chunk, file, acc, rest)# the handle comes back paired with what it readdef slurp.next(  got: File & Result<&1, &1, U32 & String, String>,  acc: String,  rest: File -> String -> IO(String)) -> IO(String):  (file, r) = got  slurp.more(r, file, acc, rest)# the whole file, read in chunks until one is empty, or the fuel isdef slurp(fuel: Nat, file: File, acc: String) -> IO(String):  match fuel:    case 0n:      slurp.end(file, acc)    case 1n+f:      do IO<String>:        got : File & Result<&1, &1, U32 & String, String> <- File.read(file, 65536)        slurp.next(got, acc, fl => a => slurp(f, fl, a))# what an opened file holds, or nothing when it would not opendef read.opened(res: Result<&1, &1, U32 & String, File>) -> IO(Maybe<&2, String>):  match res:    case Fail{_e}:      IO.pure(Maybe<&2, String>, None{})    case Done{file}:      do IO<Maybe<&2, String>>:        text : String <- slurp(U32.to_nat(100000), file, "")        return Some{text}# a file's text, or None when it cannot be openeddef read(path: String) -> IO(Maybe<&2, String>):  do IO<Maybe<&2, String>>:    r : Result<&1, &1, U32 & String, File> <- File.open(path, "r")    read.opened(r)# whether a write reported successdef write.ok(res: Result<&1, &1, U32 & String, Unit>) -> Bool:  match res:    case Fail{_e}:      False{}    case Done{_u}:      True{}# a write's outcome, once the handle is shutdef write.done(written: File & Result<&1, &1, U32 & String, Unit>) -> IO(Bool):  (file, r) = written  do IO<Bool>:    File.close(file)    return write.ok(r)# the text written to an opened filedef write.opened(res: Result<&1, &1, U32 & String, File>, text: String) -> IO(Bool):  match res:    case Fail{_e}:      IO.pure(Bool, False{})    case Done{file}:      do IO<Bool>:        w : File & Result<&1, &1, U32 & String, Unit> <- File.write(file, text)        write.done(w)# a file replaced with this text; False when it could not be writtendef write(path: String, text: String) -> IO(Bool):  do IO<Bool>:    r : Result<&1, &1, U32 & String, File> <- File.open(path, "w")    write.opened(r, text)# a file's text, or "" when there is nonedef text_of(got: Maybe<&2, String>) -> String:  match got:    case None{}:      ""    case Some{s}:      s