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Reading/writing buffers can fail

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So, make them return and Either and wrap the scheme definitions in an
exception handler that returns an error code on failure
This commit is contained in:
Edwin Brady 2019-09-28 18:33:46 +01:00
parent bf69b89b0d
commit 78e44a4353
5 changed files with 39 additions and 11 deletions
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16
libs/base/Data/Buffer.idr
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@ -75,15 +75,21 @@ bufferData buf
unpackTo (val :: acc) (loc - 1)
export
readBufferFromFile : BinaryFile -> Buffer -> (maxbytes : Int) -> IO Buffer
readBufferFromFile : BinaryFile -> Buffer -> (maxbytes : Int) ->
IO (Either FileError Buffer)
readBufferFromFile (FHandle h) (MkBuffer buf size loc) max
= do read <- schemeCall Int "blodwen-readbuffer" [h, buf, loc, max]
pure (MkBuffer buf size (loc + read))
if read >= 0
then pure (Right (MkBuffer buf size (loc + read)))
else pure (Left FileReadError)
export
writeBufferToFile : BinaryFile -> Buffer -> (maxbytes : Int) -> IO Buffer
writeBufferToFile : BinaryFile -> Buffer -> (maxbytes : Int) ->
IO (Either FileError Buffer)
writeBufferToFile (FHandle h) (MkBuffer buf size loc) max
= do let maxwrite = size - loc
let max' = if maxwrite < max then maxwrite else max
schemeCall () "blodwen-writebuffer" [h, buf, loc, max']
pure (MkBuffer buf size (loc + max'))
written <- schemeCall Int "blodwen-writebuffer" [h, buf, loc, max']
if written == max'
then pure (Right (MkBuffer buf size (loc + max')))
else pure (Left FileWriteError)

7
support/chez/support.ss
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@ -85,10 +85,13 @@
(utf8->string newvec)))
(define (blodwen-readbuffer h buf loc max)
(get-bytevector-n! h buf loc max))
(guard (x (#t -1))
(get-bytevector-n! h buf loc max)))
(define (blodwen-writebuffer h buf loc max)
(put-bytevector h buf loc max))
(guard (x (#t -1))
(put-bytevector h buf loc max)
max))
;; Files: Much of the following adapted from idris-chez, thanks to Niklas
;; Larsson

8
support/racket/support.rkt
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@ -85,10 +85,14 @@
(utf8->string newvec)))
(define (blodwen-readbuffer h buf loc max)
(get-bytevector-n! h buf loc max))
(with-handlers
([(lambda (x) #t) (lambda (exn) -1)])
(get-bytevector-n! h buf loc max)))
(define (blodwen-writebuffer h buf loc max)
(put-bytevector h buf loc max))
(with-handlers
([(lambda (x) #t) (lambda (exn) -1)])
(put-bytevector h buf loc max)))
;; Files : Much of the following adapted from idris-chez, thanks to Niklas
;; Larsson

18
tests/chez/chez004/Buffer.idr
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@ -27,13 +27,27 @@ main
Right f <- openBinaryFile "test.buf" WriteTruncate
| Left err => putStrLn "File error on write"
writeBufferToFile f buf 100
Right _ <- writeBufferToFile f buf 100
| Left err => do putStrLn "Buffer write fail"
closeFile f
closeFile f
Right f <- openBinaryFile "test.buf" Read
| Left err => putStrLn "File error on read"
buf2 <- newBuffer 100
readBufferFromFile f buf2 100
Right _ <- readBufferFromFile f buf2 100
| Left err => do putStrLn "Buffer read fail"
closeFile f
closeFile f
ds <- bufferData buf2
printLn ds
Right f <- openBinaryFile "test.buf" Read
| Left err => putStrLn "File error on read"
buf3 <- newBuffer 99
Right _ <- readBufferFromFile f buf3 100
| Left err => do putStrLn "Buffer read fail"
closeFile f
closeFile f

1
tests/chez/chez004/expected
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@ -5,5 +5,6 @@
"there!"
[0, 94, 0, 0, 0, 0, 0, 0, 0, 0, 123, 20, 174, 71, 225, 154, 87, 64, 0, 0, 72, 101, 108, 108, 111, 32, 116, 104, 101, 114, 101, 33, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
[0, 94, 0, 0, 0, 0, 0, 0, 0, 0, 123, 20, 174, 71, 225, 154, 87, 64, 0, 0, 72, 101, 108, 108, 111, 32, 116, 104, 101, 114, 101, 33, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]
Buffer read fail
1/1: Building Buffer (Buffer.idr)
Main> Main> Bye for now!