Some buffer updates

Initialising buffers from files, error checking on creation, resizing.

libs/base/Data/Buffer.idr

@@ -7,20 +7,23 @@ data Buffer : Type where
      MkBuffer : AnyPtr -> (size : Int) -> (loc : Int) -> Buffer
 
 export
-newBuffer : Int -> IO Buffer
+rawSize : Buffer -> IO Int
+rawSize (MkBuffer buf _ _)
+    = schemeCall Int "blodwen-buffer-size" [buf]
+
+export
+newBuffer : Int -> IO (Maybe Buffer)
 newBuffer size
     = do buf <- schemeCall AnyPtr "blodwen-new-buffer" [size]
-         pure (MkBuffer buf size 0)
+         sz <- schemeCall Int "blodwen-buffer-size" [buf]
+         if sz == 0
+            then pure Nothing
+            else pure $ Just $ MkBuffer buf size 0
 
 export
 resetBuffer : Buffer -> Buffer
 resetBuffer (MkBuffer ptr s l) = MkBuffer ptr s 0
 
-export
-rawSize : Buffer -> IO Int
-rawSize (MkBuffer buf _ _)
-    = schemeCall Int "blodwen-buffer-size" [buf]
-
 export
 size : Buffer -> Int
 size (MkBuffer _ s _) = s
@@ -93,11 +96,22 @@ export
 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]
+    = do read <- schemeCall Int "blodwen-readbuffer-bytes" [h, buf, loc, max]
          if read >= 0
             then pure (Right (MkBuffer buf size (loc + read)))
             else pure (Left FileReadError)
 
+-- Create a new buffer by reading all the contents from the given file
+-- Fails if no bytes can be read or buffer can't be created
+export
+createBufferFromFile : BinaryFile -> IO (Either FileError Buffer)
+createBufferFromFile (FHandle h)
+    = do buf <- schemeCall AnyPtr "blodwen-readbuffer" [h]
+         sz <- schemeCall Int "blodwen-buffer-size" [buf]
+         if sz >= 0
+            then pure (Right (MkBuffer buf sz sz))
+            else pure (Left FileReadError)
+
 export
 writeBufferToFile : BinaryFile -> Buffer -> (maxbytes : Int) ->
                     IO (Either FileError Buffer)
@@ -108,3 +122,15 @@ writeBufferToFile (FHandle h) (MkBuffer buf size loc) max
          if written == max'
             then pure (Right (MkBuffer buf size (loc + max')))
             else pure (Left FileWriteError)
+
+export
+resizeBuffer : Buffer -> Int -> IO (Maybe Buffer)
+resizeBuffer old newsize
+    = do Just buf <- newBuffer newsize
+              | Nothing => pure Nothing
+         -- If the new buffer is smaller than the old one, just copy what
+         -- fits
+         let oldsize = size old
+         let len = if newsize < oldsize then newsize else oldsize
+         copyData old 0 len buf 0
+         pure (Just buf)

support/chez/support.ss

@@ -93,10 +93,14 @@
 (define (blodwen-buffer-copydata buf start len dest loc)
   (bytevector-copy! buf start dest loc len))
 
-(define (blodwen-readbuffer h buf loc max)
+(define (blodwen-readbuffer-bytes h buf loc max)
   (guard (x (#t -1))
     (get-bytevector-n! h buf loc max)))
 
+(define (blodwen-readbuffer h)
+  (guard (x (#t (bytevector)))
+    (get-bytevector-all h)))
+
 (define (blodwen-writebuffer h buf loc max)
   (guard (x (#t -1))
      (put-bytevector h buf loc max)
@@ -152,6 +156,9 @@
             (string-append str "\n"))
         ""))
 
+(define (blodwen-file-size p)
+    (port-length p))
+
 (define (blodwen-eof p)
     (if (port-eof? p)
         1

support/racket/support.rkt

@@ -11,7 +11,7 @@
 (define blodwen-shl (lambda (x y) (arithmetic-shift x y)))
 (define blodwen-shr (lambda (x y) (arithmetic-shift x (- y))))
 (define blodwen-and (lambda (x y) (bitwise-and x y)))
-(define blodwen-or (lambda (x y) (bitwise-or x y)))
+(define blodwen-or (lambda (x y) (bitwise-ior x y)))
 (define blodwen-xor (lambda (x y) (bitwise-xor x y)))
 
 (define cast-num 
@@ -93,11 +93,16 @@
 (define (blodwen-buffer-copydata buf start len dest loc)
   (bytevector-copy! buf start dest loc len))
 
-(define (blodwen-readbuffer h buf loc max)
+(define (blodwen-readbuffer-bytes h buf loc max)
   (with-handlers
     ([(lambda (x) #t) (lambda (exn) -1)])
     (get-bytevector-n! h buf loc max)))
 
+(define (blodwen-readbuffer h)
+  (with-handlers
+    ([(lambda (x) #t) (lambda (exn) (make-bytevector 0))])
+    (get-bytevector-all h)))
+
 (define (blodwen-writebuffer h buf loc max)
   (with-handlers
     ([(lambda (x) #t) (lambda (exn) -1)])

tests/chez/chez004/Buffer.idr

@@ -3,7 +3,8 @@ import System.File
 
 main : IO ()
 main
-    = do buf <- newBuffer 100
+    = do Just buf <- newBuffer 100
+              | Nothing => putStrLn "Buffer creation failed"
          s <- rawSize buf
          printLn s
 
@@ -34,8 +35,7 @@ main
 
          Right f <- openBinaryFile "test.buf" Read
              | Left err => putStrLn "File error on read"
-         buf2 <- newBuffer 100
-         Right _ <- readBufferFromFile f buf2 100
+         Right buf2 <- createBufferFromFile f
              | Left err => do putStrLn "Buffer read fail"
                               closeFile f
          closeFile f
@@ -45,7 +45,8 @@ main
 
          Right f <- openBinaryFile "test.buf" Read
              | Left err => putStrLn "File error on read"
-         buf3 <- newBuffer 99
+         Just buf3 <- newBuffer 99
+              | Nothing => putStrLn "Buffer creation failed"
          Right _ <- readBufferFromFile f buf3 100
              | Left err => do putStrLn "Buffer read fail"
                               closeFile f