blkdev: make load command stop and the end of the stream

This allows us to reliably and easily load a file until the end of it.

kernel/blockdev.asm

@@ -146,16 +146,6 @@ blkGetC:
 	ld	ix, (BLOCKDEV_GETC)
 	jr	_blkCall
 
-; Repeatedly call blkGetC until the call is a success.
-blkGetCW:
-	ld	ix, (BLOCKDEV_GETC)
-.loop:
-	push	ix		; fs messes with IX a lot
-	call	callIX
-	pop	ix
-	jr	nz, .loop
-	ret
-
 ; Reads B chars from blkGetC and copy them in (HL).
 ; Sets Z if successful, unset Z if there was an error.
 blkRead:

kernel/blockdev_cmds.asm

@@ -45,9 +45,11 @@ blkSeekCmd:
 	ret
 
 ; Load the specified number of bytes (max 0xff) from IO and write them in the
-; current memory pointer (which doesn't change). This gets chars from
+; current memory pointer (which doesn't change). If the blkdev hits end of
-; blkGetCW.
+; stream before we reach our specified number of bytes, we stop loading.
-; Control is returned to the shell only after all bytes are read.
+;
+; Returns a SHELL_ERR_IO_ERROR only if we couldn't read any byte (if the first
+; call to GetC failed)
 ;
 ; Example: load 42
 blkLoadCmd:
@@ -59,11 +61,15 @@ blkLoad:
 	ld	a, (hl)
 	ld	b, a
 	ld	hl, (SHELL_MEM_PTR)
-.loop:  call	blkGetCW
+	call	blkGetC
 	jr	nz, .ioError
+.loop:
 	ld	(hl), a
 	inc	hl
+	call	blkGetC
+	jr	nz, .loopend
 	djnz	.loop
+.loopend:
 	; success
 	xor	a
 	jr	.end