From 0938ae44f669ea5241297fb26e5a72e8c7fd4820 Mon Sep 17 00:00:00 2001
From: Thomas Gazagnaire <thomas@gazagnaire.org>
Date: Tue, 4 Apr 2017 11:44:23 +0200
Subject: [PATCH] miragesdk: fail early on short read/write returning 0

Signed-off-by: Thomas Gazagnaire <thomas@gazagnaire.org>
---
 projects/miragesdk/src/sdk/IO.ml | 24 +++++++++++++++---------
 1 file changed, 15 insertions(+), 9 deletions(-)

diff --git a/projects/miragesdk/src/sdk/IO.ml b/projects/miragesdk/src/sdk/IO.ml
index a03189370..44c318344 100644
--- a/projects/miragesdk/src/sdk/IO.ml
+++ b/projects/miragesdk/src/sdk/IO.ml
@@ -9,7 +9,8 @@ let rec really_write fd buf off len =
   | len ->
     Log.debug (fun l -> l "really_write off=%d len=%d" off len);
     Lwt_unix.write fd buf off len >>= fun n ->
-    really_write fd buf (off+n) (len-n)
+    if n = 0 then Lwt.fail_with "write 0"
+    else really_write fd buf (off+n) (len-n)
 
 let write fd buf = really_write fd buf 0 (String.length buf)
 
@@ -19,7 +20,8 @@ let rec really_read fd buf off len =
   | len ->
     Log.debug (fun l -> l "really_read off=%d len=%d" off len);
     Lwt_unix.read fd buf off len >>= fun n ->
-    really_read fd buf (off+n) (len-n)
+    if n = 0 then Lwt.fail_with "read 0"
+    else really_read fd buf (off+n) (len-n)
 
 let read_all fd =
   Log.debug (fun l -> l "read_all");
@@ -27,9 +29,11 @@ let read_all fd =
   let buf = Bytes.create len in
   let rec loop acc =
     Lwt_unix.read fd buf 0 len >>= fun n ->
-    let acc = String.sub buf 0 n :: acc in
-    if n <= len then Lwt.return (List.rev acc)
-    else loop acc
+    if n = 0 then Lwt.fail_with "read 0"
+    else
+      let acc = String.sub buf 0 n :: acc in
+      if n <= len then Lwt.return (List.rev acc)
+      else loop acc
   in
   loop [] >|= fun bufs ->
   String.concat "" bufs
@@ -39,10 +43,12 @@ let read_n fd len =
   let buf = Bytes.create len in
   let rec loop acc len =
     Lwt_unix.read fd buf 0 len >>= fun n ->
-    let acc = String.sub buf 0 n :: acc in
-    match len - n with
-    | 0 -> Lwt.return (List.rev acc)
-    | r -> loop acc r
+    if n = 0 then Lwt.fail_with "read 0"
+    else
+      let acc = String.sub buf 0 n :: acc in
+      match len - n with
+      | 0 -> Lwt.return (List.rev acc)
+      | r -> loop acc r
   in
   loop [] len >|= fun bufs ->
   String.concat "" bufs