From 5bd7fc86c307756b0969cfeafa70c8aef41ad63b Mon Sep 17 00:00:00 2001
From: Frank Freihube <frank.freihube@rmcan.com>
Date: Fri, 29 Apr 2016 07:56:35 +0200
Subject: [PATCH] make changes configurable through io_semantics()

---
 core/cfs/cfs-coffee.c | 15 +++++++++++++--
 core/cfs/cfs-coffee.h |  9 +++++++++
 2 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/core/cfs/cfs-coffee.c b/core/cfs/cfs-coffee.c
index 07df6121b..d4d988ae8 100644
--- a/core/cfs/cfs-coffee.c
+++ b/core/cfs/cfs-coffee.c
@@ -1098,9 +1098,20 @@ cfs_read(int fd, void *buf, unsigned size)
 
   fdp = &coffee_fd_set[fd];
   file = fdp->file;
-  while(fdp->offset + size > file->end) {
-    ((char*)buf)[--size] = 0;
+  
+#if COFFEE_IO_SEMANTICS
+  if(fdp->io_flags & CFS_COFFEE_IO_FIRM_SIZE) {
+    while(fdp->offset + size > file->end) {
+      ((char*)buf)[--size] = 0;
+    }
+  } else {
+#endif
+    if(fdp->offset + size > file->end) {
+      size = file->end - fdp->offset;
+    }
+#if COFFEE_IO_SEMANTICS
   }
+#endif
 
   /* If the file is not modified, read directly from the file extent. */
   if(!FILE_MODIFIED(file)) {
diff --git a/core/cfs/cfs-coffee.h b/core/cfs/cfs-coffee.h
index 2c62f2512..96d382980 100644
--- a/core/cfs/cfs-coffee.h
+++ b/core/cfs/cfs-coffee.h
@@ -63,6 +63,15 @@
  */
 #define CFS_COFFEE_IO_FIRM_SIZE		0x2
 
+/**
+ * Instruct Coffee to set unused bytes in the destination buffer to zero.
+ * Trailing zeros may cause a wrong file size, this option ensures that
+ * the corresponding bytes get set, so Coffee does not read unexpected data.
+ *
+ * \sa cfs_coffee_set_io_semantics()
+ */
+#define CFS_COFFEE_IO_ENSURE_READ_LENGTH		0x4
+
 /**
  * \file
  *	Header for the Coffee file system.