kern/cbuf: new cbuf_range_valid function

2 files changed, 12 insertions, 5 deletions

diff --git a/kern/cbuf.c b/kern/cbuf.c
index cd8ee87d..f00532ef 100644
--- a/kern/cbuf.c
+++ b/kern/cbuf.c
@@ -78,13 +78,13 @@ cbuf_write(struct cbuf *cbuf, size_t index, const void *buf, size_t size)
     char *start, *end, *buf_end;
     size_t new_end, skip;
 
-    if ((cbuf->end - index) > cbuf_size(cbuf)) {
+    if (!cbuf_range_valid(cbuf, index, cbuf->end)) {
         return ERROR_INVAL;
     }
 
     new_end = index + size;
 
-    if ((new_end - cbuf->start) > cbuf_size(cbuf)) {
+    if (!cbuf_range_valid(cbuf, cbuf->start, new_end)) {
         cbuf->end = new_end;
 
         if (size > cbuf_capacity(cbuf)) {
@@ -118,13 +118,13 @@ cbuf_read(const struct cbuf *cbuf, size_t index, void *buf, size_t *sizep)
     const char *start, *end, *buf_end;
     size_t size;
 
-    size = cbuf->end - index;
-
     /* At least one byte must be available */
-    if ((size - 1) >= cbuf_size(cbuf)) {
+    if (!cbuf_range_valid(cbuf, index, index + 1)) {
         return ERROR_INVAL;
     }
 
+    size = cbuf->end - index;
+
     if (*sizep > size) {
         *sizep = size;
     }
diff --git a/kern/cbuf.h b/kern/cbuf.h
index 0558cc09..a30e5f28 100644
--- a/kern/cbuf.h
+++ b/kern/cbuf.h
@@ -21,6 +21,7 @@
 #ifndef _KERN_CBUF_H
 #define _KERN_CBUF_H
 
+#include <stdbool.h>
 #include <stddef.h>
 
 /*
@@ -66,6 +67,12 @@ cbuf_clear(struct cbuf *cbuf)
     cbuf->start = cbuf->end;
 }
 
+static inline bool
+cbuf_range_valid(const struct cbuf *cbuf, size_t start, size_t end)
+{
+    return ((end - start) <= cbuf_size(cbuf));
+}
+
 /*
  * Initialize a circular buffer.
  *