add misc/bsize.h

misc/bsize.h

@@ -0,0 +1,124 @@
+/**
+ * @file bsize.h
+ * @author Ambroz Bizjak <ambrop7@gmail.com>
+ * 
+ * @section LICENSE
+ * 
+ * This file is part of BadVPN.
+ * 
+ * BadVPN is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation.
+ * 
+ * BadVPN is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ * 
+ * @section DESCRIPTION
+ * 
+ * Arithmetic with overflow detection.
+ */
+
+#ifndef BADVPN_MISC_BSIZE_H
+#define BADVPN_MISC_BSIZE_H
+
+#include <stddef.h>
+#include <limits.h>
+
+typedef struct {
+    int is_overflow;
+    size_t value;
+} bsize_t;
+
+static bsize_t bsize_fromsize (size_t v);
+static bsize_t bsize_fromint (int v);
+static int bsize_tosize (bsize_t s, size_t *out);
+static int bsize_toint (bsize_t s, int *out);
+static bsize_t bsize_add (bsize_t s1, bsize_t s2);
+static bsize_t bsize_max (bsize_t s1, bsize_t s2);
+
+bsize_t bsize_fromsize (size_t v)
+{
+    bsize_t s;
+    s.is_overflow = 0;
+    s.value = v;
+    return s;
+}
+
+bsize_t bsize_fromint (int v)
+{
+    bsize_t s;
+    
+    if (v < 0 || v > SIZE_MAX) {
+        s.is_overflow = 1;
+    } else {
+        s.is_overflow = 0;
+        s.value = v;
+    }
+    
+    return s;
+}
+
+int bsize_tosize (bsize_t s, size_t *out)
+{
+    if (s.is_overflow) {
+        return 0;
+    }
+    
+    if (out) {
+        *out = s.value;
+    }
+    
+    return 1;
+}
+
+int bsize_toint (bsize_t s, int *out)
+{
+    if (s.is_overflow || s.value > INT_MAX) {
+        return 0;
+    }
+    
+    if (out) {
+        *out = s.value;
+    }
+    
+    return 1;
+}
+
+bsize_t bsize_add (bsize_t s1, bsize_t s2)
+{
+    bsize_t s;
+    
+    if (s1.is_overflow || s2.is_overflow || s2.value > SIZE_MAX - s1.value) {
+        s.is_overflow = 1;
+    } else {
+        s.is_overflow = 0;
+        s.value = s1.value + s2.value;
+    }
+    
+    return s;
+}
+
+bsize_t bsize_max (bsize_t s1, bsize_t s2)
+{
+    bsize_t s;
+    
+    if (s1.is_overflow || s2.is_overflow) {
+        s.is_overflow = 1;
+    } else {
+        s.is_overflow = 0;
+        s.value = s1.value;
+        if (s.value < s2.value) {
+            s.value = s2.value;
+        }
+    }
+    
+    return s;
+}
+
+#endif