MINOR: sample: provide smp_is_rw() and smp_make_rw()

At some places, smp_dup() is inappropriately called to ensure a modification
is possible while in fact we only need to ensure the sample may be modified
in place. Let's provide smp_is_rw() to check for this capability and
smp_make_rw() to perform the smp_dup() when it is not the case.

Note that smp_is_rw() will also try to add the trailing zero on strings when
needed if possible, to avoid a useless duplication.

diff --git a/include/proto/sample.h b/include/proto/sample.h
index 9b5d026169efbac5afccaeee74ec4fad7549423a..ecb2eb49770a3b2476cd8fbeb8394e6fc7d0c82d 100644 (file)
--- a/include/proto/sample.h
+++ b/include/proto/sample.h
@@ -118,4 +118,48 @@ int smp_make_safe(struct sample *smp)
        return smp && (smp_is_safe(smp) || smp_dup(smp));
 }
 
+/* Returns 1 if a sample may be safely modified in place. It performs a few
+ * checks on the string length versus size, same for the binary version, and
+ * ensures that strings are properly terminated by a zero, and of course that
+ * the size is allocate and that the SMP_F_CONST flag is not set. If only the
+ * trailing zero is missing, it is appended. Otherwise it returns 0, meaning
+ * the caller may need to call smp_dup() before going further.
+ */
+static inline
+int smp_is_rw(struct sample *smp)
+{
+       if (smp->flags & SMP_F_CONST)
+               return 0;
+
+       switch (smp->data.type) {
+       case SMP_T_STR:
+               if (!smp->data.u.str.size ||
+                   smp->data.u.str.len < 0 ||
+                   smp->data.u.str.len >= smp->data.u.str.size)
+                       return 0;
+
+               if (smp->data.u.str.str[smp->data.u.str.len] != 0)
+                       smp->data.u.str.str[smp->data.u.str.len] = 0;
+               return 1;
+
+       case SMP_T_BIN:
+               return smp->data.u.str.size &&
+                      smp->data.u.str.len >= 0 &&
+                      smp->data.u.str.len <= smp->data.u.str.size;
+
+       default:
+               return 1;
+       }
+}
+
+/* checks that a sample may freely be modified, or duplicates it to normalize
+ * it and make it R/W. Returns 1 on success, 0 if the sample must not be used.
+ * The function also checks for NULL to simplify the calling code.
+ */
+static inline
+int smp_make_rw(struct sample *smp)
+{
+       return smp && (smp_is_rw(smp) || smp_dup(smp));
+}
+
 #endif /* _PROTO_SAMPLE_H */