buffer: Make the use of static areas more convenient

Make three wrapper functions to tidy up the process of making a
bufferlist holding a single static buffer.

The lack of any decent handling of const in buffer::list makes me wax
wroth, but it's a bit much to fix right now.

Signed-off-by: Adam C. Emerson <aemerson@redhat.com>

diff --git a/src/common/buffer.cc b/src/common/buffer.cc
index 77dcc685caaa390a951aac4d69de281aaeda575e..5d8dcf5c27d79c07f9c89b3aea5c08c8b694f385 100644 (file)
--- a/src/common/buffer.cc
+++ b/src/common/buffer.cc
@@ -2498,6 +2498,25 @@ void buffer::list::hexdump(std::ostream &out, bool trailing_newline) const
   out.flags(original_flags);
 }
 
+
+buffer::list buffer::list::static_from_mem(char* c, size_t l) {
+  list bl;
+  bl.push_back(ptr(create_static(l, c)));
+  return bl;
+}
+
+buffer::list buffer::list::static_from_cstring(char* c) {
+  return static_from_mem(c, std::strlen(c));
+}
+
+buffer::list buffer::list::static_from_string(string& s) {
+  // C++14 just has string::data return a char* from a non-const
+  // string.
+  return static_from_mem(const_cast<char*>(s.data()), s.length());
+  // But the way buffer::list mostly doesn't work in a sane way with
+  // const makes me generally sad.
+}
+
 std::ostream& buffer::operator<<(std::ostream& out, const buffer::raw &r) {
   return out << "buffer::raw(" << (void*)r.data << " len " << r.len << " nref " << r.nref.read() << ")";
 }

diff --git a/src/include/buffer.h b/src/include/buffer.h
index d8f8999b6ce93a0e313c6483fb08f9a87ec29817..177e95f8a8753e3441c1d0dae8a440ac4b345218 100644 (file)
--- a/src/include/buffer.h
+++ b/src/include/buffer.h
@@ -883,6 +883,13 @@ namespace buffer CEPH_BUFFER_API {
     }
     uint32_t crc32c(uint32_t crc) const;
     void invalidate_crc();
+
+    // These functions return a bufferlist with a pointer to a single
+    // static buffer. They /must/ not outlive the memory they
+    // reference.
+    static list static_from_mem(char* c, size_t l);
+    static list static_from_cstring(char* c);
+    static list static_from_string(std::string& s);
   };
 
   /*