common: add prepare_iovs to bufferlist

Enable bufferlist that have more than IOV_MAX buffers to build a vector of iov.

Signed-off-by: Xuehan Xu <xxhdx1985126@gmail.com>

diff --git a/src/include/buffer.h b/src/include/buffer.h
index 7c8f90e9fb5d3ad55757a8eceb422ec726594c0f..adf56400ecae07dd19121a02f364259d0cac60d7 100644 (file)
--- a/src/include/buffer.h
+++ b/src/include/buffer.h
@@ -1196,6 +1196,40 @@ struct error_code;
        ++n;
       }
     }
+
+    // vector<pair<offset, length>, iov>
+    using iov_vec_t =
+      std::vector<std::pair<std::pair<uint64_t, uint64_t>, std::vector<iovec>>>;
+
+    iov_vec_t prepare_iovs()
+    {
+      iov_vec_t iovs;
+      size_t iovs_i = 0;
+      size_t index = 0;
+      uint64_t off = 0;
+      iovs.resize(_num / IOV_MAX + 1);
+      iovs[iovs_i].second.resize(
+       std::min(_num - IOV_MAX * iovs_i, (size_t)IOV_MAX));
+      iovs[iovs_i].first.first = off;
+      iovs[iovs_i].first.second = 0;
+      for (auto& bp : _buffers) {
+       if (index == IOV_MAX) {
+         iovs_i++;
+         index = 0;
+         iovs[iovs_i].first.first = off;
+         iovs[iovs_i].first.second = 0;
+         iovs[iovs_i].second.resize(
+           std::min(_num - IOV_MAX * iovs_i, (size_t)IOV_MAX));
+       }
+       iovs[iovs_i].second[index].iov_base = (void*)bp.c_str();
+       iovs[iovs_i].second[index++].iov_len = bp.length();
+       off += bp.length();
+       iovs[iovs_i].first.second += bp.length();
+      }
+
+      return iovs;
+    }
+
     uint32_t crc32c(uint32_t crc) const;
     void invalidate_crc();