From 9aaaccaf2a50ce19168068a58cbcc254ab255665 Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Thu, 12 Dec 2019 11:08:32 -0800
Subject: [PATCH] track StructTop::member_indicies

needed to allow iteration by storage offset
---
 src/data.cpp   | 5 ++++-
 src/dataimpl.h | 2 ++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/data.cpp b/src/data.cpp
index db27b4f..a7a7cc4 100644
--- a/src/data.cpp
+++ b/src/data.cpp
@@ -30,11 +30,13 @@ Value::Value(const std::shared_ptr<const impl::FieldDesc>& desc)
 
     top->desc = desc;
     top->valid.resize(desc->next_offset-desc->offset);
-    top->members.resize(desc->next_offset-desc->offset);
+    top->member_indicies.resize(top->valid.size());
+    top->members.resize(top->valid.size());
     {
         auto& root = top->members[0];
         root.init(desc.get());
         root.top = top.get();
+        top->member_indicies[0u] = 0u;
     }
 
     for(auto& pair : desc->mlookup) {
@@ -42,6 +44,7 @@ Value::Value(const std::shared_ptr<const impl::FieldDesc>& desc)
         auto& mem = top->members.at(cfld->offset-desc->offset);
         mem.top = top.get();
         mem.init(cfld);
+        top->member_indicies[cfld->offset] = pair.second;
     }
 
     this->desc = desc.get();
diff --git a/src/dataimpl.h b/src/dataimpl.h
index 2721e12..b8ea0de 100644
--- a/src/dataimpl.h
+++ b/src/dataimpl.h
@@ -108,6 +108,8 @@ struct StructTop {
     // type of first top level struct.  always !NULL.
     // Actually the first element of a vector<const FieldDesc>
     std::shared_ptr<const FieldDesc> desc;
+    // map from FieldStorage offsets to FieldDesc offsets.  inverse of FieldDesc::offset
+    std::vector<size_t> member_indicies;
     // our members (inclusive).  always size()>=1
     std::vector<FieldStorage> members;
 };