Merge branch 'develop' into json-view/5869-7-check-utf8

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

include/nlohmann/detail/view/builder.hpp

@@ -543,7 +543,15 @@ run_found:
     NLOHMANN_VIEW_NOINLINE void arena_grow(std::size_t n)
     {
         const std::size_t used = arena_used();
-        m_doc.arena.resize((std::max)(m_doc.arena.size() * 2, used + n + 256));
+        std::size_t wanted = used + n + 256;
+        if (m_doc.arena.empty())
+        {
+            // the first growth: a decoded string is never longer than its source,
+            // so a fraction of the input (capped, as the buffer is zero-filled)
+            // covers the escapes of a typical document without regrowing it
+            wanted = (std::max)(wanted, (std::min)((static_cast<std::size_t>(m_end - m_begin) / 4) + 16, std::size_t{4096}));
+        }
+        m_doc.arena.resize((std::max)(m_doc.arena.size() * 2, wanted));
         m_arena_write = m_doc.arena.data() + used;
         m_arena_end = m_doc.arena.data() + m_doc.arena.size();
     }

include/nlohmann/detail/view/document_data.hpp

@@ -82,14 +82,17 @@ struct document_data
     };
     std::unique_ptr<edit_state> edits; ///< created by the first edit
 
+    /// the most nodes that are allocated together with the header (16 KiB)
+    static constexpr std::size_t max_inline_nodes = 1024;
+
     /// One allocation for the header and room for `count` nodes, so that a
     /// small document needs one allocation instead of two. Large documents get
     /// a separate node array instead (so it can be trimmed). When a document
-    /// outgrows the inline array, that array stays unused: at most 256 nodes
-    /// (4 KiB), and only for documents whose estimate was too small.
+    /// outgrows the inline array, that array stays unused: at most 1024 nodes
+    /// (16 KiB), and only for documents whose estimate was too small.
     static document_data* create(std::size_t count)
     {
-        count = count <= 256 ? count : 0;
+        count = count <= max_inline_nodes ? count : 0;
         void* mem = ::operator new (sizeof(document_data) + (count * sizeof(node)));
         auto* d = new (mem) document_data(); // NOLINT(cppcoreguidelines-owning-memory): owned by the returned pointer, freed by deleter
         // (aligned: sizeof is a multiple of the alignment; through void*, as GCC's -Wcast-align wants)