ArrayBuilder: replace shared with unique

include/awkward/builder/ArrayBuilder.h

@@ -233,7 +233,7 @@ namespace awkward {
     /// @brief Internal function to replace the root node of the ArrayBuilder's
     /// Builder tree with a new root.
     void
-      maybeupdate(const BuilderPtr& tmp);
+      maybeupdate(const BuilderPtr builder);
 
 private:
     /// @brief Constant equal to `nullptr`.

include/awkward/builder/BoolBuilder.h

@@ -30,7 +30,7 @@ namespace awkward {
     /// these are passed to every Builder's constructor.
     /// @param buffer Contains the accumulated boolean values.
     BoolBuilder(const ArrayBuilderOptions& options,
-                const GrowableBuffer<uint8_t>& buffer);
+                GrowableBuffer<uint8_t> buffer);
 
     /// @brief User-friendly name of this class: `"BoolBuilder"`.
     const std::string
@@ -93,7 +93,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/Builder.h

@@ -153,7 +153,7 @@ namespace awkward {
     /// Record keys are checked in round-robin order. The best performance
     /// will be achieved by filling them in the same order for each record.
     /// Lookup time for random order scales with the number of fields.
-    virtual const BuilderPtr
+    virtual void
       field(const char* key, bool check) = 0;
 
     /// @brief Ends a record.

include/awkward/builder/Complex128Builder.h

@@ -44,7 +44,7 @@ namespace awkward {
     /// these are passed to every Builder's constructor.
     /// @param buffer Contains the accumulated real numbers.
     Complex128Builder(const ArrayBuilderOptions& options,
-                      const GrowableBuffer<std::complex<double>>& buffer);
+                      GrowableBuffer<std::complex<double>> buffer);
 
     /// @brief User-friendly name of this class: `"Complex128Builder"`.
     const std::string
@@ -107,7 +107,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/DatetimeBuilder.h

@@ -27,7 +27,7 @@ namespace awkward {
     /// these are passed to every Builder's constructor.
     /// @param buffer Contains the accumulated integers.
     DatetimeBuilder(const ArrayBuilderOptions& options,
-                    const GrowableBuffer<int64_t>& content,
+                    GrowableBuffer<int64_t> content,
                     const std::string& units);
 
     /// @brief User-friendly name of this class: `"DatetimeBuilder"`.
@@ -91,7 +91,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/Float64Builder.h

@@ -37,10 +37,10 @@ namespace awkward {
     /// these are passed to every Builder's constructor.
     /// @param buffer Contains the accumulated real numbers.
     Float64Builder(const ArrayBuilderOptions& options,
-                   const GrowableBuffer<double>& buffer);
+                   GrowableBuffer<double> buffer);
 
     /// @brief Contains the accumulated real numbers (`double`).
-    const GrowableBuffer<double>
+    const GrowableBuffer<double>&
       buffer() const;
 
     /// @brief User-friendly name of this class: `"Float64Builder"`.
@@ -104,7 +104,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/GrowableBuffer.h

@@ -5,6 +5,7 @@
 
 #include "awkward/common.h"
 #include "awkward/builder/ArrayBuilderOptions.h"
+#include "awkward/kernel-dispatch.h"
 
 #include <memory>
 
@@ -23,22 +24,13 @@ namespace awkward {
   /// data grow.
   ///
   /// When {@link ArrayBuilder#snapshot ArrayBuilder::snapshot} is called,
-  /// these buffers are shared with the new Content array. The GrowableBuffer
-  /// can still grow because the Content array only sees the part of its
-  /// reservation that existed at the time of the snapshot (new elements are
-  /// beyond its {@link Content#length Content::length}).
+  /// these buffers are copied to the new Content array.
   ///
   /// If a GrowableBuffer resizes itself by allocating a new array, it
-  /// decreases the reference counter for the shared buffer, but the Content
-  /// still owns it, and thus becomes the sole owner.
-  ///
-  /// The only disadvantage to this scheme is that the Content might forever
-  /// have a reservation that is larger than it needs and it is unable to
-  /// delete or take advantage of. However, many operations require buffers
-  /// to be rewritten; under normal circumstances, it would soon be replaced
-  /// by a more appropriately sized buffer.
+  /// copies the buffer it owns.
   template <typename T>
   class LIBAWKWARD_EXPORT_SYMBOL GrowableBuffer {
+    using UniquePtr = kernel::UniquePtr<T>;
   public:
     /// @brief Creates an empty GrowableBuffer.
     ///
@@ -53,7 +45,7 @@ namespace awkward {
     /// of `minreserve` and
     /// {@link ArrayBuilderOptions#initial ArrayBuilderOptions::initial}.
     static GrowableBuffer<T>
-      empty(const ArrayBuilderOptions& options, int64_t minreserve);
+      empty_reserved(const ArrayBuilderOptions& options, int64_t minreserve);
 
     /// @brief Creates a GrowableBuffer in which all elements are initialized
     /// to a given value.
@@ -90,7 +82,7 @@ namespace awkward {
     /// Although the #length increments every time #append is called,
     /// it is always less than or equal to #reserved because of reallocations.
     GrowableBuffer(const ArrayBuilderOptions& options,
-                   std::shared_ptr<T> ptr,
+                   GrowableBuffer::UniquePtr ptr,
                    int64_t length,
                    int64_t reserved);
 
@@ -99,10 +91,15 @@ namespace awkward {
     /// {@link ArrayBuilderOptions#initial ArrayBuilderOptions::initial}.
     GrowableBuffer(const ArrayBuilderOptions& options);
 
-    /// @brief Reference-counted pointer to the array buffer.
-    const std::shared_ptr<T>
+    /// @brief Reference to a unique pointer to the array buffer.
+    const GrowableBuffer::UniquePtr&
       ptr() const;
 
+    /// @brief FIXME: needed for uproot.cpp - remove when it's gone.
+    /// Note, it transfers ownership of the array buffer.
+    GrowableBuffer::UniquePtr
+      get_ptr();
+
     /// @brief Currently used number of elements.
     ///
     /// Although the #length increments every time #append is called,
@@ -135,10 +132,6 @@ namespace awkward {
     /// @brief Discards accumulated data, the #reserved returns to
     /// {@link ArrayBuilderOptions#initial ArrayBuilderOptions::initial},
     /// and a new #ptr is allocated.
-    ///
-    /// The old data are only discarded in the sense of decrementing their
-    /// reference count. If any old snapshots are still using the data,
-    /// they are not invalidated.
     void
       clear();
 
@@ -158,7 +151,7 @@ namespace awkward {
   private:
     const ArrayBuilderOptions options_;
     // @brief See #ptr.
-    std::shared_ptr<T> ptr_;
+    UniquePtr ptr_;
     // @brief See #length.
     int64_t length_;
     // @brief See #reserved.

include/awkward/builder/Int64Builder.h

@@ -27,10 +27,10 @@ namespace awkward {
     /// these are passed to every Builder's constructor.
     /// @param buffer Contains the accumulated integers.
     Int64Builder(const ArrayBuilderOptions& options,
-                 const GrowableBuffer<int64_t>& buffer);
+                 GrowableBuffer<int64_t> buffer);
 
     /// @brief Contains the accumulated integers.
-    const GrowableBuffer<int64_t>
+    const GrowableBuffer<int64_t>&
       buffer() const;
 
     /// @brief User-friendly name of this class: `"Int64Builder"`.
@@ -94,7 +94,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/ListBuilder.h

@@ -34,7 +34,7 @@ namespace awkward {
     /// #beginlist and before #endlist and is #active; if `false`,
     /// it is not.
     ListBuilder(const ArrayBuilderOptions& options,
-                const GrowableBuffer<int64_t>& offsets,
+                GrowableBuffer<int64_t> offsets,
                 const BuilderPtr& content,
                 bool begun);
 
@@ -100,7 +100,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr
@@ -115,15 +115,14 @@ namespace awkward {
 
     bool begun() { return begun_; }
 
+    void
+      maybeupdate(const BuilderPtr builder);
+
   private:
     const ArrayBuilderOptions options_;
     GrowableBuffer<int64_t> offsets_;
     BuilderPtr content_;
     bool begun_;
-
-  public:
-    void
-      maybeupdate(const BuilderPtr& tmp);
   };
 }
 

include/awkward/builder/OptionBuilder.h

@@ -44,8 +44,8 @@ namespace awkward {
     /// {@link IndexedArrayOf#index IndexedOptionArray::index}).
     /// @param content Builder for the non-missing data.
     OptionBuilder(const ArrayBuilderOptions& options,
-                  const GrowableBuffer<int64_t>& index,
-                  const BuilderPtr& content);
+                  GrowableBuffer<int64_t> index,
+                  const BuilderPtr content);
 
     /// @brief User-friendly name of this class: `"OptionBuilder"`.
     const std::string
@@ -108,26 +108,25 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr
       endrecord() override;
 
     const GrowableBuffer<int64_t>& buffer() const { return index_; }
 
-    GrowableBuffer<int64_t>& index() { return index_; }
+    const GrowableBuffer<int64_t>& index() { return index_; }
 
     const BuilderPtr builder() const { return content_; }
 
+    void
+      maybeupdate(const BuilderPtr builder);
+
   private:
     const ArrayBuilderOptions options_;
     GrowableBuffer<int64_t> index_;
     BuilderPtr content_;
-
-  public:
-    void
-      maybeupdate(const BuilderPtr& tmp);
   };
 
 }

include/awkward/builder/RecordBuilder.h

@@ -118,7 +118,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr
@@ -135,11 +135,14 @@ namespace awkward {
 
     int64_t nextindex() { return nextindex_; }
 
+    void
+      maybeupdate(int64_t i, const BuilderPtr builder);
+
   private:
-    const BuilderPtr
+    void
       field_fast(const char* key);
 
-    const BuilderPtr
+    void
       field_check(const char* key);
 
     const ArrayBuilderOptions options_;
@@ -153,10 +156,6 @@ namespace awkward {
     int64_t nextindex_;
     int64_t nexttotry_;
     int64_t keys_size_;
-
-  public:
-    void
-      maybeupdate(int64_t i, const BuilderPtr& tmp);
   };
 }
 

include/awkward/builder/StringBuilder.h

@@ -36,8 +36,8 @@ namespace awkward {
     /// if `"utf-8"`, it is encoded with variable-width UTF-8.
     /// Currently, no other encodings have been defined.
     StringBuilder(const ArrayBuilderOptions& options,
-                  const GrowableBuffer<int64_t>& offsets,
-                  const GrowableBuffer<uint8_t>& content,
+                  GrowableBuffer<int64_t> offsets,
+                  GrowableBuffer<uint8_t> content,
                   const char* encoding);
 
     /// @brief If `nullptr`, the string is an unencoded bytestring;
@@ -107,7 +107,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr

include/awkward/builder/TupleBuilder.h

@@ -104,7 +104,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr
@@ -119,16 +119,15 @@ namespace awkward {
 
     int64_t nextindex() { return nextindex_; }
 
+    void
+      maybeupdate(int64_t i, const BuilderPtr builder);
+
   private:
     const ArrayBuilderOptions options_;
     std::vector<BuilderPtr> contents_;
     int64_t length_;
     bool begun_;
     int64_t nextindex_;
-
-  public:
-    void
-      maybeupdate(int64_t i, const BuilderPtr& tmp);
   };
 }
 

include/awkward/builder/UnionBuilder.h

@@ -33,8 +33,8 @@ namespace awkward {
     /// {@link UnionArrayOf#index UnionArray::index}).
     /// @param contents A Builder for each of the union's possibilities.
     UnionBuilder(const ArrayBuilderOptions& options,
-                 const GrowableBuffer<int8_t>& tags,
-                 const GrowableBuffer<int64_t>& index,
+                 GrowableBuffer<int8_t> tags,
+                 GrowableBuffer<int64_t> index,
                  std::vector<BuilderPtr>& contents);
 
     /// @brief User-friendly name of this class: `"UnionBuilder"`.
@@ -99,7 +99,7 @@ namespace awkward {
     const BuilderPtr
       beginrecord(const char* name, bool check) override;
 
-    const BuilderPtr
+    void
       field(const char* key, bool check) override;
 
     const BuilderPtr