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diff --git a/incbwt/bits/array.h b/incbwt/bits/array.h
new file mode 100644
index 0000000..18b09cc
--- /dev/null
+++ b/incbwt/bits/array.h
@@ -0,0 +1,155 @@
+#ifndef ARRAY_H
+#define ARRAY_H
+
+#include <fstream>
+#include <list>
+
+#include "../misc/definitions.h"
+#include "bitbuffer.h"
+
+
+namespace CSA
+{
+
+/*
+  Delta-coded array for storing positive integers.
+  Do not try to encode value 0!
+*/
+
+
+class ArrayEncoder
+{
+  public:
+    const static usint SUPERBLOCK_SIZE = MEGABYTE;
+
+    // We assume superblock size is divisible by block and sample size.
+    ArrayEncoder(usint block_bytes, usint superblock_size = SUPERBLOCK_SIZE);
+    ~ArrayEncoder();
+
+    void addItem(usint value);
+
+    void addNewBlock();
+
+    usint items, blocks;
+    usint block_size, superblock_bytes;
+
+    WriteBuffer*      buffer;
+
+    std::list<usint*> array_blocks;
+    usint*            array;
+    usint             blocks_in_superblock, current_blocks;
+
+    std::list<usint*> sample_blocks;
+    usint*            samples;
+    usint             samples_in_superblock, current_samples;
+
+  protected:
+
+    // These are not allowed.
+    ArrayEncoder();
+    ArrayEncoder(const ArrayEncoder&);
+    ArrayEncoder& operator = (const ArrayEncoder&);
+};
+
+
+class Array
+{
+  public:
+    const static usint INDEX_RATE = 5;
+
+    Array(std::ifstream& file);
+    Array(ArrayEncoder& encoder);
+    ~Array();
+
+//--------------------------------------------------------------------------
+
+    void writeTo(std::ofstream& file) const;
+
+    inline usint getSize() const { return this->items; }
+    inline usint getBlockSize() const { return this->block_size; }
+
+    usint reportSize() const;
+
+//--------------------------------------------------------------------------
+
+    class Iterator
+    {
+      public:
+        Iterator(const Array& par);
+        ~Iterator();
+
+        // Returns 0 if the index is invalid.
+        usint getItem(usint index);
+        usint nextItem();
+
+        inline bool hasNext() const
+        {
+          return (this->sample + this->cur < this->parent.getSize());
+        }
+
+      private:
+        const Array& parent;
+
+        usint block, sample, cur, block_items;
+
+        ReadBuffer buffer, samples;
+
+        /*
+          This function returns the sample corresponding to the block the given
+          index might be found in. Parameter is assumed to be valid.
+        */
+        usint sampleForIndex(usint index);
+
+        inline void getSample(usint sample_number)
+        {
+          this->block = sample_number;
+          this->sample = this->samples.readItem(sample_number);
+          this->cur = 0;
+          this->block_items = this->samples.readItem() - this->sample;
+          this->buffer.moveBuffer(this->parent.array + (this->block * this->parent.block_size));
+        }
+
+        // These are not allowed.
+        Iterator();
+        Iterator(const Iterator&);
+        Iterator& operator = (const Iterator&);
+    };
+
+//--------------------------------------------------------------------------
+
+  protected:
+    usint          items;
+
+    ReadBuffer*    buffer;
+    const usint*   array;
+    bool           delete_array;  // Do we own the array?
+    usint          block_size;
+    usint          number_of_blocks;
+
+    /*
+      Each sample tells how many items are contained in the previous blocks.
+    */
+    ReadBuffer*    samples;
+    usint          integer_bits;
+
+    ReadBuffer*    item_index;
+    usint          index_rate;
+
+    /*
+      Build a higher level index for faster queries.
+      The index consists of about (number of samples) / INDEX_RATE pointers.
+      The array cannot be used without the index.
+    */
+    void buildIndex();
+
+    // These are not allowed.
+    Array();
+    Array(const Array&);
+    Array& operator = (const Array&);
+};
+
+
+} // namespace CSA
+
+
+#endif // ARRAY_H