CoordinateSequence: create using external buffer

Author: dbaston

capi/geos_c.cpp

@@ -983,6 +983,12 @@ extern "C" {
         return GEOSCoordSeq_create_r(handle, size, dims);
     }
 
+    CoordinateSequence*
+    GEOSCoordSeq_createFromBuffer(double* buf, unsigned int size, int hasZ, int hasM)
+    {
+        return GEOSCoordSeq_createFromBuffer_r(handle, buf, size, hasZ, hasM);
+    }
+
     CoordinateSequence*
     GEOSCoordSeq_copyFromBuffer(const double* buf, unsigned int size, int hasZ, int hasM)
     {

capi/geos_c.h.in

@@ -396,6 +396,14 @@ extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_create_r(
     unsigned int size,
     unsigned int dims);
 
+/** \see GEOSCoordSeq_createFromBuffer */
+extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_createFromBuffer_r(
+        GEOSContextHandle_t handle,
+        double* buf,
+        unsigned int size,
+        int hasZ,
+        int hasM);
+
 /** \see GEOSCoordSeq_copyFromBuffer */
 extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_copyFromBuffer_r(
         GEOSContextHandle_t handle,
@@ -2023,11 +2031,24 @@ extern void GEOS_DLL GEOSFree(void *buffer);
 extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_create(unsigned int size, unsigned int dims);
 
 /**
-* Create a coordinate sequence by copying from a buffer of doubles (XYXY or XYZXYZ)
+* Create a coordinate sequence using from a buffer of interleaved doubles (XYXY, XYZXYZ, etc.)
+* If possible, the CoordinateSequence will use the values directly from the buffer without
+* copying. (Currently, this is supported for XYZ and XYZM buffers only.)
+*
+* \param buf pointer to buffer
+* \param size number of coordinates in the sequence
+* \param hasZ does buffer have Z values?
+* \param hasM does buffer have M values?
+* \return the sequence or NULL on exception
+*/
+extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_createFromBuffer(double* buf, unsigned int size, int hasZ, int hasM);
+
+/**
+* Create a coordinate sequence by copying from a buffer of doubles (XYXY, XYZXYZ, etc.)
 * \param buf pointer to buffer
 * \param size number of coordinates in the sequence
 * \param hasZ does buffer have Z values?
-* \param hasM does buffer have M values? (they will be ignored)
+* \param hasM does buffer have M values?
 * \return the sequence or NULL on exception
 */
 extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_copyFromBuffer(const double* buf, unsigned int size, int hasZ, int hasM);
@@ -2044,7 +2065,7 @@ extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_copyFromBuffer(const double* buf
 extern GEOSCoordSequence GEOS_DLL *GEOSCoordSeq_copyFromArrays(const double* x, const double* y, const double* z, const double* m, unsigned int size);
 
 /**
-* Copy the contents of a coordinate sequence to a buffer of doubles (XYXY or XYZXYZ)
+* Copy the contents of a coordinate sequence to a buffer of doubles (XYXY, XYZXYZ, etc.)
 * \param s sequence to copy
 * \param buf buffer to which coordinates should be copied
 * \param hasZ copy Z values to buffer?

capi/geos_ts_c.cpp

@@ -2430,6 +2430,14 @@ extern "C" {
         });
     }
 
+    CoordinateSequence*
+    GEOSCoordSeq_createFromBuffer_r(GEOSContextHandle_t extHandle, double* buf, unsigned int size, int hasZ, int hasM)
+    {
+        return execute(extHandle, [&]() {
+            return new CoordinateSequence(buf, size, hasZ, hasM);
+        });
+    }
+
     CoordinateSequence*
     GEOSCoordSeq_copyFromBuffer_r(GEOSContextHandle_t extHandle, const double* buf, unsigned int size, int hasZ, int hasM)
     {

include/geos/geom/CoordinateSequence.h

@@ -19,6 +19,7 @@
 
 #include <geos/geom/Coordinate.h> // for applyCoordinateFilter
 #include <geos/geom/CoordinateSequenceIterator.h>
+#include <geos/util/Vector.h>
 
 #include <cassert>
 #include <vector>
@@ -89,12 +90,28 @@ class GEOS_DLL CoordinateSequence {
      * are not actually stored in the sequence.
      *
      * @param size size of the sequence to create
-     * @param hasz true if the stored
-     * @param hasm
-     * @param initialize
+     * @param hasz true if the sequence should store z values
+     * @param hasm true if the sequence should store m values
+     * @param initialize true if the sequence should be initialized to default coordinate values
      */
     CoordinateSequence(std::size_t size, bool hasz, bool hasm, bool initialize = true);
 
+    /**
+     * Create a CoordinateSequence from an externally-owned buffer
+     * of packed Coordinates. If Coordinates are added to the CoordinateSequence
+     * or the CoordinateSequence requires repacking, the values will
+     * be copied into a new buffer owned by this CoordinateSeuqnce.
+     * Code using a CoordinateSequence constructed in this way must not
+     * attempt to access references to coordinates with dimensions that
+     * are not actually stored in the sequence.
+     *
+     * @param buf buffer of interleaved coordinates
+     * @param size number of coordinates in the buffer
+     * @param hasz true if the buffer has z values
+     * @param hasm true if the buffer has m values
+     */
+    CoordinateSequence(double* buf, std::size_t size, bool hasz, bool hasm);
+
     /**
      * Create a CoordinateSequence from a list of XYZ coordinates.
      * Code using the sequence may only access references to CoordinateXY
@@ -688,7 +705,7 @@ class GEOS_DLL CoordinateSequence {
     }
 
 private:
-    std::vector<double> m_vect; // Vector to store values
+    geos::util::Vector<double> m_vect; // Vector to store values
 
     uint8_t m_stride;           // Stride of stored values, corresponding to underlying type
 
@@ -707,9 +724,7 @@ class GEOS_DLL CoordinateSequence {
     }
 
     void make_space(std::size_t pos, std::size_t n) {
-        m_vect.insert(std::next(m_vect.begin(), static_cast<std::ptrdiff_t>(pos * stride())),
-                      m_stride * n,
-                      DoubleNotANumber);
+        m_vect.make_space(m_vect.begin() + pos * stride(), n * stride());
     }
 
     std::uint8_t stride() const {

include/geos/util/Vector.h

@@ -0,0 +1,256 @@
+/**********************************************************************
+ *
+ * GEOS - Geometry Engine Open Source
+ * http://geos.osgeo.org
+ *
+ * Copyright (C) 2022 ISciences LLC
+ *
+ * This is free software; you can redistribute and/or modify it under
+ * the terms of the GNU Lesser General Public Licence as published
+ * by the Free Software Foundation.
+ * See the COPYING file for more information.
+ *
+ **********************************************************************/
+
+#pragma once
+
+#include <cstdint>
+#include <cstring>
+#include <iterator>
+
+namespace geos {
+namespace util {
+
+/**
+ * \brief
+ * A partial re-implementation of std::vector intended for use by
+ * CoordinateSequence. Unlike std::vector, it can be backed by an
+ * external buffer or an internally-owned buffed.
+ */
+template<typename T>
+class Vector {
+
+public:
+    Vector() :
+        m_buf(nullptr),
+        m_capacity(0),
+        m_size(0)
+    {}
+
+    Vector(std::size_t sz) :
+        m_buf(nullptr),
+        m_capacity(0),
+        m_size(static_cast<std::uint32_t>(0))
+    {
+        resize(sz);
+    }
+
+    Vector(std::size_t sz, T* buf) :
+        m_buf(buf),
+        m_capacity(0),
+        m_size(static_cast<std::uint32_t>(sz))
+    {}
+
+    Vector(const Vector& other) : Vector() {
+        if (!other.empty()) {
+            m_buf = make_space(nullptr, other.size());
+            std::memcpy(m_buf, other.m_buf, other.size()*sizeof(T));
+        }
+    }
+
+    Vector& operator=(const Vector& other) {
+        clear();
+
+        if (!other.empty()) {
+            m_buf = make_space(nullptr, other.size());
+            std::memcpy(m_buf, other.m_buf, other.size()*sizeof(T));
+        }
+
+        return *this;
+    }
+
+    Vector(Vector&& other) :
+        m_buf(other.m_buf),
+        m_capacity(other.m_capacity),
+        m_size(other.m_size)
+    {
+        other.m_buf = nullptr;
+        other.m_capacity = 0;
+        other.m_size = 0;
+    }
+
+    Vector& operator=(Vector&& other) {
+        if (owned()) {
+            delete[] m_buf;
+        }
+
+        m_buf = other.m_buf;
+        m_capacity = other.m_capacity;
+        m_size = other.m_size;
+        other.m_buf = nullptr;
+        other.m_capacity = 0;
+        other.m_size = 0;
+
+        return *this;
+    }
+
+    ~Vector() {
+        if (owned()) {
+            delete[] m_buf;
+        }
+    }
+
+    void push_back(T item) {
+        growIfNeeded(1);
+        assert(size() < capacity());
+        m_buf[m_size++] = item;
+    }
+
+    void pop_back() {
+        assert(size() > 0);
+        m_size--;
+    }
+
+    T* make_space(T* pos, std::size_t n) {
+        auto loc = pos == nullptr ? 0 : pos - begin();
+        growIfNeeded(n);
+        pos = begin() + loc;
+
+        if (pos != end()) {
+            auto num_to_move = static_cast<std::size_t>(end() - pos);
+            std::memmove(pos + n, pos, num_to_move*sizeof(T));
+        }
+        m_size += static_cast<std::uint32_t>(n);
+
+        return pos;
+    }
+
+    void insert(T* pos, std::size_t n, const T& value) {
+        pos = make_space(pos, n);
+        std::fill(pos, pos + n, value);
+    }
+
+    template<typename Iter>
+    void insert(T* pos, Iter from, Iter to) {
+        auto n = static_cast<std::size_t>(to - from);
+
+        if (from >= begin() && from < end()) {
+            // from and to may be invalidated
+            auto from_n = from - begin();
+            auto to_n = to - begin();
+
+            pos = make_space(pos, n);
+
+            from = begin() + from_n;
+            to = begin() + to_n;
+        } else {
+            pos = make_space(pos, n);
+        }
+
+        std::copy(from, to, pos);
+    }
+
+    template<typename Iter>
+    void assign(Iter from, Iter to) {
+        assert(static_cast<std::size_t>(to - from) <= size());
+        std::copy(from, to, begin());
+    }
+
+    void reserve(std::size_t sz) {
+        if (sz <= capacity()) {
+            return;
+        }
+
+        T* tmp = sz > 0 ? new T[sz] : nullptr;
+        if (tmp && !empty()) {
+            std::memcpy(tmp, m_buf, m_size * sizeof(T));
+        }
+        if (owned()) {
+            delete[] m_buf;
+        }
+        m_buf = tmp;
+        m_capacity = static_cast<std::uint32_t>(sz);
+    }
+
+    void resize(std::size_t sz) {
+        reserve(sz);
+        m_size = static_cast<std::uint32_t>(sz);
+    }
+
+    void clear() {
+        m_size = 0;
+    }
+
+    std::size_t capacity() const {
+        return m_capacity;
+    }
+
+    std::size_t size() const {
+        return m_size;
+    }
+
+    bool empty() const {
+        return m_size == 0;
+    }
+
+    bool owned() const {
+        return data() == nullptr || !(capacity() == 0 && size() > 0);
+    }
+
+    const T& operator[](std::size_t i) const {
+        return *(data() + i);
+    }
+
+    T& operator[](std::size_t i) {
+        return *(data() + i);
+    }
+
+    T* release() {
+        m_capacity = 0;
+        return m_buf;
+    }
+
+    T* data() {
+        return m_buf;
+    }
+
+    const T* data() const {
+        return m_buf;
+    }
+
+    T* begin() {
+        return data();
+    };
+
+    T* end() {
+        return data() + size();
+    }
+
+    const T* begin() const {
+        return data();
+    };
+
+    const T* end() const {
+        return data() + size();
+    }
+
+private:
+
+    void growIfNeeded(std::size_t num_to_add) {
+        if (size() + num_to_add > capacity()) {
+            auto new_capacity = capacity() == 0 ?
+                        std::max(size() + num_to_add, static_cast<std::size_t>(4)) :
+                        static_cast<std::size_t>(static_cast<double>(capacity()) * 1.5);
+            new_capacity = std::max(new_capacity, capacity() + num_to_add);
+            reserve(new_capacity);
+        }
+    }
+
+    T* m_buf;
+    std::uint32_t m_capacity;
+    std::uint32_t m_size;
+};
+
+
+}
+}