BaseTable.cc

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// -*- lsst-c++ -*-

#include <memory>

#include "boost/shared_ptr.hpp"  // only for ndarray

#include "lsst/afw/table/BaseColumnView.h"
#include "lsst/afw/table/BaseRecord.h"
#include "lsst/afw/table/BaseTable.h"
#include "lsst/afw/table/Catalog.h"
#include "lsst/afw/table/SchemaMapper.h"
#include "lsst/afw/table/io/FitsWriter.h"
#include "lsst/afw/table/detail/Access.h"

namespace lsst {
namespace afw {
namespace table {

// =============== Block ====================================================================================

//  This is a block of memory that doles out record-sized chunks when a table asks for them.
//  It inherits from ndarray::Manager so we can return ndarrays that refer to the memory in the
//  block with correct reference counting (ndarray::Manager is just an empty base class with an
//  internal reference count - it's like a shared_ptr without the pointer and template parameter.
//
//  Records are allocated in Blocks for two reasons:
//    - it allows tables to be either totally contiguous in memory (enabling column views) or
//      not (enabling dynamic addition of records) all in one class.
//    - it saves us from ever having to reallocate all the records associated with a table
//      when we run out of space (that's what a std::vector-like model would require).  This keeps
//      records and/or iterators to them from being invalidated, and it keeps tables from having
//      to track all the records whose data it owns.

namespace {

class Block : public ndarray::Manager {
public:
    typedef boost::intrusive_ptr<Block> Ptr;

    // If the last chunk allocated isn't needed after all (usually because of an exception in a constructor)
    // we reuse it immediately.  If it wasn't the last chunk allocated, it can't be reclaimed until
    // the entire block goes out of scope.
    static void reclaim(std::size_t recordSize, void *data, ndarray::Manager::Ptr const &manager) {
        Ptr block = boost::static_pointer_cast<Block>(manager);
        if (reinterpret_cast<char *>(data) + recordSize == block->_next) {
            block->_next -= recordSize;
        }
    }

    // Ensure we have space for at least the given number of records as a contiguous block.
    // May not actually allocate anything if we already do.
    static void preallocate(std::size_t recordSize, std::size_t recordCount, ndarray::Manager::Ptr &manager) {
        Ptr block = boost::static_pointer_cast<Block>(manager);
        if (!block || static_cast<std::size_t>(block->_end - block->_next) < recordSize * recordCount) {
            block = Ptr(new Block(recordSize, recordCount));
            manager = block;
        }
    }

    static std::size_t getBufferSize(std::size_t recordSize, ndarray::Manager::Ptr const &manager) {
        Ptr block = boost::static_pointer_cast<Block>(manager);
        return static_cast<std::size_t>(block->_end - block->_next) / recordSize;
    }

    // Get the next chunk from the block, making a new block and installing it into the table
    // if we're all out of space.
    static void *get(std::size_t recordSize, ndarray::Manager::Ptr &manager) {
        Ptr block = boost::static_pointer_cast<Block>(manager);
        if (!block || block->_next == block->_end) {
            block = Ptr(new Block(recordSize, BaseTable::nRecordsPerBlock));
            manager = block;
        }
        void *r = block->_next;
        block->_next += recordSize;
        return r;
    }

    // Block is also keeper of the special number that says what alignment boundaries are needed for
    // schemas.  Before we start using a schema, we need to first ensure it meets that requirement,
    // and pad it if not.
    static void padSchema(Schema &schema) {
        static int const MIN_RECORD_ALIGN = sizeof(AllocType);
        int remainder = schema.getRecordSize() % MIN_RECORD_ALIGN;
        if (remainder) {
            detail::Access::padSchema(schema, MIN_RECORD_ALIGN - remainder);
        }
    }

private:
    struct AllocType {
        double element[2];
    };

    explicit Block(std::size_t recordSize, std::size_t recordCount)
            : _mem(new AllocType[(recordSize * recordCount) / sizeof(AllocType)]),
              _next(reinterpret_cast<char *>(_mem.get())),
              _end(_next + recordSize * recordCount) {
        assert((recordSize * recordCount) % sizeof(AllocType) == 0);
        std::fill(_next, _end, 0);  // initialize to zero; we'll later initialize floats to NaN.
    }

    std::unique_ptr<AllocType[]> _mem;
    char *_next;
    char *_end;
};

}  // namespace

// =============== BaseTable implementation (see header for docs) ===========================================

void BaseTable::preallocate(std::size_t n) { Block::preallocate(_schema.getRecordSize(), n, _manager); }

std::size_t BaseTable::getBufferSize() const {
    if (_manager) {
        return Block::getBufferSize(_schema.getRecordSize(), _manager);
    } else {
        return 0;
    }
}

std::shared_ptr<BaseTable> BaseTable::make(Schema const &schema) {
    return std::shared_ptr<BaseTable>(new BaseTable(schema));
}

std::shared_ptr<BaseRecord> BaseTable::copyRecord(BaseRecord const &input) {
    std::shared_ptr<BaseRecord> output = makeRecord();
    output->assign(input);
    return output;
}

std::shared_ptr<BaseRecord> BaseTable::copyRecord(BaseRecord const &input, SchemaMapper const &mapper) {
    std::shared_ptr<BaseRecord> output = makeRecord();
    output->assign(input, mapper);
    return output;
}

std::shared_ptr<io::FitsWriter> BaseTable::makeFitsWriter(fits::Fits *fitsfile, int flags) const {
    return std::make_shared<io::FitsWriter>(fitsfile, flags);
}

std::shared_ptr<BaseTable> BaseTable::_clone() const {
    return std::shared_ptr<BaseTable>(new BaseTable(*this));
}

std::shared_ptr<BaseRecord> BaseTable::_makeRecord() {
    return constructRecord<BaseRecord>();
}

BaseTable::BaseTable(Schema const &schema) : _schema(schema) {
    Block::padSchema(_schema);
    _schema.disconnectAliases();
    _schema.getAliasMap()->_table = this;
}

BaseTable::~BaseTable() { _schema.getAliasMap()->_table = 0; }

namespace {

// A Schema Functor used to set destroy variable-length array fields using an explicit call to their
// destructor (necessary since we used placement new).  All other fields are ignored, as they're POD.
struct RecordDestroyer {
    template <typename T>
    void operator()(SchemaItem<T> const &item) const {}

    template <typename T>
    void operator()(SchemaItem<Array<T> > const &item) const {
        typedef ndarray::Array<T, 1, 1> Element;
        if (item.key.isVariableLength()) {
            (*reinterpret_cast<Element *>(data + item.key.getOffset())).~Element();
        }
    }

    void operator()(SchemaItem<std::string> const &item) const {
        if (item.key.isVariableLength()) {
            using std::string;  // invoking the destructor on a qualified name doesn't compile in gcc 4.8.1
                                // https://stackoverflow.com/q/24593942
            (*reinterpret_cast<string *>(data + item.key.getOffset())).~string();
        }
    }

    char *data;
};

}  // namespace

detail::RecordData BaseTable::_makeNewRecordData() {
    auto data = Block::get(_schema.getRecordSize(), _manager);
    return detail::RecordData{
        data,
        shared_from_this(),
        _manager  // manager always points to the most recently-used block.
    };
}

void BaseTable::_destroy(BaseRecord &record) {
    assert(record._table.get() == this);
    RecordDestroyer f = {reinterpret_cast<char *>(record._data)};
    _schema.forEach(f);
    if (record._manager == _manager) Block::reclaim(_schema.getRecordSize(), record._data, _manager);
}

/*
 *  JFB has no idea whether the default value below is sensible, or even whether
 *  it should be expressed ultimately as an approximate size in bytes rather than a
 *  number of records; the answer probably depends on both the typical size of
 *  records and the typical number of records.
 */
int BaseTable::nRecordsPerBlock = 100;

// =============== BaseCatalog instantiation =================================================================

template class CatalogT<BaseRecord>;
template class CatalogT<BaseRecord const>;
}  // namespace table
}  // namespace afw
}  // namespace lsst