xref: /dports/deskutils/akregator/akregator-21.12.3/plugins/mk4storage/metakit/src/store.cpp

// store.cpp --
// This is part of Metakit, the homepage is http://www.equi4.com/metakit.html

/** @file
 * Storage management and several other loose ends
 */

#include "header.h"
#include "handler.h"  // 19990906
#include "store.h"
#include "field.h"
#include "persist.h"
#include "format.h"   // 19990906

#include "mk4io.h"    // 19991104

#if !q4_INLINE
#endif

/////////////////////////////////////////////////////////////////////////////

c4_Dependencies::c4_Dependencies()
{
    _refs.SetSize(0, 3); // a little optimization
}

c4_Dependencies::~c4_Dependencies()
{
}

void c4_Dependencies::Add(c4_Sequence *seq_)
{
    for (int i = 0; i < _refs.GetSize(); ++i) {
        d4_assert(_refs.GetAt(i) != seq_);
    }

    _refs.Add(seq_);
}

bool c4_Dependencies::Remove(c4_Sequence *seq_)
{
    int n = _refs.GetSize() - 1;
    d4_assert(n >= 0);

    for (int i = 0; i <= n; ++i) {
        if (_refs.GetAt(i) == seq_) {
            _refs.SetAt(i, _refs.GetAt(n));
            _refs.SetSize(n);
            return n > 0;
        }
    }

    d4_assert(0); // dependency not found
    return true;
}

/////////////////////////////////////////////////////////////////////////////

c4_Notifier::~c4_Notifier()
{
    if (_type > kNone && _origin->GetDependencies()) {
        c4_PtrArray &refs = _origin->GetDependencies()->_refs;

        for (int i = 0; i < refs.GetSize(); ++i) {
            c4_Sequence *seq = (c4_Sequence *)refs.GetAt(i);
            d4_assert(seq != 0);

            seq->PostChange(*this);

            if (_chain && _chain->_origin == seq) {
                c4_Notifier *next = _chain->_next;
                _chain->_next = nullptr;

                delete _chain;

                _chain = next;
            }
        }
    }

    d4_assert(!_chain);
    d4_assert(!_next);
}

void c4_Notifier::StartSetAt(int index_, c4_Cursor &cursor_)
{
    _type = kSetAt;
    _index = index_;
    _cursor = &cursor_;

    Notify();
}

void c4_Notifier::StartInsertAt(int i_, c4_Cursor &cursor_, int n_)
{
    _type = kInsertAt;
    _index = i_;
    _cursor = &cursor_;
    _count = n_;

    Notify();
}

void c4_Notifier::StartRemoveAt(int index_, int count_)
{
    _type = kRemoveAt;
    _index = index_;
    _count = count_;

    Notify();
}

void c4_Notifier::StartMove(int from_, int to_)
{
    _type = kMove;
    _index = from_;
    _count = to_;

    Notify();
}

void c4_Notifier::StartSet(int i_, int propId_, const c4_Bytes &buf_)
{
    _type = kSet;
    _index = i_;
    _propId = propId_;
    _bytes = &buf_;

    Notify();
}

void c4_Notifier::Notify()
{
    d4_assert(_origin->GetDependencies() != 0);
    c4_PtrArray &refs = _origin->GetDependencies()->_refs;

    int n = refs.GetSize();
    d4_assert(n > 0);

    c4_Notifier **rover = &_chain;

    for (int i = 0; i < n; ++i) {
        c4_Sequence *seq = (c4_Sequence *)refs.GetAt(i);
        d4_assert(seq != 0);

        c4_Notifier *ptr = seq->PreChange(*this);
        if (ptr) {
            d4_assert(ptr->_origin == seq);

            d4_assert(!*rover);
            *rover = ptr;
            rover = &ptr->_next;
        }
    }
}

/////////////////////////////////////////////////////////////////////////////

/** @class c4_Storage
 *
 *  Manager for persistent storage of view structures.
 *
 *  The storage class uses a view, with additional functionality to be able
 *  to store and reload the data it contains (including nested subviews).
 *
 *  By default, data is loaded on demand, i.e. whenever data which has
 *  not yet been referenced is used for the first time.  Loading is limited
 *  to the lifetime of this storage object, since the storage object carries
 *  the file descriptor with it that is needed to access the data file.
 *
 *  To save changes, call the Commit member.  This is the only time
 *  that data is written to file - when using a read-only file simply avoid
 *  calling Commit.
 *
 *  The LoadFromStream and SaveToStream members can be used to
 *  serialize the contents of this storage row using only sequential I/O
 *  (no seeking, only read or write calls).
 *
 *  The data storage mechanism implementation provides fail-safe operation:
 *  if anything prevents Commit from completing its task, the last
 *  successfully committed version of the saved data will be recovered on
 *  the next open. This also includes changes made to the table structure.
 *
 *  The following code creates a view with 1 row and stores it on file:
 * @code
 *    c4_StringProp pName ("Name");
 *    c4_IntProp pAge ("Age");
 *
 *    c4_Storage storage ("myfile.dat", true);
 *    c4_View myView = storage.GetAs("Musicians[Name:S,Age:I]");
 *
 *    myView.Add(pName ["John Williams"] + pAge [43]);
 *
 *    storage.Commit();
 * @endcode
 */

c4_Storage::c4_Storage()
{
    // changed to r/o, now that commits don't crash on it anymore
    Initialize(*d4_new c4_Strategy, true, 0);
}

c4_Storage::c4_Storage(c4_Strategy &strategy_, bool owned_, int mode_)
{
    Initialize(strategy_, owned_, mode_);
    Persist()->LoadAll();
}

c4_Storage::c4_Storage(const char *fname_, int mode_)
{
    c4_FileStrategy *strat = d4_new c4_FileStrategy;
    strat->DataOpen(fname_, mode_);

    Initialize(*strat, true, mode_);
    if (strat->IsValid()) {
        Persist()->LoadAll();
    }
}

c4_Storage::c4_Storage(const c4_View &root_)
{
    if (root_.Persist() != nullptr) {
        // only restore if view was indeed persistent
        *(c4_View *)this = root_;
    } else {
        // if this was not possible, start with a fresh empty storage
        Initialize(*d4_new c4_Strategy, true, 0);
    }
}

c4_Storage::~c4_Storage()
{
    // cannot unmap here, because there may still be an autocommit pending
    //((c4_HandlerSeq*) _seq)->UnmapAll();
}

void c4_Storage::Initialize(c4_Strategy &strategy_, bool owned_, int mode_)
{
    c4_Persist *pers = d4_new c4_Persist(strategy_, owned_, mode_);
    c4_HandlerSeq *seq = d4_new c4_HandlerSeq(pers);
    seq->DefineRoot();
    *(c4_View *)this = seq;
    pers->SetRoot(seq);
}

/// Get or set a named view in this storage object
c4_ViewRef c4_Storage::View(const char *name_)
{
    /*
    The easy solution would seem to be:

    c4_ViewProp prop (name_);
    return prop (Contents());

    But this does not work, because the return value would point to
    an object allocated on the stack.

    Instead, make sure the view *has* such a property, and use the
    one inside the c4_Handler for it (since this will stay around).
     */

    //  int n = _root->PropIndex(c4_ViewProp (name_));

    c4_ViewProp prop(name_);
    int n = AddProperty(prop);
    d4_assert(n >= 0);

    // the following is an expression of the form "property (rowref)"
    return NthProperty(n)(GetAt(0));
}

/// Get a named view, redefining it to match the given structure
c4_View c4_Storage::GetAs(const char *description_)
{
    d4_assert(description_ != 0);

    // Dec 2001: now that GetAs is being used so much more frequently,
    // add a quick check to see whether restructuring is needed at all
    const char *q = strchr(description_, '[');
    if (q != nullptr) {
        c4_String vname(description_, q - description_);
        const char *d = Description(vname);
        if (d != nullptr) {
            c4_String desc(d);
            if (("[" + desc + "]").CompareNoCase(q) == 0) {
                return View(vname);
            }
        }
    }

    c4_Field *field = d4_new c4_Field(description_);
    d4_assert(field != 0);

    d4_assert(!*description_);

    c4_String name = field->Name();
    d4_assert(!name.IsEmpty());

    c4_Field &curr = Persist()->Root().Definition();

    c4_String newField = "," + field->Description();
    bool keep = newField.Find('[') >= 0;

    c4_String newDef;

    // go through all subfields
    for (int i = 0; i < curr.NumSubFields(); ++i) {
        c4_Field &of = curr.SubField(i);
        if (of.Name().CompareNoCase(name) == 0) {
            if (field->IsRepeating()) {
                newDef += newField;
            }
            // else new is not a repeating entry, so drop this entire field

            newField.Empty(); // don't append it later on
            continue;
        }

        newDef += "," + of.Description(); // keep original field
    }

    if (keep) {
        // added 19990824 ignore if deletion
        newDef += newField;
    }
    // appends new definition if not found earlier

    delete field;

    const char *p = newDef;
    SetStructure(*p ? ++p : p); // skip the leading comma

    if (!keep) {
        // 19990916: avoid adding an empty view again
        return c4_View();
    }

    return View(name);
}

/// Define the complete view structure of the storage
void c4_Storage::SetStructure(const char *description_)
{
    d4_assert(description_ != 0);

    if (description_ != Description()) {
        c4_String s = "[" + c4_String(description_) + "]";
        description_ = s;

        c4_Field *field = d4_new c4_Field(description_);
        d4_assert(!*description_);

        d4_assert(field != 0);
        Persist()->Root().Restructure(*field, false);
    }
}

/// Return the strategy object associated with this storage
c4_Strategy &c4_Storage::Strategy() const
{
    return Persist()->Strategy();
}

/// Return a description of the view structure (default is all)
const char *c4_Storage::Description(const char *name_)
{
    if (name_ == nullptr || *name_ == 0) {
        return c4_View::Description();
    }

    c4_View v = View(name_);
    return v.Description();
}

/// Define the storage to use for differential commits
bool c4_Storage::SetAside(c4_Storage &aside_)
{
    c4_Persist *pers = Persist();
    bool f = pers->SetAside(aside_);
    // adjust our copy when the root view has been replaced
    *(c4_View *)this = &pers->Root();
    return f;
}

/// Return storage used for differential commits, or null
c4_Storage *c4_Storage::GetAside() const
{
    return Persist()->GetAside();
}

/// Flush pending changes to file right now
bool c4_Storage::Commit(bool full_)
{
    return Strategy().IsValid() && Persist()->Commit(full_);
}

/** (Re)initialize for on-demand loading
 *
 *  Calling Rollback will cancel all uncommitted changes.
 */
bool c4_Storage::Rollback(bool full_)
{
    c4_Persist *pers = Persist();
    bool f = Strategy().IsValid() && pers->Rollback(full_);
    // adjust our copy when the root view has been replaced
    *(c4_View *)this = &pers->Root();
    return f;
}

/// Set storage up to always call Commit in the destructor
bool c4_Storage::AutoCommit(bool flag_)
{
    return Persist()->AutoCommit(flag_);
}

/// Load contents from the specified input stream
bool c4_Storage::LoadFrom(c4_Stream &stream_)
{
    c4_HandlerSeq *newRoot = c4_Persist::Load(&stream_);
    if (newRoot == nullptr) {
        return false;
    }

    // fix commit-after-load bug, by using a full view copy
    // this is inefficient, but avoids mapping/strategy problems
    c4_View temp(newRoot);

    SetSize(0);
    SetStructure(temp.Description());
    InsertAt(0, temp);

    return true;
}

/// Save contents to the specified output stream
void c4_Storage::SaveTo(c4_Stream &stream_)
{
    c4_Persist::Save(&stream_, Persist()->Root());
}

t4_i32 c4_Storage::FreeSpace(t4_i32 *bytes_)
{
    return Persist()->FreeBytes(bytes_);
}

/////////////////////////////////////////////////////////////////////////////

c4_DerivedSeq::c4_DerivedSeq(c4_Sequence &seq_) : _seq(seq_)
{
    _seq.Attach(this);
}

c4_DerivedSeq::~c4_DerivedSeq()
{
    _seq.Detach(this);
}

int c4_DerivedSeq::RemapIndex(int index_, const c4_Sequence *seq_) const
{
    return seq_ == this ? index_ : _seq.RemapIndex(index_, seq_);
}

int c4_DerivedSeq::NumRows() const
{
    return _seq.NumRows();
}

int c4_DerivedSeq::NumHandlers() const
{
    return _seq.NumHandlers();
}

c4_Handler &c4_DerivedSeq::NthHandler(int colNum_) const
{
    return _seq.NthHandler(colNum_);
}

const c4_Sequence *c4_DerivedSeq::HandlerContext(int colNum_) const
{
    return _seq.HandlerContext(colNum_);
}

int c4_DerivedSeq::AddHandler(c4_Handler *handler_)
{
    return _seq.AddHandler(handler_);
}

c4_Handler *c4_DerivedSeq::CreateHandler(const c4_Property &prop_)
{
    return _seq.CreateHandler(prop_);
}

void c4_DerivedSeq::SetNumRows(int size_)
{
    _seq.SetNumRows(size_);
}

c4_Notifier *c4_DerivedSeq::PreChange(c4_Notifier &nf_)
{
    if (!GetDependencies()) {
        return nullptr;
    }

    c4_Notifier *chg = d4_new c4_Notifier(this);

    switch (nf_._type) {
    case c4_Notifier::kSetAt:
        chg->StartSetAt(nf_._index, *nf_._cursor);
        break;

    case c4_Notifier::kSet:
        chg->StartSet(nf_._index, nf_._propId, *nf_._bytes)
        ;
        break;

    case c4_Notifier::kInsertAt:
        chg->StartInsertAt(nf_._index, *nf_._cursor,
                           nf_._count);
        break;

    case c4_Notifier::kRemoveAt:
        chg->StartRemoveAt(nf_._index, nf_._count);
        break;

    case c4_Notifier::kMove:
        chg->StartMove(nf_._index, nf_._count);
        break;
    }

    return chg;
}

/////////////////////////////////////////////////////////////////////////////

c4_StreamStrategy::c4_StreamStrategy(t4_i32 buflen_) : _stream(nullptr)
    , _buffer
        (d4_new t4_byte[buflen_])
    , _buflen(buflen_)
    , _position(0)
{
    _mapStart = _buffer;
    _dataSize = buflen_;
}

c4_StreamStrategy::c4_StreamStrategy(c4_Stream *stream_) : _stream(stream_)
    , _buffer(nullptr)
    , _buflen(0)
    , _position(0)
{
}

c4_StreamStrategy::~c4_StreamStrategy()
{
    _mapStart = nullptr;
    _dataSize = 0;

    if (_buffer != nullptr) {
        delete [] _buffer;
    }
}

bool c4_StreamStrategy::IsValid() const
{
    return true;
}

int c4_StreamStrategy::DataRead(t4_i32 pos_, void *buffer_, int length_)
{
    if (_buffer != nullptr) {
        d4_assert(pos_ <= _buflen);
        _position = pos_ + _baseOffset;

        if (length_ > _buflen - _position) {
            length_ = _buflen - _position;
        }
        if (length_ > 0) {
            memcpy(buffer_, _buffer + _position, length_);
        }
    } else {
        d4_assert(_position == pos_ + _baseOffset);
        length_ = _stream != nullptr ? _stream->Read(buffer_, length_) : 0;
    }

    _position += length_;
    return length_;
}

void c4_StreamStrategy::DataWrite(t4_i32 pos_, const void *buffer_, int length_)
{
    if (_buffer != nullptr) {
        d4_assert(pos_ <= _buflen);
        _position = pos_ + _baseOffset;

        int n = length_;
        if (n > _buflen - _position) {
            n = _buflen - _position;
        }
        if (n > 0) {
            memcpy(_buffer + _position, buffer_, n);
        }
    } else {
        d4_assert(_position == pos_ + _baseOffset);
        if (_stream != nullptr && !_stream->Write(buffer_, length_)) {
            ++_failure;
        }
    }

    _position += length_;
}

t4_i32 c4_StreamStrategy::FileSize()
{
    return _position;
}

/////////////////////////////////////////////////////////////////////////////