src/pdf/SkPDFDocumentPriv.h

/*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
#ifndef SkPDFDocumentPriv_DEFINED
#define SkPDFDocumentPriv_DEFINED

#include "SkCanvas.h"
#include "SkPDFCanon.h"
#include "SkPDFDocument.h"
#include "SkPDFFont.h"
#include "SkPDFMetadata.h"
#include "SkUUID.h"

#include <atomic>

class SkPDFDevice;
class SkPDFTag;
class SkExecutor;

const char* SkPDFGetNodeIdKey();

struct SkPDFFileOffset {
    int fValue;
};

struct SkPDFOffsetMap {
    void set(SkPDFIndirectReference, SkPDFFileOffset);
    SkPDFFileOffset get(SkPDFIndirectReference r);
    std::vector<SkPDFFileOffset> fOffsets;
};

// Logically part of SkPDFDocument (like SkPDFCanon), but separate to
// keep similar functionality together.
struct SkPDFObjectSerializer {
    std::atomic<int> fNextObjectNumber = {1};
    SkPDFIndirectReference reserve() { return SkPDFIndirectReference{fNextObjectNumber++}; }
    SkPDFOffsetMap fOffsets;
    size_t fBaseOffset = SIZE_MAX;

    SkPDFObjectSerializer();
    ~SkPDFObjectSerializer();
    SkPDFObjectSerializer(SkPDFObjectSerializer&&) = delete;
    SkPDFObjectSerializer& operator=(SkPDFObjectSerializer&&) = delete;
    SkPDFObjectSerializer(const SkPDFObjectSerializer&) = delete;
    SkPDFObjectSerializer& operator=(const SkPDFObjectSerializer&) = delete;

    SkWStream* beginObject(SkPDFIndirectReference, SkWStream*);
    void endObject(SkWStream*);
    void serializeHeader(SkWStream*);
    void serializeObject(const sk_sp<SkPDFObject>&, SkWStream*);
    void serializeFooter(SkWStream*,
                         SkPDFIndirectReference infoDict,
                         SkPDFIndirectReference docCatalog,
                         SkUUID uuid);
    SkPDFFileOffset offset(SkWStream*);
};

/** Concrete implementation of SkDocument that creates PDF files. This
    class does not produced linearized or optimized PDFs; instead it
    it attempts to use a minimum amount of RAM. */
class SkPDFDocument : public SkDocument {
public:
    SkPDFDocument(SkWStream*, SkPDF::Metadata);
    ~SkPDFDocument() override;
    SkCanvas* onBeginPage(SkScalar, SkScalar) override;
    void onEndPage() override;
    void onClose(SkWStream*) override;
    void onAbort() override;

    /**
       Serialize the object, as well as any other objects it
       indirectly refers to.  If any any other objects have been added
       to the SkPDFObjNumMap without serializing them, they will be
       serialized as well.

       It might go without saying that objects should not be changed
       after calling serialize, since those changes will be too late.
     */
    SkPDFIndirectReference serialize(const sk_sp<SkPDFObject>&);
    SkPDFIndirectReference emit(const SkPDFObject&, SkPDFIndirectReference);
    SkPDFIndirectReference emit(const SkPDFObject& o) { return this->emit(o, this->reserveRef()); }
    SkPDFCanon* canon() { return &fCanon; }
    const SkPDF::Metadata& metadata() const { return fMetadata; }

    sk_sp<SkPDFDict> getPage(int pageIndex) const;
    // Returns -1 if no mark ID.
    int getMarkIdForNodeId(int nodeId);

    SkPDFIndirectReference reserveRef();
    SkWStream* beginObject(SkPDFIndirectReference);
    void endObject();

    SkExecutor* executor() const { return fExecutor; }

private:
    sk_sp<SkPDFTag> recursiveBuildTagTree(const SkPDF::StructureElementNode& node,
                                          sk_sp<SkPDFTag> parent);

    SkPDFObjectSerializer fObjectSerializer;
    SkPDFCanon fCanon;
    SkCanvas fCanvas;
    std::vector<sk_sp<SkPDFDict>> fPages;
    sk_sp<SkPDFDict> fDests;
    sk_sp<SkPDFDevice> fPageDevice;
    SkUUID fUUID;
    SkPDFIndirectReference fInfoDict;
    SkPDFIndirectReference fXMP;
    SkPDF::Metadata fMetadata;
    SkScalar fRasterScale = 1;
    SkScalar fInverseRasterScale = 1;
    SkExecutor* fExecutor = nullptr;

    // For tagged PDFs.

    // The tag root, which owns its child tags and so on.
    sk_sp<SkPDFTag> fTagRoot;
    // Array of page -> array of marks mapping to tags.
    SkTArray<SkTArray<sk_sp<SkPDFTag>>> fMarksPerPage;
    // A mapping from node ID to tag for fast lookup.
    SkTHashMap<int, sk_sp<SkPDFTag>> fNodeIdToTag;

    std::atomic<int> fOutstandingRefs = {0};
    SkMutex fMutex;
    SkSemaphore fSemaphore;

    void reset();
};

#endif  // SkPDFDocumentPriv_DEFINED