Preliminary implementation of json mode

The json mode implemented in this commit is not the final version, or are the command line arguments used to invoke it.

Preliminary implementation of json mode
The json mode implemented in this commit is not the final version, or are the command line arguments used to invoke it.
Jay Berkenbilt
1 parent fa366435
Showing 1 changed file with 239 additions and 0 deletions
qpdf/qpdf.cc
@@ -17,6 +17,7 @@
 #include <qpdf/QPDFPageDocumentHelper.hh>
 #include <qpdf/QPDFPageObjectHelper.hh>
 #include <qpdf/QPDFPageLabelDocumentHelper.hh>
+#include <qpdf/QPDFOutlineDocumentHelper.hh>
 #include <qpdf/QPDFExc.hh>
 #include <qpdf/QPDFWriter.hh>
@@ -117,6 +118,7 @@ struct Options
         show_filtered_stream_data(false),
         show_pages(false),
         show_page_images(false),
+        show_json(false),
         check(false),
         require_outfile(true),
         infilename(0),
@@ -189,6 +191,7 @@ struct Options
     bool show_filtered_stream_data;
     bool show_pages;
     bool show_page_images;
+    bool show_json;
     bool check;
     std::vector<PageSpec> page_specs;
     std::map<std::string, RotationSpec> rotations;
@@ -549,6 +552,75 @@ void usage(std::string const&amp; msg)
     exit(EXIT_ERROR);
 }
+static JSON json_schema()
+{
+    // This JSON object doubles as a schema and as documentation for
+    // our JSON output. Any schema mismatch is a bug in qpdf. This
+    // helps to enforce our policy of consistently providing a known
+    // structure where every documented key will always be present,
+    // which makes it easier to consume our JSON. This is discussed in
+    // more depth in the manual.
+    JSON schema = JSON::makeDictionary();
+    schema.addDictionaryMember(
+        "version", JSON::makeString(
+            "JSON format serial number; increased for non-compatible changes"));
+    schema.addDictionaryMember(
+        "objects", JSON::makeString(
+            "Original objects; keys are 'trailer' or 'n n R'"));
+    JSON page = schema.addDictionaryMember("pages", JSON::makeArray()).
+        addArrayElement(JSON::makeDictionary());
+    page.addDictionaryMember(
+        "object",
+        JSON::makeString("reference to original page object"));
+    JSON image = page.addDictionaryMember("images", JSON::makeArray()).
+        addArrayElement(JSON::makeDictionary());
+    image.addDictionaryMember(
+        "object",
+        JSON::makeString("reference to image stream"));
+    image.addDictionaryMember(
+        "width",
+        JSON::makeString("image width"));
+    image.addDictionaryMember(
+        "height",
+        JSON::makeString("image height"));
+    image.addDictionaryMember("filter", JSON::makeArray()).
+        addArrayElement(
+            JSON::makeString("filters applied to image data"));
+    image.addDictionaryMember("decodeparms", JSON::makeArray()).
+        addArrayElement(
+            JSON::makeString("decode parameters for image data"));
+    image.addDictionaryMember(
+        "filterable",
+        JSON::makeString("whether image data can be decoded"
+                         " using the decode level qpdf was invoked with"));
+    page.addDictionaryMember("contents", JSON::makeArray()).
+        addArrayElement(
+            JSON::makeString("reference to each content stream"));
+    page.addDictionaryMember(
+        "label",
+        JSON::makeString("page label dictionary, or null if none"));
+    JSON labels = schema.addDictionaryMember("pagelabels", JSON::makeArray()).
+        addArrayElement(JSON::makeDictionary());
+    labels.addDictionaryMember(
+        "index",
+        JSON::makeString("starting page position starting from zero"));
+    labels.addDictionaryMember(
+        "label",
+        JSON::makeString("page label dictionary"));
+    JSON outline = page.addDictionaryMember("outlines", JSON::makeArray()).
+        addArrayElement(JSON::makeDictionary());
+    outline.addDictionaryMember(
+        "object",
+        JSON::makeString("reference to outline that targets this page"));
+    outline.addDictionaryMember(
+        "title",
+        JSON::makeString("outline title"));
+    outline.addDictionaryMember(
+        "destination",
+        JSON::makeString("outline destination dictionary"));
+    return schema;
+}
+
 static std::string show_bool(bool v)
 {
     return v ? "allowed" : "not allowed";
@@ -1613,6 +1685,11 @@ static void parse_options(int argc, char* argv[], Options&amp; o)
             {
                 o.show_page_images = true;
             }
+            else if (strcmp(arg, "show-json") == 0)
+            {
+                o.show_json = true;
+                o.require_outfile = false;
+            }
             else if (strcmp(arg, "check") == 0)
             {
                 o.check = true;
@@ -1884,6 +1961,164 @@ static void do_show_pages(QPDF&amp; pdf, Options&amp; o)
     }
 }
+static void do_show_json(QPDF& pdf, Options& o)
+{
+    JSON j = JSON::makeDictionary();
+    // This version is updated every time a non-backward-compatible
+    // change is made to the JSON format. Clients of the JSON are to
+    // ignore unrecognized keys, so we only update the version of a
+    // key disappears or if its value changes meaning.
+    j.addDictionaryMember("version", JSON::makeInt(1));
+
+    // Objects
+
+    // Add all objects. Do this first before other code below modifies
+    // things by doing stuff like calling
+    // pushInheritedAttributesToPage.
+    JSON j_objects = j.addDictionaryMember("objects", JSON::makeDictionary());
+    j_objects.addDictionaryMember("trailer", pdf.getTrailer().getJSON(true));
+    std::vector<QPDFObjectHandle> objects = pdf.getAllObjects();
+    for (std::vector<QPDFObjectHandle>::iterator iter = objects.begin();
+         iter != objects.end(); ++iter)
+    {
+        j_objects.addDictionaryMember(
+            (*iter).unparse(), (*iter).getJSON(true));
+    }
+
+    // Pages
+
+    JSON j_pages = j.addDictionaryMember("pages", JSON::makeArray());
+    QPDFPageDocumentHelper dh(pdf);
+    QPDFPageLabelDocumentHelper pldh(pdf);
+    QPDFOutlineDocumentHelper odh(pdf);
+    dh.pushInheritedAttributesToPage();
+    std::vector<QPDFPageObjectHelper> pages = dh.getAllPages();
+    size_t pageno = 0;
+    for (std::vector<QPDFPageObjectHelper>::iterator iter = pages.begin();
+         iter != pages.end(); ++iter, ++pageno)
+    {
+        JSON j_page = j_pages.addArrayElement(JSON::makeDictionary());
+        QPDFPageObjectHelper& ph(*iter);
+        QPDFObjectHandle page = ph.getObjectHandle();
+        j_page.addDictionaryMember("object", page.getJSON());
+        JSON j_images = j_page.addDictionaryMember(
+            "images", JSON::makeArray());
+        std::map<std::string, QPDFObjectHandle> images =
+            ph.getPageImages();
+        for (std::map<std::string, QPDFObjectHandle>::iterator iter =
+                 images.begin();
+             iter != images.end(); ++iter)
+        {
+            JSON j_image = j_images.addArrayElement(JSON::makeDictionary());
+            j_image.addDictionaryMember(
+                "name", JSON::makeString((*iter).first));
+            QPDFObjectHandle image = (*iter).second;
+            QPDFObjectHandle dict = image.getDict();
+            j_image.addDictionaryMember("object", image.getJSON());
+            j_image.addDictionaryMember(
+                "width", dict.getKey("/Width").getJSON());
+            j_image.addDictionaryMember(
+                "height", dict.getKey("/Height").getJSON());
+            QPDFObjectHandle filters = dict.getKey("/Filter").wrapInArray();
+            j_image.addDictionaryMember(
+                "filter", filters.getJSON());
+            QPDFObjectHandle decode_parms = dict.getKey("/DecodeParms");
+            QPDFObjectHandle dp_array;
+            if (decode_parms.isArray())
+            {
+                dp_array = decode_parms;
+            }
+            else
+            {
+                dp_array = QPDFObjectHandle::newArray();
+                for (int i = 0; i < filters.getArrayNItems(); ++i)
+                {
+                    dp_array.appendItem(decode_parms);
+                }
+            }
+            j_image.addDictionaryMember("decodeparms", dp_array.getJSON());
+            j_image.addDictionaryMember(
+                "filterable",
+                JSON::makeBool(
+                    image.pipeStreamData(0, 0, o.decode_level, true)));
+        }
+        j_page.addDictionaryMember("images", j_images);
+        JSON j_contents = j_page.addDictionaryMember(
+            "contents", JSON::makeArray());
+        std::vector<QPDFObjectHandle> content = ph.getPageContents();
+        for (std::vector<QPDFObjectHandle>::iterator iter = content.begin();
+             iter != content.end(); ++iter)
+        {
+            j_contents.addArrayElement((*iter).getJSON());
+        }
+        j_page.addDictionaryMember(
+            "label", pldh.getLabelForPage(pageno).getJSON());
+        JSON j_outlines = j_page.addDictionaryMember(
+            "outlines", JSON::makeArray());
+        std::list<QPDFOutlineObjectHelper> outlines =
+            odh.getOutlinesForPage(page.getObjGen());
+        for (std::list<QPDFOutlineObjectHelper>::iterator oiter =
+                 outlines.begin();
+             oiter != outlines.end(); ++oiter)
+        {
+            JSON j_outline = j_outlines.addArrayElement(JSON::makeDictionary());
+            j_outline.addDictionaryMember(
+                "object", (*oiter).getObjectHandle().getJSON());
+            j_outline.addDictionaryMember(
+                "title", JSON::makeString((*oiter).getTitle()));
+            j_outline.addDictionaryMember(
+                "destination", (*oiter).getDest().getJSON(true));
+        }
+    }
+
+    // Page labels
+
+    JSON j_labels = j.addDictionaryMember("pagelabels", JSON::makeArray());
+    if (pldh.hasPageLabels())
+    {
+        std::vector<QPDFObjectHandle> labels;
+        pldh.getLabelsForPageRange(0, pages.size() - 1, 0, labels);
+        for (std::vector<QPDFObjectHandle>::iterator iter = labels.begin();
+             iter != labels.end(); ++iter)
+        {
+            std::vector<QPDFObjectHandle>::iterator next = iter;
+            ++next;
+            if (next == labels.end())
+            {
+                // This can't happen, so ignore it. This could only
+                // happen if getLabelsForPageRange somehow returned an
+                // odd number of items.
+                break;
+            }
+            JSON j_label = j_labels.addArrayElement(JSON::makeDictionary());
+            j_label.addDictionaryMember("index", (*iter).getJSON());
+            ++iter;
+            j_label.addDictionaryMember("label", (*iter).getJSON());
+        }
+    }
+
+    // Check against schema
+
+    JSON schema = json_schema();
+    std::list<std::string> errors;
+    if (! j.checkSchema(schema, errors))
+    {
+        std::cerr
+            << whoami << " didn't create JSON that complies with its own\n\
+rules. Please report this as a bug at\n\
+   https://github.com/qpdf/qpdf/issues/new\n\
+ideally with the file that caused the error and the output below. Thanks!\n\
+\n";
+        for (std::list<std::string>::iterator iter = errors.begin();
+             iter != errors.end(); ++iter)
+        {
+            std::cerr << (*iter) << std::endl;
+        }
+    }
+
+    std::cout << j.serialize() << std::endl;
+}
+
 static void do_inspection(QPDF& pdf, Options& o)
 {
     int exit_code = 0;
@@ -1891,6 +2126,10 @@ static void do_inspection(QPDF&amp; pdf, Options&amp; o)
     {
         do_check(pdf, o, exit_code);
     }
+    if (o.show_json)
+    {
+        do_show_json(pdf, o);
+    }
     if (o.show_npages)
     {
         QTC::TC("qpdf", "qpdf npages");