Top-level json: write incrementally

This commit just changes the order in which fields are written to the
json without changing their content. All the json files in the test
suite were modified with this script to ensure that we didn't get any
changes other than ordering.

----------
#!/usr/bin/env python3
import json
import sys

def json_dumps(data):
    return json.dumps(data, ensure_ascii=False,
                      indent=2, separators=(',', ': '))

for filename in sys.argv[1:]:
    with open(filename, 'r') as f:
        data = json.loads(f.read())
    newdata = {}
    for i in ('version', 'parameters', 'pages', 'pagelabels',
              'acroform', 'attachments', 'encrypt', 'outlines',
              'objects', 'objectinfo'):
        if i in data:
            newdata[i] = data[i]
print(json_dumps(newdata))
----------

1 files changed, 49 insertions, 33 deletions

diff --git a/libqpdf/QPDFJob.cc b/libqpdf/QPDFJob.cc
index 468a0046..3591468d 100644
--- a/libqpdf/QPDFJob.cc
+++ b/libqpdf/QPDFJob.cc
@@ -1042,11 +1042,11 @@ QPDFJob::getWantedJSONObjects()
 }
 
 void
-QPDFJob::doJSONObjects(QPDF& pdf, JSON& j)
+QPDFJob::doJSONObjects(Pipeline* p, bool& first, QPDF& pdf)
 {
     bool all_objects = m->json_objects.empty();
     std::set<QPDFObjGen> wanted_og = getWantedJSONObjects();
-    JSON j_objects = j.addDictionaryMember("objects", JSON::makeDictionary());
+    JSON j_objects = JSON::makeDictionary();
     if (all_objects || m->json_objects.count("trailer")) {
         j_objects.addDictionaryMember(
             "trailer", pdf.getTrailer().getJSON(true));
@@ -1057,15 +1057,15 @@ QPDFJob::doJSONObjects(QPDF& pdf, JSON& j)
             j_objects.addDictionaryMember(obj.unparse(), obj.getJSON(true));
         }
     }
+    JSON::writeDictionaryItem(p, first, "objects", j_objects, 0);
 }
 
 void
-QPDFJob::doJSONObjectinfo(QPDF& pdf, JSON& j)
+QPDFJob::doJSONObjectinfo(Pipeline* p, bool& first, QPDF& pdf)
 {
     bool all_objects = m->json_objects.empty();
     std::set<QPDFObjGen> wanted_og = getWantedJSONObjects();
-    JSON j_objectinfo =
-        j.addDictionaryMember("objectinfo", JSON::makeDictionary());
+    JSON j_objectinfo = JSON::makeDictionary();
     for (auto& obj: pdf.getAllObjects()) {
         if (all_objects || wanted_og.count(obj.getObjGen())) {
             auto j_details = j_objectinfo.addDictionaryMember(
@@ -1084,12 +1084,13 @@ QPDFJob::doJSONObjectinfo(QPDF& pdf, JSON& j)
                            : JSON::makeNull()));
         }
     }
+    JSON::writeDictionaryItem(p, first, "objectinfo", j_objectinfo, 0);
 }
 
 void
-QPDFJob::doJSONPages(QPDF& pdf, JSON& j)
+QPDFJob::doJSONPages(Pipeline* p, bool& first, QPDF& pdf)
 {
-    JSON j_pages = j.addDictionaryMember("pages", JSON::makeArray());
+    JSON j_pages = JSON::makeArray();
     QPDFPageDocumentHelper pdh(pdf);
     QPDFPageLabelDocumentHelper pldh(pdf);
     QPDFOutlineDocumentHelper odh(pdf);
@@ -1158,12 +1159,13 @@ QPDFJob::doJSONPages(QPDF& pdf, JSON& j)
         }
         j_page.addDictionaryMember("pageposfrom1", JSON::makeInt(1 + pageno));
     }
+    JSON::writeDictionaryItem(p, first, "pages", j_pages, 0);
 }
 
 void
-QPDFJob::doJSONPageLabels(QPDF& pdf, JSON& j)
+QPDFJob::doJSONPageLabels(Pipeline* p, bool& first, QPDF& pdf)
 {
-    JSON j_labels = j.addDictionaryMember("pagelabels", JSON::makeArray());
+    JSON j_labels = JSON::makeArray();
     QPDFPageLabelDocumentHelper pldh(pdf);
     QPDFPageDocumentHelper pdh(pdf);
     std::vector<QPDFPageObjectHelper> pages = pdh.getAllPages();
@@ -1186,6 +1188,7 @@ QPDFJob::doJSONPageLabels(QPDF& pdf, JSON& j)
             j_label.addDictionaryMember("label", (*iter).getJSON());
         }
     }
+    JSON::writeDictionaryItem(p, first, "pagelabels", j_labels, 0);
 }
 
 static void
@@ -1215,7 +1218,7 @@ add_outlines_to_json(
 }
 
 void
-QPDFJob::doJSONOutlines(QPDF& pdf, JSON& j)
+QPDFJob::doJSONOutlines(Pipeline* p, bool& first, QPDF& pdf)
 {
     std::map<QPDFObjGen, int> page_numbers;
     QPDFPageDocumentHelper dh(pdf);
@@ -1226,15 +1229,16 @@ QPDFJob::doJSONOutlines(QPDF& pdf, JSON& j)
         page_numbers[oh.getObjGen()] = ++n;
     }
 
-    JSON j_outlines = j.addDictionaryMember("outlines", JSON::makeArray());
+    JSON j_outlines = JSON::makeArray();
     QPDFOutlineDocumentHelper odh(pdf);
     add_outlines_to_json(odh.getTopLevelOutlines(), j_outlines, page_numbers);
+    JSON::writeDictionaryItem(p, first, "outlines", j_outlines, 0);
 }
 
 void
-QPDFJob::doJSONAcroform(QPDF& pdf, JSON& j)
+QPDFJob::doJSONAcroform(Pipeline* p, bool& first, QPDF& pdf)
 {
-    JSON j_acroform = j.addDictionaryMember("acroform", JSON::makeDictionary());
+    JSON j_acroform = JSON::makeDictionary();
     QPDFAcroFormDocumentHelper afdh(pdf);
     j_acroform.addDictionaryMember(
         "hasacroform", JSON::makeBool(afdh.hasAcroForm()));
@@ -1297,10 +1301,11 @@ QPDFJob::doJSONAcroform(QPDF& pdf, JSON& j)
                 "annotationflags", JSON::makeInt(aoh.getFlags()));
         }
     }
+    JSON::writeDictionaryItem(p, first, "acroform", j_acroform, 0);
 }
 
 void
-QPDFJob::doJSONEncrypt(QPDF& pdf, JSON& j)
+QPDFJob::doJSONEncrypt(Pipeline* p, bool& first, QPDF& pdf)
 {
     int R = 0;
     int P = 0;
@@ -1310,7 +1315,7 @@ QPDFJob::doJSONEncrypt(QPDF& pdf, JSON& j)
     QPDF::encryption_method_e file_method = QPDF::e_none;
     bool is_encrypted =
         pdf.isEncrypted(R, P, V, stream_method, string_method, file_method);
-    JSON j_encrypt = j.addDictionaryMember("encrypt", JSON::makeDictionary());
+    JSON j_encrypt = JSON::makeDictionary();
     j_encrypt.addDictionaryMember("encrypted", JSON::makeBool(is_encrypted));
     j_encrypt.addDictionaryMember(
         "userpasswordmatched",
@@ -1381,13 +1386,13 @@ QPDFJob::doJSONEncrypt(QPDF& pdf, JSON& j)
         "stringmethod", JSON::makeString(s_string_method));
     j_parameters.addDictionaryMember(
         "filemethod", JSON::makeString(s_file_method));
+    JSON::writeDictionaryItem(p, first, "encrypt", j_encrypt, 0);
 }
 
 void
-QPDFJob::doJSONAttachments(QPDF& pdf, JSON& j)
+QPDFJob::doJSONAttachments(Pipeline* p, bool& first, QPDF& pdf)
 {
-    JSON j_attachments =
-        j.addDictionaryMember("attachments", JSON::makeDictionary());
+    JSON j_attachments = JSON::makeDictionary();
     QPDFEmbeddedFileDocumentHelper efdh(pdf);
     for (auto const& iter: efdh.getEmbeddedFiles()) {
         std::string const& key = iter.first;
@@ -1402,6 +1407,7 @@ QPDFJob::doJSONAttachments(QPDF& pdf, JSON& j)
             "preferredcontents",
             JSON::makeString(fsoh->getEmbeddedFileStream().unparse()));
     }
+    JSON::writeDictionaryItem(p, first, "attachments", j_attachments, 0);
 }
 
 JSON
@@ -1600,13 +1606,14 @@ QPDFJob::doJSON(QPDF& pdf, Pipeline* p)
         p = pl_str.get();
     }
 
-    JSON j = JSON::makeDictionary();
+    bool first = true;
+    JSON::writeDictionaryOpen(p, first, 0);
     // 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));
-    JSON j_params = j.addDictionaryMember("parameters", JSON::makeDictionary());
+    JSON::writeDictionaryItem(p, first, "version", JSON::makeInt(1), 0);
+    JSON j_params = JSON::makeDictionary();
     std::string decode_level_str;
     switch (m->decode_level) {
     case qpdf_dl_none:
@@ -1624,28 +1631,36 @@ QPDFJob::doJSON(QPDF& pdf, Pipeline* p)
     }
     j_params.addDictionaryMember(
         "decodelevel", JSON::makeString(decode_level_str));
+    JSON::writeDictionaryItem(p, first, "parameters", j_params, 0);
 
     bool all_keys = m->json_keys.empty();
     // The list of selectable top-level keys id duplicated in the
     // following places: job.yml, QPDFJob::json_schema, and
     // QPDFJob::doJSON.
+
+    // We do pages and pagelabels first since they have the side
+    // effect of repairing the pages tree, which could potentially
+    // impact object references in remaining items.
     if (all_keys || m->json_keys.count("pages")) {
-        doJSONPages(pdf, j);
+        doJSONPages(p, first, pdf);
     }
     if (all_keys || m->json_keys.count("pagelabels")) {
-        doJSONPageLabels(pdf, j);
-    }
-    if (all_keys || m->json_keys.count("outlines")) {
-        doJSONOutlines(pdf, j);
+        doJSONPageLabels(p, first, pdf);
     }
+
+    // The non-special keys are output in alphabetical order, but the
+    // order doesn't actually matter.
     if (all_keys || m->json_keys.count("acroform")) {
-        doJSONAcroform(pdf, j);
+        doJSONAcroform(p, first, pdf);
+    }
+    if (all_keys || m->json_keys.count("attachments")) {
+        doJSONAttachments(p, first, pdf);
     }
     if (all_keys || m->json_keys.count("encrypt")) {
-        doJSONEncrypt(pdf, j);
+        doJSONEncrypt(p, first, pdf);
     }
-    if (all_keys || m->json_keys.count("attachments")) {
-        doJSONAttachments(pdf, j);
+    if (all_keys || m->json_keys.count("outlines")) {
+        doJSONOutlines(p, first, pdf);
     }
 
     // We do objects and objectinfo last so their information is
@@ -1653,13 +1668,14 @@ QPDFJob::doJSON(QPDF& pdf, Pipeline* p)
     // file with any page tree problems and the page tree not
     // flattened, select objects/objectinfo without other keys.
     if (all_keys || m->json_keys.count("objects")) {
-        doJSONObjects(pdf, j);
+        doJSONObjects(p, first, pdf);
     }
     if (all_keys || m->json_keys.count("objectinfo")) {
-        doJSONObjectinfo(pdf, j);
+        doJSONObjectinfo(p, first, pdf);
     }
 
-    *p << j.unparse() << "\n";
+    JSON::writeDictionaryClose(p, first, 0);
+    *p << "\n";
 
     if (this->m->test_json_schema) {
         // Check against schema