Add qpdf_empty_pdf to C API

ChangeLog

@@ -1,5 +1,7 @@
 2022-02-05  Jay Berkenbilt  <ejb@ql.org>
 
+	* Expose QPDF::emptyPDF to the C API as qpdf_empty_pdf()
+
 	* Add comments letting people know that the version string
 	returned by QPDF::QPDFVersion and qpdf_get_qpdf_version is static.
 

TODO

@@ -1,9 +1,6 @@
 10.6
 ====
 
-* Expose emptyPDF to the C API. Ensure that qpdf_get_qpdf_version is
-  always static.
-
 * Consider doing one big commit to reformat the entire codebase using
   clang-format or a similar tool. Consider using blame.ignoreRevsFile
   or similar (or otherwise study git blame to see how to minimize the

include/qpdf/qpdf-c.h

@@ -178,9 +178,9 @@ extern "C" {
     char const* qpdf_get_qpdf_version();
 
     /* Returns dynamically allocated qpdf_data pointer; must be freed
-     * by calling qpdf_cleanup. You must call qpdf_read or one of the
+     * by calling qpdf_cleanup. You must call qpdf_read, one of the
-     * other qpdf_read_* functions before calling any function that
+     * other qpdf_read_* functions, or qpdf_empty_pdf before calling
-     * would need to operate on the PDF file.
+     * any function that would need to operate on the PDF file.
      */
     QPDF_DLL
     qpdf_data qpdf_init();
@@ -289,6 +289,13 @@ extern "C" {
 				     unsigned long long size,
 				     char const* password);
 
+    /* Calling qpdf_empty_pdf initializes this qpdf object with an
+     * empty PDF, making it possible to create a PDF from scratch
+     * using the C API. Added in 10.6.
+     */
+    QPDF_DLL
+    QPDF_ERROR_CODE qpdf_empty_pdf(qpdf_data qpdf);
+
     /* Read functions below must be called after qpdf_read or
      * qpdf_read_memory. */
 

libqpdf/qpdf-c.cc

@@ -356,6 +356,14 @@ QPDF_ERROR_CODE qpdf_read_memory(qpdf_data qpdf,
     return status;
 }
 
+QPDF_ERROR_CODE qpdf_empty_pdf(qpdf_data qpdf)
+{
+    qpdf->filename = "empty PDF";
+    qpdf->qpdf->emptyPDF();
+    QTC::TC("qpdf", "qpdf-c called qpdf_empty_pdf");
+    return QPDF_SUCCESS;
+}
+
 char const* qpdf_get_pdf_version(qpdf_data qpdf)
 {
     QTC::TC("qpdf", "qpdf-c called qpdf_get_pdf_version");

qpdf/qpdf-ctest.c

@@ -1242,6 +1242,19 @@ static void test40(char const* infile,
     report_errors();
 }
 
+static void test41(char const* infile,
+		   char const* password,
+		   char const* outfile,
+		   char const* xarg)
+{
+    /* Empty PDF -- infile is ignored*/
+    assert(qpdf_empty_pdf(qpdf) == 0);
+    qpdf_init_write(qpdf, outfile);
+    qpdf_set_static_ID(qpdf, QPDF_TRUE);
+    qpdf_write(qpdf);
+    report_errors();
+}
+
 int main(int argc, char* argv[])
 {
     char* p = 0;
@@ -1322,6 +1335,7 @@ int main(int argc, char* argv[])
 	  (n == 38) ? test38 :
 	  (n == 39) ? test39 :
 	  (n == 40) ? test40 :
+	  (n == 41) ? test41 :
 	  0);
 
     if (fn == 0)

qpdf/qpdf.testcov

@@ -639,3 +639,4 @@ QPDFJob json encrypt no key length 0
 QPDFJob json encrypt duplicate key length 0
 QPDFJob json encrypt missing password 0
 QPDFJob json pages no file 0
+qpdf-c called qpdf_empty_pdf 0

qpdf/qtest/qpdf.test

@@ -3553,7 +3553,7 @@ my @capi = (
     [8, 'no original object ids'],
     [9, 'uncompressed streams'],
     );
-$n_tests += (2 * @capi) + 3;
+$n_tests += (2 * @capi) + 5;
 foreach my $d (@capi)
 {
     my ($n, $description) = @$d;
@@ -3590,6 +3590,14 @@ $td->runtest("write damaged",
 	      $td->EXIT_STATUS => 0},
 	     $td->NORMALIZE_NEWLINES);
 
+$td->runtest("empty PDF",
+	     {$td->COMMAND => "qpdf-ctest 41 - '' a.pdf"},
+	     {$td->STRING => "C test 41 done\n", $td->EXIT_STATUS => 0},
+	     $td->NORMALIZE_NEWLINES);
+$td->runtest("check output",
+	     {$td->FILE => "a.pdf"},
+	     {$td->FILE => "c-empty.pdf"});
+
 show_ntests();
 # ----------
 $td->notify("--- Deterministic ID Tests ---");

qpdf/qtest/qpdf/c-empty.pdf

@@ -0,0 +1,17 @@
+%PDF-1.3
+%¿÷¢þ
+1 0 obj
+<< /Pages 2 0 R /Type /Catalog >>
+endobj
+2 0 obj
+<< /Count 0 /Kids [ ] /Type /Pages >>
+endobj
+xref
+0 3
+0000000000 65535 f 
+0000000015 00000 n 
+0000000064 00000 n 
+trailer << /Root 1 0 R /Size 3 /ID [<31415926535897932384626433832795><31415926535897932384626433832795>] >>
+startxref
+117
+%%EOF