Be tolerant of zero-page jobs

https://github.com/OpenPrinting/cups-filters/issues/117

src/job.cc

@@ -26,17 +26,18 @@
 job::job(FILE *out, const std::string &job_name)
     : out_(out),
       job_name_(job_name),
-      page_params_() {
+      page_params_(),
+      pages_(0) {
   // Delete dubious characters from job name
   std::replace_if(job_name_.begin(), job_name_.end(), [](char c) {
       return c < 32 || c >= 127 || c == '"' || c == '\\';
     }, ' ');
-
-  begin_job();
 }
 
 job::~job() {
-  end_job();
+  if (pages_ != 0) {
+    end_job();
+  }
 }
 
 void job::begin_job() {
@@ -86,6 +87,11 @@ void job::encode_page(const page_params &page_params,
                       int lines,
                       int linesize,
                       nextline_fn nextline) {
+  if (pages_ == 0) {
+    begin_job();
+  }
+  ++pages_;
+
   if (!(page_params_ == page_params)) {
     page_params_ = page_params;
     write_page_header();

src/job.h

@@ -55,6 +55,10 @@ class job {
                    int linesize,
                    nextline_fn nextline);
 
+  int pages() const {
+    return pages_;
+  }
+
  private:
   void begin_job();
   void end_job();
@@ -63,6 +67,7 @@ class job {
   FILE *out_;
   std::string job_name_;
   page_params page_params_;
+  int pages_;
 };
 
 #endif  // JOB_H

src/main.cc

@@ -170,7 +170,6 @@ int main(int argc, char *argv[]) {
     return 1;
   }
 
-  int pages = 0;
   {
     job job(stdout, ascii_job_name(job_id, job_user, job_name));
     cups_page_header2_t header;
@@ -179,11 +178,11 @@ int main(int argc, char *argv[]) {
           || header.cupsBitsPerColor != 1
           || header.cupsNumColors != 1
           || header.cupsBytesPerLine > 10000) {
-        fprintf(stderr, "ERROR: " PACKAGE ": Page %d: Bogus raster data.\n", pages + 1);
+        fprintf(stderr, "ERROR: " PACKAGE ": Page %d: Bogus raster data.\n", job.pages() + 1);
         dump_page_header(header);
         return 1;
       }
-      if (pages == 0) {
+      if (job.pages() == 0) {
         fprintf(stderr, "DEBUG: " PACKAGE ": Page header of first page\n");
         dump_page_header(header);
       }
@@ -191,13 +190,12 @@ int main(int argc, char *argv[]) {
                       header.cupsHeight,
                       header.cupsBytesPerLine,
                       next_line);
-      fprintf(stderr, "PAGE: %d %d\n", ++pages, header.NumCopies);
+      fprintf(stderr, "PAGE: %d %d\n", job.pages(), header.NumCopies);
     }
-  }
 
-  if (pages == 0) {
-    fprintf(stderr, "ERROR: " PACKAGE ": No pages were found.\n");
-    return 1;
+    if (job.pages() == 0) {
+      fprintf(stderr, "ERROR: " PACKAGE ": No pages were found.\n");
+    }
   }
 
   fflush(stdout);