Fix handling of 0-length streams (Issue #111)

.gitignore

@@ -16,6 +16,7 @@
 /examples/md2pdf
 /examples/pdf2text
 /examples/pdfioinfo
+/examples/pdfiomerge
 /Makefile
 /packages
 /pdfio.pc

CHANGES.md

@@ -7,6 +7,7 @@ v1.5.1 - YYYY-MM-DD
 - Fixed output of special characters in name values (Issue #106)
 - Fixed output of special characters in string values (Issue #107)
 - Fixed output of large integers in dictionaries (Issue #108)
+- Fixed handling of 0-length streams (Issue #111)
 
 
 v1.5.0 - 2025-03-06

examples/Makefile

@@ -24,7 +24,8 @@ TARGETS		=	\
 			image2pdf \
 			md2pdf \
 			pdf2text \
-			pdfioinfo
+			pdfioinfo \
+			pdfiomerge
 
 
 # Make everything
@@ -61,5 +62,10 @@ pdfioinfo:	pdfioinfo.c
 	$(CC) $(CFLAGS) -o $@ pdfioinfo.c $(LIBS)
 
 
+# pdfiomerge
+pdfiomerge:	pdfiomerge.c
+	$(CC) $(CFLAGS) -o $@ pdfiomerge.c $(LIBS)
+
+
 # Common dependencies...
 $(TARGETS):	Makefile ../pdfio.h ../pdfio-content.h

examples/pdfiomerge.c

@@ -0,0 +1,146 @@
+//
+// PDF merge program for PDFio.
+//
+// Copyright © 2025 by Michael R Sweet.
+//
+// Licensed under Apache License v2.0.  See the file "LICENSE" for more
+// information.
+//
+// Usage:
+//
+//   ./pdfmerge [-o OUTPUT.pdf] INPUT.pdf [... INPUT.pdf]
+//   ./pdfmerge INPUT.pdf [... INPUT.pdf] >OUTPUT.pdf
+//
+
+#include <pdfio.h>
+#include <string.h>
+
+
+//
+// Local functions...
+//
+
+static ssize_t	output_cb(void *output_cbdata, const void *buffer, size_t bytes);
+static int	usage(FILE *out);
+
+
+//
+// 'main()' - Main entry.
+//
+
+int					// O - Exit status
+main(int  argc,				// I - Number of command-line arguments
+     char *argv[])			// I - Command-line arguments
+{
+  int		i;			// Looping var
+  const char	*opt;			// Current option
+  pdfio_file_t	*inpdf,			// Input PDF file
+		*outpdf = NULL;		// Output PDF file
+
+
+  // Parse command-line...
+  for (i = 1; i < argc; i ++)
+  {
+    if (!strcmp(argv[i], "--help"))
+    {
+      return (usage(stdout));
+    }
+    else if (!strncmp(argv[i], "--", 2))
+    {
+      fprintf(stderr, "pdfmerge: Unknown option '%s'.\n", argv[i]);
+      return (usage(stderr));
+    }
+    else if (argv[i][0] == '-')
+    {
+      for (opt = argv[i] + 1; *opt; opt ++)
+      {
+        switch (*opt)
+        {
+          case 'o' : // -o OUTPUT.pdf
+              if (outpdf)
+              {
+                fputs("pdfmerge: Only one output file can be specified.\n", stderr);
+                return (usage(stderr));
+              }
+
+              i ++;
+              if (i >= argc)
+              {
+                fputs("pdfmerge: Missing output filename after '-o'.\n", stderr);
+                return (usage(stderr));
+              }
+
+              if ((outpdf = pdfioFileCreate(argv[i], /*version*/NULL, /*media_box*/NULL, /*crop_box*/NULL, /*error_cb*/NULL, /*error_data*/NULL)) == NULL)
+                return (1);
+              break;
+
+          default :
+              fprintf(stderr, "pdfmerge: Unknown option '-%c'.\n", *opt);
+              return (usage(stderr));
+        }
+      }
+    }
+    else if ((inpdf = pdfioFileOpen(argv[i], /*password_cb*/NULL, /*password_data*/NULL, /*error_cb*/NULL, /*error_data*/NULL)) == NULL)
+    {
+      return (1);
+    }
+    else
+    {
+      // Copy PDF file...
+      size_t	p,			// Current page
+		nump;			// Number of pages
+
+      if (!outpdf)
+      {
+	if ((outpdf = pdfioFileCreateOutput(output_cb, /*output_cbdata*/NULL, /*version*/NULL, /*media_box*/NULL, /*crop_box*/NULL, /*error_cb*/NULL, /*error_data*/NULL)) == NULL)
+	  return (1);
+      }
+
+      for (p = 0, nump = pdfioFileGetNumPages(inpdf); p < nump; p ++)
+      {
+        if (!pdfioPageCopy(outpdf, pdfioFileGetPage(inpdf, p)))
+          return (1);
+      }
+
+      pdfioFileClose(inpdf);
+    }
+  }
+
+  if (!outpdf)
+    return (usage(stderr));
+
+  pdfioFileClose(outpdf);
+
+  return (0);
+}
+
+
+//
+// 'output_cb()' - Write PDF data to the standard output...
+//
+
+static ssize_t				// O - Number of bytes written
+output_cb(void       *output_cbdata,	// I - Callback data (not used)
+          const void *buffer,		// I - Buffer to write
+          size_t     bytes)		// I - Number of bytes to write
+{
+  (void)output_cbdata;
+
+  return ((ssize_t)fwrite(buffer, 1, bytes, stdout));
+}
+
+
+//
+// 'usage()' - Show program usage.
+//
+
+static int				// O - Exit status
+usage(FILE *out)			// I - stdout or stderr
+{
+  fputs("Usage: pdfmerge [OPTIONS] INPUT.pdf [... INPUT.pdf] >OUTPUT.pdf\n", out);
+  fputs("Options:\n", out);
+  fputs("  --help                   Show help.\n", out);
+  fputs("  -o OUTPUT.pdf            Send output to filename instead of stdout.\n", out);
+
+  return (out == stdout ? 0 : 1);
+}

pdfio-object.c

@@ -307,6 +307,7 @@ pdfioObjGetLength(pdfio_obj_t *obj)	// I - Object
 
   if ((lenobj = pdfioDictGetObj(obj->value.value.dict, "Length")) == NULL)
   {
+    if (!_pdfioDictGetValue(obj->value.value.dict, "Length"))
       _pdfioFileError(obj->pdf, "Unable to get length of stream.");
     return (0);
   }

pdfio-stream.c

@@ -439,7 +439,7 @@ _pdfioStreamOpen(pdfio_obj_t *obj,	// I - Object
   st->pdf = obj->pdf;
   st->obj = obj;
 
-  if ((st->remaining = pdfioObjGetLength(obj)) == 0)
+  if ((st->remaining = pdfioObjGetLength(obj)) == 0 && !_pdfioDictGetValue(pdfioObjGetDict(obj), "Length"))
   {
     _pdfioFileError(obj->pdf, "No stream data.");
     goto error;