pdf: Drop generation number from public interfaces.

The generation number is only needed for decryption, and is assumed
to be zero or irrelevant for all other uses.

Store the original object number and generation in the xref slot, so
that we can decrypt them even when the objects have been renumbered,
without needing to pass the original object number around through
the stream loading APIs.

1 files changed, 55 insertions, 56 deletions

diff --git a/source/pdf/pdf-stream.c b/source/pdf/pdf-stream.c
index 6e64ae63..f54c2f91 100644
--- a/source/pdf/pdf-stream.c
+++ b/source/pdf/pdf-stream.c
@@ -4,14 +4,14 @@
  * Check if an object is a stream or not.
  */
 int
-pdf_obj_num_is_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
+pdf_obj_num_is_stream(fz_context *ctx, pdf_document *doc, int num)
 {
 	pdf_xref_entry *entry;
 
 	if (num <= 0 || num >= pdf_xref_len(ctx, doc))
 		return 0;
 
-	entry = pdf_cache_object(ctx, doc, num, gen);
+	entry = pdf_cache_object(ctx, doc, num);
 
 	return entry->stm_ofs != 0 || entry->stm_buf;
 }
@@ -21,7 +21,7 @@ pdf_is_stream(fz_context *ctx, pdf_obj *obj)
 {
 	pdf_document *doc = pdf_get_bound_document(ctx, obj);
 	int num = pdf_obj_parent_num(ctx, obj);
-	return pdf_obj_num_is_stream(ctx, doc, num, 0);
+	return pdf_obj_num_is_stream(ctx, doc, num);
 }
 
 /*
@@ -68,7 +68,7 @@ pdf_load_jbig2_globals(fz_context *ctx, pdf_document *doc, pdf_obj *dict)
 
 	fz_try(ctx)
 	{
-		buf = pdf_load_stream(ctx, doc, pdf_to_num(ctx, dict), pdf_to_gen(ctx, dict));
+		buf = pdf_load_stream(ctx, doc, pdf_to_num(ctx, dict));
 		globals = fz_load_jbig2_globals(ctx, buf);
 		pdf_store_item(ctx, dict, globals, buf->len);
 	}
@@ -251,16 +251,26 @@ build_filter_chain(fz_context *ctx, fz_stream *chain, pdf_document *doc, pdf_obj
  * orig_num and orig_gen are used purely to seed the encryption.
  */
 static fz_stream *
-pdf_open_raw_filter(fz_context *ctx, fz_stream *chain, pdf_document *doc, pdf_obj *stmobj, int num, int orig_num, int orig_gen, fz_off_t offset)
+pdf_open_raw_filter(fz_context *ctx, fz_stream *chain, pdf_document *doc, pdf_obj *stmobj, int num, int *orig_num, int *orig_gen, fz_off_t offset)
 {
+	pdf_xref_entry *x = NULL;
 	int hascrypt;
 	int len;
 
 	if (num > 0 && num < pdf_xref_len(ctx, doc))
 	{
-		pdf_xref_entry *entry = pdf_get_xref_entry(ctx, doc, num);
-		if (entry->stm_buf)
-			return fz_open_buffer(ctx, entry->stm_buf);
+		x = pdf_get_xref_entry(ctx, doc, num);
+		*orig_num = x->num;
+		*orig_gen = x->gen;
+		if (x->stm_buf)
+			return fz_open_buffer(ctx, x->stm_buf);
+	}
+	else
+	{
+		/* We only end up here when called from pdf_open_stream_with_offset to parse new format XRef sections. */
+		/* New style XRef sections must have generation number 0. */
+		*orig_num = num;
+		*orig_gen = 0;
 	}
 
 	/* don't close chain when we close this filter */
@@ -271,7 +281,7 @@ pdf_open_raw_filter(fz_context *ctx, fz_stream *chain, pdf_document *doc, pdf_ob
 
 	hascrypt = pdf_stream_has_crypt(ctx, stmobj);
 	if (doc->crypt && !hascrypt)
-		chain = pdf_open_crypt(ctx, chain, doc->crypt, orig_num, orig_gen);
+		chain = pdf_open_crypt(ctx, chain, doc->crypt, *orig_num, *orig_gen);
 
 	return chain;
 }
@@ -281,15 +291,16 @@ pdf_open_raw_filter(fz_context *ctx, fz_stream *chain, pdf_document *doc, pdf_ob
  * to stream length and decrypting.
  */
 static fz_stream *
-pdf_open_filter(fz_context *ctx, pdf_document *doc, fz_stream *chain, pdf_obj *stmobj, int num, int orig_num, int orig_gen, fz_off_t offset, fz_compression_params *imparams)
+pdf_open_filter(fz_context *ctx, pdf_document *doc, fz_stream *chain, pdf_obj *stmobj, int num, fz_off_t offset, fz_compression_params *imparams)
 {
 	pdf_obj *filters;
 	pdf_obj *params;
+	int orig_num, orig_gen;
 
 	filters = pdf_dict_geta(ctx, stmobj, PDF_NAME_Filter, PDF_NAME_F);
 	params = pdf_dict_geta(ctx, stmobj, PDF_NAME_DecodeParms, PDF_NAME_DP);
 
-	chain = pdf_open_raw_filter(ctx, chain, doc, stmobj, num, orig_num, orig_gen, offset);
+	chain = pdf_open_raw_filter(ctx, chain, doc, stmobj, num, &orig_num, &orig_gen, offset);
 
 	fz_var(chain);
 
@@ -371,39 +382,34 @@ pdf_load_compressed_inline_image(fz_context *ctx, pdf_document *doc, pdf_obj *di
  * Open a stream for reading the raw (compressed but decrypted) data.
  */
 fz_stream *
-pdf_open_raw_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
-{
-	return pdf_open_raw_renumbered_stream(ctx, doc, num, gen, num, gen);
-}
-
-fz_stream *
-pdf_open_raw_renumbered_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int orig_num, int orig_gen)
+pdf_open_raw_stream(fz_context *ctx, pdf_document *doc, int num)
 {
 	pdf_xref_entry *x;
+	int orig_num, orig_gen;
 
 	if (num <= 0 || num >= pdf_xref_len(ctx, doc))
-		fz_throw(ctx, FZ_ERROR_GENERIC, "object id out of range (%d %d R)", num, gen);
+		fz_throw(ctx, FZ_ERROR_GENERIC, "object id out of range (%d 0 R)", num);
 
-	x = pdf_cache_object(ctx, doc, num, gen);
+	x = pdf_cache_object(ctx, doc, num);
 	if (x->stm_ofs == 0)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "object is not a stream");
 
-	return pdf_open_raw_filter(ctx, doc->file, doc, x->obj, num, orig_num, orig_gen, x->stm_ofs);
+	return pdf_open_raw_filter(ctx, doc->file, doc, x->obj, num, &orig_num, &orig_gen, x->stm_ofs);
 }
 
 static fz_stream *
-pdf_open_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int orig_num, int orig_gen, fz_compression_params *params)
+pdf_open_image_stream(fz_context *ctx, pdf_document *doc, int num, fz_compression_params *params)
 {
 	pdf_xref_entry *x;
 
 	if (num <= 0 || num >= pdf_xref_len(ctx, doc))
-		fz_throw(ctx, FZ_ERROR_GENERIC, "object id out of range (%d %d R)", num, gen);
+		fz_throw(ctx, FZ_ERROR_GENERIC, "object id out of range (%d 0 R)", num);
 
-	x = pdf_cache_object(ctx, doc, num, gen);
+	x = pdf_cache_object(ctx, doc, num);
 	if (x->stm_ofs == 0 && x->stm_buf == NULL)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "object is not a stream");
 
-	return pdf_open_filter(ctx, doc, doc->file, x->obj, num, orig_num, orig_gen, x->stm_ofs, params);
+	return pdf_open_filter(ctx, doc, doc->file, x->obj, num, x->stm_ofs, params);
 }
 
 /*
@@ -412,51 +418,45 @@ pdf_open_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int
  * Using doc->file while a stream is open is a Bad idea.
  */
 fz_stream *
-pdf_open_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
+pdf_open_stream(fz_context *ctx, pdf_document *doc, int num)
 {
-	return pdf_open_image_stream(ctx, doc, num, gen, num, gen, NULL);
+	return pdf_open_image_stream(ctx, doc, num, NULL);
 }
 
 fz_stream *
-pdf_open_stream_with_offset(fz_context *ctx, pdf_document *doc, int num, int gen, pdf_obj *dict, fz_off_t stm_ofs)
+pdf_open_stream_with_offset(fz_context *ctx, pdf_document *doc, int num, pdf_obj *dict, fz_off_t stm_ofs)
 {
 	if (stm_ofs == 0)
 		fz_throw(ctx, FZ_ERROR_GENERIC, "object is not a stream");
-
-	return pdf_open_filter(ctx, doc, doc->file, dict, num, num, gen, stm_ofs, NULL);
+	return pdf_open_filter(ctx, doc, doc->file, dict, num, stm_ofs, NULL);
 }
 
 /*
  * Load raw (compressed but decrypted) contents of a stream into buf.
  */
 fz_buffer *
-pdf_load_raw_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
-{
-	return pdf_load_raw_renumbered_stream(ctx, doc, num, gen, num, gen);
-}
-
-fz_buffer *
-pdf_load_raw_renumbered_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int orig_num, int orig_gen)
+pdf_load_raw_stream(fz_context *ctx, pdf_document *doc, int num)
 {
 	fz_stream *stm;
 	pdf_obj *dict;
 	int len;
 	fz_buffer *buf;
+	pdf_xref_entry *x;
 
 	if (num > 0 && num < pdf_xref_len(ctx, doc))
 	{
-		pdf_xref_entry *entry = pdf_get_xref_entry(ctx, doc, num);
-		if (entry->stm_buf)
-			return fz_keep_buffer(ctx, entry->stm_buf);
+		x = pdf_get_xref_entry(ctx, doc, num);
+		if (x->stm_buf)
+			return fz_keep_buffer(ctx, x->stm_buf);
 	}
 
-	dict = pdf_load_object(ctx, doc, num, gen);
+	dict = pdf_load_object(ctx, doc, num);
 
 	len = pdf_to_int(ctx, pdf_dict_get(ctx, dict, PDF_NAME_Length));
 
 	pdf_drop_obj(ctx, dict);
 
-	stm = pdf_open_raw_renumbered_stream(ctx, doc, num, gen, orig_num, orig_gen);
+	stm = pdf_open_raw_stream(ctx, doc, num);
 
 	buf = fz_read_all(ctx, stm, len);
 
@@ -534,7 +534,7 @@ can_reuse_buffer(fz_context *ctx, pdf_xref_entry *entry, fz_compression_params *
 }
 
 static fz_buffer *
-pdf_load_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int orig_num, int orig_gen, fz_compression_params *params, int *truncated)
+pdf_load_image_stream(fz_context *ctx, pdf_document *doc, int num, fz_compression_params *params, int *truncated)
 {
 	fz_stream *stm = NULL;
 	pdf_obj *dict, *obj;
@@ -552,7 +552,7 @@ pdf_load_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int
 			return fz_keep_buffer(ctx, entry->stm_buf);
 	}
 
-	dict = pdf_load_object(ctx, doc, num, gen);
+	dict = pdf_load_object(ctx, doc, num);
 
 	len = pdf_to_int(ctx, pdf_dict_get(ctx, dict, PDF_NAME_Length));
 	obj = pdf_dict_get(ctx, dict, PDF_NAME_Filter);
@@ -563,7 +563,7 @@ pdf_load_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int
 
 	pdf_drop_obj(ctx, dict);
 
-	stm = pdf_open_image_stream(ctx, doc, num, gen, orig_num, orig_gen, params);
+	stm = pdf_open_image_stream(ctx, doc, num, params);
 
 	fz_try(ctx)
 	{
@@ -588,25 +588,25 @@ pdf_load_image_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int
  * Load uncompressed contents of a stream into buf.
  */
 fz_buffer *
-pdf_load_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
+pdf_load_stream(fz_context *ctx, pdf_document *doc, int num)
 {
-	return pdf_load_image_stream(ctx, doc, num, gen, num, gen, NULL, NULL);
+	return pdf_load_image_stream(ctx, doc, num, NULL, NULL);
 }
 
 fz_buffer *
-pdf_load_renumbered_stream(fz_context *ctx, pdf_document *doc, int num, int gen, int orig_num, int orig_gen, int *truncated)
+pdf_load_stream_truncated(fz_context *ctx, pdf_document *doc, int num, int *truncated)
 {
-	return pdf_load_image_stream(ctx, doc, num, gen, orig_num, orig_gen, NULL, truncated);
+	return pdf_load_image_stream(ctx, doc, num, NULL, truncated);
 }
 
 fz_compressed_buffer *
-pdf_load_compressed_stream(fz_context *ctx, pdf_document *doc, int num, int gen)
+pdf_load_compressed_stream(fz_context *ctx, pdf_document *doc, int num)
 {
 	fz_compressed_buffer *bc = fz_malloc_struct(ctx, fz_compressed_buffer);
 
 	fz_try(ctx)
 	{
-		bc->buffer = pdf_load_image_stream(ctx, doc, num, gen, num, gen, &bc->params, NULL);
+		bc->buffer = pdf_load_image_stream(ctx, doc, num, &bc->params, NULL);
 	}
 	fz_catch(ctx)
 	{
@@ -631,7 +631,7 @@ pdf_open_object_array(fz_context *ctx, pdf_document *doc, pdf_obj *list)
 		pdf_obj *obj = pdf_array_get(ctx, list, i);
 		fz_try(ctx)
 		{
-			fz_concat_push(ctx, stm, pdf_open_stream(ctx, doc, pdf_to_num(ctx, obj), pdf_to_gen(ctx, obj)));
+			fz_concat_push(ctx, stm, pdf_open_stream(ctx, doc, pdf_to_num(ctx, obj)));
 		}
 		fz_catch(ctx)
 		{
@@ -647,15 +647,14 @@ pdf_open_object_array(fz_context *ctx, pdf_document *doc, pdf_obj *list)
 fz_stream *
 pdf_open_contents_stream(fz_context *ctx, pdf_document *doc, pdf_obj *obj)
 {
-	int num, gen;
+	int num;
 
 	if (pdf_is_array(ctx, obj))
 		return pdf_open_object_array(ctx, doc, obj);
 
 	num = pdf_to_num(ctx, obj);
-	gen = pdf_to_gen(ctx, obj);
 	if (pdf_is_stream(ctx, obj))
-		return pdf_open_image_stream(ctx, doc, num, gen, num, gen, NULL);
+		return pdf_open_image_stream(ctx, doc, num, NULL);
 
-	fz_throw(ctx, FZ_ERROR_GENERIC, "pdf object stream missing (%d %d R)", num, gen);
+	fz_throw(ctx, FZ_ERROR_GENERIC, "pdf object stream missing (%d 0 R)", num);
 }