Support for extracting attachments from PDF file

This commit adds Alt-S command which invokes the external utility "extr"
passing it the full pathname of the open PDF file and the current page
number. The utility extracts all attachments on this page (if there are
any) and saves them in the same directory as the PDF file. The file
names given to attachments are decoded from within the PDF file itself,
i.e. they are the same as the original file names of the files embedded
in the PDF.

Conflicts:

	pdfreader.lua

Makefile

@@ -109,7 +109,7 @@ LUALIB := $(LUADIR)/src/libluajit.a
 
 POPENNSLIB := $(POPENNSDIR)/libpopen_noshell.a
 
-all: kpdfview
+all: kpdfview extr
 
 VERSION?=$(shell git describe HEAD)
 kpdfview: kpdfview.o einkfb.o pdf.o k2pdfopt.o blitbuffer.o drawcontext.o input.o $(POPENNSLIB) util.o ft.o lfs.o mupdfimg.o $(MUPDFLIBS) $(THIRDPARTYLIBS) $(LUALIB) djvu.o $(DJVULIBS) cre.o $(CRENGINELIBS) pic.o pic_jpeg.o
@@ -144,6 +144,12 @@ kpdfview: kpdfview.o einkfb.o pdf.o k2pdfopt.o blitbuffer.o drawcontext.o input.
 		$(EMU_LDFLAGS) \
 		$(DYNAMICLIBSTDCPP)
 
+extr:	extr.o
+	$(CC) $(CFLAGS) extr.o $(MUPDFLIBS) $(THIRDPARTYLIBS) -lm -o extr
+
+extr.o:	%.o: %.c
+	$(CC) -c -I$(MUPDFDIR)/pdf -I$(MUPDFDIR)/fitz $< -o $@
+
 slider_watcher.o: %.o: %.c
 	$(CC) -c $(CFLAGS) $< -o $@
 
@@ -207,7 +213,7 @@ fetchthirdparty:
 	cd popen-noshell && test -f Makefile || patch -N -p0 < popen_noshell-buildfix.patch
 
 clean:
-	rm -f *.o kpdfview slider_watcher
+	rm -f *.o kpdfview slider_watcher extr
 
 cleanthirdparty:
 	$(MAKE) -C $(LUADIR) CC="$(HOSTCC)" CFLAGS="$(BASE_CFLAGS)" clean
@@ -268,13 +274,14 @@ INSTALL_DIR=kindlepdfviewer
 LUA_FILES=reader.lua
 
 customupdate: all
-	# ensure that build binary is for ARM
+	# ensure that the binaries were built for ARM
 	file kpdfview | grep ARM || exit 1
-	$(STRIP) --strip-unneeded kpdfview
+	file extr | grep ARM || exit 1
+	$(STRIP) --strip-unneeded kpdfview extr
 	rm -f kindlepdfviewer-$(VERSION).zip
 	rm -rf $(INSTALL_DIR)
 	mkdir -p $(INSTALL_DIR)/{history,screenshots}
-	cp -p README.md COPYING kpdfview kpdf.sh $(LUA_FILES) $(INSTALL_DIR)
+	cp -p README.md COPYING kpdfview extr kpdf.sh $(LUA_FILES) $(INSTALL_DIR)
 	mkdir $(INSTALL_DIR)/data
 	cp -rpL data/*.css $(INSTALL_DIR)/data
 	cp -rpL fonts $(INSTALL_DIR)

extr.c

@@ -0,0 +1,106 @@
+/*
+    extr: Extract attachments from PDF file
+
+	Usage: extr /dir/file.pdf pageno
+	Returns 0 if one or more attachments saved, otherwise returns non-zero.
+	Prints the number of saved attachments on stdout.
+	Attachments are saved in /dir directory with the appropriate filenames.
+
+    Copyright (C) 2012 Tigran Aivazian <tigran@bibles.org.uk>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#include "mupdf-internal.h"
+#include <libgen.h>
+
+/* doc is shared between save_attachments() and dump_stream() */
+static pdf_document *doc;
+
+void dump_stream(int i, FILE *fout)
+{
+	fz_stream *stm = pdf_open_stream(doc, i, 0);
+	static unsigned char buf[8192];
+	while (1) {
+		int n = fz_read(stm, buf, sizeof buf);
+		if (n == 0) break;
+		fwrite(buf, 1, n, fout);
+	}
+	fz_close(stm);
+}
+
+/* returns the number of attachments saved */
+int save_attachments(int pageno, char *targetdir)
+{
+	pdf_page *page = pdf_load_page(doc, pageno-1);
+	pdf_annot *annot;
+	int saved_count = 0;
+
+	for (annot = page->annots; annot ; annot = annot->next) {
+		pdf_obj *fs_obj = pdf_dict_gets(annot->obj, "FS");
+		if (fs_obj) {
+			pdf_obj *ef_obj;
+			char *name = pdf_to_str_buf(pdf_dict_gets(fs_obj, "F"));
+			ef_obj = pdf_dict_gets(fs_obj, "EF");
+			if (ef_obj) {
+				pdf_obj *f_obj = pdf_dict_gets(ef_obj, "F");
+				if (f_obj && pdf_is_indirect(f_obj)) {
+					static char pathname[PATH_MAX];
+					sprintf(pathname, "%s/%s", targetdir, name);
+					FILE *fout = fopen(pathname, "w");
+					if (!fout) {
+						fprintf(stderr, "extr: cannot write to file %s\n", name);
+						exit(1);
+					}
+					dump_stream(pdf_to_num(f_obj), fout);
+					fclose(fout);
+					saved_count++;
+				}
+			}
+		}
+	}
+	return saved_count;
+}
+
+int main(int argc, char *argv[])
+{
+	int saved = 0;
+
+	if (argc != 3) {
+		printf("Usage: extr file.pdf pageno\n");
+		exit(1);
+	}
+
+	char *filename = strdup(argv[1]);
+	char *dir = dirname(strdup(filename));
+	int pageno = atoi(argv[2]);
+
+	fz_context *ctx = fz_new_context(NULL, NULL, FZ_STORE_UNLIMITED);
+	if (!ctx) {
+		fprintf(stderr, "extr: cannot create context\n");
+		exit(1);
+	}
+
+	fz_var(doc);
+	fz_try(ctx) {
+		doc = pdf_open_document(ctx, filename);
+		saved = save_attachments(pageno, dir);
+	}
+	fz_catch(ctx)
+	{
+	}
+
+	printf("%d\n", saved);
+	return 0;
+}