Add ClosedFileInputSource

ClosedFileInputSource is an input source that keeps the file closed
when not reading it.

ChangeLog

@@ -1,5 +1,10 @@
 2018-06-22  Jay Berkenbilt  <ejb@ql.org>
 
+	* Add ClosedFileInputSource class, and input source that keeps its
+	input file closed when not reading it. At the expense of some
+	performance, this allows you to operate on many files without
+	opening too many files at the operating system level.
+
 	* Add new option --preserved-unreferenced-resources, which
 	suppresses removal of unreferenced objects from page resource
 	dictionaries during page splitting operations.

include/qpdf/ClosedFileInputSource.hh

@@ -0,0 +1,83 @@
+// Copyright (c) 2005-2018 Jay Berkenbilt
+//
+// This file is part of qpdf.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Versions of qpdf prior to version 7 were released under the terms
+// of version 2.0 of the Artistic License. At your option, you may
+// continue to consider qpdf to be licensed under those terms. Please
+// see the manual for additional information.
+
+#ifndef __QPDF_CLOSEDFILEINPUTSOURCE_HH__
+#define __QPDF_CLOSEDFILEINPUTSOURCE_HH__
+
+// This is an input source that reads from files, like
+// FileInputSource, except that it opens and close the file
+// surrounding every operation. This decreases effiency, but it allows
+// many more of these to exist at once than the maximum number of open
+// file descriptors. This is used for merging large numbers of files.
+
+#include <qpdf/InputSource.hh>
+#include <qpdf/PointerHolder.hh>
+
+class FileInputSource;
+
+class ClosedFileInputSource: public InputSource
+{
+  public:
+    QPDF_DLL
+    ClosedFileInputSource(char const* filename);
+    QPDF_DLL
+    virtual ~ClosedFileInputSource();
+    QPDF_DLL
+    virtual qpdf_offset_t findAndSkipNextEOL();
+    QPDF_DLL
+    virtual std::string const& getName() const;
+    QPDF_DLL
+    virtual qpdf_offset_t tell();
+    QPDF_DLL
+    virtual void seek(qpdf_offset_t offset, int whence);
+    QPDF_DLL
+    virtual void rewind();
+    QPDF_DLL
+    virtual size_t read(char* buffer, size_t length);
+    QPDF_DLL
+    virtual void unreadCh(char ch);
+
+  private:
+    ClosedFileInputSource(ClosedFileInputSource const&);
+    ClosedFileInputSource& operator=(ClosedFileInputSource const&);
+
+    void before();
+    void after();
+
+    class Members
+    {
+        friend class ClosedFileInputSource;
+
+      public:
+        QPDF_DLL
+        ~Members();
+
+      private:
+        Members(char const* filename);
+
+        std::string filename;
+        qpdf_offset_t offset;
+        FileInputSource* fis;
+    };
+    PointerHolder<Members> m;
+};
+
+#endif // __QPDF_CLOSEDFILEINPUTSOURCE_HH__

libqpdf/ClosedFileInputSource.cc

@@ -0,0 +1,103 @@
+#include <qpdf/ClosedFileInputSource.hh>
+#include <qpdf/FileInputSource.hh>
+
+ClosedFileInputSource::Members::Members(char const* filename) :
+    filename(filename),
+    offset(0),
+    fis(0)
+{
+}
+
+ClosedFileInputSource::Members::~Members()
+{
+    if (fis)
+    {
+        delete fis;
+    }
+}
+
+ClosedFileInputSource::ClosedFileInputSource(char const* filename) :
+    m(new Members(filename))
+{
+}
+
+ClosedFileInputSource::~ClosedFileInputSource()
+{
+}
+
+void
+ClosedFileInputSource::before()
+{
+    if (0 == this->m->fis)
+    {
+        this->m->fis = new FileInputSource();
+        this->m->fis->setFilename(this->m->filename.c_str());
+        this->m->fis->seek(this->m->offset, SEEK_SET);
+        this->m->fis->setLastOffset(this->last_offset);
+    }
+}
+
+void
+ClosedFileInputSource::after()
+{
+    this->last_offset = this->m->fis->getLastOffset();
+    this->m->offset = this->m->fis->tell();
+    delete this->m->fis;
+    this->m->fis = 0;
+}
+
+qpdf_offset_t
+ClosedFileInputSource::findAndSkipNextEOL()
+{
+    before();
+    qpdf_offset_t r = this->m->fis->findAndSkipNextEOL();
+    after();
+    return r;
+}
+
+std::string const&
+ClosedFileInputSource::getName() const
+{
+    return this->m->filename;
+}
+
+qpdf_offset_t
+ClosedFileInputSource::tell()
+{
+    before();
+    qpdf_offset_t r = this->m->fis->tell();
+    after();
+    return r;
+}
+
+void
+ClosedFileInputSource::seek(qpdf_offset_t offset, int whence)
+{
+    before();
+    this->m->fis->seek(offset, whence);
+    after();
+}
+
+void
+ClosedFileInputSource::rewind()
+{
+    this->m->offset = 0;
+}
+
+size_t
+ClosedFileInputSource::read(char* buffer, size_t length)
+{
+    before();
+    size_t r = this->m->fis->read(buffer, length);
+    after();
+    return r;
+}
+
+void
+ClosedFileInputSource::unreadCh(char ch)
+{
+    before();
+    this->m->fis->unreadCh(ch);
+    // Don't call after -- the file has to stay open after this
+    // operation.
+}

libqpdf/build.mk

@@ -9,6 +9,7 @@ SRCS_libqpdf = \
 	libqpdf/BitWriter.cc \
 	libqpdf/Buffer.cc \
 	libqpdf/BufferInputSource.cc \
+	libqpdf/ClosedFileInputSource.cc \
 	libqpdf/ContentNormalizer.cc \
 	libqpdf/FileInputSource.cc \
 	libqpdf/InputSource.cc \

libtests/build.mk

@@ -3,6 +3,7 @@ BINS_libtests = \
 	ascii85 \
 	bits \
 	buffer \
+	closed_file_input_source \
 	concatenate \
 	dct_compress \
 	dct_uncompress \

libtests/closed_file_input_source.cc

@@ -0,0 +1,62 @@
+#include <qpdf/ClosedFileInputSource.hh>
+#include <qpdf/FileInputSource.hh>
+
+#include <stdio.h>
+#include <string.h>
+#include <iostream>
+#include <stdlib.h>
+
+void check(std::string const& what, bool result)
+{
+    if (! result)
+    {
+        std::cout << "FAIL: " << what << std::endl;
+    }
+}
+
+void do_tests(InputSource* is)
+{
+    check("get name", "input" == is->getName());
+    check("initial tell", 0 == is->tell());
+    is->seek(11, SEEK_SET);
+    check("tell after SEEK_SET", 11 == is->tell());
+    check("read offset 11", "Offset 11" == is->readLine(100));
+    check("last offset after read 11", 11 == is->getLastOffset());
+    check("tell after read", 21 == is->tell());
+    is->findAndSkipNextEOL();
+    check("tell after findAndSkipNextEOL", 522 == is->tell());
+    is->unreadCh('Q');
+    char b[1];
+    b[0] = '\0';
+    check("read unread character", 1 == is->read(b, 1));
+    check("last offset after read unread", 521 == is->getLastOffset());
+    check("got character", 'Q' == b[0]);
+    is->seek(0, SEEK_END);
+    check("tell at end", 556 == is->tell());
+    is->seek(-25, SEEK_END);
+    check("tell before end", 531 == is->tell());
+    check("last offset unchanged after seek", 521 == is->getLastOffset());
+    is->seek(-9, SEEK_CUR);
+    check("tell after SEEK_CUR", 522 == is->tell());
+    check("read offset 522", "9 before" == is->readLine(100));
+    check("last offset after read", 522 == is->getLastOffset());
+    is->rewind();
+    check("last offset unchanged after rewind", 522 == is->getLastOffset());
+    check("tell after rewind", 0 == is->tell());
+    check("read offset at beginning", "!00000000?" == is->readLine(100));
+    check("last offset after read 0", 0 == is->getLastOffset());
+}
+
+int main()
+{
+    // This test is designed to work with a specified input file.
+    std::cout << "testing with ClosedFileInputSource\n";
+    ClosedFileInputSource cf("input");
+    do_tests(&cf);
+    std::cout << "testing with FileInputSource\n";
+    FileInputSource f;
+    f.setFilename("input");
+    do_tests(&f);
+    std::cout << "all assertions passed" << std::endl;
+    return 0;
+}

libtests/qtest/closedfile.test

@@ -0,0 +1,16 @@
+#!/usr/bin/env perl
+require 5.008;
+use warnings;
+use strict;
+
+chdir("closedfile") or die "chdir testdir failed: $!\n";
+
+require TestDriver;
+
+my $td = new TestDriver('closed_file_input_source');
+
+$td->runtest("closed file input source",
+             {$td->COMMAND => "closed_file_input_source"},
+             {$td->FILE => "output", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+$td->report(1);

libtests/qtest/closedfile/input

@@ -0,0 +1,5 @@
+!00000000?
+Offset 11
+wwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwwww
+9 before
+This is 25 from the end.

libtests/qtest/closedfile/output

@@ -0,0 +1,3 @@
+testing with ClosedFileInputSource
+testing with FileInputSource
+all assertions passed