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authorJay Berkenbilt <ejb@ql.org>2015-10-25 16:09:25 +0100
committerJay Berkenbilt <ejb@ql.org>2015-10-31 23:56:42 +0100
commitb8bdef0ad12883d72ced5eb443e6e34a93bbbb91 (patch)
tree473250ef5919bba535743c2381b86c64ebe810a8 /manual/qpdf-manual.xml
parent607c39211224e0d3bc2ab7066f16ff4952851ee9 (diff)
downloadqpdf-b8bdef0ad12883d72ced5eb443e6e34a93bbbb91.tar.zst
Implement deterministic ID
For non-encrypted files, determinstic ID generation uses file contents instead of timestamp and file name. At a small runtime cost, this enables generation of the same /ID if the same inputs are converted in the same way multiple times.
Diffstat (limited to 'manual/qpdf-manual.xml')
-rw-r--r--manual/qpdf-manual.xml23
1 files changed, 21 insertions, 2 deletions
diff --git a/manual/qpdf-manual.xml b/manual/qpdf-manual.xml
index 3174e68a..093d5b5b 100644
--- a/manual/qpdf-manual.xml
+++ b/manual/qpdf-manual.xml
@@ -991,11 +991,30 @@ outfile.pdf</option>
file should be given. The following options are available:
<variablelist>
<varlistentry>
+ <term><option>--deterministic-id</option></term>
+ <listitem>
+ <para>
+ Causes generation of a deterministic value for /ID. This
+ prevents use of timestamp and output file name information in
+ the /ID generation. Instead, at some slight additional runtime
+ cost, the /ID field is generated to include a digest of the
+ significant parts of the content of the output PDF file. This
+ means that a given qpdf operation should generate the same /ID
+ each time it is run, which can be useful when caching results
+ or for generation of some test data. Use of this flag is not
+ compatible with creation of encrypted files.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
<term><option>--static-id</option></term>
<listitem>
<para>
- Causes generation of a fixed value for /ID. This is intended
- for testing only. Never use it for production files.
+ Causes generation of a fixed value for /ID. This is intended
+ for testing only. Never use it for production files. If you
+ are trying to get the same /ID each time for a given file and
+ you are not generating encrypted files, consider using the
+ <option>--deterministic-id</option> option.
</para>
</listitem>
</varlistentry>