more info
git-svn-id: https://asn1c.svn.sourceforge.net/svnroot/asn1c/trunk@726 59561ff5-6e30-0410-9f3c-9617f08c8826
diff --git a/examples/sample.source.PKIX1/README b/examples/sample.source.PKIX1/README
index 8adf5a9..d204dab 100644
--- a/examples/sample.source.PKIX1/README
+++ b/examples/sample.source.PKIX1/README
@@ -1,7 +1,41 @@
+GENERAL INFORMATION
+===================
+
The X.509 (PKIX1) certificate decoder. Invoking `make` will compile the ASN.1
specifications from the rfc3280.txt in the above directory.
The ../../skeletons/asn-decoder-template.c will supply the missing
"int main()" routine which drives the decoding process.
+x509dump USAGE
+==============
+
+To use the code, you'll have to prepare an X.509 certificate in DER encoding.
+The typical X.509 certificate will have a PEM form (DER encoded data wrapped
+in base64, wrapped in PEM "BEGIN" and "END" sections). The openssl x509 utility
+may be used to convert between PEM and DER.
+
+ EXAMPLE: Convert 'certificate.pem' into 'certificate.der':
+
+ openssl x509 -inform PEM -in certificate.pem \
+ -outform DER -out certificate.der
+
+After convertsion, the x509dump utility may be used to dump the contents
+of the DER-encoded X.509 certificate:
+
+ ./x509dump -x certificate.der # Print as XML (BASIC-XER)
+
+The full list of recognized command line options may be obtained with
+
+ > ./x509dump -h
+ Usage: ./x509dump [options] <data.ber> ...
+ Where options are:
+ -b <size> Set the i/o buffer size (default is 8192)
+ -c Check ASN.1 constraints after decoding
+ -d Enable debugging (-dd is even better)
+ -n <num> Process files <num> times
+ -s <size> Set the stack usage limit
+ -p Print out the decoded contents
+ -x Print out as XML
+