=head1 NAME
- BIO_f_md - message digest BIO
+BIO_f_md, BIO_set_md, BIO_get_md, BIO_get_md_ctx - message digest BIO filter
=head1 SYNOPSIS
digest calculation and returns the digest value. BIO_puts() is
not supported.
-BIO_reset() reinitializes a digest BIO.
+BIO_reset() reinitialises a digest BIO.
BIO_set_md() sets the message digest of BIO B<b> to B<md>: this
-must be called to initialise a digest BIO before any data is
+must be called to initialize a digest BIO before any data is
passed through it. It is a BIO_ctrl() macro.
BIO_get_md() places the a pointer to the digest BIOs digest method
BIO_get_md_ctx() returns the digest BIOs context into B<mdcp>.
-
-
=head1 NOTES
The context returned by BIO_get_md_ctx() can be used in calls
a chain containing digest BIOs then this can be done by prepending
a buffering BIO.
+Before OpenSSL 1.0.0 the call to BIO_get_md_ctx() would only work if the BIO
+had been initialized for example by calling BIO_set_md() ). In OpenSSL
+1.0.0 and later the context is always returned and the BIO is state is set
+to initialized. This allows applications to initialize the context externally
+if the standard calls such as BIO_set_md() are not sufficiently flexible.
+
=head1 RETURN VALUES
BIO_f_md() returns the digest BIO method.