=head1 NAME

TPM_IO_Hash_Start   - indicate the beginging of a TPM TIS hash operation

TPM_IO_Hash_Data    - hash the provided data

TPM_IO_Hash_End     - indicate the end of a TPM TIS hash operation

=head1 LIBRARY

TPM library (libtpms, -ltpms)

=head1 SYNOPSIS

B<#include <libtpms/tpm_types.h>>

B<#include <libtpms/tpm_tis.h>>

B<#include <libtpms/tpm_error.h>>

B<TPM_RESULT TPM_IO_Hash_Start(void);>

B<TPM_RESULT TPM_IO_Hash_Data(const unsigned char> *I<data>B<,
                            uint32_t> I<data_length>B<);>

B<TPM_RESULT TPM_IO_Hash_End(void);>

=head1 DESCRIPTION

The B<TPM_IO_Hash_Start()> function can be used by an implementation of the
TPM TIS hardware interface to indicate the beginning of a hash operation.
Following the TPM TIS interface specification it resets several PCRs and
terminates existing transport sessions. 
The B<TPM_IO_Hash_Data()> function is used to send the data to be hashed to
the TPM.
The B<TPM_IO_Hash_End()> function calculates the final hash and stores it
in the locality 4 PCR.
The 3 functions must be called in the order they were explained.

The implementation of the above functions handles all TPM-internal actions
such as the setting and clearing of permanent flags and PCRs and the
calculation of the hash. Any functionality related to the TPM's TIS interface
and the handling of flags, locality and state has to be implemented by the
caller.

=head1 ERRORS

=over 4

=item B<TPM_SUCCESS>

The function completed successfully.

=item B<TPM_FAIL>

General failure.

=item B<TPM_INVALID_POSTINIT>

The B<TPM_IO_Hash_Start()> function was called before the TPM received
a TPM_Startup command.

=item B<TPM_SHA_THREAD>

The B<TPM_IO_Hash_Data()> or B<TPM_IO_Hash_End()> functions were called before
the B<TPM_IO_Hash_Start()> function.

=back

For a complete list of TPM error codes please consult the include file
B<libtpms/tpm_error.h>

=head1 SEE ALSO

B<TPMLIB_MainInit>(3), B<TPMLIB_Terminate>(3), B<TPMLIB_RegisterCallbacks>(3),
B<TPMLIB_Process>(3)

=cut