File: gpgme.info,  Node: Signature Notation Data,  Prev: Signature.php">Creating a Signature,  Up: Sign

7.6.4.3 Signature Notation Data
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Using the following functions, you can attach arbitrary notation data to
a signature.  This information is then available to the user when the
signature is verified.

 -- Function: void gpgme_sig_notation_clear (gpgme_ctx_t CTX)
     SINCE: 1.1.0

     The function ‘gpgme_sig_notation_clear’ removes the notation data
     from the context CTX.  Subsequent signing operations from this
     context will not include any notation data.

     Every context starts with an empty notation data list.

 -- Function: gpgme_error_t gpgme_sig_notation_add (gpgme_ctx_t CTX,
          const char *NAME, const char *VALUE,
          gpgme_sig_notation_flags_t FLAGS)
     SINCE: 1.1.0

     The function ‘gpgme_sig_notation_add’ adds the notation data with
     the name NAME and the value VALUE to the context CTX.

     Subsequent signing operations will include this notation data, as
     well as any other notation data that was added since the creation
     of the context or the last ‘gpgme_sig_notation_clear’ operation.

     The arguments NAME and VALUE must be ‘NUL’-terminated strings in
     human-readable form.  The flag ‘GPGME_SIG_NOTATION_HUMAN_READABLE’
     is implied (non-human-readable notation data is currently not
     supported).  The strings must be in UTF-8 encoding.

     If NAME is ‘NULL’, then VALUE should be a policy URL.

     The function ‘gpgme_sig_notation_add’ returns the error code
     ‘GPG_ERR_NO_ERROR’ if the notation data could be added
     successfully, ‘GPG_ERR_INV_VALUE’ if CTX is not a valid pointer, or
     if NAME, VALUE and FLAGS are an invalid combination.  The function
     also passes through any errors that are reported by the crypto
     engine support routines.

 -- Function: gpgme_sig_notation_t gpgme_sig_notation_get
          (const gpgme_ctx_t CTX)
     SINCE: 1.1.0

     The function ‘gpgme_sig_notation_get’ returns the linked list of
     notation data structures that are contained in the context CTX.

     If CTX is not a valid pointer, or there is no notation data added
     for this context, ‘NULL’ is returned.