These functions allow an ASN1_STRING structure to be manipulated.
ASN1_STRING_length() returns the length of the content of x.
ASN1_STRING_data() returns an internal pointer to the data of x.
Since this is an internal pointer it should not be freed or
modified in any way.
ASN1_STRING_dup() returns a copy of the structure a.
ASN1_STRING_cmp() compares a and b returning 0 if the two
are identical. The string types and content are compared.
ASN1_STRING_set() sets the data of string str to the buffer
data or length len. The supplied data is copied. If len
is -1 then the length is determined by strlen(data).
ASN1_STRING_type() returns the type of x, using standard constants
such as V_ASN1_OCTET_STRING.
ASN1_STRING_to_UTF8() converts the string in to UTF8 format, the
converted data is allocated in a buffer in *out. The length of
out is returned or a negative error code. The buffer *out
should be free using OPENSSL_free().
Almost all ASN1 types in OpenSSL are represented as an ASN1_STRING
structure. Other types such as ASN1_OCTET_STRING are simply typedefed
to ASN1_STRING and the functions call the ASN1_STRING equivalents.
ASN1_STRING is also used for some CHOICE types which consist
entirely of primitive string types such as DirectoryString and
These functions should not be used to examine or modify ASN1_INTEGER
or ASN1_ENUMERATED types: the relevant INTEGER or ENUMERATED
utility functions should be used instead.
In general it cannot be assumed that the data returned by ASN1_STRING_data()
is null terminated or does not contain embedded nulls. The actual format
of the data will depend on the actual string type itself: for example
for and IA5String the data will be ASCII, for a BMPString two bytes per
character in big endian format, UTF8String will be in UTF8 format.
Similar care should be take to ensure the data is in the correct format
when calling ASN1_STRING_set().