.\"	$OpenBSD: BIO_f_base64.3,v 1.15 2023/09/11 04:00:40 jsg Exp $
.\"	OpenSSL fc1d88f0 Wed Jul 2 22:42:40 2014 -0400
.\"
.\" This file was written by Dr. Stephen Henson <steve@openssl.org>.
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.Dd $Mdocdate: September 11 2023 $
.Dt BIO_F_BASE64 3
.Os
.Sh NAME
.Nm BIO_f_base64
.\" .Nm EVP_ENCODE_LENGTH and
.\" .Nm EVP_DECODE_LENGTH are intentionally undocumented
.\" because they are internal implementation details of BIO_f_base64(3)
.\" and practically unused outside evp/bio_b64.c.
.Nd base64 BIO filter
.Sh SYNOPSIS
.In openssl/bio.h
.In openssl/evp.h
.Ft const BIO_METHOD *
.Fo BIO_f_base64
.Fa void
.Fc
.Sh DESCRIPTION
.Fn BIO_f_base64
returns the base64 BIO method.
This is a filter BIO that base64 encodes any data written through it
and decodes any data read through it.
.Pp
Base64 BIOs do not support
.Xr BIO_gets 3
or
.Xr BIO_puts 3 .
.Pp
.Xr BIO_flush 3
on a base64 BIO that is being written through
is used to signal that no more data is to be encoded:
this is used to flush the final block through the BIO.
.Pp
To encode the data all on one line and to expect the data to be all
on one line, initialize the base64 BIO as follows:
.Bd -literal -offset indent
BIO *b64 = BIO_new(BIO_f_base64());
BIO_set_flags(b64, BIO_FLAGS_BASE64_NO_NL);
.Ed
.Sh RETURN VALUES
.Fn BIO_f_base64
returns the base64 BIO method.
.Pp
When called on a base64 BIO object,
.Xr BIO_method_type 3
returns the constant
.Dv BIO_TYPE_BASE64
and
.Xr BIO_method_name 3
returns a pointer to the static string
.Qq base64 encoding .
.Sh EXAMPLES
Base64 encode the string "hello, world\en"
and write the result to standard output:
.Bd -literal -offset indent
BIO *bio, *b64;
char message[] = "hello, world\en";

b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stdout, BIO_NOCLOSE);
BIO_push(b64, bio);
BIO_write(b64, message, strlen(message));
BIO_flush(b64);

BIO_free_all(b64);
.Ed
.Pp
Read Base64-encoded data from standard input
and write the decoded data to standard output:
.Bd -literal -offset indent
BIO *bio, *b64, *bio_out;
char inbuf[512];
int inlen;

b64 = BIO_new(BIO_f_base64());
bio = BIO_new_fp(stdin, BIO_NOCLOSE);
bio_out = BIO_new_fp(stdout, BIO_NOCLOSE);
BIO_push(b64, bio);
while((inlen = BIO_read(b64, inbuf, 512)) > 0)
	BIO_write(bio_out, inbuf, inlen);

BIO_flush(bio_out);
BIO_free_all(b64);
.Ed
.Sh SEE ALSO
.Xr BIO_new 3 ,
.Xr EVP_EncodeInit 3
.Sh HISTORY
.Fn BIO_f_base64
first appeared in SSLeay 0.6.5 and has been available since
.Ox 2.4 .
.Sh BUGS
The ambiguity of EOF in base64-encoded data can cause additional
data following the base64-encoded block to be misinterpreted.
.Pp
There should be some way of specifying a test that the BIO can perform
to reliably determine EOF (for example a MIME boundary).