.\" $OpenBSD: ASN1_bn_print.3,v 1.2 2022/12/14 20:27:28 schwarze Exp $
.\"
.\" Copyright (c) 2021 Ingo Schwarze <schwarze@openbsd.org>
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.Dd $Mdocdate: December 14 2022 $
.Dt ASN1_BN_PRINT 3
.Os
.Sh NAME
.Nm ASN1_bn_print
.Nd pretty-print a BIGNUM object
.Sh SYNOPSIS
.In openssl/asn1.h
.Ft int
.Fo ASN1_bn_print
.Fa "BIO *bio_out"
.Fa "const char *label"
.Fa "const BIGNUM *bn"
.Fa "unsigned char *buffer"
.Fa "int indent"
.Fc
.Sh DESCRIPTION
.Fn ASN1_bn_print
prints
.Fa bn
to
.Fa bio_out
in human-readable form.
Despite its name and the header file,
this function has nothing to do with ASN.1.
.Pp
The caller is responsible for providing a
.Fa buffer
that is at least
.Fn BN_num_bytes bn
+ 1 bytes long.
To avoid a buffer overrun, be careful to not forget the
.Dq plus one .
It is unspecified what the buffer may contain after the function returns.
.Pp
If
.Fa indent
is greater than zero,
.Fa indent
space characters are printed first, but not more than 128.
.Pp
The NUL-terminated
.Fa label
is printed next.
.Pp
After that, there are three cases:
.Bl -bullet
.It
If
.Fa bn
represents the number zero,
.Qq 0
is printed.
.It
If
.Fa bn
can be represented by the data type
.Vt unsigned long ,
it is printed in decimal notation,
followed by hexadecimal notation in parentheses,
both optionally preceded by a minus sign.
.It
Otherwise, the string
.Qq Pq Negative
is printed if appropriate, a new output line is started,
and the indentation is increased by four space characters.
The bytes of the value of
.Fa bn
are then printed in big-endian order, each byte represented
by a two-digit hexadecimal number,
and each but the last byte followed by a colon.
A new output line is started after every group of 15 bytes.
.El
.Pp
Finally, a newline character is printed to end the output.
.Pp
If
.Fa bn
is a
.Dv NULL
pointer, all arguments are ignored and nothing is printed.
.Sh RETURN VALUES
.Fn ASN1_bn_print
returns 1
if successful or if
.Fa bn
is a
.Dv NULL
pointer.
It returns 0 if printing fails.
.Sh SEE ALSO
.Xr ASN1_buf_print 3 ,
.Xr BIO_new 3 ,
.Xr BIO_write 3 ,
.Xr BN_is_negative 3 ,
.Xr BN_is_zero 3 ,
.Xr BN_new 3 ,
.Xr BN_num_bytes 3 ,
.Xr BN_print 3
.Sh HISTORY
.Fn ASN1_bn_print
first appeared in OpenSSL 1.0.0 and has been available since
.Ox 4.9 .