A2D_ASN1_OBJECT(3) | Library Functions Manual | A2D_ASN1_OBJECT(3)

# NAME

`a2d_ASN1_OBJECT` — DER content octets of an ASN.1 object identifier

# SYNOPSIS

library “libcrypto”
`#include <openssl/asn1.h>`

int
`a2d_ASN1_OBJECT`(unsigned char *der_out, int olen, const char *val_in, int ilen);

# DESCRIPTION

`a2d_ASN1_OBJECT`() accepts an ASCII string val_in of ilen bytes and interprets it as the numerical form of an ASN.1 object identifier. It writes the content octets of the DER encoding of the object identifier to the buffer der_out which is olen bytes long. The identifier and length octets of the DER encoding are not written.

If ilen is -1, the strlen(3) of val_in is used instead.

If der_out is a `NULL` pointer, writing the content octets is skipped and only the return value is calculated.

# RETURN VALUES

`a2d_ASN1_OBJECT`() returns the number of content octets that were or would be written or 0 if ilen is 0, if val_in is not a valid representation of an object identifier, if memory allocation fails, or if the number of content octets would be larger than olen.

# SEE ALSO

ASN1_OBJECT_new(3), i2d_ASN1_OBJECT(3), OBJ_create(3)

# STANDARDS

ITU-T Recommendation X.690, also known as ISO/IEC 8825-1: Information technology - ASN.1 encoding rules: Specification of Basic Encoding Rules (BER), Canonical Encoding Rules (CER) and Distinguished Encoding Rules (DER), section 8.19: Encoding of an object identifier value

# HISTORY

`a2d_ASN1_OBJECT`() first appeared in SSLeay 0.8.0 and has been available since OpenBSD 2.4.

June 8, 2025 | Debian