---
name: "asn1_length_der"
section: "3"
platform: "linux"
package: "libtasn1"
version: "4.21.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/asn1_length_der"
---

# asn1\_length\_der(3)

API function

## NAME

asn1\_length\_der - API function

## SYNOPSIS

**#include \<libtasn1.h\>**

**void asn1\_length\_der(unsigned long int** *len***, unsigned char \*** *der***, int \*** *der\_len***);**

## ARGUMENTS

- unsigned long int len

  value to convert.

- unsigned char \* der

  buffer to hold the returned encoding (may be **NULL**).

- int \* der\_len

  number of meaningful bytes of ANS (der\[0\]..der\[der\_len-1\]).

## DESCRIPTION

Creates the DER encoding of the provided length value. The  *der* buffer must have enough room for the output. The maximum length this function will encode is **ASN1\_MAX\_LENGTH\_SIZE**.

To know the size of the DER encoding use a **NULL** value for  *der* .

## COPYRIGHT

Copyright © 2006-2025 Free Software Foundation, Inc..\
 Copying and distribution of this file, with or without modification, are permitted in any medium without royalty provided the copyright notice and this notice are preserved.

## SEE ALSO

The full documentation for **libtasn1** is maintained as a Texinfo manual.  If the **info** and **libtasn1** programs are properly installed at your site, the command

-

  **info libtasn1**

should give you access to the complete manual. As an alternative you may obtain the manual from:

-

  **https://www.gnu.org/software/libtasn1/manual/**