ngtcp2_crypto_hp_mask
=====================

Synopsis
--------

*#include <ngtcp2/ngtcp2_crypto.h>*

.. function:: int ngtcp2_crypto_hp_mask(uint8_t *dest, const ngtcp2_crypto_cipher *hp, const ngtcp2_crypto_cipher_ctx *hp_ctx, const uint8_t *sample)

    
    `ngtcp2_crypto_hp_mask` generates a mask which is used in packet
    header encryption.  The mask is written to the buffer pointed by
    *dest*.  The sample is passed as *sample* which is
    :macro:`NGTCP2_HP_SAMPLELEN` bytes long.  The length of mask must
    be at least :macro:`NGTCP2_HP_MASKLEN`.  The library only uses the
    first :macro:`NGTCP2_HP_MASKLEN` bytes of the produced mask.  The
    buffer pointed by *dest* must have at least
    :macro:`NGTCP2_HP_SAMPLELEN` bytes available.
    
    This function returns 0 if it succeeds, or -1.