File content as of revision 172:7d866c31b3c5:

/* mbed Microcontroller Library
 * Copyright (c) 2015-2016 Nuvoton
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#if DEVICE_TRNG

#include <stdlib.h>
#include <string.h>
#include "cmsis.h"
#include "us_ticker_api.h"
#include "trng_api.h"

/*
 * Get Random number generator.
 */
static volatile int  g_PRNG_done;
volatile int  g_AES_done;

void CRYPTO_IRQHandler()
{
    if (PRNG_GET_INT_FLAG()) {
        g_PRNG_done = 1;
        PRNG_CLR_INT_FLAG();
    } else	if (AES_GET_INT_FLAG()) {
        g_AES_done = 1;
        AES_CLR_INT_FLAG();
    }
}

static void trng_get(unsigned char *pConversionData)
{
    uint32_t *p32ConversionData;

    p32ConversionData = (uint32_t *)pConversionData;

    PRNG_Open(PRNG_KEY_SIZE_256, 1, us_ticker_read());
    PRNG_Start();
    while (!g_PRNG_done);

    PRNG_Read(p32ConversionData);
}

void trng_init(trng_t *obj)
{
    (void)obj;
    /* Unlock protected registers */
    SYS_UnlockReg();
    /* Enable IP clock */
    CLK_EnableModuleClock(CRPT_MODULE);

    /* Lock protected registers */
    SYS_LockReg();

    NVIC_EnableIRQ(CRPT_IRQn);
    PRNG_ENABLE_INT();
}

void trng_free(trng_t *obj)
{
    (void)obj;
    PRNG_DISABLE_INT();
    NVIC_DisableIRQ(CRPT_IRQn);
}

int trng_get_bytes(trng_t *obj, uint8_t *output, size_t length, size_t *output_length)
{
    (void)obj;

    *output_length = 0;
    if (length < 32) {
        unsigned char tmpBuff[32];
        trng_get(tmpBuff);
        memcpy(output, &tmpBuff, length);
        *output_length = length;
    } else {
        for (unsigned i = 0; i < (length/32); i++) {
            trng_get(output);
            *output_length += 32;
            output += 32;
        }
    }

    return 0;
}

#endif