tests/suites/test_suite_mps.function

/* BEGIN_HEADER */

#include <stdlib.h>

/* TODO: How are test suites supposed to include internal headers? */
#include "../library/mps_reader.h"

/*
 * Compile-time configuration for test suite.
 */

/* Comment/Uncomment this to disable/enable the
 * testing of the various MPS layers.
 * This can be useful for time-consuming instrumentation
 * tasks such as the conversion of E-ACSL annotations
 * into runtime assertions. */
#define TEST_SUITE_MPS_READER

/* End of compile-time configuration. */

/* END_HEADER */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_single_step_single_round( int with_acc )
{
    /* This test exercises the most basic use of the MPS reader:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in a single go.
     * - After processing, the consuming layer commit the data
     *   and returns back to the producing layer.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's request can be fulfilled from the data
     *             that the producer has provided.
     */
    unsigned char bufA[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    if( with_acc == 0 )
        mbedtls_mps_reader_init( &rd, NULL, 0 );
    else
        mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );
    /* Consumption (upper layer) */
    /* Consume exactly what's available */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 100, bufA, 100 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Wrapup (lower layer) */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_single_step_multiple_rounds( int with_acc )
{
    /* This test exercises multiple rounds o fthe basic use of the MPS reader:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in a single go.
     * - After processing, the consuming layer commit the data
     *   and returns back to the producing layer.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's request can be fulfilled from the data
     *             that the producer has provided.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    if( with_acc == 0 )
        mbedtls_mps_reader_init( &rd, NULL, 0 );
    else
        mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );
    /* Consumption (upper layer) */
    /* Consume exactly what's available */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 100, bufA, 100 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, sizeof( bufB ) ) == 0 );
    /* Consumption */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 100, bufB, 100 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Wrapup (lower layer) */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_multiple_steps_single_round( int with_acc )
{
    /* This test exercises one round of the following:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in multiple calls
     *   to `mbedtls_mps_reader_get()`, without comitting in between.
     * - After processing, the consuming layer commit the data
     *   and returns back to the producing layer.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's request can be fulfilled from the data
     *             that the producer has provided.
     */

    /* Lower layer provides data that the upper layer fully consumes
     * through multiple `get` calls. */
    unsigned char buf[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    if( with_acc == 0 )
        mbedtls_mps_reader_init( &rd, NULL, 0 );
    else
        mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 10, buf, 10 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 70, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 70, buf + 10, 70 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 30, &tmp, &tmp_len ) == 0 );
    ASSERT_COMPARE( tmp, tmp_len, buf + 80, 20 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Wrapup (lower layer) */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_multiple_steps_multiple_rounds( int with_acc )
{
    /* This test exercises one round of fetching a buffer in multiple chunks
     * and passing it back to the producer afterwards, followed by another
     * single-step sequence of feed-fetch-commit-reclaim.
     */
    unsigned char bufA[100], bufB[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    if( with_acc == 0 )
        mbedtls_mps_reader_init( &rd, NULL, 0 );
    else
        mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 10, bufA, 10 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 70, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 70, bufA + 10, 70 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 30, &tmp, &tmp_len ) == 0 );
    ASSERT_COMPARE( tmp, tmp_len, bufA + 80, 20 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, sizeof( bufB ) ) == 0 );
    /* Consumption */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 100, bufB, 100 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_needed_disabled()
{
    /* This test exercises the behaviour of the MPS reader when a read requests
     * of the consumer exceeds what has been provided by the producer, and when
     * no accumulator is available in the reader.
     *
     * In this case, we expect the reader to fail.
     */

    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, NULL, 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 50, buf, 50 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );
    /* Wrapup (lower layer) */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_NEED_ACCUMULATOR );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_needed_buffer_too_small()
{
    /* This test exercises the behaviour of the MPS reader with accumulator
     * in the situation where a read requests goes beyond the bounds of the
     * current read buffer, _and_ the reader's accumulator is too small to
     * hold the requested amount of data.
     *
     * In this case, we expect the reader to fail. */

    unsigned char buf[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 50, buf, 50 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );
    /* Wrapup (lower layer) */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing( int option )
{
    /* This test exercises the behaviour of the reader when the
     * accumulator is used to fufill the consumer's request.
     *
     * More detailed:
     * - The producer feeds some data.
     * - The consumer asks for more data than what's available.
     * - The reader remembers the request and goes back to
     *   producing mode, waiting for more data from the producer.
     * - The producer provides another chunk of data which is
     *   sufficient to fulfill the original read request.
     * - The consumer retries the original read request, which
     *   should now succeed.
     *
     * This test comes in multiple variants controlled by the
     * `option` parameter and documented below.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[40];
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 80, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 80, bufA, 80 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
    switch( option )
    {
        case 0:  /* Single uncommitted fetch at pausing */
        case 1:
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            break;
        default: /* Multiple uncommitted fetches at pausing */
            break;
    }
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, sizeof( bufB ) ) == 0 );

    /* Consumption */
    switch( option )
    {
        case 0: /* Single fetch at pausing, re-fetch with commit. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            break;

        case 1: /* Single fetch at pausing, re-fetch without commit. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            break;

        case 2: /* Multiple fetches at pausing, repeat without commit. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            break;

        case 3: /* Multiple fetches at pausing, repeat with commit 1. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            break;

        case 4: /* Multiple fetches at pausing, repeat with commit 2. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            break;

        case 5: /* Multiple fetches at pausing, repeat with commit 3. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            break;

        default:
            TEST_ASSERT( 0 );
    }

    /* In all cases, fetch the rest of the second buffer. */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 90, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 90, bufB + 10, 90 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );

    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_multiple_feeds( int option )
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - The consumer has asked for mre than what's available, so the
     *   reader pauses and waits for further input data via
     *   `mbedtls_mps_reader_feed()`
     * - Multiple such calls to `mbedtls_mps_reader_feed()` are necessary
     *   to fulfill the original request, and the reader needs to do
     *   the necessary bookkeeping under the hood.
     *
     * This test comes in a few variants differing in the number and
     * size of feed calls that the producer issues while the reader is
     * accumulating the necessary data - see the comments below.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[70];
    mbedtls_mps_reader rd;
    mbedtls_mps_size_t fetch_len;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 80, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 80, bufA, 80 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* 20 left, ask for 70 -> 50 overhead */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 70, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    switch( option )
    {
        case 0: /* 10 + 10 + 80 byte feed */
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, 10 ) ==
                         MBEDTLS_ERR_MPS_READER_NEED_MORE );
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + 10, 10 ) ==
                         MBEDTLS_ERR_MPS_READER_NEED_MORE );
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + 20, 80 ) == 0 );
            break;

        case 1: /* 50 x 1byte */
            for( int num_feed=0; num_feed<49; num_feed++ )
            {
                TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + num_feed, 1 ) ==
                             MBEDTLS_ERR_MPS_READER_NEED_MORE );
            }
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + 49, 1 ) == 0 );
            break;

        case 2: /* 49 x 1byte + 51bytes */
            for( int num_feed=0; num_feed<49; num_feed++ )
            {
                TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + num_feed, 1 ) ==
                             MBEDTLS_ERR_MPS_READER_NEED_MORE );
            }
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB + 49, 51 ) == 0 );
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }

    /* Consumption */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 70, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 20, bufA + 80, 20 );
    ASSERT_COMPARE( tmp + 20, 50, bufB, 50 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 1000, &tmp, &fetch_len ) == 0 );
    switch( option )
    {
        case 0:
            TEST_ASSERT( fetch_len == 50 );
            break;

        case 1:
            TEST_ASSERT( fetch_len == 0 );
            break;

        case 2:
            TEST_ASSERT( fetch_len == 50 );
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );

    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */


/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_reclaim_data_left( int option )
{
    /* This test exercises the behaviour of the MPS reader when a
     * call to mbedtls_mps_reader_reclaim() is made before all data
     * provided by the producer has been fetched and committed. */

    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, NULL, 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );

    /* Consumption (upper layer) */
    switch( option )
    {
        case 0:
            /* Fetch (but not commit) the entire buffer. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, sizeof( buf ), &tmp, NULL )
                         == 0 );
            ASSERT_COMPARE( tmp, 100, buf, 100 );
            break;

        case 1:
            /* Fetch (but not commit) parts of the buffer. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, sizeof( buf ) / 2,
                                             &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, sizeof( buf ) / 2, buf, sizeof( buf ) / 2 );
            break;

        case 2:
            /* Fetch and commit parts of the buffer, then
             * fetch but not commit the rest of the buffer. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, sizeof( buf ) / 2,
                                             &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, sizeof( buf ) / 2, buf, sizeof( buf ) / 2 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, sizeof( buf ) / 2,
                                             &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, sizeof( buf ) / 2,
                            buf + sizeof( buf ) / 2,
                            sizeof( buf ) / 2 );
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }

    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_DATA_LEFT );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_reclaim_data_left_retry()
{
    /* This test exercises the behaviour of the MPS reader when an attempt
     * by the producer to reclaim the reader fails because of more data pending
     * to be processed, and the consumer subsequently fetches more data. */
    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;

    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, NULL, 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 50, buf, 50 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 50, buf + 50, 50 );
    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_DATA_LEFT );
    /* Consumption */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 50, buf + 50, 50 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_multiple_pausing( int option )
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - A read request via `mbedtls_mps_reader_get()` can't
     *   be served and the reader is paused to accumulate
     *   the desired amount of data from the producer.
     * - Once enough data is availble, the consumer successfully
     *   reads the data from the reader, but afterwards exceeds
     *   the available data again - pausing is necessary for a
     *   second time.
     */

    unsigned char bufA[100], bufB[20], bufC[10];
    unsigned char *tmp;
    unsigned char acc[50];
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);
    for( int i=0; (unsigned) i < sizeof( bufC ); i++ )
        bufC[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 80, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 80, bufA, 80 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, sizeof( bufB ) ) == 0 );

    switch( option )
    {
        case 0: /* Fetch same chunks, commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * large enough. */

            /* Consume */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, &tmp_len ) == 0 );
            ASSERT_COMPARE( tmp, tmp_len, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

            /* Prepare */
            TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufC, sizeof( bufC ) ) == 0 );;

            /* Consume */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufB + 10, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufC, 10 );
            break;

        case 1: /* Fetch same chunks, commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * not large enough. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 51, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

            /* Prepare */
            TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
            break;

        case 2: /* Fetch same chunks, don't commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * large enough. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

            /* Prepare */
            TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufC, sizeof( bufC ) ) == 0 );;

            /* Consume */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 50, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 20, bufA + 80, 20 );
            ASSERT_COMPARE( tmp + 20, 20, bufB, 20 );
            ASSERT_COMPARE( tmp + 40, 10, bufC, 10 );
            break;

        case 3: /* Fetch same chunks, don't commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * not large enough. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 80, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 10, bufA + 90, 10 );
            ASSERT_COMPARE( tmp + 10, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 21, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );

            /* Prepare */
            TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL );
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }

    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER:MBEDTLS_MPS_STATE_VALIDATION */
void mbedtls_mps_reader_random_usage( int num_out_chunks,
                                      int max_chunk_size,
                                      int max_request,
                                      int acc_size )

{
    /* Randomly pass a reader object back and forth between lower and
     * upper layer and let each of them call the respective reader API
     * functions in a random fashion.
     *
     * On the lower layer, we're tracking and concatenating
     * the data passed to successful feed calls.
     *
     * For the upper layer, we track and concatenate buffers
     * obtained from successful get calls.
     *
     * As long as the lower layer calls reclaim at least once, (resetting the
     * fetched but not-yet-committed data), this should always lead to the same
     * stream of outgoing/incoming data for the lower/upper layers, even if
     * most of the random calls fail.
     *
     * NOTE: This test uses rand() for random data, which is not optimal.
     *       Instead, it would be better to get the random data from a
     *       static buffer. This both eases reproducibility and allows
     *       simple conversion to a fuzz target.
     */
    int ret;
    unsigned char *acc = NULL;
    unsigned char *outgoing = NULL, *incoming = NULL;
    unsigned char *cur_chunk = NULL;
    size_t cur_out_chunk, out_pos, in_commit, in_fetch;
    int rand_op;  /* Lower layer:
                   * - Reclaim (0)
                   * - Feed (1)
                   * Upper layer:
                   * - Get, do tolerate smaller output (0)
                   * - Get, don't tolerate smaller output (1)
                   * - Commit (2) */
    int mode = 0; /* Lower layer (0) or Upper layer (1) */
    int reclaimed = 1; /* Have to call reclaim at least once before
                        * returning the reader to the upper layer. */
    mbedtls_mps_reader rd;

    if( acc_size > 0 )
    {
        ASSERT_ALLOC( acc, acc_size );
    }

    /* This probably needs to be changed because we want
     * our tests to be deterministic. */
    //    srand( time( NULL ) );

    ASSERT_ALLOC( outgoing, num_out_chunks * max_chunk_size );
    ASSERT_ALLOC( incoming, num_out_chunks * max_chunk_size );

    mbedtls_mps_reader_init( &rd, acc, acc_size );

    cur_out_chunk = 0;
    in_commit = 0;
    in_fetch = 0;
    out_pos = 0;
    while( cur_out_chunk < (unsigned) num_out_chunks )
    {
        if( mode == 0 )
        {
            /* Choose randomly between reclaim and feed */
            rand_op = rand() % 2;

            if( rand_op == 0 )
            {
                /* Reclaim */
                ret = mbedtls_mps_reader_reclaim( &rd, NULL );

                if( ret == 0 )
                {
                    TEST_ASSERT( cur_chunk != NULL );
                    mbedtls_free( cur_chunk );
                    cur_chunk = NULL;
                }
                reclaimed = 1;
            }
            else
            {
                /* Feed reader with a random chunk */
                unsigned char *tmp = NULL;
                size_t tmp_size;
                if( cur_out_chunk == (unsigned) num_out_chunks )
                    continue;

                tmp_size = ( rand() % max_chunk_size ) + 1;
                ASSERT_ALLOC( tmp, tmp_size );

                TEST_ASSERT( mbedtls_test_rnd_std_rand( NULL, tmp, tmp_size ) == 0 );
                ret = mbedtls_mps_reader_feed( &rd, tmp, tmp_size );

                if( ret == 0 || ret == MBEDTLS_ERR_MPS_READER_NEED_MORE )
                {
                    cur_out_chunk++;
                    memcpy( outgoing + out_pos, tmp, tmp_size );
                    out_pos += tmp_size;
                }

                if( ret == 0 )
                {
                    TEST_ASSERT( cur_chunk == NULL );
                    cur_chunk = tmp;
                }
                else
                {
                    mbedtls_free( tmp );
                }

            }

            /* Randomly switch to consumption mode if reclaim
             * was called at least once. */
            if( reclaimed == 1 && rand() % 3 == 0 )
            {
                in_fetch = 0;
                mode = 1;
            }
        }
        else
        {
            /* Choose randomly between get tolerating fewer data,
             * get not tolerating fewer data, and commit. */
            rand_op = rand() % 3;
            if( rand_op == 0 || rand_op == 1 )
            {
                mbedtls_mps_size_t get_size, real_size;
                unsigned char *chunk_get;
                get_size = ( rand() % max_request ) + 1;
                if( rand_op == 0 )
                {
                    ret = mbedtls_mps_reader_get( &rd, get_size, &chunk_get,
                                              &real_size );
                }
                else
                {
                    real_size = get_size;
                    ret = mbedtls_mps_reader_get( &rd, get_size, &chunk_get, NULL );
                }

                /* Check if output is in accordance with what was written */
                if( ret == 0 )
                {
                    memcpy( incoming + in_commit + in_fetch,
                            chunk_get, real_size );
                    TEST_ASSERT( memcmp( incoming + in_commit + in_fetch,
                                         outgoing + in_commit + in_fetch,
                                         real_size ) == 0 );
                    in_fetch += real_size;
                }
            }
            else if( rand_op == 2 ) /* Commit */
            {
                ret = mbedtls_mps_reader_commit( &rd );
                if( ret == 0 )
                {
                    in_commit += in_fetch;
                    in_fetch = 0;
                }
            }

            /* Randomly switch back to preparation */
            if( rand() % 3 == 0 )
            {
                reclaimed = 0;
                mode = 0;
            }
        }
    }

    /* Cleanup */
    mbedtls_mps_reader_free( &rd );
    mbedtls_free( incoming );
    mbedtls_free( outgoing );
    mbedtls_free( acc );
    mbedtls_free( cur_chunk );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_reader_inconsistent_usage( int option )
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - The consumer asks for more data than what's available
     * - The reader is paused and receives more data from the
     *   producer until the original read request can be fulfilled.
     * - The consumer does not repeat the original request but
     *   requests data in a different way.
     *
     * The reader does not guarantee that inconsistent read requests
     * after pausing will succeed, and this test triggers some cases
     * where the request fails.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[40];
    mbedtls_mps_reader rd;
    int success = 0;
    for( int i=0; (unsigned) i < sizeof( bufA ); i++ )
        bufA[i] = (unsigned char) i;
    for( int i=0; (unsigned) i < sizeof( bufB ); i++ )
        bufB[i] = ~ ((unsigned char) i);

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, acc, sizeof( acc ) );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufA, sizeof( bufA ) ) == 0 );
    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 80, &tmp, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 20, &tmp, NULL ) ==
                 MBEDTLS_ERR_MPS_READER_OUT_OF_DATA );
    /* Preparation */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, bufB, sizeof( bufB ) ) == 0 );
    /* Consumption */
    switch( option )
    {
        case 0:
            /* Ask for buffered data in a single chunk, no commit */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 30, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 20, bufA + 80, 20 );
            ASSERT_COMPARE( tmp + 20, 10, bufB, 10 );
            success = 1;
            break;

        case 1:
            /* Ask for buffered data in a single chunk, with commit */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 30, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 20, bufA + 80, 20 );
            ASSERT_COMPARE( tmp + 20, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            success = 1;
            break;

        case 2:
            /* Ask for more than was requested when pausing, #1 */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 31, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS );
            break;

        case 3:
            /* Ask for more than was requested when pausing #2 */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, (mbedtls_mps_size_t) -1, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS );
            break;

        case 4:
            /* Asking for buffered data in different
             * chunks than before CAN fail. */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 15, bufA + 80, 15 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 10, &tmp, NULL ) ==
                         MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS );
            break;

        case 5:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - no commits */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 15, bufA + 80, 15 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 5, bufA + 95, 5 );
            ASSERT_COMPARE( tmp + 5, 10, bufB, 10 );
            success = 1;
            break;

        case 6:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - intermediate commit */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 15, bufA + 80, 15 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 5, bufA + 95, 5 );
            ASSERT_COMPARE( tmp + 5, 10, bufB, 10 );
            success = 1;
            break;

        case 7:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - end commit */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 15, bufA + 80, 15 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 5, bufA + 95, 5 );
            ASSERT_COMPARE( tmp + 5, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            success = 1;
            break;

        case 8:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - intermediate & end commit */
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            ASSERT_COMPARE( tmp, 15, bufA + 80, 15 );
            TEST_ASSERT( mbedtls_mps_reader_get( &rd, 15, &tmp, NULL ) == 0 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            ASSERT_COMPARE( tmp, 5, bufA + 95, 5 );
            ASSERT_COMPARE( tmp + 5, 10, bufB, 10 );
            TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );
            success = 1;
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }

    if( success == 1 )
    {
        /* In all succeeding cases, fetch the rest of the second buffer. */
        TEST_ASSERT( mbedtls_mps_reader_get( &rd, 90, &tmp, NULL ) == 0 );
        ASSERT_COMPARE( tmp, 90, bufB + 10, 90 );
        TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );

        /* Wrapup */
        TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    }

    /* Wrapup */
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_feed_empty( int option )
{
    /* This test exercises the behaviour of the reader when it is
     * fed a NULL buffer. */
    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for( int i=0; (unsigned) i < sizeof( buf ); i++ )
        buf[i] = (unsigned char) i;

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init( &rd, NULL, 0 );
    switch( option )
    {
        case 0: /* NULL buffer */
            TEST_ASSERT( mbedtls_mps_reader_feed( &rd, NULL, sizeof( buf ) ) ==
                         MBEDTLS_ERR_MPS_READER_INVALID_ARG );
            break;

        default:
            TEST_ASSERT( 0 );
            break;
    }
    /* Subsequent feed-calls should still succeed. */
    TEST_ASSERT( mbedtls_mps_reader_feed( &rd, buf, sizeof( buf ) ) == 0 );

    /* Consumption (upper layer) */
    TEST_ASSERT( mbedtls_mps_reader_get( &rd, 100, &tmp, NULL ) == 0 );
    ASSERT_COMPARE( tmp, 100, buf, 100 );
    TEST_ASSERT( mbedtls_mps_reader_commit( &rd ) == 0 );

    /* Wrapup */
    TEST_ASSERT( mbedtls_mps_reader_reclaim( &rd, NULL ) == 0 );
    mbedtls_mps_reader_free( &rd );
}
/* END_CASE */