mps_reader.c | Explore in Territory

/*
 *  Message Processing Stack, Reader implementation
 *
 *  Copyright The Mbed TLS Contributors
 *  SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
 */

#include "common.h"

#if defined(MBEDTLS_SSL_PROTO_TLS1_3)

#include "mps_reader.h"
#include "mps_common.h"
#include "mps_trace.h"

#include <string.h>

#if defined(MBEDTLS_MPS_ENABLE_TRACE)
static int mbedtls_mps_trace_id = MBEDTLS_MPS_TRACE_BIT_READER;
#endif /* MBEDTLS_MPS_ENABLE_TRACE */

/*
 * GENERAL NOTE ON CODING STYLE
 *
 * The following code intentionally separates memory loads
 * and stores from other operations (arithmetic or branches).
 * This leads to the introduction of many local variables
 * and significantly increases the C-code line count, but
 * should not increase the size of generated assembly.
 *
 * The reason for this is twofold:
 * (1) It will ease verification efforts using the VST
 *     (Verified Software Toolchain)
 *     whose program logic cannot directly reason
 *     about instructions containing a load or store in
 *     addition to other operations (e.g. *p = *q or
 *     tmp = *p + 42).
 * (2) Operating on local variables and writing the results
 *     back to the target contexts on success only
 *     allows to maintain structure invariants even
 *     on failure - this in turn has two benefits:
 *     (2.a) If for some reason an error code is not caught
 *           and operation continues, functions are nonetheless
 *           called with sane contexts, reducing the risk
 *           of dangerous behavior.
 *     (2.b) Randomized testing is easier if structures
 *           remain intact even in the face of failing
 *           and/or non-sensical calls.
 *     Moreover, it might even reduce code-size because
 *     the compiler need not write back temporary results
 *     to memory in case of failure.
 *
 */

static inline int mps_reader_is_accumulating(
    mbedtls_mps_reader const *rd)
{ … }

static inline int mps_reader_is_producing(
    mbedtls_mps_reader const *rd)
{ … }

static inline int mps_reader_is_consuming(
    mbedtls_mps_reader const *rd)
{ … }

static inline mbedtls_mps_size_t mps_reader_get_fragment_offset(
    mbedtls_mps_reader const *rd)
{ … }

static inline mbedtls_mps_size_t mps_reader_serving_from_accumulator(
    mbedtls_mps_reader const *rd)
{ … }

static inline void mps_reader_zero(mbedtls_mps_reader *rd)
{ … }

int mbedtls_mps_reader_init(mbedtls_mps_reader *rd,
                            unsigned char *acc,
                            mbedtls_mps_size_t acc_len)
{ … }

int mbedtls_mps_reader_free(mbedtls_mps_reader *rd)
{ … }

int mbedtls_mps_reader_feed(mbedtls_mps_reader *rd,
                            unsigned char *new_frag,
                            mbedtls_mps_size_t new_frag_len)
{ … }


int mbedtls_mps_reader_get(mbedtls_mps_reader *rd,
                           mbedtls_mps_size_t desired,
                           unsigned char **buffer,
                           mbedtls_mps_size_t *buflen)
{ … }

int mbedtls_mps_reader_commit(mbedtls_mps_reader *rd)
{ … }

int mbedtls_mps_reader_reclaim(mbedtls_mps_reader *rd,
                               int *paused)
{ … }

#endif /* MBEDTLS_SSL_PROTO_TLS1_3 */
godot/thirdparty/mbedtls/library/mps_reader.c
