android/libwvdrmengine/oemcrypto/odk/src/odk_overflow.c

// Copyright 2019 Google LLC. All rights reserved. This file and proprietary
// source code may only be used and distributed under the Widevine
// License Agreement.

#include "odk_overflow.h"

#include <stddef.h>
#include <stdint.h>

int odk_sub_overflow_u64(uint64_t a, uint64_t b, uint64_t* c) {
  if (a >= b) {
    if (c) {
      *c = a - b;
    }
    return 0;
  }
  return 1;
}

int odk_add_overflow_u64(uint64_t a, uint64_t b, uint64_t* c) {
  if (UINT64_MAX - a >= b) {
    if (c) {
      *c = a + b;
    }
    return 0;
  }
  return 1;
}

int odk_add_overflow_ux(size_t a, size_t b, size_t* c) {
  if (SIZE_MAX - a >= b) {
    if (c) {
      *c = a + b;
    }
    return 0;
  }
  return 1;
}

int odk_mul_overflow_ux(size_t a, size_t b, size_t* c) {
  if (b > 0 && a > SIZE_MAX / b) {
    return 1;
  }
  if (c) {
    *c = a * b;
  }
  return 0;
}