src/cc/frontends/b/type_helper.h

/*
 * Copyright (c) 2015 PLUMgrid, Inc.
 *
 * 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.
 */

#pragma once

namespace ebpf {
namespace cc {

// Represent the numeric type of a protocol field
enum FieldType {
  INVALID = 0,
  UINT8_T,
  UINT16_T,
  UINT32_T,
  UINT64_T,
#ifdef __SIZEOF_INT128__
  UINT128_T,
#endif
  VOID
};

static inline size_t enum_to_size(const FieldType t) {
  switch (t) {
    case UINT8_T: return sizeof(uint8_t);
    case UINT16_T: return sizeof(uint16_t);
    case UINT32_T: return sizeof(uint32_t);
    case UINT64_T: return sizeof(uint64_t);
#ifdef __SIZEOF_INT128__
    case UINT128_T: return sizeof(__uint128_t);
#endif
    default:
      return 0;
  }
}

/// Convert a bit size to the next highest power of 2
static inline int next_base2(int v) {
  --v;
  v |= v >> 1;
  v |= v >> 2;
  v |= v >> 4;
  v |= v >> 8;
  v |= v >> 16;
  ++v;
  return v;
}

static inline const char* bits_to_uint(int v) {
  v = next_base2(v);
  if (v <= 8) {
    return "uint8_t";
  } else if (v == 16) {
    return "uint16_t";
  } else if (v == 32) {
    return "uint32_t";
  } else if (v == 64) {
    return "uint64_t";
  } else if (v >= 128) {
    /* in plumlet 128-bit integers should be 8-byte aligned,
     * all other ints should have natural alignment */
    return "unsigned __int128 __attribute__((packed, aligned(8)))";
  }
  return "void";
}

static inline FieldType bits_to_enum(int v) {
  v = next_base2(v);
  if (v <= 8) {
    return UINT8_T;
  } else if (v == 16) {
    return UINT16_T;
  } else if (v == 32) {
    return UINT32_T;
  } else if (v == 64) {
    return UINT64_T;
#ifdef __SIZEOF_INT128__
  } else if (v >= 128) {
    return UINT128_T;
#endif
  }
  return VOID;
}

static inline size_t bits_to_size(int v) {
  return enum_to_size(bits_to_enum(v));
}

static inline size_t align_offset(size_t offset, FieldType ft) {
  switch (ft) {
    case UINT8_T:
      return offset % 8 > 0 ? offset + (8 - offset % 8) : offset;
    case UINT16_T:
      return offset % 16 > 0 ? offset + (16 - offset % 16) : offset;
    case UINT32_T:
      return offset % 32 > 0 ? offset + (32 - offset % 32) : offset;
    case UINT64_T:
#ifdef __SIZEOF_INT128__
    case UINT128_T:
#endif
      return offset % 64 > 0 ? offset + (64 - offset % 64) : offset;
    default:
      ;
  }
  return offset;
}

}  // namespace cc
}  // namespace ebpf