// Copyright 2019 The Fuchsia Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be found in the LICENSE file.

#include "src/lib/digest/node-digest.h"

#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <zircon/assert.h>
#include <zircon/types.h>

#include <algorithm>

#include <fbl/algorithm.h>

namespace digest {

zx_status_t NodeDigest::SetNodeSize(size_t node_size) {
  if (!IsValidNodeSize(node_size)) {
    return ZX_ERR_INVALID_ARGS;
  }
  node_size_ = node_size;
  return ZX_OK;
}

zx_status_t NodeDigest::Reset(size_t data_off, size_t data_len) {
  if (data_len < data_off || !IsAligned(data_off)) {
    return ZX_ERR_INVALID_ARGS;
  }
  to_append_ = std::min(data_len - data_off, node_size_);
  pad_len_ = node_size_ - to_append_;
  digest_.Init();
  uint64_t locality = id_ ^ data_off;
  digest_.Update(&locality, sizeof(locality));
  uint32_t length = static_cast<uint32_t>(to_append_);
  digest_.Update(&length, sizeof(length));
  // Handle special zero-length case immediately.
  if (length == 0) {
    digest_.Final();
  }
  return ZX_OK;
}

size_t NodeDigest::Append(const void* buf, size_t buf_len) {
  size_t len = std::min(buf_len, to_append_);
  if (len == 0) {
    return 0;
  }
  digest_.Update(buf, len);
  to_append_ -= len;
  if (to_append_ == 0) {
    if (pad_len_ > 0) {
      PadWithZeros();
    } else {
      digest_.Final();
    }
  }
  return len;
}

void NodeDigest::PadWithZeros() {
  static const uint8_t kZeroes[64] = {0};
  size_t padding = to_append_ + pad_len_;
  if (padding == 0) {
    return;
  }
  while (padding > sizeof(kZeroes)) {
    digest_.Update(kZeroes, sizeof(kZeroes));
    padding -= sizeof(kZeroes);
  }
  digest_.Update(kZeroes, padding);
  digest_.Final();
  to_append_ = 0;
  pad_len_ = 0;
}

}  // namespace digest