Buffers.h

#pragma once
 
#include "AudioTools/CoreAudio/AudioBasic/Collections.h"
#include "AudioTools/CoreAudio/AudioBasic/Str.h"
#include "AudioTools/CoreAudio/AudioLogger.h"
 
namespace audio_tools {
 
template <typename T>
class BaseBuffer {
 public:
  BaseBuffer() = default;
  virtual ~BaseBuffer() = default;
  BaseBuffer(BaseBuffer const &) = delete;
  // BaseBuffer &operator=(BaseBuffer const &) = delete;
 
  virtual bool read(T &result) = 0;
 
  virtual int readArray(T data[], int len) {
    if (data == nullptr) {
      LOGE("NPE");
      return 0;
    }
    int lenResult = min(len, available());
    for (int j = 0; j < lenResult; j++) {
      read(data[j]);
    }
    LOGD("readArray %d -> %d", len, lenResult);
    return lenResult;
  }
 
  virtual int clearArray(int len) {
    int lenResult = min(len, available());
    T dummy[lenResult];
    readArray(dummy, lenResult);
    return lenResult;
  }
 
  virtual int writeArray(const T data[], int len) {
    // LOGD("%s: %d", LOG_METHOD, len);
    // CHECK_MEMORY();
 
    int result = 0;
    for (int j = 0; j < len; j++) {
      if (!write(data[j])) {
        break;
      }
      result = j + 1;
    }
    // CHECK_MEMORY();
    LOGD("writeArray %d -> %d", len, result);
    return result;
  }
 
  virtual int writeArrayOverwrite(const T data[], int len) {
    int to_delete = len - availableForWrite();
    if (to_delete > 0) {
      clearArray(to_delete);
    }
    return writeArray(data, len);
  }
 
  virtual bool peek(T &result) = 0;
 
  virtual bool isFull() { return availableForWrite() == 0; }
 
  bool isEmpty() { return available() == 0; }
 
  virtual bool write(T data) = 0;
 
  virtual void reset() = 0;
 
  void clear() { reset(); }
 
  virtual int available() = 0;
 
  virtual int availableForWrite() = 0;
 
  virtual T *address() = 0;
 
  virtual size_t size() = 0;
 
  virtual float levelPercent() {
    // prevent div by 0.
    if (size() == 0) return 0.0f;
    return 100.0f * static_cast<float>(available()) /
           static_cast<float>(size());
  }
 
  virtual bool resize(int bytes) {
    LOGE("resize not implemented for this buffer");
    return false;
  }
};
 
/***
 * @brief A FrameBuffer reads multiple values for array of 2 dimensional frames
 */
template <typename T>
class FrameBuffer {
 public:
  FrameBuffer(BaseBuffer<T> &buffer) { p_buffer = &buffer; }
  int readFrames(T data[][2], int len) {
    LOGD("%s: %d", LOG_METHOD, len);
    // CHECK_MEMORY();
    int result = min(len, p_buffer->available());
    for (int j = 0; j < result; j++) {
      T sample = 0;
      p_buffer->read(sample);
      data[j][0] = sample;
      data[j][1] = sample;
    }
    // CHECK_MEMORY();
    return result;
  }
 
  template <int rows, int channels>
  int readFrames(T (&data)[rows][channels]) {
    int lenResult = min(rows, p_buffer->available());
    for (int j = 0; j < lenResult; j++) {
      T sample = 0;
      p_buffer->read(sample);
      for (int i = 0; i < channels; i++) {
        // data[j][i] = htons(sample);
        data[j][i] = sample;
      }
    }
    return lenResult;
  }
 
 protected:
  BaseBuffer<T> *p_buffer = nullptr;
};
 
template <typename T>
class SingleBuffer : public BaseBuffer<T> {
 public:
  SingleBuffer(int size) {
    buffer.resize(size);
    reset();
  }
 
  SingleBuffer() { reset(); }
 
  void onExternalBufferRefilled(void *data, int len) {
    this->owns_buffer = false;
    this->buffer = (uint8_t *)data;
    this->current_read_pos = 0;
    this->current_write_pos = len;
  }
 
  int writeArray(const T data[], int len) override {
    if (size() == 0) resize(len);
    return BaseBuffer<T>::writeArray(data, len);
  }
 
  bool write(T sample) override {
    bool result = false;
    if (current_write_pos < buffer.size()) {
      buffer[current_write_pos++] = sample;
      result = true;
    }
    return result;
  }
 
  bool read(T &result) override {
    bool success = false;
    if (current_read_pos < current_write_pos) {
      result = buffer[current_read_pos++];
      success = true;
    }
    return success;
  }
 
  bool peek(T &result) override {
    bool success = false;
    if (current_read_pos < current_write_pos) {
      result = buffer[current_read_pos];
      success = true;
    }
    return success;
  }
 
  int available() override {
    int result = current_write_pos - current_read_pos;
    return max(result, 0);
  }
 
  int availableForWrite() override { return buffer.size() - current_write_pos; }
 
  bool isFull() override { return availableForWrite() <= 0; }
 
  int clearArray(int len) override {
    int len_available = available();
    if (len > available()) {
      reset();
      return len_available;
    }
    current_read_pos += len;
    len_available -= len;
    memmove(buffer.data(), buffer.data() + current_read_pos, len_available * sizeof(T));
    current_read_pos = 0;
    current_write_pos = len_available;
 
    if (is_clear_with_zero) {
      memset(buffer.data() + current_write_pos, 0,
             buffer.size() - current_write_pos);
    }
 
    return len;
  }
 
  void trim() {
    int av = available();
    memmove(buffer.data(), buffer.data() + current_read_pos, av * sizeof(T));
    current_write_pos = av;
    current_read_pos = 0;
  }
 
  T *address() override { return buffer.data(); }
 
  T *data() { return buffer.data() + current_read_pos; }
 
  void reset() override {
    current_read_pos = 0;
    current_write_pos = 0;
    if (is_clear_with_zero) {
      memset(buffer.data(), 0, buffer.size());
    }
  }
 
  size_t setAvailable(size_t available_size) {
    size_t result = min(available_size, (size_t)buffer.size());
    current_read_pos = 0;
    current_write_pos = result;
    return result;
  }
 
  size_t size() override { return buffer.size(); }
 
  bool resize(int size) {
    if (buffer.size() < size) {
      TRACED();
      buffer.resize(size);
    }
    return true;
  }
 
  void setClearWithZero(bool flag) { is_clear_with_zero = flag; }
 
  void setWritePos(int pos) { current_write_pos = pos; }
 
  int id = 0;
  bool active = true;
  uint64_t timestamp = 0;
 
 protected:
  int current_read_pos = 0;
  int current_write_pos = 0;
  bool owns_buffer = true;
  bool is_clear_with_zero = false;
  Vector<T> buffer{0};
};
 
template <typename T>
class RingBuffer : public BaseBuffer<T> {
 public:
  RingBuffer(int size) {
    resize(size);
    reset();
  }
 
  bool read(T &result) override {
    if (isEmpty()) {
      return false;
    }
 
    result = _aucBuffer[_iTail];
    _iTail = nextIndex(_iTail);
    _numElems--;
 
    return true;
  }
 
  // peeks the actual entry from the buffer
  bool peek(T &result) override {
    if (isEmpty()) {
      return false;
    }
 
    result = _aucBuffer[_iTail];
    return true;
  }
 
  virtual int peekArray(T *data, int n) {
    if (isEmpty()) return -1;
    int result = 0;
    int count = _numElems;
    int tail = _iTail;
    for (int j = 0; j < n; j++) {
      data[j] = _aucBuffer[tail];
      tail = nextIndex(tail);
      count--;
      result++;
      if (count == 0) break;
    }
    return result;
  }
 
  // checks if the buffer is full
  virtual bool isFull() override { return available() == max_size; }
 
  bool isEmpty() { return available() == 0; }
 
  // write add an entry to the buffer
  virtual bool write(T data) override {
    bool result = false;
    if (!isFull()) {
      _aucBuffer[_iHead] = data;
      _iHead = nextIndex(_iHead);
      _numElems++;
      result = true;
    }
    return result;
  }
 
  // clears the buffer
  virtual void reset() override {
    _iHead = 0;
    _iTail = 0;
    _numElems = 0;
  }
 
  // provides the number of entries that are available to read
  virtual int available() override { return _numElems; }
 
  // provides the number of entries that are available to write
  virtual int availableForWrite() override { return (max_size - _numElems); }
 
  // returns the address of the start of the physical read buffer
  virtual T *address() override { return _aucBuffer.data(); }
 
  virtual bool resize(int len) {
    if (max_size != len) {
      LOGI("resize: %d", len);
      _aucBuffer.resize(len);
      max_size = len;
    }
    return true;
  }
 
  virtual size_t size() override { return max_size; }
 
 protected:
  Vector<T> _aucBuffer;
  int _iHead;
  int _iTail;
  int _numElems;
  int max_size = 0;
 
  int nextIndex(int index) { 
    if (max_size == 0) return 0;
    return (uint32_t)(index + 1) % max_size; }
};
 
template <class File, typename T>
class RingBufferFile : public BaseBuffer<T> {
 public:
  RingBufferFile(int size) { resize(size); }
  RingBufferFile(int size, File &file) {
    resize(size);
    begin(file);
  }
  ~RingBufferFile() {
    if (p_file) p_file->close();
  }
 
  bool begin(File &bufferFile) {
    if (bufferFile) {
      p_file = &bufferFile;
    } else {
      LOGE("file is not valid");
    }
    return bufferFile;
  }
 
  bool read(T &result) override { return readArray(&result, 1) == 1; }
 
  int readArray(T data[], int count) override {
    if (p_file == nullptr) return 0;
    int read_count = min(count, available());
 
    OffsetInfo offset = getOffset(read_pos, read_count);
    if (!file_seek(offset.pos)) return false;
    int n = file_read(data, offset.len);
    if (offset.len1 > 0) {
      file_seek(0);
      n += file_read(data + offset.len, offset.len1);
      read_pos = offset.len1;
    } else {
      read_pos += read_count;
    }
 
     for (int i = 0; i < count; i++) {
      LOGI("read #%d value %d", offset.pos, (int)data[i]);
    }
   
    element_count -= read_count;
    return read_count;
  }
 
  bool peek(T &result) override {
    if (p_file == nullptr || isEmpty()) {
      return false;
    }
 
    if (!file_seek(read_pos)) return false;
    size_t count = file_read(&result, 1);
    return count == 1;
  }
 
  int peekArray(T data[], int count) {
    if (p_file == nullptr) return 0;
    int read_count = min(count, available());
 
    OffsetInfo offset = getOffset(read_pos, read_count);
    if (!file_seek(offset.pos)) return false;
    int n = file_read(data, offset.len);
    if (offset.len1 > 0) {
      file_seek(0);
      n += file_read(data + offset.len, offset.len1);
    }
    assert(n == read_count);
    return read_count;
  }
 
  bool write(T data) override { return writeArray(&data, 1); }
 
  int writeArray(const T data[], int len) override {
    if (p_file == nullptr) return 0;
    for (int i = 0; i < len; i++) {
      LOGI("write #%d value %d", write_pos, (int)data[i]);
    }
 
    int write_count = min(len, availableForWrite());
    OffsetInfo offset = getOffset(write_pos, write_count);
 
    if (!file_seek(offset.pos)) return false;
    int n = file_write(data, offset.len);
    if (offset.len1 > 0) {
      file_seek(0);
      n += file_write(data + offset.len, offset.len1);
      write_pos = offset.len1;
    } else {
      write_pos += write_count;
    }
    element_count += write_count;
    return write_count;
  }
 
  bool isFull() override { return available() == max_size; }
 
  bool isEmpty() { return available() == 0; }
 
  void reset() override {
    write_pos = 0;
    read_pos = 0;
    element_count = 0;
    if (p_file != nullptr) file_seek(0);
  }
 
  int available() override { return element_count; }
 
  int availableForWrite() override { return (max_size - element_count); }
 
  size_t size() override { return max_size; }
 
  bool resize(int size) {
    max_size = size;
    return true;
  }
 
  // not supported
  T *address() override { return nullptr; }
 
 protected:
  File *p_file = nullptr;
  int write_pos = 0;
  int read_pos = 0;
  int element_count = 0;
  int max_size = 0;
 
  struct OffsetInfo {
    int pos = 0;   // start pos
    int len = 0;   // length of first part
    int len1 = 0;  // length of second part on overflow
  };
 
  OffsetInfo getOffset(int pos, int len) {
    OffsetInfo result;
    result.pos = pos;
    int overflow = (pos + len) - max_size;
    if (overflow <= 0) {
      // we can write the complete data
      result.len = len;
      result.len1 = 0;
    } else {
      // we need to split the data
      result.len = len - overflow;
      result.len1 = overflow;
    }
    return result;
  }
 
  bool file_seek(int pos) {
    int file_pos = pos * sizeof(T);
    if (p_file->position() != file_pos) {
      LOGD("file_seek: %d", pos);
      if (!p_file->seek(file_pos)) {
        LOGE("seek %d", file_pos);
        return false;
      }
    }
    return true;
  }
 
  int file_write(const T *data, int count) {
    LOGD("file_write: %d", count);
    if (p_file == nullptr) return 0;
    int to_write_bytes = sizeof(T) * count;
    int bytes_written = p_file->write((const uint8_t *)data, to_write_bytes);
    p_file->flush();
    int elements_written = bytes_written / sizeof(T);
    if (bytes_written != to_write_bytes) {
      LOGE("write: %d -> %d bytes", to_write_bytes, bytes_written);
    }
    return elements_written;
  }
 
  int file_read(T *result, int count) {
    LOGD("file_read: %d", count);
    int read_bytes = count * sizeof(T);
    int result_bytes = p_file->readBytes((char *)result, read_bytes);
    int result_count = result_bytes / sizeof(T);
    if (result_count != count) {
      LOGE("readBytes: %d -> %d", read_bytes, result_bytes);
    }
    return result_count;
  }
};
 
template <typename T>
class NBuffer : public BaseBuffer<T> {
 public:
  NBuffer(int size, int count) { resize(size, count); }
 
  virtual ~NBuffer() { freeMemory(); }
 
  bool read(T &result) override {
    if (available() == 0) return false;
    return actual_read_buffer->read(result);
  }
 
  bool peek(T &result) override {
    if (available() == 0) return false;
    return actual_read_buffer->peek(result);
  }
 
  bool isFull() { return availableForWrite() == 0; }
 
  bool write(T data) {
    bool result = false;
    if (actual_write_buffer == nullptr) {
      actual_write_buffer = getNextAvailableBuffer();
    }
    if (actual_write_buffer != nullptr) {
      result = actual_write_buffer->write(data);
      // if buffer is full move to next available
      if (actual_write_buffer->isFull()) {
        addFilledBuffer(actual_write_buffer);
        actual_write_buffer = getNextAvailableBuffer();
      }
    }
 
    if (start_time == 0l) {
      start_time = millis();
    }
    if (result) sample_count++;
 
    return result;
  }
 
  int available() {
    if (actual_read_buffer == nullptr) {
      actual_read_buffer = getNextFilledBuffer();
    }
    if (actual_read_buffer == nullptr) {
      return 0;
    }
    int result = actual_read_buffer->available();
    if (result == 0) {
      // make current read buffer available again
      resetCurrent();
      result =
          (actual_read_buffer == nullptr) ? 0 : actual_read_buffer->available();
    }
    return result;
  }
 
  int availableForWrite() {
    if (actual_write_buffer == nullptr) {
      actual_write_buffer = getNextAvailableBuffer();
    }
    // if we used up all buffers - there is nothing available any more
    if (actual_write_buffer == nullptr) {
      return 0;
    }
    // check on actual buffer
    if (actual_write_buffer->isFull()) {
      // if buffer is full we move it to filled buffers ang get the next
      // available
      addFilledBuffer(actual_write_buffer);
      actual_write_buffer = getNextAvailableBuffer();
    }
    return actual_write_buffer->availableForWrite();
  }
 
  void reset() {
    TRACED();
    while (actual_read_buffer != nullptr) {
      actual_read_buffer->reset();
      addAvailableBuffer(actual_read_buffer);
      // get next read buffer
      actual_read_buffer = getNextFilledBuffer();
    }
  }
 
  unsigned long sampleRate() {
    unsigned long run_time = (millis() - start_time);
    return run_time == 0 ? 0 : sample_count * 1000 / run_time;
  }
 
  T *address() {
    return actual_read_buffer == nullptr ? nullptr
                                         : actual_read_buffer->address();
  }
 
  virtual int bufferCountFilled() { return filled_buffers.size(); }
 
  virtual int bufferCountEmpty() { return available_buffers.size(); }
 
  virtual bool resize(int bytes) {
    int count = bytes / buffer_size;
    return resize(buffer_size, count);
  }
 
  virtual bool resize(int size, int count) {
    if (buffer_size == size && buffer_count == count) return true;
    freeMemory();
    filled_buffers.resize(count);
    available_buffers.resize(count);
    // filled_buffers.clear();
    // available_buffers.clear();
 
    buffer_count = count;
    buffer_size = size;
    for (int j = 0; j < count; j++) {
      BaseBuffer<T> *buffer = new SingleBuffer<T>(size);
      LOGD("new buffer %p", buffer);
      available_buffers.enqueue(buffer);
    }
    return true;
  }
 
  size_t size() { return buffer_size * buffer_count; }
 
 protected:
  int buffer_size = 1024;
  uint16_t buffer_count = 0;
  BaseBuffer<T> *actual_read_buffer = nullptr;
  BaseBuffer<T> *actual_write_buffer = nullptr;
  QueueFromVector<BaseBuffer<T> *> available_buffers{0, nullptr};
  QueueFromVector<BaseBuffer<T> *> filled_buffers{0, nullptr};
  unsigned long start_time = 0;
  unsigned long sample_count = 0;
 
  NBuffer() = default;
 
  void freeMemory() {
    if (actual_write_buffer) {
      LOGD("deleting %p", actual_write_buffer);
      delete actual_write_buffer;
      actual_write_buffer = nullptr;
    }
    if (actual_read_buffer) {
      LOGD("deleting %p", actual_read_buffer);
      delete actual_read_buffer;
      actual_read_buffer = nullptr;
    }
 
    BaseBuffer<T> *ptr = getNextAvailableBuffer();
    while (ptr != nullptr) {
      LOGD("deleting %p", ptr);
      delete ptr;
      ptr = getNextAvailableBuffer();
    }
 
    ptr = getNextFilledBuffer();
    while (ptr != nullptr) {
      LOGD("deleting %p", ptr);
      delete ptr;
      ptr = getNextFilledBuffer();
    }
  }
 
  void resetCurrent() {
    if (actual_read_buffer != nullptr) {
      actual_read_buffer->reset();
      addAvailableBuffer(actual_read_buffer);
    }
    // get next read buffer
    actual_read_buffer = getNextFilledBuffer();
  }
 
  virtual BaseBuffer<T> *getNextAvailableBuffer() {
    if (available_buffers.empty()) return nullptr;
    BaseBuffer<T> *result = nullptr;
    available_buffers.dequeue(result);
    return result;
  }
 
  virtual bool addAvailableBuffer(BaseBuffer<T> *buffer) {
    return available_buffers.enqueue(buffer);
  }
 
  virtual BaseBuffer<T> *getNextFilledBuffer() {
    if (filled_buffers.empty()) return nullptr;
    BaseBuffer<T> *result = nullptr;
    filled_buffers.dequeue(result);
    return result;
  }
 
  virtual bool addFilledBuffer(BaseBuffer<T> *buffer) {
    return filled_buffers.enqueue(buffer);
  }
};
 
template <typename T>
class NBufferExt : public NBuffer<T> {
 public:
  NBufferExt(int size, int count) { resize(size, count); }
 
  SingleBuffer<T> *writeEnd() {
    actual_write_buffer = getNextAvailableBuffer();
    if (actual_write_buffer != nullptr) {
      addFilledBuffer(actual_write_buffer);
    }
    return (SingleBuffer<T> *)actual_write_buffer;
  }
 
  SingleBuffer<T> *readEnd() {
    // make current read buffer available again
    resetCurrent();
    return (SingleBuffer<T> *)actual_read_buffer;
  }
 
  SingleBuffer<T> *getBuffer(int id) {
    for (auto &buffer : this->filled_buffers.toVector()) {
      SingleBuffer<T> *sbuffer = (SingleBuffer<T> *)&buffer;
      if (sbuffer->id == id) {
        return sbuffer;
      }
    }
    return nullptr;
  }
 
  using NBuffer<T>::resize;
 
 protected:
  using NBuffer<T>::resetCurrent;
  using NBuffer<T>::addFilledBuffer;
  using NBuffer<T>::getNextAvailableBuffer;
  using NBuffer<T>::actual_write_buffer;
  using NBuffer<T>::actual_read_buffer;
  using NBuffer<T>::buffer_size;
};
 
/***
 * @brief A File backed buffer which uses the provided files for buffering with
 * the indicated max size. A file is made available for reading as soon as it
 * reached the size limit. You must provide the files opened in "Write" mode
 * with the addFile() method!
 * @ingroup buffers
 * @tparam File: file class
 * @tparam T: buffered data type
 */
template <class File, typename T>
class NBufferFile : public BaseBuffer<T> {
 public:
  NBufferFile(int fileSize) { number_of_objects_per_file = fileSize; }
  ~NBufferFile() { end(); }
 
  const char *nextFileName() {
    next_file_name.set("buffer-");
    char number[40];
    snprintf(number, 40, "%d", file_count);
    next_file_name.add(number);
    next_file_name.add(".tmp");
    return next_file_name.c_str();
  }
 
  bool addFile(File &file) {
    if (!file) return false;
    empty_files.enqueue(file);
    file_count++;
    return true;
  }
 
  bool read(T &result) override { return readArray(&result, 1) == 1; }
 
  int readArray(T data[], int len) override {
    // make sure we have a read file
    if (!read_file) {
      if (!filled_files.dequeue(read_file)) {
        // no more data
        return 0;
      }
      read_file.seek(0);
    }
    // read the data
    int result = read_file.readBytes((char *)data, len * sizeof(T)) / sizeof(T);
 
    // if we have consumed all content
    if (result < len) {
      read_file.seek(0);
      empty_files.enqueue(read_file);
      read_file = empty;
    }
    return result;
  }
 
  bool peek(T &data) override {
    size_t pos = read_file.position();
    bool result = read(data);
    read_file.seek(pos);
    return result;
  }
 
  bool write(T sample) override { return writeArray(&sample, 1) == 1; }
 
  int writeArray(const T data[], int len) override {
    if (!write_file || write_file.size() + len > number_of_objects_per_file) {
      // moved to filled files
      if (write_file) {
        write_file.seek(0);
        filled_files.enqueue(write_file);
      }
      // get next empty file
      if (!empty_files.dequeue(write_file)) return false;
    }
    int result = write_file.write((uint8_t *)data, len * sizeof(T));
    return result / sizeof(T);
  }
 
  int available() override {
    return filled_files.size() * number_of_objects_per_file +
           (read_file.available() / sizeof(T));
  }
 
  // provides the number of entries that are available to write
  int availableForWrite() override {
    int open_current =
        number_of_objects_per_file - (write_file.available() / sizeof(T));
    return empty_files.size() * number_of_objects_per_file +
           write_file.available() + open_current;
  }
 
  size_t size() override { return number_of_objects_per_file * file_count; }
 
  void end() {
    cleanupFile(read_file);
    cleanupFile(write_file);
    File file;
    while (empty_files.dequeue(file)) cleanupFile(file);
    while (filled_files.dequeue(file)) cleanupFile(file);
  }
 
  void setFileDeleteCallback(void (*cb)(const char *filename)) {
    file_delete_callback = cb;
  }
 
  void reset() {
    if (read_file) {
      read_file.seek(0);
      empty_files.enqueue(read_file);
      read_file = empty;
    }
    if (write_file) {
      write_file.seek(0);
      empty_files.enqueue(write_file);
      write_file = empty;
    }
    File file;
    while (filled_files.dequeue(file)) {
      file.seek(0);
      empty_files.enqueue(file);
    }
  }
  T *address() { return nullptr; }
 
 protected:
  Queue<File> empty_files;
  Queue<File> filled_files;
  File read_file;
  File write_file;
  File empty;
  int number_of_objects_per_file = 0;  // number of objects per file
  int file_count = 0;                  // number of files
  const uint16_t max_file_name = 256;
  Str next_file_name;
  void (*file_delete_callback)(const char *filename);
 
  void cleanupFile(File &file) {
    if (!file) return;
    // after close the file name is gone
    int len = strlen(file.name());
    char file_name[len + 1];
    strncpy(file_name, file.name(), len);
    file.close();
    file_delete_callback(file_name);
  }
};
 
template <typename T>
class BufferedArray {
 public:
  BufferedArray(Stream &input, int len) {
    LOGI("BufferedArray(%d)", len);
    array.resize(len);
    p_stream = &input;
  }
  // access values, the offset and length are specified in samples of type <T>
  int16_t *getValues(size_t offset, size_t length) {
    LOGD("getValues(%d,%d) - max %d", offset, length, array.size());
    if (offset == 0) {
      // we restart at the beginning
      last_end = 0;
      actual_end = length;
    } else {
      // if first position is at end we do not want to read the full buffer
      last_end = actual_end >= 0 ? actual_end : offset;
      // increase actual end if bigger then old
      actual_end = offset + length > actual_end ? offset + length : actual_end;
    }
    int size = actual_end - last_end;
    if (size > 0) {
      LOGD("readBytes(%d,%d)", last_end, size);
      assert(last_end + size <= array.size());
      p_stream->readBytes((uint8_t *)(&array[last_end]), size * 2);
    }
    assert(offset < actual_end);
    return &array[offset];
  }
 
 protected:
  int actual_end = -1;
  int last_end = 0;
  Vector<T> array;
  Stream *p_stream = nullptr;
};
 
}  // namespace audio_tools