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93 lines
2.6 KiB
93 lines
2.6 KiB
#ifndef TEENSY_RESAMPLING_INDEXABLE_FILE_H
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#define TEENSY_RESAMPLING_INDEXABLE_FILE_H
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#include <Arduino.h>
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#include <SD.h>
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#include <vector>
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namespace newdigate {
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struct indexedbuffer {
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uint32_t index;
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int16_t buffer_size;
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int16_t *buffer;
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};
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constexpr bool isPowerOf2(size_t value){
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return !(value == 0) && !(value & (value - 1));
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}
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template<size_t BUFFER_SIZE, size_t MAX_NUM_BUFFERS> // BUFFER_SIZE needs to be a power of two
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class IndexableFile {
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public:
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static_assert(isPowerOf2(BUFFER_SIZE), "BUFFER_SIZE must be a power of 2");
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static constexpr size_t element_size = sizeof(int16_t);
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size_t buffer_to_index_shift;
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IndexableFile(const char *filename) :
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_buffers(),
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buffer_to_index_shift(log2(BUFFER_SIZE)) {
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_filename = new char[strlen(filename)+1] {0};
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memcpy(_filename, filename, strlen(filename));
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_file = SD.open(_filename);
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}
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int16_t &operator[](int i) {
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int32_t indexFor_i = i >> buffer_to_index_shift;
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indexedbuffer *match = find_with_index(indexFor_i);
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if (match == nullptr) {
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if (_buffers.size() > MAX_NUM_BUFFERS - 1) {
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indexedbuffer *first = _buffers[0];
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_buffers.erase(_buffers.begin());
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delete [] first->buffer;
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delete first;
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}
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indexedbuffer *next = new indexedbuffer();
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next->index = indexFor_i;
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next->buffer = new int16_t[BUFFER_SIZE];
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size_t basePos = indexFor_i << buffer_to_index_shift;
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size_t seekPos = basePos * element_size;
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_file.seek(seekPos);
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int16_t bytesRead = _file.read(next->buffer, BUFFER_SIZE * element_size);
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#ifndef TEENSYDUINO
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if (!_file.available()){
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_file.close();
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__disable_irq();
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_file = SD.open(_filename);
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__enable_irq();
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}
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#endif
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next->buffer_size = bytesRead;
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_buffers.push_back(next);
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match = next;
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}
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return match->buffer[i % BUFFER_SIZE];
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}
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void close() {
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if (_file)
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_file.close();
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if (_filename)
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delete [] _filename;
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_filename = nullptr;
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}
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private:
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File _file;
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char *_filename;
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std::vector<indexedbuffer*> _buffers;
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indexedbuffer* find_with_index(uint32_t i) {
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for (auto && x : _buffers){
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if (x->index == i) {
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return x;
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}
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}
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return nullptr;
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}
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};
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}
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#endif
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