65 lines
1.4 KiB
C++
65 lines
1.4 KiB
C++
class File {
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static constexpr const int32_t F_EOF = -1;
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FS& fs;
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uint32_t totalSize;
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uint32_t curAbsPos = 0; // position withithin the whole file
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uint32_t curCluster = 0; // cluster we are currently reading
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uint32_t posInCluster = 0; // position within the current cluster
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public:
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File(FS& fs, uint32_t firstCluster, uint32_t size) : fs(fs), totalSize(size), curCluster(firstCluster) {
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}
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/** the file's size */
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uint32_t getSize() const {return totalSize;}
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uint32_t read(uint32_t size, uint8_t* dst) {
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uint32_t total = 0;
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while(true) {
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const uint32_t read = _read(size, dst);
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if (read == F_EOF) {break;}
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size -= read;
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dst += read;
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total += read;
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}
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return total;
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}
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private:
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int32_t _read(uint32_t readSize, uint8_t* dst) {
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// EOF reached?
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if (curAbsPos >= totalSize) {
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return F_EOF;
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}
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// end of current cluster reached? -> determine the next one
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if (posInCluster == fs.tmp.bytesPerCluster) {
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curCluster = fs.getNextCluster(curCluster);
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posInCluster = 0;
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}
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// how many bytes are left in the current cluster?
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const uint32_t remainingInCluster = fs.tmp.bytesPerCluster - posInCluster;
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// determine how many bytes to read
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const uint32_t toRead = std::min(remainingInCluster, readSize);
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const uint32_t offset = fs.clusterToAbsPos(curCluster) + posInCluster;
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const uint32_t read = fs.dev.read(offset, toRead, dst);
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posInCluster += read;
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curAbsPos += read;
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return read;
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}
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};
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