103 lines
2.3 KiB
C++
103 lines
2.3 KiB
C++
/*
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* \brief File node
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* \author Norman Feske
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* \date 2012-04-11
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*/
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#ifndef _FILE_H_
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#define _FILE_H_
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/* Genode includes */
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#include <base/allocator.h>
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/* local includes */
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#include <node.h>
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#include <chunk.h>
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namespace File_system {
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class File : public Node
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{
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private:
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typedef Chunk<4096> Chunk_level_3;
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typedef Chunk_index<128, Chunk_level_3> Chunk_level_2;
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typedef Chunk_index<64, Chunk_level_2> Chunk_level_1;
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typedef Chunk_index<64, Chunk_level_1> Chunk_level_0;
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Chunk_level_0 _chunk;
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file_size_t _length;
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public:
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File(Allocator &alloc, char const *name)
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: _chunk(alloc, 0), _length(0) { Node::name(name); }
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size_t read(char *dst, size_t len, seek_off_t seek_offset)
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{
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file_size_t const chunk_used_size = _chunk.used_size();
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if (seek_offset >= _length)
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return 0;
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/*
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* Constrain read transaction to available chunk data
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*
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* Note that 'chunk_used_size' may be lower than '_length'
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* because 'Chunk' may have truncated tailing zeros.
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*/
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if (seek_offset + len >= _length)
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len = _length - seek_offset;
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file_size_t read_len = len;
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if (seek_offset + read_len > chunk_used_size) {
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if (chunk_used_size >= seek_offset)
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read_len = chunk_used_size - seek_offset;
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else
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read_len = 0;
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}
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_chunk.read(dst, read_len, seek_offset);
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/* add zero padding if needed */
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if (read_len < len)
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memset(dst + read_len, 0, len - read_len);
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return len;
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}
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size_t write(char const *src, size_t len, seek_off_t seek_offset)
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{
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if (seek_offset == (seek_off_t)(~0))
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seek_offset = _chunk.used_size();
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if (seek_offset + len >= Chunk_level_0::SIZE)
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throw Size_limit_reached();
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_chunk.write(src, len, (size_t)seek_offset);
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/*
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* Keep track of file length. We cannot use 'chunk.used_size()'
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* as file length because trailing zeros may by represented
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* by zero chunks, which do not contribute to 'used_size()'.
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*/
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_length = max(_length, seek_offset + len);
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return 0;
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}
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file_size_t length() const { return _length; }
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void truncate(file_size_t size)
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{
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if (size < _chunk.used_size())
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_chunk.truncate(size);
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else
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_length = size;
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}
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};
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}
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#endif /* _FILE_H_ */
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