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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,141 @@ | ||
| package fat | ||
|
|
||
| import ( | ||
| "errors" | ||
| "fmt" | ||
| ) | ||
|
|
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| type BlockDeviceExtended interface { | ||
| BlockDevice | ||
| Size() int64 | ||
| BlockSize() int | ||
| } | ||
|
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| const blkmapsize = 512 | ||
|
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| type BlockMap struct { | ||
| data map[int64][blkmapsize]byte | ||
| } | ||
|
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| func (b *BlockMap) BlockSize() int { return blkmapsize } | ||
|
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| func (b *BlockMap) Size() int64 { | ||
| const kilobyte = 1000 | ||
| const megabyte = 1000 * kilobyte | ||
| const gigabyte = 1000 * megabyte | ||
| return 4 * gigabyte // 4GB does not overflow uint32, so likely safe for use with FAT32? | ||
| } | ||
|
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| func (b *BlockMap) ReadBlocks(dst []byte, startBlock int64) (int, error) { | ||
| if startBlock < 0 { | ||
| return 0, errors.New("invalid startBlock") | ||
| } | ||
|
|
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| lastbidx := len(dst) / blkmapsize | ||
| if len(dst)%blkmapsize != 0 { | ||
| return 0, errors.New("dst size not multiple of block size") | ||
| } | ||
| for bidx := int64(0); bidx < int64(lastbidx); bidx++ { | ||
| block := b.data[bidx] | ||
| copy(dst[:], block[:]) | ||
| dst = dst[blkmapsize:] | ||
| } | ||
| return len(dst), nil | ||
| } | ||
|
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| func (b *BlockMap) WriteBlocks(data []byte, startBlock int64) (int, error) { | ||
| if startBlock < 0 { | ||
| return 0, errors.New("invalid startBlock") | ||
| } | ||
|
|
||
| lastbidx := len(data) / blkmapsize | ||
| if len(data)%blkmapsize != 0 { | ||
| return 0, errors.New("data size not multiple of block size") | ||
| } | ||
| var auxblk [blkmapsize]byte | ||
| for bidx := int64(0); bidx < int64(lastbidx); bidx++ { | ||
| copy(auxblk[:], data[:]) | ||
| b.data[bidx] = auxblk | ||
| data = data[blkmapsize:] | ||
| auxblk = [blkmapsize]byte{} | ||
| } | ||
| return len(data), nil | ||
| } | ||
|
|
||
| func (b *BlockMap) EraseBlocks(startBlock, numBlocks int64) error { | ||
| if startBlock < 0 || numBlocks <= 0 { | ||
| return errors.New("invalid erase parameters") | ||
| } | ||
| end := startBlock + numBlocks | ||
| if end < startBlock { | ||
| return errors.New("overflow") | ||
| } | ||
| if len(b.data) > 1024 { | ||
| // Optimized for maps with many entries. | ||
| for i := startBlock; i < end; i++ { | ||
| delete(b.data, i) | ||
| } | ||
| } else { | ||
| // Optimized for maps with few entries. | ||
| for blkidx := range b.data { | ||
| if blkidx >= startBlock && blkidx < end { | ||
| delete(b.data, blkidx) | ||
| } | ||
| } | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| type BlockByteSlice struct { | ||
| blk blkIdxer | ||
| buf []byte | ||
| } | ||
|
|
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| func (b *BlockByteSlice) BlockSize() int { return int(b.blk.size()) } | ||
|
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| func (b *BlockByteSlice) ReadBlocks(dst []byte, startBlock int64) (int, error) { | ||
| if b.blk.off(int64(len(dst))) != 0 { | ||
| return 0, errors.New("startBlock not aligned to block size") | ||
| } else if startBlock < 0 { | ||
| return 0, errors.New("invalid startBlock") | ||
| } | ||
| off := startBlock * b.blk.size() | ||
| end := off + int64(len(dst)) | ||
| if end > int64(len(b.buf)) { | ||
| return 0, fmt.Errorf("read past end of buffer: %d > %d", end, len(b.buf)) | ||
| // return 0, errors.New("read past end of buffer") | ||
| } | ||
|
|
||
| return copy(dst, b.buf[off:end]), nil | ||
| } | ||
| func (b *BlockByteSlice) WriteBlocks(data []byte, startBlock int64) (int, error) { | ||
| if b.blk.off(int64(len(data))) != 0 { | ||
| return 0, errors.New("startBlock not aligned to block size") | ||
| } else if startBlock < 0 { | ||
| return 0, errors.New("invalid startBlock") | ||
| } | ||
| off := startBlock * b.blk.size() | ||
| end := off + int64(len(data)) | ||
| if end > int64(len(b.buf)) { | ||
| return 0, fmt.Errorf("write past end of buffer: %d > %d", end, len(b.buf)) | ||
| // return 0, errors.New("write past end of buffer") | ||
| } | ||
|
|
||
| return copy(b.buf[off:end], data), nil | ||
| } | ||
| func (b *BlockByteSlice) EraseBlocks(startBlock, numBlocks int64) error { | ||
| if startBlock < 0 || numBlocks <= 0 { | ||
| return errors.New("invalid erase parameters") | ||
| } | ||
| start := startBlock * b.blk.size() | ||
| end := start + numBlocks*b.blk.size() | ||
| if end > int64(len(b.buf)) { | ||
| return errors.New("erase past end of buffer") | ||
| } | ||
| clear(b.buf[start:end]) | ||
| return nil | ||
| } | ||
|
|
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| func (b *BlockByteSlice) Size() int64 { | ||
| return int64(len(b.buf)) | ||
| } |