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35 lines
740 B
Go
35 lines
740 B
Go
package restorer
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import (
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"github.com/restic/restic/internal/restic"
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)
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// WriteAt writes p to f.File at offset. It tries to do a sparse write
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// and updates f.size.
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func (f *partialFile) WriteAt(p []byte, offset int64) (n int, err error) {
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if !f.sparse {
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return f.File.WriteAt(p, offset)
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}
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n = len(p)
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// Skip the longest all-zero prefix of p.
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// If it's long enough, we can punch a hole in the file.
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skipped := restic.ZeroPrefixLen(p)
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p = p[skipped:]
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offset += int64(skipped)
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switch {
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case len(p) == 0:
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// All zeros, file already big enough. A previous WriteAt or
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// Truncate will have produced the zeros in f.File.
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default:
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var n2 int
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n2, err = f.File.WriteAt(p, offset)
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n = skipped + n2
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}
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return n, err
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}
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