45 lines
1.9 KiB
Go
45 lines
1.9 KiB
Go
// Package chunksize calculates a suitable chunk size for large uploads
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package chunksize
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import (
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"github.com/rclone/rclone/fs"
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)
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// Calculator calculates the minimum chunk size needed to fit within
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// the maximum number of parts, rounded up to the nearest fs.Mebi.
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//
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// For most backends, (chunk_size) * (concurrent_upload_routines)
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// memory will be required so we want to use the smallest possible
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// chunk size that's going to allow the upload to proceed. Rounding up
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// to the nearest fs.Mebi on the assumption that some backends may
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// only allow integer type parameters when specifying the chunk size.
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//
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// Returns the default chunk size if it is sufficiently large enough
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// to support the given file size otherwise returns the smallest chunk
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// size necessary to allow the upload to proceed.
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func Calculator(o interface{}, size int64, maxParts int, defaultChunkSize fs.SizeSuffix) fs.SizeSuffix {
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// If streaming then use default chunk size
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if size < 0 {
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fs.Debugf(o, "Streaming upload with chunk_size %s allows uploads of up to %s and will fail only when that limit is reached.", defaultChunkSize, fs.SizeSuffix(maxParts)*defaultChunkSize)
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return defaultChunkSize
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}
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fileSize := fs.SizeSuffix(size)
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requiredChunks := fileSize / defaultChunkSize
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if requiredChunks < fs.SizeSuffix(maxParts) || (requiredChunks == fs.SizeSuffix(maxParts) && fileSize%defaultChunkSize == 0) {
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return defaultChunkSize
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}
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minChunk := fileSize / fs.SizeSuffix(maxParts)
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remainder := minChunk % fs.Mebi
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if remainder != 0 {
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minChunk += fs.Mebi - remainder
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}
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if fileSize/minChunk == fs.SizeSuffix(maxParts) && fileSize%fs.SizeSuffix(maxParts) != 0 { // when right on the boundary, we need to add a MiB
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minChunk += fs.Mebi
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}
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fs.Debugf(o, "size: %v, parts: %v, default: %v, new: %v; default chunk size insufficient, returned new chunk size", fileSize, maxParts, defaultChunkSize, minChunk)
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return minChunk
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}
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