mirror of https://github.com/pkg/sftp.git
97 lines
2.1 KiB
Go
97 lines
2.1 KiB
Go
package sftp
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import (
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"sync"
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)
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type allocator struct {
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sync.Mutex
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available [][]byte
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// map key is the request order
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used map[uint32][][]byte
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}
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func newAllocator() *allocator {
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return &allocator{
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// micro optimization: initialize available pages with an initial capacity
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available: make([][]byte, 0, SftpServerWorkerCount*2),
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used: make(map[uint32][][]byte),
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}
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}
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// GetPage returns a previously allocated and unused []byte or create a new one.
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// The slice have a fixed size = maxMsgLength, this value is suitable for both
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// receiving new packets and reading the files to serve
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func (a *allocator) GetPage(requestOrderID uint32) []byte {
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a.Lock()
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defer a.Unlock()
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var result []byte
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// get an available page and remove it from the available ones.
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if len(a.available) > 0 {
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truncLength := len(a.available) - 1
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result = a.available[truncLength]
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a.available[truncLength] = nil // clear out the internal pointer
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a.available = a.available[:truncLength] // truncate the slice
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}
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// no preallocated slice found, just allocate a new one
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if result == nil {
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result = make([]byte, maxMsgLength)
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}
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// put result in used pages
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a.used[requestOrderID] = append(a.used[requestOrderID], result)
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return result
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}
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// ReleasePages marks unused all pages in use for the given requestID
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func (a *allocator) ReleasePages(requestOrderID uint32) {
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a.Lock()
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defer a.Unlock()
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if used := a.used[requestOrderID]; len(used) > 0 {
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a.available = append(a.available, used...)
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}
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delete(a.used, requestOrderID)
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}
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// Free removes all the used and available pages.
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// Call this method when the allocator is not needed anymore
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func (a *allocator) Free() {
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a.Lock()
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defer a.Unlock()
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a.available = nil
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a.used = make(map[uint32][][]byte)
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}
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func (a *allocator) countUsedPages() int {
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a.Lock()
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defer a.Unlock()
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num := 0
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for _, p := range a.used {
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num += len(p)
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}
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return num
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}
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func (a *allocator) countAvailablePages() int {
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a.Lock()
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defer a.Unlock()
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return len(a.available)
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}
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func (a *allocator) isRequestOrderIDUsed(requestOrderID uint32) bool {
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a.Lock()
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defer a.Unlock()
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_, ok := a.used[requestOrderID]
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return ok
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}
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