78 lines
1.5 KiB
Go
78 lines
1.5 KiB
Go
package redis
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import (
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"context"
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"sync"
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)
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// ScanIterator is used to incrementally iterate over a collection of elements.
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// It's safe for concurrent use by multiple goroutines.
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type ScanIterator struct {
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mu sync.Mutex // protects Scanner and pos
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cmd *ScanCmd
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pos int
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}
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// Err returns the last iterator error, if any.
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func (it *ScanIterator) Err() error {
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it.mu.Lock()
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err := it.cmd.Err()
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it.mu.Unlock()
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return err
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}
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// Next advances the cursor and returns true if more values can be read.
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func (it *ScanIterator) Next(ctx context.Context) bool {
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it.mu.Lock()
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defer it.mu.Unlock()
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// Instantly return on errors.
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if it.cmd.Err() != nil {
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return false
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}
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// Advance cursor, check if we are still within range.
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if it.pos < len(it.cmd.page) {
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it.pos++
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return true
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}
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for {
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// Return if there is no more data to fetch.
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if it.cmd.cursor == 0 {
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return false
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}
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// Fetch next page.
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switch it.cmd.args[0] {
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case "scan", "qscan":
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it.cmd.args[1] = it.cmd.cursor
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default:
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it.cmd.args[2] = it.cmd.cursor
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}
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err := it.cmd.process(ctx, it.cmd)
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if err != nil {
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return false
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}
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it.pos = 1
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// Redis can occasionally return empty page.
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if len(it.cmd.page) > 0 {
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return true
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}
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}
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}
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// Val returns the key/field at the current cursor position.
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func (it *ScanIterator) Val() string {
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var v string
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it.mu.Lock()
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if it.cmd.Err() == nil && it.pos > 0 && it.pos <= len(it.cmd.page) {
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v = it.cmd.page[it.pos-1]
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}
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it.mu.Unlock()
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return v
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}
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