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| 1 // Copyright 2015 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 package rawdatastore | |
| 6 | |
| 7 import ( | |
| 8 "golang.org/x/net/context" | |
| 9 ) | |
| 10 | |
| 11 type key int | |
| 12 | |
| 13 var ( | |
| 14 rawDatastoreKey key | |
| 15 rawDatastoreFilterKey key = 1 | |
| 16 ) | |
| 17 | |
| 18 // Factory is the function signature for factory methods compatible with | |
| 19 // SetFactory. | |
| 20 type Factory func(context.Context) Interface | |
| 21 | |
| 22 // Filter is the function signature for a filter RDS implementation. It | |
| 23 // gets the current RDS implementation, and returns a new RDS implementation | |
| 24 // backed by the one passed in. | |
| 25 type Filter func(context.Context, Interface) Interface | |
| 26 | |
| 27 // getUnfiltered gets gets the Interface implementation from context without | |
| 28 // any of the filters applied. | |
| 29 func getUnfiltered(c context.Context) Interface { | |
| 30 if f, ok := c.Value(rawDatastoreKey).(Factory); ok && f != nil { | |
| 31 return f(c) | |
| 32 } | |
| 33 return nil | |
| 34 } | |
| 35 | |
| 36 // Get gets the Interface implementation from context. | |
| 37 func Get(c context.Context) Interface { | |
| 38 ret := getUnfiltered(c) | |
| 39 if ret == nil { | |
| 40 return nil | |
| 41 } | |
| 42 for _, f := range getCurFilters(c) { | |
| 43 ret = f(c, ret) | |
| 44 } | |
| 45 return applyCheckFilter(c, ret) | |
| 46 } | |
| 47 | |
| 48 // SetFactory sets the function to produce Datastore instances, as returned by | |
| 49 // the Get method. | |
| 50 func SetFactory(c context.Context, rdsf Factory) context.Context { | |
| 51 return context.WithValue(c, rawDatastoreKey, rdsf) | |
| 52 } | |
| 53 | |
| 54 // Set sets the current Datastore object in the context. Useful for testing with | |
| 55 // a quick mock. This is just a shorthand SetFactory invocation to set a factory | |
| 56 // which always returns the same object. | |
| 57 func Set(c context.Context, rds Interface) context.Context { | |
| 58 return SetFactory(c, func(context.Context) Interface { return rds }) | |
| 59 } | |
| 60 | |
| 61 func getCurFilters(c context.Context) []Filter { | |
| 62 curFiltsI := c.Value(rawDatastoreFilterKey) | |
| 63 if curFiltsI != nil { | |
| 64 return curFiltsI.([]Filter) | |
| 65 } | |
| 66 return nil | |
| 67 } | |
| 68 | |
| 69 // AddFilters adds Interface filters to the context. | |
| 70 func AddFilters(c context.Context, filts ...Filter) context.Context { | |
| 71 if len(filts) == 0 { | |
| 72 return c | |
| 73 } | |
| 74 cur := getCurFilters(c) | |
| 75 newFilts := make([]Filter, 0, len(cur)+len(filts)) | |
| 76 newFilts = append(newFilts, getCurFilters(c)...) | |
| 77 newFilts = append(newFilts, filts...) | |
| 78 return context.WithValue(c, rawDatastoreFilterKey, newFilts) | |
| 79 } | |
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