1 /* 2 * Copyright 2012 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkTLS_DEFINED 9 #define SkTLS_DEFINED 10 11 #include "SkTypes.h" 12 13 /** 14 * Maintains a per-thread cache, using a CreateProc as the key into that cache. 15 */ 16 class SkTLS { 17 public: 18 typedef void* (*CreateProc)(); 19 typedef void (*DeleteProc)(void*); 20 21 /** 22 * If Get() has previously been called with this CreateProc, then this 23 * returns its cached data, otherwise it returns nullptr. The CreateProc is 24 * never invoked in Find, it is only used as a key for searching the 25 * cache. 26 */ 27 static void* Find(CreateProc); 28 29 /** 30 * Return the cached data that was returned by the CreateProc. This proc 31 * is only called the first time Get is called, and there after it is 32 * cached (per-thread), using the CreateProc as a key to look it up. 33 * 34 * When this thread, or Delete is called, the cached data is removed, and 35 * if a DeleteProc was specified, it is passed the pointer to the cached 36 * data. 37 */ 38 static void* Get(CreateProc, DeleteProc); 39 40 /** 41 * Remove (optionally calling the DeleteProc if it was specificed in Get) 42 * the cached data associated with this CreateProc. If no associated cached 43 * data is found, do nothing. 44 */ 45 static void Delete(CreateProc); 46 47 private: 48 // Our implementation requires only 1 TLS slot, as we manage multiple values 49 // ourselves in a list, with the platform specific value as our head. 50 51 /** 52 * Implemented by the platform, to return the value of our (one) slot per-thread 53 * 54 * If forceCreateTheSlot is true, then we must have created the "slot" for 55 * our TLS, even though we know that the return value will be nullptr in that 56 * case (i.e. no-slot and first-time-slot both return nullptr). This ensures 57 * that after calling GetSpecific, we know that we can legally call 58 * SetSpecific. 59 * 60 * If forceCreateTheSlot is false, then the impl can either create the 61 * slot or not. 62 */ 63 static void* PlatformGetSpecific(bool forceCreateTheSlot); 64 65 /** 66 * Implemented by the platform, to set the value for our (one) slot per-thread 67 * 68 * The implementation can rely on GetSpecific(true) having been previously 69 * called before SetSpecific is called. 70 */ 71 static void PlatformSetSpecific(void*); 72 73 public: 74 /** 75 * Will delete our internal list. To be called by the platform if/when its 76 * TLS slot is deleted (often at thread shutdown). 77 * 78 * Public *only* for the platform's use, not to be called by a client. 79 */ 80 static void Destructor(void* ptr); 81 }; 82 83 #endif 84
