1 // 2 // SkTLS.h 3 // 4 // 5 // Created by Mike Reed on 4/21/12. 6 // Copyright (c) 2012 __MyCompanyName__. All rights reserved. 7 // 8 9 #ifndef SkTLS_DEFINED 10 #define SkTLS_DEFINED 11 12 #include "SkTypes.h" 13 14 /** 15 * Maintains a per-thread cache, using a CreateProc as the key into that cache. 16 */ 17 class SkTLS { 18 public: 19 typedef void* (*CreateProc)(); 20 typedef void (*DeleteProc)(void*); 21 22 /** 23 * If Get() has previously been called with this CreateProc, then this 24 * returns its cached data, otherwise it returns NULL. The CreateProc is 25 * never invoked in Find, it is only used as a key for searching the 26 * cache. 27 */ 28 static void* Find(CreateProc); 29 30 /** 31 * Return the cached data that was returned by the CreateProc. This proc 32 * is only called the first time Get is called, and there after it is 33 * cached (per-thread), using the CreateProc as a key to look it up. 34 * 35 * When this thread, or Delete is called, the cached data is removed, and 36 * if a DeleteProc was specified, it is passed the pointer to the cached 37 * data. 38 */ 39 static void* Get(CreateProc, DeleteProc); 40 41 /** 42 * Remove (optionally calling the DeleteProc if it was specificed in Get) 43 * the cached data associated with this CreateProc. If no associated cached 44 * data is found, do nothing. 45 */ 46 static void Delete(CreateProc); 47 48 private: 49 // Our implementation requires only 1 TLS slot, as we manage multiple values 50 // ourselves in a list, with the platform specific value as our head. 51 52 /** 53 * Implemented by the platform, to return the value of our (one) slot per-thread 54 * 55 * If forceCreateTheSlot is true, then we must have created the "slot" for 56 * our TLS, even though we know that the return value will be NULL in that 57 * case (i.e. no-slot and first-time-slot both return NULL). This ensures 58 * that after calling GetSpecific, we know that we can legally call 59 * SetSpecific. 60 * 61 * If forceCreateTheSlot is false, then the impl can either create the 62 * slot or not. 63 */ 64 static void* PlatformGetSpecific(bool forceCreateTheSlot); 65 66 /** 67 * Implemented by the platform, to set the value for our (one) slot per-thread 68 * 69 * The implementation can rely on GetSpecific(true) having been previously 70 * called before SetSpecific is called. 71 */ 72 static void PlatformSetSpecific(void*); 73 74 public: 75 /** 76 * Will delete our internal list. To be called by the platform if/when its 77 * TLS slot is deleted (often at thread shutdown). 78 * 79 * Public *only* for the platform's use, not to be called by a client. 80 */ 81 static void Destructor(void* ptr); 82 }; 83 84 #endif 85