diff options
Diffstat (limited to 'absl/strings/internal/cord_internal.h')
| -rw-r--r-- | absl/strings/internal/cord_internal.h | 21 |
1 files changed, 18 insertions, 3 deletions
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h index bddc9815..371a7f9c 100644 --- a/absl/strings/internal/cord_internal.h +++ b/absl/strings/internal/cord_internal.h @@ -37,13 +37,19 @@ class CordzInfo; // Default feature enable states for cord ring buffers enum CordFeatureDefaults { + kCordEnableBtreeDefault = false, kCordEnableRingBufferDefault = false, kCordShallowSubcordsDefault = false }; +extern std::atomic<bool> cord_btree_enabled; extern std::atomic<bool> cord_ring_buffer_enabled; extern std::atomic<bool> shallow_subcords_enabled; +inline void enable_cord_btree(bool enable) { + cord_btree_enabled.store(enable, std::memory_order_relaxed); +} + inline void enable_cord_ring_buffer(bool enable) { cord_ring_buffer_enabled.store(enable, std::memory_order_relaxed); } @@ -193,7 +199,16 @@ struct CordRep { // If tag < FLAT, it represents CordRepKind and indicates the type of node. // Otherwise, the node type is CordRepFlat and the tag is the encoded size. uint8_t tag; - char storage[1]; // Starting point for flat array: MUST BE LAST FIELD + + // `storage` provides two main purposes: + // - the starting point for FlatCordRep.Data() [flexible-array-member] + // - 3 bytes of additional storage for use by derived classes. + // The latter is used by CordrepConcat and CordRepBtree. CordRepConcat stores + // a 'depth' value in storage[0], and the (future) CordRepBtree class stores + // `height`, `begin` and `end` in the 3 entries. Otherwise we would need to + // allocate room for these in the derived class, as not all compilers reuse + // padding space from the base class (clang and gcc do, MSVC does not, etc) + uint8_t storage[3]; inline CordRepRing* ring(); inline const CordRepRing* ring() const; @@ -228,8 +243,8 @@ struct CordRepConcat : public CordRep { CordRep* left; CordRep* right; - uint8_t depth() const { return static_cast<uint8_t>(storage[0]); } - void set_depth(uint8_t depth) { storage[0] = static_cast<char>(depth); } + uint8_t depth() const { return storage[0]; } + void set_depth(uint8_t depth) { storage[0] = depth; } }; struct CordRepSubstring : public CordRep { |