diff options
Diffstat (limited to 'absl/strings/internal/cord_internal.h')
| -rw-r--r-- | absl/strings/internal/cord_internal.h | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/absl/strings/internal/cord_internal.h b/absl/strings/internal/cord_internal.h index 813b3f35..1e2436ba 100644 --- a/absl/strings/internal/cord_internal.h +++ b/absl/strings/internal/cord_internal.h @@ -154,9 +154,9 @@ class CordRepRing; // Various representations that we allow enum CordRepKind { CONCAT = 0, - EXTERNAL = 1, - SUBSTRING = 2, - RING = 3, + SUBSTRING = 1, + RING = 2, + EXTERNAL = 3, // We have different tags for different sized flat arrays, // starting with FLAT, and limited to MAX_FLAT_TAG. The 224 value is based on @@ -168,6 +168,16 @@ enum CordRepKind { MAX_FLAT_TAG = 224 }; +// There are various locations where we want to check if some rep is a 'plain' +// data edge, i.e. an external or flat rep. By having FLAT == EXTERNAL + 1, we +// can perform this check in a single branch as 'tag >= EXTERNAL' +// Likewise, we have some locations where we check for 'ring or external/flat', +// so likewise align RING to EXTERNAL. +// Note that we can leave this optimization to the compiler. The compiler will +// DTRT when it sees a condition like `tag == EXTERNAL || tag >= FLAT`. +static_assert(EXTERNAL == RING + 1, "RING and EXTERNAL values not consecutive"); +static_assert(FLAT == EXTERNAL + 1, "EXTERNAL and FLAT values not consecutive"); + struct CordRep { CordRep() = default; constexpr CordRep(Refcount::Immortal immortal, size_t l) |