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-rw-r--r--absl/strings/cord.h95
1 files changed, 46 insertions, 49 deletions
diff --git a/absl/strings/cord.h b/absl/strings/cord.h
index b8b251b0..653a1181 100644
--- a/absl/strings/cord.h
+++ b/absl/strings/cord.h
@@ -644,14 +644,12 @@ class Cord {
// InlineRep holds either a tree pointer, or an array of kMaxInline bytes.
class InlineRep {
public:
- static constexpr unsigned char kMaxInline = 15;
+ static constexpr unsigned char kMaxInline = cord_internal::kMaxInline;
static_assert(kMaxInline >= sizeof(absl::cord_internal::CordRep*), "");
- // Tag byte & kMaxInline means we are storing a pointer.
- static constexpr unsigned char kTreeFlag = 1 << 4;
- // Tag byte & kProfiledFlag means we are profiling the Cord.
- static constexpr unsigned char kProfiledFlag = 1 << 5;
+ static constexpr unsigned char kTreeFlag = cord_internal::kTreeFlag;
+ static constexpr unsigned char kProfiledFlag = cord_internal::kProfiledFlag;
- constexpr InlineRep() : data_{} {}
+ constexpr InlineRep() : data_() {}
InlineRep(const InlineRep& src);
InlineRep(InlineRep&& src);
InlineRep& operator=(const InlineRep& src);
@@ -684,16 +682,16 @@ class Cord {
void GetAppendRegion(char** region, size_t* size, size_t max_length);
void GetAppendRegion(char** region, size_t* size);
bool IsSame(const InlineRep& other) const {
- return memcmp(data_, other.data_, sizeof(data_)) == 0;
+ return memcmp(&data_, &other.data_, sizeof(data_)) == 0;
}
int BitwiseCompare(const InlineRep& other) const {
uint64_t x, y;
- // Use memcpy to avoid anti-aliasing issues.
- memcpy(&x, data_, sizeof(x));
- memcpy(&y, other.data_, sizeof(y));
+ // Use memcpy to avoid aliasing issues.
+ memcpy(&x, &data_, sizeof(x));
+ memcpy(&y, &other.data_, sizeof(y));
if (x == y) {
- memcpy(&x, data_ + 8, sizeof(x));
- memcpy(&y, other.data_ + 8, sizeof(y));
+ memcpy(&x, reinterpret_cast<const char*>(&data_) + 8, sizeof(x));
+ memcpy(&y, reinterpret_cast<const char*>(&other.data_) + 8, sizeof(y));
if (x == y) return 0;
}
return absl::big_endian::FromHost64(x) < absl::big_endian::FromHost64(y)
@@ -706,16 +704,16 @@ class Cord {
// to 15 bytes does not cause a memory allocation.
absl::strings_internal::STLStringResizeUninitialized(dst,
sizeof(data_) - 1);
- memcpy(&(*dst)[0], data_, sizeof(data_) - 1);
+ memcpy(&(*dst)[0], &data_, sizeof(data_) - 1);
// erase is faster than resize because the logic for memory allocation is
// not needed.
- dst->erase(data_[kMaxInline]);
+ dst->erase(tagged_size());
}
// Copies the inline contents into `dst`. Assumes the cord is not empty.
void CopyToArray(char* dst) const;
- bool is_tree() const { return data_[kMaxInline] > kMaxInline; }
+ bool is_tree() const { return tagged_size() > kMaxInline; }
private:
friend class Cord;
@@ -724,10 +722,18 @@ class Cord {
// Unrefs the tree, stops profiling, and zeroes the contents
void ClearSlow();
- // If the data has length <= kMaxInline, we store it in data_[0..len-1],
- // and store the length in data_[kMaxInline]. Else we store it in a tree
- // and store a pointer to that tree in data_[0..sizeof(CordRep*)-1].
- alignas(absl::cord_internal::CordRep*) char data_[kMaxInline + 1];
+ void ResetToEmpty() { data_ = {}; }
+
+ // This uses reinterpret_cast instead of the union to avoid accessing the
+ // inactive union element. The tagged size is not a common prefix.
+ void set_tagged_size(char new_tag) {
+ reinterpret_cast<char*>(&data_)[kMaxInline] = new_tag;
+ }
+ char tagged_size() const {
+ return reinterpret_cast<const char*>(&data_)[kMaxInline];
+ }
+
+ cord_internal::InlineData data_;
};
InlineRep contents_;
@@ -879,12 +885,12 @@ Cord MakeCordFromExternal(absl::string_view data, Releaser&& releaser) {
}
inline Cord::InlineRep::InlineRep(const Cord::InlineRep& src) {
- cord_internal::SmallMemmove(data_, src.data_, sizeof(data_));
+ data_ = src.data_;
}
inline Cord::InlineRep::InlineRep(Cord::InlineRep&& src) {
- memcpy(data_, src.data_, sizeof(data_));
- memset(src.data_, 0, sizeof(data_));
+ data_ = src.data_;
+ src.ResetToEmpty();
}
inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) {
@@ -892,7 +898,7 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(const Cord::InlineRep& src) {
return *this;
}
if (!is_tree() && !src.is_tree()) {
- cord_internal::SmallMemmove(data_, src.data_, sizeof(data_));
+ data_ = src.data_;
return *this;
}
AssignSlow(src);
@@ -904,8 +910,8 @@ inline Cord::InlineRep& Cord::InlineRep::operator=(
if (is_tree()) {
ClearSlow();
}
- memcpy(data_, src.data_, sizeof(data_));
- memset(src.data_, 0, sizeof(data_));
+ data_ = src.data_;
+ src.ResetToEmpty();
return *this;
}
@@ -914,43 +920,39 @@ inline void Cord::InlineRep::Swap(Cord::InlineRep* rhs) {
return;
}
- Cord::InlineRep tmp;
- cord_internal::SmallMemmove(tmp.data_, data_, sizeof(data_));
- cord_internal::SmallMemmove(data_, rhs->data_, sizeof(data_));
- cord_internal::SmallMemmove(rhs->data_, tmp.data_, sizeof(data_));
+ std::swap(data_, rhs->data_);
}
inline const char* Cord::InlineRep::data() const {
- return is_tree() ? nullptr : data_;
+ return is_tree() ? nullptr : data_.as_chars;
}
inline absl::cord_internal::CordRep* Cord::InlineRep::tree() const {
if (is_tree()) {
- absl::cord_internal::CordRep* rep;
- memcpy(&rep, data_, sizeof(rep));
- return rep;
+ return data_.as_tree.rep;
} else {
return nullptr;
}
}
-inline bool Cord::InlineRep::empty() const { return data_[kMaxInline] == 0; }
+inline bool Cord::InlineRep::empty() const { return tagged_size() == 0; }
inline size_t Cord::InlineRep::size() const {
- const char tag = data_[kMaxInline];
+ const char tag = tagged_size();
if (tag <= kMaxInline) return tag;
return static_cast<size_t>(tree()->length);
}
inline void Cord::InlineRep::set_tree(absl::cord_internal::CordRep* rep) {
if (rep == nullptr) {
- memset(data_, 0, sizeof(data_));
+ ResetToEmpty();
} else {
bool was_tree = is_tree();
- memcpy(data_, &rep, sizeof(rep));
- memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1);
+ data_.as_tree = {rep, {}, tagged_size()};
if (!was_tree) {
- data_[kMaxInline] = kTreeFlag;
+ // If we were not a tree already, set the tag.
+ // Otherwise, leave it alone because it might have the profile bit on.
+ set_tagged_size(kTreeFlag);
}
}
}
@@ -961,25 +963,20 @@ inline void Cord::InlineRep::replace_tree(absl::cord_internal::CordRep* rep) {
set_tree(rep);
return;
}
- memcpy(data_, &rep, sizeof(rep));
- memset(data_ + sizeof(rep), 0, sizeof(data_) - sizeof(rep) - 1);
+ data_.as_tree = {rep, {}, tagged_size()};
}
inline absl::cord_internal::CordRep* Cord::InlineRep::clear() {
- const char tag = data_[kMaxInline];
- absl::cord_internal::CordRep* result = nullptr;
- if (tag > kMaxInline) {
- memcpy(&result, data_, sizeof(result));
- }
- memset(data_, 0, sizeof(data_)); // Clear the cord
+ absl::cord_internal::CordRep* result = tree();
+ ResetToEmpty();
return result;
}
inline void Cord::InlineRep::CopyToArray(char* dst) const {
assert(!is_tree());
- size_t n = data_[kMaxInline];
+ size_t n = tagged_size();
assert(n != 0);
- cord_internal::SmallMemmove(dst, data_, n);
+ cord_internal::SmallMemmove(dst, data_.as_chars, n);
}
constexpr inline Cord::Cord() noexcept {}
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-21 03:00:20 +0000