class CordRepBtreeReader
Defined at line 79 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
CordRepBtreeReader implements logic to iterate over cord btrees.
References to the underlying data are returned as absl::string_view values.
The most typical use case is a forward only iteration over tree data.
The class also provides `Skip()`, `Seek()` and `Read()` methods similar to
CordRepBtreeNavigator that allow more advanced navigation.
Example: iterate over all data inside a cord btree:
CordRepBtreeReader reader;
for (string_view sv = reader.Init(tree); !sv.Empty(); sv = sv.Next()) {
DoSomethingWithDataIn(sv);
}
All navigation methods always return the next 'chunk' of data. The class
assumes that all data is directly 'consumed' by the caller. For example:
invoking `Skip()` will skip the desired number of bytes, and directly
read and return the next chunk of data directly after the skipped bytes.
Example: iterate over all data inside a btree skipping the first 100 bytes:
CordRepBtreeReader reader;
absl::string_view sv = reader.Init(tree);
if (sv.length() > 100) {
sv.RemovePrefix(100);
} else {
sv = reader.Skip(100 - sv.length());
}
while (!sv.empty()) {
DoSomethingWithDataIn(sv);
absl::string_view sv = reader.Next();
}
It is important to notice that `remaining` is based on the end position of
the last data edge returned to the caller, not the cumulative data returned
to the caller which can be less in cases of skipping or seeking over data.
For example, consider a cord btree with five data edges: "abc", "def", "ghi",
"jkl" and "mno":
absl::string_view sv;
CordRepBtreeReader reader;
sv = reader.Init(tree); // sv = "abc", remaining = 12
sv = reader.Skip(4); // sv = "hi", remaining = 6
sv = reader.Skip(2); // sv = "l", remaining = 3
sv = reader.Next(); // sv = "mno", remaining = 0
sv = reader.Seek(1); // sv = "bc", remaining = 12
Public Methods
bool operator bool ()Returns true if this instance is not empty.
Defined at line 85 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
CordRepBtree * btree ()Returns the tree referenced by this instance or nullptr if empty.
Defined at line 88 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
CordRep * node ()Returns the current data edge inside the referenced btree.
Requires that the current instance is not empty.
Defined at line 92 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
size_t remaining ()Returns the number of remaining bytes available for iteration, which is the
number of bytes directly following the end of the last chunk returned.
This value will be zero if we iterated over the last edge in the bound
tree, in which case any call to Next() or Skip() will return an empty
string_view reflecting the EOF state.
Note that a call to `Seek()` resets `remaining` to a value based on the
end position of the chunk returned by that call.
Defined at line 105 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
void Reset ()Resets this instance to an empty value.
Defined at line 108 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
size_t length ()Returns the length of the referenced tree.
Requires that the current instance is not empty.
Defined at line 162 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
absl::string_view Init (CordRepBtree * tree)Initializes this instance with `tree`. `tree` must not be null.
Returns a reference to the first data edge of the provided tree.
Defined at line 167 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
absl::string_view Next ()Navigates to and returns the next data edge of the referenced tree.
Returns an empty string_view if an attempt is made to read beyond the end
of the tree, i.e.: if `remaining()` is zero indicating an EOF condition.
Requires that the current instance is not empty.
Defined at line 174 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
absl::string_view Skip (size_t skip)Skips the provided amount of bytes and returns a reference to the data
directly following the skipped bytes.
Defined at line 182 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h
absl::string_view Read (size_t n, size_t chunk_size, CordRep *& tree)Reads `n` bytes into `tree`.
If `chunk_size` is zero, starts reading at the next data edge. If
`chunk_size` is non zero, the read starts at the last `chunk_size` bytes of
the last returned data edge. Effectively, this means that the read starts
at offset `consumed() - chunk_size`.
Requires that `chunk_size` is less than or equal to the length of the
last returned data edge. The purpose of `chunk_size` is to simplify code
partially consuming a returned chunk and wanting to include the remaining
bytes in the Read call. For example, the below code will read 1000 bytes of
data into a cord tree if the first chunk starts with "big:":
CordRepBtreeReader reader;
absl::string_view sv = reader.Init(tree);
if (absl::StartsWith(sv, "big:")) {
CordRepBtree tree;
sv = reader.Read(1000, sv.size() - 4 /* "big:" */,
&tree
);
}
This method will return an empty string view if all remaining data was
read. If `n` exceeded the amount of remaining data this function will
return an empty string view and `tree` will be set to nullptr.
In both cases, `consumed` will be set to `length`.
absl::string_view Seek (size_t offset)Navigates to the chunk at offset `offset`.
Returns a reference into the navigated to chunk, adjusted for the relative
position of `offset` into that chunk. For example, calling `Seek(13)` on a
cord tree containing 2 chunks of 10 and 20 bytes respectively will return
a string view into the second chunk starting at offset 3 with a size of 17.
Returns an empty string view if `offset` is equal to or greater than the
length of the referenced tree.
Defined at line 197 of file ../../third_party/abseil-cpp/absl/strings/internal/cord_rep_btree_reader.h