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Adding Slice::difference_offset() function

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Summary:
There are some use cases in MyRocks to compare two slices
and to return the first byte where they differ. It may be
useful to add it as a RocksDB Slice function.

Test Plan: db_test

Reviewers: sdong, rven, igor

Reviewed By: igor

Subscribers: jkedgar, dhruba

Differential Revision: https://reviews.facebook.net/D46935
This commit is contained in:
Yoshinori Matsunobu 2015-09-14 17:23:39 -07:00
parent 5ce63e30ea
commit 4886073174
2 changed files with 14 additions and 0 deletions
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2
db/db_test.cc
View File

@ -5937,6 +5937,8 @@ TEST_F(DBTest, PrefixScan) {
snprintf(buf, sizeof(buf), "03______:");
prefix = Slice(buf, 8);
key = Slice(buf, 9);
ASSERT_EQ(key.difference_offset(prefix), 8);
ASSERT_EQ(prefix.difference_offset(key), 8);
// db configs
env_->count_random_reads_ = true;
Options options = CurrentOptions();

12
include/rocksdb/slice.h
View File

@ -88,6 +88,9 @@ class Slice {
(memcmp(data_, x.data_, x.size_) == 0));
}
// Compare two slices and returns the first byte where they differ
size_t difference_offset(const Slice& b) const;
// private: make these public for rocksdbjni access
const char* data_;
size_t size_;
@ -125,6 +128,15 @@ inline int Slice::compare(const Slice& b) const {
return r;
}
inline size_t Slice::difference_offset(const Slice& b) const {
size_t off = 0;
const size_t len = (size_ < b.size_) ? size_ : b.size_;
for (; off < len; off++) {
if (data_[off] != b.data_[off]) break;
}
return off;
}
} // namespace rocksdb
#endif // STORAGE_ROCKSDB_INCLUDE_SLICE_H_