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WriteBatch::Put() overload that gathers key and value from arrays of slices

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Summary: In our project, when writing to the database, we want to form the value as the concatenation of a small header and a larger payload.  It's a shame to have to copy the payload just so we can give RocksDB API a linear view of the value.  Since RocksDB makes a copy internally, it's easy to support gather writes.

Test Plan: write_batch_test, new test case

Reviewers: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D13947
This commit is contained in:
lovro
2013-11-07 12:37:58 -08:00
parent 1510339e52
commit 8a46ecd357
6 changed files with 65 additions and 0 deletions
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12
util/coding.cc
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@@ -107,6 +107,18 @@ void PutLengthPrefixedSlice(std::string* dst, const Slice& value) {
dst->append(value.data(), value.size());
}
void PutLengthPrefixedSliceParts(std::string* dst,
const SliceParts& slice_parts) {
uint32_t total_bytes = 0;
for (int i = 0; i < slice_parts.num_parts; ++i) {
total_bytes += slice_parts.parts[i].size();
}
PutVarint32(dst, total_bytes);
for (int i = 0; i < slice_parts.num_parts; ++i) {
dst->append(slice_parts.parts[i].data(), slice_parts.parts[i].size());
}
}
int VarintLength(uint64_t v) {
int len = 1;
while (v >= 128) {

2
util/coding.h
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@@ -30,6 +30,8 @@ extern void PutFixed64(std::string* dst, uint64_t value);
extern void PutVarint32(std::string* dst, uint32_t value);
extern void PutVarint64(std::string* dst, uint64_t value);
extern void PutLengthPrefixedSlice(std::string* dst, const Slice& value);
extern void PutLengthPrefixedSliceParts(std::string* dst,
const SliceParts& slice_parts);
// Standard Get... routines parse a value from the beginning of a Slice
// and advance the slice past the parsed value.