1 /**
2 * @author Deon Nicholas (dnicholas@fb.com)
3 * Copyright 2013 Facebook
4 */
5
6 #include "stringappend2.h"
7
8 #include <memory>
9 #include <string>
10 #include <assert.h>
11
12 #include "rocksdb/slice.h"
13 #include "rocksdb/merge_operator.h"
14 #include "utilities/merge_operators.h"
15
16 namespace rocksdb {
17
18 // Constructor: also specify the delimiter character.
StringAppendTESTOperator(char delim_char)19 StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
20 : delim_(delim_char) {
21 }
22
23 // Implementation for the merge operation (concatenates two strings)
FullMergeV2(const MergeOperationInput & merge_in,MergeOperationOutput * merge_out) const24 bool StringAppendTESTOperator::FullMergeV2(
25 const MergeOperationInput& merge_in,
26 MergeOperationOutput* merge_out) const {
27 // Clear the *new_value for writing.
28 merge_out->new_value.clear();
29
30 if (merge_in.existing_value == nullptr && merge_in.operand_list.size() == 1) {
31 // Only one operand
32 merge_out->existing_operand = merge_in.operand_list.back();
33 return true;
34 }
35
36 // Compute the space needed for the final result.
37 size_t numBytes = 0;
38 for (auto it = merge_in.operand_list.begin();
39 it != merge_in.operand_list.end(); ++it) {
40 numBytes += it->size() + 1; // Plus 1 for the delimiter
41 }
42
43 // Only print the delimiter after the first entry has been printed
44 bool printDelim = false;
45
46 // Prepend the *existing_value if one exists.
47 if (merge_in.existing_value) {
48 merge_out->new_value.reserve(numBytes + merge_in.existing_value->size());
49 merge_out->new_value.append(merge_in.existing_value->data(),
50 merge_in.existing_value->size());
51 printDelim = true;
52 } else if (numBytes) {
53 merge_out->new_value.reserve(
54 numBytes - 1); // Minus 1 since we have one less delimiter
55 }
56
57 // Concatenate the sequence of strings (and add a delimiter between each)
58 for (auto it = merge_in.operand_list.begin();
59 it != merge_in.operand_list.end(); ++it) {
60 if (printDelim) {
61 merge_out->new_value.append(1, delim_);
62 }
63 merge_out->new_value.append(it->data(), it->size());
64 printDelim = true;
65 }
66
67 return true;
68 }
69
PartialMergeMulti(const Slice &,const std::deque<Slice> &,std::string *,Logger *) const70 bool StringAppendTESTOperator::PartialMergeMulti(
71 const Slice& /*key*/, const std::deque<Slice>& /*operand_list*/,
72 std::string* /*new_value*/, Logger* /*logger*/) const {
73 return false;
74 }
75
76 // A version of PartialMerge that actually performs "partial merging".
77 // Use this to simulate the exact behaviour of the StringAppendOperator.
_AssocPartialMergeMulti(const Slice &,const std::deque<Slice> & operand_list,std::string * new_value,Logger *) const78 bool StringAppendTESTOperator::_AssocPartialMergeMulti(
79 const Slice& /*key*/, const std::deque<Slice>& operand_list,
80 std::string* new_value, Logger* /*logger*/) const {
81 // Clear the *new_value for writing
82 assert(new_value);
83 new_value->clear();
84 assert(operand_list.size() >= 2);
85
86 // Generic append
87 // Determine and reserve correct size for *new_value.
88 size_t size = 0;
89 for (const auto& operand : operand_list) {
90 size += operand.size();
91 }
92 size += operand_list.size() - 1; // Delimiters
93 new_value->reserve(size);
94
95 // Apply concatenation
96 new_value->assign(operand_list.front().data(), operand_list.front().size());
97
98 for (std::deque<Slice>::const_iterator it = operand_list.begin() + 1;
99 it != operand_list.end(); ++it) {
100 new_value->append(1, delim_);
101 new_value->append(it->data(), it->size());
102 }
103
104 return true;
105 }
106
Name() const107 const char* StringAppendTESTOperator::Name() const {
108 return "StringAppendTESTOperator";
109 }
110
111
112 std::shared_ptr<MergeOperator>
CreateStringAppendTESTOperator()113 MergeOperators::CreateStringAppendTESTOperator() {
114 return std::make_shared<StringAppendTESTOperator>(',');
115 }
116
117 } // namespace rocksdb
118