1 /**
2 * @author Deon Nicholas (dnicholas@fb.com)
3 * Copyright 2013 Facebook
4 */
5
6 #include "stringappend2.h"
7
8 #include <assert.h>
9
10 #include <memory>
11 #include <string>
12
13 #include "rocksdb/merge_operator.h"
14 #include "rocksdb/slice.h"
15 #include "rocksdb/utilities/options_type.h"
16 #include "utilities/merge_operators.h"
17
18 namespace ROCKSDB_NAMESPACE {
19 namespace {
20 static std::unordered_map<std::string, OptionTypeInfo>
21 stringappend2_merge_type_info = {
22 #ifndef ROCKSDB_LITE
23 {"delimiter",
24 {0, OptionType::kString, OptionVerificationType::kNormal,
25 OptionTypeFlags::kNone}},
26 #endif // ROCKSDB_LITE
27 };
28 } // namespace
29
30 // Constructor: also specify the delimiter character.
StringAppendTESTOperator(char delim_char)31 StringAppendTESTOperator::StringAppendTESTOperator(char delim_char)
32 : delim_(1, delim_char) {
33 RegisterOptions("Delimiter", &delim_, &stringappend2_merge_type_info);
34 }
35
StringAppendTESTOperator(const std::string & delim)36 StringAppendTESTOperator::StringAppendTESTOperator(const std::string& delim)
37 : delim_(delim) {
38 RegisterOptions("Delimiter", &delim_, &stringappend2_merge_type_info);
39 }
40
41 // Implementation for the merge operation (concatenates two strings)
FullMergeV2(const MergeOperationInput & merge_in,MergeOperationOutput * merge_out) const42 bool StringAppendTESTOperator::FullMergeV2(
43 const MergeOperationInput& merge_in,
44 MergeOperationOutput* merge_out) const {
45 // Clear the *new_value for writing.
46 merge_out->new_value.clear();
47
48 if (merge_in.existing_value == nullptr && merge_in.operand_list.size() == 1) {
49 // Only one operand
50 merge_out->existing_operand = merge_in.operand_list.back();
51 return true;
52 }
53
54 // Compute the space needed for the final result.
55 size_t numBytes = 0;
56
57 for (auto it = merge_in.operand_list.begin();
58 it != merge_in.operand_list.end(); ++it) {
59 numBytes += it->size() + delim_.size();
60 }
61
62 // Only print the delimiter after the first entry has been printed
63 bool printDelim = false;
64
65 // Prepend the *existing_value if one exists.
66 if (merge_in.existing_value) {
67 merge_out->new_value.reserve(numBytes + merge_in.existing_value->size());
68 merge_out->new_value.append(merge_in.existing_value->data(),
69 merge_in.existing_value->size());
70 printDelim = true;
71 } else if (numBytes) {
72 // Without the existing (initial) value, the delimiter before the first of
73 // subsequent operands becomes redundant.
74 merge_out->new_value.reserve(numBytes - delim_.size());
75 }
76
77 // Concatenate the sequence of strings (and add a delimiter between each)
78 for (auto it = merge_in.operand_list.begin();
79 it != merge_in.operand_list.end(); ++it) {
80 if (printDelim) {
81 merge_out->new_value.append(delim_);
82 }
83 merge_out->new_value.append(it->data(), it->size());
84 printDelim = true;
85 }
86
87 return true;
88 }
89
PartialMergeMulti(const Slice &,const std::deque<Slice> &,std::string *,Logger *) const90 bool StringAppendTESTOperator::PartialMergeMulti(
91 const Slice& /*key*/, const std::deque<Slice>& /*operand_list*/,
92 std::string* /*new_value*/, Logger* /*logger*/) const {
93 return false;
94 }
95
96 // A version of PartialMerge that actually performs "partial merging".
97 // Use this to simulate the exact behaviour of the StringAppendOperator.
_AssocPartialMergeMulti(const Slice &,const std::deque<Slice> & operand_list,std::string * new_value,Logger *) const98 bool StringAppendTESTOperator::_AssocPartialMergeMulti(
99 const Slice& /*key*/, const std::deque<Slice>& operand_list,
100 std::string* new_value, Logger* /*logger*/) const {
101 // Clear the *new_value for writing
102 assert(new_value);
103 new_value->clear();
104 assert(operand_list.size() >= 2);
105
106 // Generic append
107 // Determine and reserve correct size for *new_value.
108 size_t size = 0;
109 for (const auto& operand : operand_list) {
110 size += operand.size();
111 }
112 size += (operand_list.size() - 1) * delim_.length(); // Delimiters
113 new_value->reserve(size);
114
115 // Apply concatenation
116 new_value->assign(operand_list.front().data(), operand_list.front().size());
117
118 for (std::deque<Slice>::const_iterator it = operand_list.begin() + 1;
119 it != operand_list.end(); ++it) {
120 new_value->append(delim_);
121 new_value->append(it->data(), it->size());
122 }
123
124 return true;
125 }
126
127 std::shared_ptr<MergeOperator>
CreateStringAppendTESTOperator()128 MergeOperators::CreateStringAppendTESTOperator() {
129 return std::make_shared<StringAppendTESTOperator>(',');
130 }
131
132 } // namespace ROCKSDB_NAMESPACE
133