ceph/src/rocksdb/utilities/merge_operators/string_append/stringappend.cc

   1 /**
   2  * A MergeOperator for rocksdb that implements string append.
   3  * @author Deon Nicholas (dnicholas@fb.com)
   4  * Copyright 2013 Facebook
   5  */
   6
   7 #include "stringappend.h"
   8
   9 #include <assert.h>
  10
  11 #include <memory>
  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     stringappend_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 // Constructor: also specify the delimiter character.
  30 StringAppendOperator::StringAppendOperator(char delim_char)
  31     : delim_(1, delim_char) {
  32   RegisterOptions("Delimiter", &delim_, &stringappend_merge_type_info);
  33 }
  34
  35 StringAppendOperator::StringAppendOperator(const std::string& delim)
  36     : delim_(delim) {
  37   RegisterOptions("Delimiter", &delim_, &stringappend_merge_type_info);
  38 }
  39
  40 // Implementation for the merge operation (concatenates two strings)
  41 bool StringAppendOperator::Merge(const Slice& /*key*/,
  42                                  const Slice* existing_value,
  43                                  const Slice& value, std::string* new_value,
  44                                  Logger* /*logger*/) const {
  45   // Clear the *new_value for writing.
  46   assert(new_value);
  47   new_value->clear();
  48
  49   if (!existing_value) {
  50     // No existing_value. Set *new_value = value
  51     new_value->assign(value.data(), value.size());
  52   } else {
  53     // Generic append (existing_value != null).
  54     // Reserve *new_value to correct size, and apply concatenation.
  55     new_value->reserve(existing_value->size() + delim_.size() + value.size());
  56     new_value->assign(existing_value->data(), existing_value->size());
  57     new_value->append(delim_);
  58     new_value->append(value.data(), value.size());
  59   }
  60
  61   return true;
  62 }
  63
  64 std::shared_ptr<MergeOperator> MergeOperators::CreateStringAppendOperator() {
  65   return std::make_shared<StringAppendOperator>(',');
  66 }
  67
  68 std::shared_ptr<MergeOperator> MergeOperators::CreateStringAppendOperator(
  69     char delim_char) {
  70   return std::make_shared<StringAppendOperator>(delim_char);
  71 }
  72
  73 std::shared_ptr<MergeOperator> MergeOperators::CreateStringAppendOperator(
  74     const std::string& delim) {
  75   return std::make_shared<StringAppendOperator>(delim);
  76 }
  77
  78 }  // namespace ROCKSDB_NAMESPACE