1 // Copyright 2012 The Chromium Authors 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef BASE_JSON_JSON_WRITER_H_ 6 #define BASE_JSON_JSON_WRITER_H_ 7 8 #include <stddef.h> 9 #include <cstdint> 10 #include <string> 11 12 #include "base/base_export.h" 13 #include "base/json/json_common.h" 14 #include "base/memory/raw_ptr.h" 15 #include "base/strings/string_piece.h" 16 #include "base/values.h" 17 #include "third_party/abseil-cpp/absl/types/optional.h" 18 19 namespace base { 20 21 enum JsonOptions { 22 // This option instructs the writer that if a Binary value is encountered, 23 // the value (and key if within a dictionary) will be omitted from the 24 // output, and success will be returned. Otherwise, if a binary value is 25 // encountered, failure will be returned. 26 OPTIONS_OMIT_BINARY_VALUES = 1 << 0, 27 28 // This option instructs the writer to write doubles that have no fractional 29 // part as a normal integer (i.e., without using exponential notation 30 // or appending a '.0') as long as the value is within the range of a 31 // 64-bit int. 32 OPTIONS_OMIT_DOUBLE_TYPE_PRESERVATION = 1 << 1, 33 34 // Return a slightly nicer formatted json string (pads with whitespace to 35 // help with readability). 36 OPTIONS_PRETTY_PRINT = 1 << 2, 37 }; 38 39 // Given a root node, generates and returns a JSON string. 40 // 41 // Returns `absl::nullopt` if 42 // * the nesting depth exceeds `max_depth`, or 43 // * the JSON contains binary values. 44 BASE_EXPORT absl::optional<std::string> WriteJson( 45 ValueView node, 46 size_t max_depth = internal::kAbsoluteMaxDepth); 47 48 // Given a root node, generates and returns a JSON string. 49 // The string is formatted according to `options` which is a bitmask of 50 // `JsonOptions`. 51 // 52 // Returns `absl::nullopt` if 53 // * the nesting depth exceeds `max_depth,` or 54 // * the JSON contains binary values 55 // (unless `JsonOptions::OPTIONS_OMIT_BINARY_VALUES` is passed). 56 BASE_EXPORT absl::optional<std::string> WriteJsonWithOptions( 57 ValueView node, 58 uint32_t options, 59 size_t max_depth = internal::kAbsoluteMaxDepth); 60 61 class BASE_EXPORT JSONWriter { 62 public: 63 using Options = JsonOptions; 64 // TODO: Once we support c++20 we replace these with 65 // `using enum ::JsonOptions`. 66 static constexpr auto OPTIONS_OMIT_BINARY_VALUES = 67 JsonOptions::OPTIONS_OMIT_BINARY_VALUES; 68 static constexpr auto OPTIONS_OMIT_DOUBLE_TYPE_PRESERVATION = 69 JsonOptions::OPTIONS_OMIT_DOUBLE_TYPE_PRESERVATION; 70 static constexpr auto OPTIONS_PRETTY_PRINT = 71 JsonOptions::OPTIONS_PRETTY_PRINT; 72 73 JSONWriter(const JSONWriter&) = delete; 74 JSONWriter& operator=(const JSONWriter&) = delete; 75 76 // Given a root node, generates a JSON string and puts it into |json|. 77 // The output string is overwritten and not appended. 78 // 79 // TODO(tc): Should we generate json if it would be invalid json (e.g., 80 // |node| is not a dictionary/list Value or if there are inf/-inf float 81 // values)? Return true on success and false on failure. 82 // 83 // Deprecated: use the standalone method `WriteJson()` instead. 84 static bool Write(ValueView node, 85 std::string* json, 86 size_t max_depth = internal::kAbsoluteMaxDepth); 87 88 // Same as above but with |options| which is a bunch of JSONWriter::Options 89 // bitwise ORed together. Return true on success and false on failure. 90 // 91 // Deprecated: use the standalone method `WriteJsonWithOptions()` instead. 92 static bool WriteWithOptions(ValueView node, 93 int options, 94 std::string* json, 95 size_t max_depth = internal::kAbsoluteMaxDepth); 96 97 private: 98 JSONWriter(int options, 99 std::string* json, 100 size_t max_depth = internal::kAbsoluteMaxDepth); 101 102 // Called recursively to build the JSON string. When completed, 103 // |json_string_| will contain the JSON. 104 bool BuildJSONString(absl::monostate node, size_t depth); 105 bool BuildJSONString(bool node, size_t depth); 106 bool BuildJSONString(int node, size_t depth); 107 bool BuildJSONString(double node, size_t depth); 108 bool BuildJSONString(StringPiece node, size_t depth); 109 bool BuildJSONString(const Value::BlobStorage& node, size_t depth); 110 bool BuildJSONString(const Value::Dict& node, size_t depth); 111 bool BuildJSONString(const Value::List& node, size_t depth); 112 113 // Adds space to json_string_ for the indent level. 114 void IndentLine(size_t depth); 115 116 bool omit_binary_values_; 117 bool omit_double_type_preservation_; 118 bool pretty_print_; 119 120 // Where we write JSON data as we generate it. 121 raw_ptr<std::string> json_string_; 122 123 // Maximum depth to write. 124 const size_t max_depth_; 125 126 // The number of times the writer has recursed (current stack depth). 127 size_t stack_depth_; 128 }; 129 130 } // namespace base 131 132 #endif // BASE_JSON_JSON_WRITER_H_ 133