Reduce allocations by pooling buffered JSON objects

[markusthoemmes]

As per title. Streams and iterators allocate a buffer to work internally, which can be reused. This does that.

The pool provided by jsoniter doesn't seem to fit our use-case, as it assumes to be passed a byte slice to read from rather than a reader.

Signed-off-by: Markus Thömmes [email protected]

Benchmark

benchmark                                                                                       old ns/op     new ns/op     delta
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v1.0-16     19402         18523         -4.53%
BenchmarkUnmarshal/base64_json_encoded_data_v1.0-16                                             11628         11660         +0.28%
BenchmarkUnmarshal/nil_data_v1.0-16                                                             16632         16376         -1.54%
BenchmarkUnmarshal/struct_data_v0.3-16                                                          18055         17013         -5.77%
BenchmarkUnmarshal/string_data_v0.3-16                                                          17674         16862         -4.59%
BenchmarkUnmarshal/struct_data_v1.0-16                                                          17987         17145         -4.68%
BenchmarkUnmarshal/string_data_v1.0-16                                                          17275         16460         -4.72%
BenchmarkUnmarshal/base64_xml_encoded_data_v1.0-16                                              12242         12249         +0.06%
BenchmarkUnmarshal/nil_data_v0.3-16                                                             15156         14909         -1.63%
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v0.3-16     19147         18010         -5.94%

benchmark                                                                                       old allocs     new allocs     delta
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v1.0-16     87             83             -4.60%
BenchmarkUnmarshal/base64_json_encoded_data_v1.0-16                                             51             49             -3.92%
BenchmarkUnmarshal/nil_data_v1.0-16                                                             73             71             -2.74%
BenchmarkUnmarshal/struct_data_v0.3-16                                                          78             76             -2.56%
BenchmarkUnmarshal/string_data_v0.3-16                                                          77             75             -2.60%
BenchmarkUnmarshal/struct_data_v1.0-16                                                          76             74             -2.63%
BenchmarkUnmarshal/string_data_v1.0-16                                                          75             73             -2.67%
BenchmarkUnmarshal/base64_xml_encoded_data_v1.0-16                                              51             49             -3.92%
BenchmarkUnmarshal/nil_data_v0.3-16                                                             73             71             -2.74%
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v0.3-16     87             83             -4.60%

benchmark                                                                                       old bytes     new bytes     delta
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v1.0-16     6024          3739          -37.93%
BenchmarkUnmarshal/base64_json_encoded_data_v1.0-16                                             3874          2708          -30.10%
BenchmarkUnmarshal/nil_data_v1.0-16                                                             4518          3352          -25.81%
BenchmarkUnmarshal/struct_data_v0.3-16                                                          4750          3584          -24.55%
BenchmarkUnmarshal/string_data_v0.3-16                                                          4734          3568          -24.63%
BenchmarkUnmarshal/struct_data_v1.0-16                                                          4574          3408          -25.49%
BenchmarkUnmarshal/string_data_v1.0-16                                                          4558          3392          -25.58%
BenchmarkUnmarshal/base64_xml_encoded_data_v1.0-16                                              3890          2725          -29.95%
BenchmarkUnmarshal/nil_data_v0.3-16                                                             4518          3352          -25.81%
BenchmarkUnmarshal/data,_attributes_and_extensions_and_specversion_with_struct_data_v0.3-16     6024          3739          -37.93%