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https://issues.apache.org/jira/browse/AVRO-1350?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13697429#comment-13697429
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Bin Guo commented on AVRO-1350:
-------------------------------
OK, I've pasted my complete test case above.
> Error in decoding enums using ResolvingDecoder
> ----------------------------------------------
>
> Key: AVRO-1350
> URL: https://issues.apache.org/jira/browse/AVRO-1350
> Project: Avro
> Issue Type: Bug
> Components: c++
> Affects Versions: 1.7.4
> Reporter: Bin Guo
>
> We can't get a correct result when decoding enums using resolving decoder.
> e.g.
> {code:title=schema}
> {
> "type" : "record",
> "name" : "TestEnum",
> "fields" : [
> {
> "name" : "MyMode",
> "type" : {
> "type" : "enum",
> "name" : "Mode",
> "symbols" : [ "MEMORY", "DISK" ]
> }
> }
> ]
> }
> {code}
> We encoded "DISK"(1), then decoded with resolving decoder, got "MEMORY"(0).
> I examined the code and found that there is a *sort* after reading names of
> reader.
> I could't quite understand the author's intention, but it really can not work
> well.
> When decoding my enum, the return value is actually the *position of the
> sorted names*, and obviously it's not correct.
> {code:title=Symbol.cc}
> Symbol Symbol::enumAdjustSymbol(const NodePtr& writer, const NodePtr& reader)
> {
> vector<string> rs;
> size_t rc = reader->names();
> for (size_t i = 0; i < rc; ++i) {
> rs.push_back(reader->nameAt(i));
> }
> sort(rs.begin(), rs.end()); // the strange sort
> {code}
> Here is my complete test case.
> {code:title=generated structure}
> enum Mode {
> MEMORY,
> DISK,
> };
> struct TestEnum {
> Mode MyMode;
> };
> {code}
> {code:title=My test case}
> #include "ts_enum.h"
> #include "avro/Compiler.hh"
> #include "avro/ValidSchema.hh"
> using namespace std;
> using namespace avro;
> using namespace enum_test;
> static const char ts_schema_string[] =
> "{ \"type\" : \"record\", \"name\" : \"TestEnum\", \"fields\" : "
> "[ { \"name\" : \"MyMode\", \"type\" : "
> "{ \"type\" : \"enum\", \"name\" : \"Mode\", "
> "\"symbols\" : [ \"MEMORY\", \"DISK\" ] } } ]}";
> int main(int argc, char * argv[]) {
> TestEnum te1, te2;
> ValidSchema reader = compileJsonSchemaFromString(ts_schema_string);
> ValidSchema writer = compileJsonSchemaFromString(ts_schema_string);
> //encode TestEnum
> auto_ptr<OutputStream> out_stream = memoryOutputStream();
> EncoderPtr encoder = binaryEncoder();
> encoder->init(*out_stream);
> te1.MyMode = DISK;
> encode(*encoder, te1);
> encoder->flush();
> //decode TestEnum
> auto_ptr<InputStream> in_stream = memoryInputStream(*out_stream);
> DecoderPtr decoder = resolvingDecoder(writer, reader,
> avro::binaryDecoder());
> decoder->init(*in_stream);
> decode(*decoder, te2);
> cout<<"TE1: "<<te1.MyMode << " | TE2: "<<te2.MyMode<<endl;
> return 0;
> }
> {code}
> The result
> -------------------
> TE1: 1 | TE2: 0
> I debuged into avro code.
> In Symbol::enumAdjustSymbol, there is a vector<string> of reader's enum
> names, and after the sort, "MEMOEY, DISK" turned to be "DISK, MEMORY".
> At last, a vector<int> of writer's enum names saved every position of the
> sorted vector<string>.
> As a result, in the returned symbol, MEMORY's position is 1 and DISK's
> position is 0.
> Finally, when we decoding the enum, the *position* is returned to the target
> object.
> I could't quite understand the author's intention here but when I commented
> the sort, everything worked well.
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