Request feature: Exemple Usage + possible bug: strings above 55 bytes not handle properly

[datgrog]

I'm playing around your rlpvalue package in order to serialize an ethereum transaction.

• The possible bug is related to the "Lorem ipsum..." exemple

RLPValue lorem("Lorem ipsum dolor sit amet, consectetur adipisicing elit");
std::string serialized_lorem = lorem.write();

for (size_t i = 0; i < lorem.size(); i++) {
    printf("\\x%.2x ", lorem.c_str()[i]);
}

It prints \xffffffb8 \x4c \x6f ... but should print \xb8 \x38 \x4c ... instead, it looks like rlpvalue does not handle properly strings with length above 55 bytes, see medium post (Ctrl+F and "Rule 2")

• Also, how does your package handle integer serialization ?

NB: On my mac, I also had to install brew install argp-standalone before doing the installation to compile properly

[xiaofo09]

Did you solve that problem ? I have same problem in the latest version including your fix.

[datgrog]

Did you solve that problem ? I have same problem in the latest version including your fix.

What input did you try to serialize ? What result do you expect from it ?

[xiaofo09]

Same input like you. below:

RLPValue lorem("Lorem ipsum dolor sit amet, consectetur adipisicing elit");
std::string serialized_lorem = lorem.write();

for (size_t i = 0; i < serialized_lorem.size(); i++) {
    printf("\\x%.2x ", serialized_lorem.c_str()[i]);
}

But it prints out \xffffffb8 \x38 \x4c ... but should print \xb8 \x38 \x4c ...

[xiaofo09]

My code is here.

/* g++ -o rlp rlp.cpp -I. -L/usr/local/lib -lrlpvalue -static */

#include <stdio.h>
#include "rlpvalue.h"

using namespace std;

int main(void)
{
    RLPValue lorem("Lorem ipsum dolor sit amet, consectetur adipisicing elit");
    std::string serialized_lorem = lorem.write();

    for (size_t i = 0; i < serialized_lorem.size(); i++) {
        printf("\\x%.2x ", serialized_lorem.c_str()[i]);
    }
    printf("\n");

    return 0;
}

[xiaofo09]

I think the data is placed in "serialized_lorem" correctly.
Is this simply a matter of output?

[jgarzik]

Recommend using ParseHex and HexStr for going to/from hexidecimal. Example:
https://github.com/bloq/rlpvalue/blob/master/test/unitester.cpp#L129

			std::string genHex = HexStr(genOutput.begin(),
						    genOutput.end());
			fprintf(stderr, "INS :%s\nGENS:%s\n",
				outs.c_str(),
				genHex.c_str());

[darcys22]

Pretty late to the party, this got me also. It isn't a bug in the serialized_lorem. Instead its an issue with how you print to hex.

In the code the length is prepended to the data using this:

static std::string encodeLength(size_t n, unsigned char offset)
{
	std::string rs;

	if (n < 56) {
		unsigned char ch = n + offset;
		rs.assign((const char *) &ch, 1);
	}

	else {
		// assert(n too big);
		std::string binlen = encodeBinary(n);

		unsigned char ch = binlen.size() + offset + 55;
		rs.assign((const char *) &ch, 1);
		rs.append(binlen);
	}

	return rs;
}

which represents the length as a single char, if the offset (0xC0 for example) pushes this above what can be represented as a single signed byte then it will be represented as a negative in std::string.

When printing if this gets interpreted as a signed char and converted to an unsigned char, then your output will be incorrect. Hence why HexStr is recommended going to hexidecimal