C++ :: PolarSSL SHA512 Wrapper - Differing Hash Lengths

I'm trying to write a little C++ wrapper around the PolarSLL SHA-512 / 384 implementation, the source code of which you can view here: [URL] .....

The problem I'm having is that the length of the digest is not always 64 bytes (for sha512) or 49 bytes (for sha384) as it's supposed to be, it often is, but not always.

I have pretty much used the code as it is on PolarSSL's website, except for wrapping it in an "impl" namespace. I also ran the self_tests, which all passed.

Here's the code I'm using to wrap the PolarSSL implementation:

namespace {
void sha4(const std::string& input, const sha_t& type, std::string& result) {
bool is_384 = (type == sha_t::SHA_384);
const unsigned char* in = reinterpret_cast<const unsigned char*>(input.c_str());

[Code] ....

When I do a strchr() for '' on the original (non-hex) values, the pointer position returned is the same as the checksums length, so I'm wondering if perhaps the sha4 implementation would shift bits around and one of them happens to become a '', null terminating the hash early?