blobaccess.cxx

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/*
  Copyright (C) 2002-2025 CERN for the benefit of the ATLAS collaboration
*/
 
#include "CoralUtilities/blobaccess.h"
 
#include <iostream>
#include "zlib.h"
#include "TMemFile.h"
#include "TTree.h"
#include "CoralBase/Blob.h"
#include "CxxUtils/base64.h"
 
namespace CoralUtilities {
 
 
// Compression Functions
// -------------------------------------------------
 
bool compressBlob(const char* in, coral::Blob& out) {
    uLongf comprLen = compressBound(strlen(in));
    coral::Blob blob;
    blob.resize(comprLen);
    unsigned char* ptr = static_cast<unsigned char*>(blob.startingAddress());
    compress(ptr, &comprLen, reinterpret_cast<const unsigned char*>(in), strlen(in));
    blob.resize(comprLen);
    out = blob;
    return true;
}
 
bool writeBlobFromString(const std::string_view in, coral::Blob& out) {
    return compressBlob(in.data(), out);
}
 
bool writeBlobFromJson(const nlohmann::json& in, coral::Blob& out) {
    return writeBlobFromString(in.dump(), out);
}
 
bool writeBlobFromTTree(TTree* tree, coral::Blob& out) {
    TMemFile fout("buffer","recreate");
    fout.cd();
    tree->CloneTree(-1, "fast")->Write();
    fout.Write();
    uLongf comprLen = fout.GetSize();
    unsigned char *buffer = new unsigned char[comprLen];
    fout.CopyTo(buffer, comprLen);
    coral::Blob blob; 
    blob.resize(comprLen);
    char* ptr = reinterpret_cast<char*>(blob.startingAddress()); 
    *ptr = *const_cast<char*>(CxxUtils::base64_encode(buffer, comprLen).c_str());
    out = blob;
    return true;
}
 
 
 
 
// Reading and Uncompressing Functions
// -------------------------------------------------
 
bool uncompressBlob(const coral::Blob &blob, std::unique_ptr<unsigned char[]> & out, unsigned long& len){
    uLongf uncompLen = 50000;
    std::unique_ptr<unsigned char[]> uncompBuf(new unsigned char[uncompLen+1]);
    uLongf actualLen{0};
    while(true) {
        actualLen = uncompLen;
        int res(uncompress(uncompBuf.get(), &actualLen, reinterpret_cast<const unsigned char*>(blob.startingAddress()), static_cast<uLongf>(blob.size())));
        if(res == Z_OK       ) break;
        if(res == Z_BUF_ERROR) { // double buffer if it was not big enough
            uncompLen *= 2;
            std::cout << "ATTENTION: Increasing buffer to " << uncompLen << std::endl;
            uncompBuf.reset(new unsigned char[uncompLen+1]);
            continue;
        }
        // something else is wrong
        uncompBuf.reset();
        return false;
    }
    uncompBuf.get()[actualLen]=0; // append 0 to terminate string
    out = std::move(uncompBuf);
    len = actualLen;
    return true;
}
     
bool readBlobAsString(const coral::Blob &blob, std::string& out){
    std::unique_ptr<unsigned char[]> bf {};
    uLongf len = 0;
    if(!uncompressBlob(blob, bf, len)) return false;
    const char* cstring = reinterpret_cast<const char*>(bf.get()); // need to cast to char*
    out.assign(cstring, len); // copy over to C++ string
    return true;
}
     
bool readBlobAsJson(const coral::Blob &blob, nlohmann::json& out){
    std::string str = "";
    if(!readBlobAsString(blob, str)) return false;
    try {
        out = nlohmann::json::parse(str);
    }
    catch(const std::exception& e) {
        std::cout << "ATTENTION: Cannot unpack Blob object as JSON!" << std::endl;
        return false;
    }
    return true;
}
 
bool readBlobAsTTree(const coral::Blob &blob, std::unique_ptr<TTree>& out,
                     const std::string_view name){
    const char* cstring = reinterpret_cast<const char*>(blob.startingAddress());
    std::string sb{};
    sb.assign(cstring, blob.size());
    std::vector<unsigned char> bdata = CxxUtils::base64_decode(sb);
    TMemFile f("buffer", reinterpret_cast<char*>(bdata.data()), bdata.size()); 
    TTree* t{nullptr};
    f.GetObject(name.data(), t);
    if(!t) {
        out.reset();
        return false;
    }
    t->LoadBaskets();
    t->SetDirectory(0);
    f.Close();
    out.reset(t);
    return true;
}
     
/*
// keep for now; msgpack maybe used later at some point
bool readBlobAsMsgpack(const coral::Blob &blob, std::string& out){
    unsigned char* bf; uLongf len;
    if(!uncompressBlob(blob, &bf, len)) return false;
    const char* temp = reinterpret_cast<char*>(bf);
    try {
        auto upd = msgpack::unpack(temp, len);
        msgpack::object obj = upd.get();
        std::stringstream ss;
        ss << obj;
        out = ss.str();
    }
    catch(const std::exception& e) {
        std::cout << "ATTENTION: Cannot unpack Blob object as Msgpack!" << std::endl;
        return false;
    }
    return true;
}
*/
 
 
 
}