I have uploaded a zip file compressed with 7-zip option add to .zip containing only a file with the name text.txt into GitHub, how I could read the content of the file text.txt without writing it to disk?
I'm downloading the zip to memory using curl:
#include <curl/curl.h>
static size_t WriteMemoryCallback(void* contents, size_t size, size_t nmemb,
void* userp) {
size_t realsize = size * nmemb;
auto& mem = *static_cast<std::string*>(userp);
mem.append(static_cast<char*>(contents), realsize);
return realsize;
}
std::string Download(const std::string& url)
{
CURL* curl_handle;
CURLcode res;
std::string chunk;
curl_global_init(CURL_GLOBAL_ALL);
curl_handle = curl_easy_init();
curl_easy_setopt(curl_handle, CURLOPT_URL, url.c_str());
curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, &chunk);
curl_easy_setopt(curl_handle, CURLOPT_USERAGENT, "libcurl-agent/1.0");
// added options that may be required
curl_easy_setopt(curl_handle, CURLOPT_FOLLOWLOCATION, 1L); // redirects
curl_easy_setopt(curl_handle, CURLOPT_HTTPPROXYTUNNEL, 1L); // corp. proxies etc.
curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L); // we want it all
// curl_easy_setopt(curl_handle, CURLOPT_REDIR_PROTOCOLS, CURLPROTO_HTTP | CURLPROTO_HTTPS);
res = curl_easy_perform(curl_handle);
if(res != CURLE_OK) {
std::cerr << "curl_easy_perform() failed: " << curl_easy_strerror(res) << '\n';
} else {
std::cout << chunk.size() << " bytes retrieved\n";
}
curl_easy_cleanup(curl_handle);
curl_global_cleanup();
return chunk;
}
int _tmain(int argc, _TCHAR* argv[])
{
std::string link = "https://github.com/.../main/text.zip";
auto data = Download(link);
}
While searching for a lib capable of uncompressing the zip on memory, I found this one: libzip (any lib is welcome).
Searching for examples I found this answer, however he's loading a zip from disk to memory and reading it content.
How I could read the zip downloaded with curl that is on the string data?
When I visualize the content of data in the debugger it shows PK, I tried passing it to zip *z, but z returns null
//Open the ZIP archive
int err = 0;
zip *z = zip_open(data.c_str(), 0, &err);
//Search for the file of given name
const char *name = "text.txt";
struct zip_stat st;
zip_stat_init(&st);
zip_stat(z, name, 0, &st);
//Alloc memory for its uncompressed contents
char *contents = new char[st.size];
//Read the compressed file
zip_file *f = zip_fopen(z, name, 0);
zip_fread(f, contents, st.size);
zip_fclose(f);
I'm ignoring everything about curl in the question because we've verified that you've got the zip file stored in memory correctly.
How I could read the zip ... that is on the string data?
Since you have the whole zip file stored in memory, you need to create a zip_source from chunk.data() and open the archive using that zip_source - and then open the individual files in the archive.
Here's how (without error checking - you need to add that):
{
// ...
zip_error_t ze; // for errors
// create a zip_source from the data you've stored in memory
zip_source_t* zs = zip_source_buffer_create(chunk.data(), chunk.size(), 0, &ze);
// open the archive from the zip_source
zip_t* zip = zip_open_from_source(zs, ZIP_CHECKCONS | ZIP_RDONLY, &ze);
// read how many files you've got in there
zip_int64_t entries = zip_get_num_entries(zip, 0);
std::cout << entries << '\n';
// loop over the entries in the archive
for(zip_int64_t idx = 0; idx < entries; ++idx) {
std::cout << zip_get_name(zip, idx, ZIP_FL_ENC_STRICT) << '\n';
// open the file at this index
zip_file_t* fp = zip_fopen_index(zip, idx, 0);
// process the file
zip_int64_t len;
char buf[1024];
while((len = zip_fread(fp, buf, sizeof buf)) > 0) {
std::cout << "read " << len << " bytes\n";
// do something with the `len` bytes you have in `buf`
}
zip_fclose(fp); // close this file
}
zip_close(zip); // close the whole archive
}