cannot open proj.db with memvfs

[gaoyuanning]

Hi I try to use the proj to load the proj.db in memory format. To do this, I use char proj_db[] to store the proj.db in binary format, and load it by memvfs. But when I run the code, I get the error of open file. I wonder if there something wrong in my codes?

Here is my code:

#include <math.h>
#include <proj.h>
#include <filemanager.hpp>
#include <stdio.h>
#include <iostream>
#include "sqlite3.h"

extern "C" unsigned char proj_db[];
extern "C" unsigned int proj_db_len;
extern "C" int sqlite3_memvfs_init(sqlite3 *, char **, const sqlite3_api_routines *);

int main(void) {

    sqlite3_initialize();
    sqlite3_memvfs_init(nullptr, nullptr, nullptr);
    auto vfs = sqlite3_vfs_find("memvfs");
    if (!vfs) {
        std::cerr << "Could not find sqlite memvfs extension\n";
        return -1;
    }
    sqlite3_vfs_register(vfs, 0);

    /* Create the context. */
    /* You may set C=PJ_DEFAULT_CTX if you are sure you will     */
    /* use PJ objects from only one thread                       */
    PJ_CONTEXT *C = proj_context_create();

    char * path = sqlite3_mprintf("file:/proj.db?ptr=0x%p&sz=%lld&freeonclose=1", (void *)proj_db, (long long)proj_db_len);
    proj_context_set_sqlite3_vfs_name(C, "memvfs");
    bool ok = proj_context_set_database_path(C, path, nullptr, nullptr);

    if (!ok)
    {
        std::cerr << "canno open set the database path\n";
        return -1;
    }

    return 0;
}

[gaoyuanning]

I found if I add SQLITE_OPEN_URI flag in sqlite3_open_v2() in below source codes, and re-compile the proj.
The above codes will work.

// proj-9.3.0/src/iso19111/factory.cpp
std::shared_ptr<SQLiteHandle> SQLiteHandle::open(PJ_CONTEXT *ctx,
                                                 const std::string &path) {

    const int sqlite3VersionNumber = sqlite3_libversion_number();
    // Minimum version for correct performance: 3.11
    if (sqlite3VersionNumber < 3 * 1000000 + 11 * 1000) {
        pj_log(ctx, PJ_LOG_ERROR,
               "SQLite3 version is %s, whereas at least 3.11 should be used",
               sqlite3_libversion());
    }

    std::string vfsName;
#ifdef ENABLE_CUSTOM_LOCKLESS_VFS
    std::unique_ptr<SQLite3VFS> vfs;
    if (ctx->custom_sqlite3_vfs_name.empty()) {
        vfs = SQLite3VFS::create(false, true, true);
        if (vfs == nullptr) {
            throw FactoryException("Open of " + path + " failed");
        }
        vfsName = vfs->name();
    } else
#endif
    {
        vfsName = ctx->custom_sqlite3_vfs_name;
    }
    sqlite3 *sqlite_handle = nullptr;
    // SQLITE_OPEN_FULLMUTEX as this will be used from concurrent threads
    if (sqlite3_open_v2(path.c_str(), &sqlite_handle,
                        SQLITE_OPEN_READONLY | SQLITE_OPEN_FULLMUTEX,
                        vfsName.empty() ? nullptr : vfsName.c_str()) !=
            SQLITE_OK ||
        !sqlite_handle) {
        if (sqlite_handle != nullptr) {
            sqlite3_close(sqlite_handle);
        }
        throw FactoryException("Open of " + path + " failed");
    }
    auto handle =
        std::shared_ptr<SQLiteHandle>(new SQLiteHandle(sqlite_handle, true));
#ifdef ENABLE_CUSTOM_LOCKLESS_VFS
    handle->vfs_ = std::move(vfs);
#endif
    handle->initialize();
    handle->checkDatabaseLayout(path, path, std::string());
    return handle;
}