feat(rust): implement rust sled demo

[hackerchai]

Signed-off-by: hackerchai i@hackerchai.com

[xushiwei]

please write a README file like this: https://github.com/goplus/llgo/blob/main/c/sqlite/README.md

[xushiwei]

It's not common to add OpenDB in a Config type.

//go:linkname Open C.sled_open_db
func Open(conf *Config) *DB

To be confirmed: how sled_open_db indicates an open error?

[luoliwoshang]

It's not common to add OpenDB in a Config type.

//go:linkname Open C.sled_open_db
func Open(conf *Config) *DB

To be confirmed: how sled_open_db indicates an open error?

In the implementation of the C wrapper in Sled, it directly calls unwrap to throw an error when there is an open error. For this C wrapper implementation, it indeed doesn't feel elegant. I think returning a null pointer for an open error might be a more elegant handling method.

/// Open a sled lock-free log-structured tree. Consumes the passed-in config.
#[no_mangle]
pub unsafe extern "C" fn sled_open_db(config: *mut Config) -> *mut Db {
    let config = Box::from_raw(config);
    Box::into_raw(Box::new(config.open().unwrap()))
}

When I call this function in C and pass in a null pointer, it directly throws an error:
Full Demo https://github.com/luoliwoshang/RustTest/blob/main/sled/test/test.c

 printf("Opening database...\n");

free(config); // mock error

void *db = sled_open_db(config);
printf("Database opened: %p\n", db);
if (db == NULL)
{
    printf("Failed to open database\n");
    sled_free_config(config);
    return 1;
}

./test
Creating config...
Config created: 0x6000031e4010
Setting path...
Path set, new config: 0x6000031e4020
Opening database...
[1]    6955 segmentation fault  ./test

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.51%. Comparing base (794df59) to head (2b19513).
Report is 11 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #450   +/-   ##
=======================================
  Coverage   97.51%   97.51%           
=======================================
  Files          19       19           
  Lines        4420     4420           
=======================================
  Hits         4310     4310           
  Misses         94       94           
  Partials       16       16           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.