FFI example with sqlite3 OR sqlite in 5 minutes using codon

[iuridiniz]

A port of: SQLite In 5 Minutes Or Less.

I hope this can help anyone wanting to make a library binding.

Note: This example only exists thanks to clarifications made by @arshajii in thread #161. Thank you very much.

Code

#!/usr/bin/env -S codon run -l /usr/lib/x86_64-linux-gnu/libsqlite3.so

from C import sqlite3_open(cobj, Ptr[Ptr[byte]]) -> i32
from C import sqlite3_close(cobj) -> i32
from C import sqlite3_exec(cobj, cobj, cobj, cobj, Ptr[Ptr[byte]]) -> i32
from C import sqlite3_errstr(i32) -> cobj
from C import sqlite3_free(cobj) -> None
import sys

# Implement https://www.sqlite.org/quickstart.html in Codon
def callback(_unused: cobj, argc: i32, _argv: Ptr[Ptr[byte]], _col_names: Ptr[Ptr[byte]]) -> i32:
    argv = [ str.from_ptr(_argv[i]) for i in range(int(argc)) ]
    col_names = [ str.from_ptr(_col_names[i]) for i in range(int(argc)) ]

    for i in range(int(argc)):
        print(f"{col_names[i]}: {argv[i]}")

    print("")

    return i32(0)

if len(sys.argv) != 3:
    print(f"Usage: {sys.argv[0]} <db> <sql>")
    exit(1)

db = cobj()
path = sys.argv[1]
query = sys.argv[2]
rc = sqlite3_open(path.c_str(), __ptr__(db))
if rc != i32(0):
    print(f"Error while calling sqlite3_open on {repr(path)}: {repr(str.from_ptr(sqlite3_errstr(rc)))}", file=sys.stderr)
    exit(1)


error = cobj()
rc = sqlite3_exec(db, query.c_str(), callback.__raw__(), cobj(), __ptr__(error))
if rc != i32(0):
    print(f"Failed to execute SQL {repr(query)}: {repr(str.from_ptr(error))}", file=sys.stderr)
    sqlite3_free(error)
    sqlite3_close(db)
    exit(1)

sqlite3_close(db)

Compile

codon build -o sqlite_qs -l sqlite3 sqlite_qs.codon 

Test

./sqlite_qs test.db.sqlite3 "CREATE TABLE foo (id INTEGER PRIMARY KEY, name TEXT);"
./sqlite_qs test.db.sqlite3 "INSERT INTO foo (name) VALUES ('bar');"
./sqlite_qs test.db.sqlite3 "INSERT INTO foo (name) VALUES ('baz');"
./sqlite_qs test.db.sqlite3 "SELECT * FROM foo;"

Test like a python script

chmod +x ./sqlite_qs.codon 
./sqlite_qs.codon 

Note: Since I'm using FFI with dinamic linking (not dlopen), you need to change the first line of script to correct path to sqlite3.so

#!/usr/bin/env -S codon run -l /usr/lib/x86_64-linux-gnu/libsqlite3.so