Migration guide

Koffi 1.x to 2.x

The API was changed in 2.x in a few ways, in order to reduce some excessively “magic” behavior and reduce the syntax differences between C and the C-like prototypes.

You may need to change your code if you use:

• Callback functions

• Opaque types

• koffi.introspect()

Callback type changes

In Koffi 1.x, callbacks were defined in a way that made them usable directly as parameter and return types, obscuring the underlying pointer. Now, you must use them through a pointer: void CallIt(CallbackType func) in Koffi 1.x becomes void CallIt(CallbackType *func) in version 2.0 and newer.

Given the following C code:

#include <string.h>

int TransferToJS(const char *name, int age, int (*cb)(const char *str, int age))
{
    char buf[64];
    snprintf(buf, sizeof(buf), "Hello %s!", str);
    return cb(buf, age);
}

The two versions below illustrate the API difference between Koffi 1.x and Koffi 2.x:

// Koffi 1.x

const TransferCallback = koffi.proto('int TransferCallback(const char *str, int age)');

const TransferToJS = lib.func('TransferToJS', 'int', ['str', 'int', TransferCallback]);
// Equivalent to: const TransferToJS = lib.func('int TransferToJS(str s, int x, TransferCallback cb)');

let ret = TransferToJS('Niels', 27, (str, age) => {
    console.log(str);
    console.log('Your age is:', age);
    return 42;
});
console.log(ret);

// Koffi 2.x

const TransferCallback = koffi.proto('int TransferCallback(const char *str, int age)');

const TransferToJS = lib.func('TransferToJS', 'int', ['str', 'int', koffi.pointer(TransferCallback)]);
// Equivalent to: const TransferToJS = lib.func('int TransferToJS(str s, int x, TransferCallback *cb)');

let ret = TransferToJS('Niels', 27, (str, age) => {
    console.log(str);
    console.log('Your age is:', age);
    return 42;
});
console.log(ret);

Koffi 1.x only supported transient callbacks, you must use Koffi 2.x for registered callbacks.

Note

The function koffi.proto() was introduced in Koffi 2.4, it was called koffi.callback() in earlier versions.

Opaque type changes

In Koffi 1.x, opaque handles were defined in a way that made them usable directly as parameter and return types, obscuring the underlying pointer. Now, in Koffi 2.0, you must use them through a pointer, and use an array for output parameters.

In addition to that, koffi.handle() has been deprecated in Koffi 2.1 and replaced with koffi.opaque(). They work the same but new code should use koffi.opaque(), the former one will eventually be removed in Koffi 3.0.

For functions that return opaque pointers or pass them by parameter:

// Koffi 1.x

const FILE = koffi.handle('FILE');
const fopen = lib.func('fopen', 'FILE', ['str', 'str']);
const fopen = lib.func('fclose', 'int', ['FILE']);

let fp = fopen('EMPTY', 'wb');
if (!fp)
    throw new Error('Failed to open file');
fclose(fp);

// Koffi 2.1

// If you use Koffi 2.0: const FILE = koffi.handle('FILE');
const FILE = koffi.opaque('FILE');
const fopen = lib.func('fopen', 'FILE *', ['str', 'str']);
const fopen = lib.func('fclose', 'int', ['FILE *']);

let fp = fopen('EMPTY', 'wb');
if (!fp)
    throw new Error('Failed to open file');
fclose(fp);

For functions that set opaque handles through output parameters (such as sqlite3_open_v2), you must now use a single element array as shown below:

// Koffi 1.x

const sqlite3 = koffi.handle('sqlite3');

const sqlite3_open_v2 = lib.func('int sqlite3_open_v2(const char *, _Out_ sqlite3 *db, int, const char *)');
const sqlite3_close_v2 = lib.func('int sqlite3_close_v2(sqlite3 db)');

const SQLITE_OPEN_READWRITE = 0x2;
const SQLITE_OPEN_CREATE = 0x4;

let db = {};

if (sqlite3_open_v2(':memory:', db, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, null) != 0)
    throw new Error('Failed to open database');

sqlite3_close_v2(db);

// Koffi 2.1

// If you use Koffi 2.0: const sqlite3 = koffi.handle('sqlite3');
const sqlite3 = koffi.opaque('sqlite3');

const sqlite3_open_v2 = lib.func('int sqlite3_open_v2(const char *, _Out_ sqlite3 **db, int, const char *)');
const sqlite3_close_v2 = lib.func('int sqlite3_close_v2(sqlite3 *db)');

const SQLITE_OPEN_READWRITE = 0x2;
const SQLITE_OPEN_CREATE = 0x4;

let db = null;

let ptr = [null];
if (sqlite3_open_v2(':memory:', ptr, SQLITE_OPEN_READWRITE | SQLITE_OPEN_CREATE, null) != 0)
    throw new Error('Failed to open database');
db = ptr[0];

sqlite3_close_v2(db);

New koffi.introspect()

In Koffi 1.x, koffi.introspect() would only work with struct types, and return the object passed to koffi.struct() to initialize the type. Now this function works with all types.

You can still get the list of struct members:

const StructType = koffi.struct('StructType', { dummy: 'int' });

// Koffi 1.x
let members = koffi.introspect(StructType);

// Koffi 2.x
let members = koffi.introspect(StructType).members;