napi-macros

Set of utility macros to make writing N-API modules a little easier.

npm install napi-macros

Then add the following to your target in your binding.gyp file

"include_dirs": [
  "<!(node -e \"require('napi-macros')\")"
],

These patterns mostly reflect how I use N-API so far. Feel free to PR more.

Usage

#include <node_api.h>
#include <napi-macros.h>

NAPI_METHOD(times_two) {
  NAPI_ARGV(1)
  NAPI_ARGV_INT32(number, 0)

  number *= 2;

  NAPI_RETURN_INT32(number)
}

NAPI_INIT() {
  NAPI_EXPORT_FUNCTION(times_two)
}

Full working example can be found in the example/ folder.

API

NAPI_INIT()

Setup init boilerplate. Pass the function body after.

static char *my_string = "hello";

NAPI_INIT() {
  EXPORT_STRING(my_string)
}

NAPI_METHOD(name)

Setup method boilerplate. Pass the function body after.

NAPI_METHOD(add) {
  NAPI_ARGV(2)
  NAPI_ARGV_INT32(a, 0)
  NAPI_ARGV_INT32(b, 1)

  a = a + b

  NAPI_RETURN_INT32(a)
}

NAPI_ARGV(n)

Setup up argv boilerplate. n is how many arguments you are expecting. Expects the napi_env to be in scope as env and the napi_callback_info to be in scope as info.

NAPI_ARGV_BUFFER(name, index)

Get a buffer out of the arguments at the corresponding index. Sets char *name and size_t name_len with the buffer and buffer length.

NAPI_ARGV_BUFFER_CAST(type, name, index)

Get a buffer out and cast the pointer to the specified type. Note that the type should include the pointer star, i.e.

NAPI_ARGV_BUFFER_CAST(uv_udp_t *, handle, 0)

Will cast the 1st argument as uv_udp_t pointer.

NAPI_ARGV_UINT32(name, index)

Get an argument as a uint32. Will throw if argument is not the right type.

NAPI_ARGV_INT32(name, index)

Get an argument as an int32. Will throw if argument is not the right type.

NAPI_ARGV_UTF8(name, length, index)

Get an argument as a utf8 string.

name will be a char[length] array.

Will throw if argument is not the right type.

NAPI_ARGV_UTF8_MALLOC(name, index)

Get an argument as a utf8 string.

name will be a char*.

Like NAPI_ARGV_UTF8() but allocates name on the heap using malloc(), which should be free()'d after usage.

NAPI_BUFFER_CAST(type, name, var)

Same as NAPI_ARGV_BUFFER_CAST but takes a generic napi_value variable instead of an argv index.

NAPI_BUFFER(name, var)

Same as NAPI_ARGV_BUFFER but takes a generic napi_value variable instead of an argv index.

NAPI_UTF8(name, size, var)

Same as NAPI_ARGV_UTF8 but takes a generic napi_value variable instead of an argv index.

NAPI_UTF8_MALLOC(name, var)

Same as NAPI_ARGV_UTF8_MALLOC but takes a generic napi_value variable instead of an argv index.

NAPI_UINT32(name, var)

Same as NAPI_ARGV_UINT32 but takes a generic napi_value variable instead of an argv index.

NAPI_INT32(name, var)

Same as NAPI_ARGV_INT32 but takes a generic napi_value variable instead of an argv index.

NAPI_EXPORT_FUNCTION(fn)

Will export a function in the Init method. Expects the env and exports to be in scope. The name of the exported function is the same name as the c function.

NAPI_EXPORT_SIZEOF(struct)

Export the size of a strict. The exported name is sizeof_{struct-name}.

NAPI_EXPORT_UINT32(name)

Export a uint32. The name of the exported number is the same name as the c variable.

NAPI_EXPORT_INT32(name)

Export an int32. The name of the exported number is the same name as the c variable.

NAPI_EXPORT_UTF8(name, len)

Export a utf8 string. len should be the length of the string. The name of the exported string is the same name as the c variable.

NAPI_EXPORT_STRING(name)

Export a null terminated string. The name of the exported string is the same name as the c variable.

NAPI_EXPORT_SIZEOF(type)

Exports sizeof(type). The name of the exported number is the same name as the c variable.

NAPI_EXPORT_SIZEOF_STRUCT(structName)

Exports sizeof(struct structName). The name of the exported number is the same name as the c variable.

NAPI_EXPORT_ALIGNMENTOF(type)

Exports the byte alignment of type. The name of the exported number is the same name as the c variable.

NAPI_EXPORT_ALIGNMENTOF_STRUCT(structName)

Exports the byte alignment of struct structName. The name of the exported number is the same name as the c variable.

NAPI_EXPORT_OFFSETOF(type, name)

Exports the byte offset of name within type. The name of the exported number is the same name as the c variables.

NAPI_EXPORT_OFFSETOF_STRUCT(structName, name)

Exports the byte offset of name within struct structName. The name of the exported number is the same name as the c variables.

NAPI_FOR_EACH(array, element)

Iterate over an array. array should be a napi_value containing a javascript array and element is the variable name an element will be exposed as. Expects the loop body to be passed after.

napi_value buffers = argv[0] // first argument is a js array
NAPI_FOR_EACH(buffers, buffer) {
  NAPI_BUFFER(cbuf, buffer)
  printf("cbuf is now a char * pointer: %s\n", cbuf);
}

NAPI_RETURN_UINT32(name)

Returns a uint32.

NAPI_RETURN_INT32(name)

Returns an int32.

NAPI_RETURN_UTF8(name, len)

Return a utf8 string. len should be the length of the string.

NAPI_RETURN_STRING(name)

Return a null terminated string.

NAPI_STATUS_THROWS(call)

Checks the return status of any napi_* function returning a napi_status type. This simplifies using a napi_status variable and comparing the result with napi_ok. It's used internally but can be used stand alone as well.

NAPI_STATUS_THROWS(
  napi_create_threadsafe_function(
    NULL,
    callback,
    0,
    async_resource_name,
    0,
    3,
    0,
    my_finalize,
    NULL,
    my_callback,
    &threadsafe_function
  )
);

Above example will fail because the first env parameter is NULL and throw the following error:

Error: napi_create_threadsafe_function(NULL, callback, 0, async_resource_name, 0, 3, 0, my_finalize, \
NULL, my_callback, &threadsafe_function) failed!

NAPI_UV_THROWS(err, fn)

Checks if a libuv call fails and if so, throws an error.

int err;
NAPI_UV_THROWS(err, uv_ip4_addr((char *) &ip, port, &addr))

NAPI_MAKE_CALLBACK(env, async_ctx, ctx, func, argc, argv, result)

Same as napi_make_callback except it checks if the JS function throw an exception and triggers a process.on('uncaughtException') if so.

License

MIT