struct-buffer
Add structure to ArrayBuffer
Install
$ npm i struct-buffer
how to use
import { float, string_t, StructBuffer, pack } from "struct-buffer";
const struct = new StructBuffer("Player", {
hp: float,
mp: float,
name: string_t[3],
});
const buffer: DataView = pack("2f3s", 10, 100, "abc");
// decode
const data = struct.decode(buffer);
// data => { hp: 10, mp: 100, name: 'abc' }
// encode
const view = struct.encode({
hp: 10,
mp: 100,
name: "abc",
});
// view => <41 20 00 00 42 c8 00 00 61 62 63>Use in browser
<script src="struct-buffer.js"></script>
<script>
const { DWORD, string_t, StructBuffer, uint32_t } = window.StructBuffer;
</script>Use "type" for conversion
import { DWORD } from "struct-buffer";
// encode
const view = DWORD[2].encode([1, 2]);
// view => <00 00 00 01 00 00 00 02>
// decode
const data = DWORD[2].decode(view);
// data => [ 1, 2 ]register Type
const myShort = registerType("short", 2, false);
const struct = new StructBuffer("Player", {
hp: myShort,
mp: myShort,
pos: myShort[2],
});
// encode
const view = struct.encode({
hp: 2,
mp: 10,
pos: [100, 200],
});
// view => <00 02 00 0a 00 64 00 c8>
// decode
const data = struct.decode(view);
// data => { hp: 2, mp: 10, pos: [ 100, 200 ] }typedef
const HANDLE = typedef("HANDLE", DWORD);
HANDLE.size // 4
HANDLE.unsigned // trueNested struct
/*
typedef struct _XINPUT_STATE {
DWORD dwPacketNumber;
XINPUT_GAMEPAD Gamepad;
} XINPUT_STATE, *PXINPUT_STATE;
typedef struct _XINPUT_GAMEPAD {
WORD wButtons;
BYTE bLeftTrigger;
BYTE bRightTrigger;
SHORT sThumbLX;
SHORT sThumbLY;
SHORT sThumbRX;
SHORT sThumbRY;
} XINPUT_GAMEPAD, *PXINPUT_GAMEPAD;
*/
XINPUT_GAMEPAD = new StructBuffer("XINPUT_GAMEPAD", {
wButtons: WORD,
bLeftTrigger: BYTE,
bRightTrigger: BYTE,
sThumbLX: int16_t,
sThumbLY: int16_t,
sThumbRX: int16_t,
sThumbRY: int16_t,
});
XINPUT_STATE = new StructBuffer("XINPUT_STATE", {
dwPacketNumber: DWORD,
Gamepad: XINPUT_GAMEPAD,
});
// decode
XINPUT_STATE.decode(
new Uint8Array([
0, 0, 0, 0, // dwPacketNumber
0, 1, // wButtons
0, // bLeftTrigger
0, // bRightTrigger
0, 1, // sThumbLX
0, 2, // sThumbLY
0, 3, // sThumbRX
0, 4, // sThumbRY
])
);
// encode
XINPUT_STATE.encode({
dwPacketNumber: 0,
Gamepad: {
wButtons: 1,
bLeftTrigger: 0,
bRightTrigger: 0,
sThumbLX: 1,
sThumbLY: 2,
sThumbRX: 3,
sThumbRY: 4,
},
});parse c-struct
import { CStruct } from "struct-buffer";
const cStruct = `
//
// Structures used by XInput APIs
//
typedef struct _XINPUT_GAMEPAD
{
WORD wButtons;
BYTE bLeftTrigger;
BYTE bRightTrigger;
SHORT sThumbLX;
SHORT sThumbLY;
SHORT sThumbRX;
SHORT sThumbRY;
} XINPUT_GAMEPAD, *PXINPUT_GAMEPAD;
typedef struct _XINPUT_STATE
{
DWORD dwPacketNumber;
XINPUT_GAMEPAD Gamepad;
} XINPUT_STATE, *PXINPUT_STATE;
typedef struct _XINPUT_VIBRATION
{
WORD wLeftMotorSpeed;
WORD wRightMotorSpeed;
} XINPUT_VIBRATION, *PXINPUT_VIBRATION;
typedef struct _XINPUT_BATTERY_INFORMATION
{
BYTE BatteryType;
BYTE BatteryLevel;
} XINPUT_BATTERY_INFORMATION, *PXINPUT_BATTERY_INFORMATION;
`;
const structs = CStruct.parse(cStruct);
sizeof(structs.XINPUT_GAMEPAD) // 12
sizeof(structs.XINPUT_STATE) // 16
sizeof(structs.XINPUT_VIBRATION) // 4
sizeof(structs.XINPUT_BATTERY_INFORMATION) // 2struct list
const User = new StructBuffer("User", {
name: string_t[2],
name2: string_t[2],
});
const Users = new StructBuffer("Users", {
users: User[2],
});
const data = Users.decode(
new Uint8Array([0x61, 0x31, 0x61, 0x32, 0x62, 0x31, 0x62, 0x32])
);
// data.users.length => 2
// data.users[0] => { name: "a1", name2: "a2" }
// data.users[1] => { name: "b1", name2: "b2" }
// or
const users = User[2].decode(
new Uint8Array([0x61, 0x31, 0x61, 0x32, 0x62, 0x31, 0x62, 0x32])
);
// users => [ { name: 'a1', name2: 'a2' }, { name: 'b1', name2: 'b2' } ]StructBuffer to c-struct
import { CStruct } from "struct-buffer";
const XINPUT_GAMEPAD = new StructBuffer("XINPUT_GAMEPAD", {
wButtons: WORD,
bLeftTrigger: BYTE,
bRightTrigger: BYTE,
sThumbLX: int16_t,
sThumbLY: int16_t,
sThumbRX: int16_t,
sThumbRY: int16_t[2],
});
const cStruct = CStruct.from(XINPUT_GAMEPAD);
// console.log(cStruct) =>
typedef struct _XINPUT_GAMEPAD
{
WORD wButtons;
BYTE bLeftTrigger;
BYTE bRightTrigger;
int16_t sThumbLX;
int16_t sThumbLY;
int16_t sThumbRX;
int16_t sThumbRY[2];
} XINPUT_GAMEPAD, *XINPUT_GAMEPAD;"string_t" Truncate when encountering 0
string_t[4].decode(new Uint8Array([0x61, 0x62, 0x63, 0x64]); // abcd
string_t[4].decode(new Uint8Array([0x61, 0x62, 0x00, 0x64]); // abbits
import { DWORD, bits, StructBuffer } from "struct-buffer";
const EFLAG_DATA = 0x00000246;
const littleEndian = true;
const EFLAG = bits(DWORD, {
CF: 0,
PF: 2,
AF: 4,
ZF: 6,
SF: 7,
TF: 8,
IF: 9,
DF: 10,
OF: 11,
});
// decode
const data = EFLAG.decode(new Uint32Array([EFLAG_DATA]), littleEndian);
// => { CF: 0, PF: 1, AF: 0, ZF: 1, SF: 0, TF: 0, IF: 1, DF: 0, OF: 0 }
// encode
const view = EFLAG.encode(
{
PF: 1,
ZF: 1,
IF: 1,
},
littleEndian
);
// => <44 02 00 00>bitFields
import { uint8_t, bitFields, StructBuffer, sbytes as b, } from "struct-buffer";
const bf = bitFields(uint8_t, {
a: 1,
b: 2,
c: 3,
});
const v = bf.encode({
a: 1,
b: 2,
c: 3,
});
// => <1D>
const data = bf.decode(b("1D"));
// => { a: 1, b: 2, c: 3 }Inject
Customize the working content of decode and encode
const c_str = new Inject(
// decode
(view: DataView, offset: number) => {
const buf: number[] = [];
let size = offset + 0;
while (true) {
let data = view.getUint8(size++);
if (data === 0) break;
buf.push(data);
}
return {
size: size - offset,
value: new TextDecoder().decode(new Uint8Array(buf)),
};
},
// encode
(value: string) => {
const bytes: Uint8Array = new TextEncoder().encode(value);
const res = realloc(bytes, bytes.byteLength + 1);
return res;
}
);See Inject.test.ts file.
pack and unpack
import { pack, pack_into, unpack, unpack_from, iter_unpack, calcsize, Struct, sbytes as b } from "struct-buffer";
pack("b2xb", 2, 1)
// => <02 00 00 01>
unpack("b2xb", b("02 00 00 01"))
// => [ 2, 1 ]
calcsize("hhl")
// => 8
const [hp, mp, name] = unpack(
">II3s",
b("00 00 00 64 00 00 00 0A 61 62 63")
);
expect(hp).toBe(100);
expect(mp).toBe(10);
expect(name).toBe('abc');Note: Without "@, =, P", the default byte order is ">"
Some utility functions
import { createDataView, makeDataView, sbytes as b, sbytes2 as b2, sview, TEXT } from "struct-buffer";
createDataView(3)
// => <00 00 00>
makeDataView([1, 2, 3])
// => <01 02 03>
b("01 02 03")
// => <01 02 03>
b2("abc\\x1\\x2\\x3")
// => <61 62 63 01 02 03>
TEXT(pack("3s2b3s2I", "abc", 1, 2, "xyz", 8, 9))
// => "abc..xyz........"test
$ npm test
build
$ npm run build
