[Node.js] 공부 4 일차 - Node.js Buffer 사용법

[Node.js] 공부 4 일차 -Node.js Buffer 사용법

개발환경

 - OS : windows

 - 개발툴 : Brackets

 - Node.js 버전 : 6.11.1 LTS

참조 Node.js API : https://nodejs.org/dist/latest-v6.x/docs/api/buffer.html

Buffer API 확인하기

Buffer.alloc(size[, fill[, encoding]])

 - size <integer> : Buffer 사이즈 지정

 - fill <string> | <Buffer> | <integer> : Buffer 초기화 시 초기 설정 값 지정 Default : 0

 - encoding <string> : Buffer 초기화 시 encoding 설정 Default: 'utf8'

var buf_01 = Buffer.alloc(10); // hex Prints: <Buffer 00 00 00 00 00 00 00 00 00 00>
 
console.log("buf_01 init : " + buf_01);
console.log("buf_01 init(hex) : " + buf_01.toString("hex"));
console.log("buf_01 init size : " + buf_01.length);
 
var buf_02 = Buffer.alloc(10, 1); // hex Prints: <Buffer 01 01 01 01 01 01 01 01 01 01>
 
console.log("buf_02 init : " + buf_02);
console.log("buf_02 init(hex) : " + buf_02.toString("hex"));
console.log("buf_02 init size : " + buf_02.length);
 
var buf_03 = Buffer.alloc(11, 'aGVsbG8gd29ybGQ=', 'base64'); // hex Prints: <Buffer 68 65 6c 6c 6f 20 77 6f 72 6c 64>
 
console.log("buf_03 init : " + buf_03);
console.log("buf_03 init(hex) : " + buf_03.toString("hex"));
console.log("buf_03 init size : " + buf_03.length);

결과 화면

buf_01 init : 
buf_01 init(hex) : 00000000000000000000
buf_01 init size : 10
buf_02 init : 
buf_02 init(hex) : 01010101010101010101
buf_02 init size : 10
buf_03 init : hello world
buf_03 init(hex) : 68656c6c6f20776f726c64
buf_03 init size : 11

buf.toString([encoding[, start[, end]]])

 - encoding <string> : 해당 값의 인코딩 방식 설정 Default: 'utf8'

 - start <integer> : 인코딩 시작 위치 Default: 0

 - end <integer> : 인코딩 종료 위치 Default: buf.length

 - Returns: <string>

var buf_04 = Buffer.alloc(26);
 
for (let i = 0; i < 26; i++) {
  buf_04[i] = i + 97;
}
 
console.log("buf_04 ascii print : " + buf_04.toString("ascii"));
console.log("buf_04 ascii print[0-10] : " + buf_04.toString('ascii', 0, 10));
console.log("buf_04 hex print : " + buf_04.toString("hex"));
console.log("buf_04 utf8 print : " + buf_04.toString("utf8"));
console.log("buf_04 binary print : " + buf_04.toString("binary"));

결과화면

buf_04 ascii print : abcdefghijklmnopqrstuvwxyz
buf_04 ascii print[0-10] : abcdefghij
buf_04 hex print : 6162636465666768696a6b6c6d6e6f707172737475767778797a
buf_04 utf8 print : abcdefghijklmnopqrstuvwxyz
buf_04 binary print : abcdefghijklmnopqrstuvwxyz

Buffer.byteLength(string[, encoding])

 - string <string> | <Buffer> | <TypedArray> | <DataView> | <ArrayBuffer> : 바이트 길이를 확인할 변수 입력 Default encoding : 'utf8'

 - Returns: <integer> : 입력된 변수의 바이트 길이를 반환한다.

var buf_05 = Buffer("테스트입니다.");
 
console.log("buf_05 init : " + buf_05);
console.log("buf_05 init size : " + buf_05.length);
console.log("buf_05 init byte size : " + Buffer.byteLength(buf_05));
 
var str_01 = '\u00bd + \u00bc = \u00be';
 
console.log("str_01 init : " + str_01);
console.log("str_01 init size : " + str_01.length);
console.log("str_01 init byte size : " + Buffer.byteLength(str_01));

결과화면

buf_05 init : 테스트입니다.
buf_05 init size : 19
buf_05 init byte size : 19
str_01 init : ½ + ¼ = ¾
str_01 init size : 9
str_01 init byte size : 12

buf.fill(value[, offset[, end]][, encoding])

 - value <string> | <Buffer> | <integer> : 해당 변수에 채워넣을 값

 - offset <integer> : 시작 위치 Default: 0

 - end <integer> : 종료 위치. Default: buf.length

 - encoding <string> : 인코딩 설정 Default: 'utf8'

 - Returns: <Buffer> : 입력된 값으로 설정된 값 반환한다.

var buf_06 = Buffer.alloc(10, 1);
 
console.log("buf_06 init : " + buf_06);
console.log("buf_06 init(hex) : " + buf_06.toString("hex"));
console.log("buf_06 init size : " + buf_06.length);
 
buf_06.fill(0x02);
 
console.log("buf_06 fill first init : " + buf_06);
console.log("buf_06 fill first init(hex) : " + buf_06.toString("hex"));
console.log("buf_06 fill first init size : " + buf_06.length);
 
buf_06.fill("A");
 
console.log("buf_06 fill second init : " + buf_06);
console.log("buf_06 fill second init(hex) : " + buf_06.toString("hex"));
console.log("buf_06 fill second init size : " + buf_06.length);

결과화면

buf_06 init : 
buf_06 init(hex) : 01010101010101010101
buf_06 init size : 10
buf_06 fill first init : 
buf_06 fill first init(hex) : 02020202020202020202
buf_06 fill first init size : 10
buf_06 fill second init : AAAAAAAAAA
buf_06 fill second init(hex) : 41414141414141414141
buf_06 fill second init size : 10

buf.writeInt32BE(value, offset[, noAssert]) : Big-Endian, buf.writeInt32LE(value, offset[, noAssert]) : Little-Endian

 - value <integer> :  Buffer에 쓰일 숫자 변수

 - offset <integer> : 해당 변수가 저장될 시작위치

 - noAssert <boolean> : 사용된 예를 확인하지 못함 생략해도 사용하는데 지장 없음 Default: false

 - Returns: <integer> buffer 변수에 해당 변수가 쓰여진 마지막 위치를 반환

var num = Number(100);
var buf_07 = Buffer.alloc(4);
 
var len_07 = buf_07.writeInt32BE(num, 0);
 
console.log("buf_07 init : " + buf_07);
console.log("buf_07.writeInt32BE(num, 0)(hex) : " + buf_07.toString("hex"));
console.log("buf_07.writeInt32BE(num, 0) size : " + buf_07.length);
console.log("len_07 : " + len_07);
 
var buf_08 = Buffer.alloc(4);
 
var len_08 = buf_08.writeInt32LE(num, 0);
 
console.log("buf_08 init : " + buf_08);
console.log("buf_08.writeInt32LE(num, 0)(hex) : " + buf_08.toString("hex"));
console.log("buf_08.writeInt32LE(num, 0) size : " + buf_08.length);
console.log("len_08 : " + len_08);
 
var buf_09 = Buffer.alloc(10);
 
var len_09 = buf_09.writeInt32LE(num, 2);
 
console.log("buf_09 init : " + buf_09);
console.log("buf_09.writeInt32LE(num, 2)(hex) : " + buf_09.toString("hex"));
console.log("buf_09.writeInt32LE(num, 2) size : " + buf_09.length);
console.log("len_09 : " + len_09);

결과화면

buf_07 init : d
buf_07.writeInt32BE(num, 0)(hex) : 00000064
buf_07.writeInt32BE(num, 0) size : 4
len_07 : 4
buf_08 init : d
buf_08.writeInt32LE(num, 0)(hex) : 64000000
buf_08.writeInt32LE(num, 0) size : 4
len_08 : 4
buf_09 init : d
buf_09.writeInt32LE(num, 2)(hex) : 00006400000000000000
buf_09.writeInt32LE(num, 2) size : 10
len_09 : 6

buf.slice([start[, end]])

 - start <integer> : 시작 위치 Default: 0

 - end <integer> : 종료 위치 Default: buf.length

 - Returns: <Buffer> : 해당 위치로 잘려진 값을 반환한다.

var buf_10 = Buffer.alloc(26);
 
for (let i = 0; i < 26; i++) {
  buf_10[i] = i + 97;
}
 
console.log("buf_10 utf8 print : " + buf_10.toString("utf8"));
console.log("buf_10 hex print : " + buf_10.toString("hex"));
 
var buf_11 = Buffer.alloc(5);
buf_11 = buf_10.slice(0, 5);
 
console.log("buf_11 utf8 print : " + buf_11.toString("utf8"));
console.log("buf_11 hex print : " + buf_11.toString("hex"));
 
var buf_12 = Buffer.alloc(5);
buf_12 = buf_10.slice(4, 6);
 
console.log("buf_12 utf8 print : " + buf_12.toString("utf8"));
console.log("buf_12 hex print : " + buf_12.toString("hex"));

결과화면

buf_10 utf8 print : abcdefghijklmnopqrstuvwxyz
buf_10 hex print : 6162636465666768696a6b6c6d6e6f707172737475767778797a
buf_11 utf8 print : abcde
buf_11 hex print : 6162636465
buf_12 utf8 print : ef
buf_12 hex print : 6566

Buffer.concat(list[, totalLength])

 - list <Array> : 합쳐질 Buffer변수의 배열

 - totalLength <integer> : 합쳐질 변수의 전체 길이

 - Returns: <Buffer> : 합쳐진 값을 반환한다.

var buf_13 = Buffer("hello");
var buf_14 = Buffer(" world");
var buf_15 = Buffer(" 환영합니다.");
 
var totalLength = buf_13.length + buf_14.length + buf_15.length;
 
console.log("buf_13 utf8 print : " + buf_13.toString("utf8"));
console.log("buf_14 utf8 print : " + buf_14.toString("utf8"));
console.log("buf_15 utf8 print : " + buf_15.toString("utf8"));
 
console.log("buf_13.length + buf_14.length + buf_15.length = " + totalLength);
 
var buf_16 = Buffer.concat([buf_13, buf_14, buf_15], totalLength);
 
console.log("buf_16 utf8 print : " + buf_16.toString("utf8"));
console.log("buf_16 hex print : " + buf_16.toString("hex"));
console.log("buf_16 length : " + buf_16.length);

결과화면

buf_13 utf8 print : hello
buf_14 utf8 print :  world
buf_15 utf8 print :  환영합니다.
buf_13.length + buf_14.length + buf_15.length = 28
buf_16 utf8 print : hello world 환영합니다.
buf_16 hex print : 68656c6c6f20776f726c6420ed9998ec9881ed95a9eb8b88eb8ba42e
buf_16 length : 28