zzz.skein

Description

Skein is a library like "java.nio.ByteBuffer" of java. In data communication, a module should efficiently manipulate byte streams. Because allocating and releasing memory is a costly task.

Skein provides functions to reuse "Buffer" in node.js, so reducing overheads. Function definitions referenced "java.nio.ByteBuffer" of java.

Installation

npm install skein

Documents

mark, position, limit, capacity

Skein uses some attributes for manipulating "Buffer" of Node.

0 <= mark <= position <= limit <= capacity

• capacity: a total size of "Buffer", size == bytes count. readonly
• limit : max index {position} can reach.
• position: index of "Buffer" to be read or written
• mark : when reset {position}, this value will be assigned to {position}

allocate, wrap

.allocate(), .wrap() are static functions that initialize "Buffer".

let buf = Skein.allocate(1024)

{buf} has 1024 bytes "Buffer". .allocate() function set attributes, capacity=1024, limit=1024, position=0, mark=0

let buf = Skein.wrap([0x00, 0x01, 0x02, 0x03]);

{buf} has 4 bytes "Buffer" and it contains [0x00, 0x01, 0x02, 0x03]. Attributes are, capacity=4, limit=4, position=0, mark=0

get, put

You can read or write a byte from Skein by calling get(), put().

let buf = Skein.wrap([0x00, 0x01, 0x02, 0x03]); let b = buf.get();

The variable 'b' has 0x00. and position=1 where you can read or write next.

b = buf.get()  // b=0x01, position=2
b = buf.get()  // b=0x02, position=3
b = buf.get()  // b=0x03, position=4
b = buf.get()  // overflow !!!,  next position=5 > limit=4

The above codes show position's role, the position has index you can read next. The last line is error(overflow), because next position 5 is over limit.

put() same as get()...

let buf = Skein.allocate(4);
buf.put(0x00);  // buf contains [0x00,,,]  position=1
buf.put(0x01);  // buf contains [0x00,0x01,,]  position=2
buf.put(0x02);  // buf contains [0x00,0x01,0x02,]  position=3
buf.put(0x03);  // buf contains [0x00,0x01,0x02,0x03]  position=4
buf.put(0x04);  // overflow !!!

flip()

flip() set {limit} to current {position} and set {position},{mark} to 0.

let buf = Skein.allocate(4);  // position=0, limit=4
buf.put(0x00);
buf.put(0x01);
buf.put(0x02);      // position=3, limit=4

buf.flip();         // position=0, limit=3

let b = buf.get();  // b = 0x00
let b = buf.get();  // b = 0x01
let b = buf.get();  // b = 0x02
let b = buf.get();  // overflow !!!   next position=4 > limit=3

In the above codes, flip() makes Skein to get the previous put data.

rewind(), clear()

rewind() only set {position},{mark} to 0. It may be used to read data again.

clear() set {limit} to {capacity} and set {position},{mark} to 0. It makes Skein to be cleared.

mark(), reset()

mark() set {mark} to current {position}

reset() set {position} to {mark}

compact()

The bytes between the buffer's current position and its limit, if any, are copied to the beginning of the buffer. compact() set {position} to next index of the bytes and set {limit} to {capacity}

let buf = Skein.allocate(10);  // position=0, limit=10
buf.put(0x00);
buf.put(0x01);
buf.put(0x02);
buf.put(0x03);
buf.put(0x04);      // position=5, limit=10   
// [0x00,0x01,0x02,0x03,0x04,,,,,]

buf.flip();         // position=0, limit=5

let b = buf.get();  // b = 0x00
let b = buf.get();  // b = 0x01
let b = buf.get();  // b = 0x02   // position=3, limit=5
// [0x00,0x01,0x02,0x03,0x04,,,,,]

buf.compact();      // position=2, limit=10
// [0x03,0x04,,,,,,,,]

buf.put(0x05);      // position=3, limit=10
// [0x03,0x04,0x05,,,,,,,]

attributes

• capacity: a total size of "Buffer", size == bytes count. readonly
• limit : max index {position} can reach.
• position: index of "Buffer" to be read or written
• buf : raw "Buffer"
• remaining : a count of remain bytes = {limit} - {position}
• hasRemaining : whether remaining > 0 or not