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Make skip() return the ByteStream, for chaining. Document the tee() method.

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Jeff Schiller 2024-01-04 22:39:25 +09:00
parent b72e629d8a
commit 208b69a65d
3 changed files with 29 additions and 5 deletions
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docs/bitjs.io.md
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@ -42,16 +42,17 @@ interpreting 2 bytes in the stream as a number is done by calling `someByteStrea
default, the byte stream is considered Little Endian, but can be changed at any point using
`someByteStream.setBigEndian()` and toggled back with `someByteStream.setLittleEndian()`.
By default, numbers are unsigned, but `peekSignedNumber(n)` and `readSignedNumber(n)` exist for signed numbers.
By default, numbers are unsigned, but `peekSignedNumber(n)` and `readSignedNumber(n)` exist for
signed numbers.
```javascript
const byteStream = new ByteStream(someArrayBuffer);
byteStream.setBigEndian();
byteStream.readNumber(2); // skip two bytes.
byteStream.skip(2); // skip two bytes.
// Interpret next 2 bytes as the string length.
const strLen = byteStream.readNumber(2);
// Read in bytes as an ASCII string.
const someString = byteStream.readNumber(strLen);
const someString = byteStream.readString(strLen);
// Interpret next byte as an int8 (0xFF would be -1).
const someVal = byteStream.readSignedNumber(1);
...
@ -59,5 +60,20 @@ By default, numbers are unsigned, but `peekSignedNumber(n)` and `readSignedNumbe
### Appending to the Stream
If you get more bytes (for example, from an asynchronous process), you can add them to the end of the
byte stream by using `someByteStream.push(nextBytesAsAnArrayBuffer)`.
If you get more bytes (for example, from an asynchronous process), you can add them to the end of
the byte stream by using `someByteStream.push(nextBytesAsAnArrayBuffer)`.
### Forking / Teeing the stream.
If you have a need to seek ahead to a different section of the stream of bytes, and want to later
return to where you left off, you should use `tee()` method to make a copy of the ByteStream. This
will let you seek to the appropriate spot to grab some bytes.
```javascript
const byteStream = new ByteStream(someArrayBuffer);
const strLen = byteStream.readNumber(4); // Bytes 0-3.
const strOffset = byteStream.readNumber(4); // Bytes 4-7.
// Grab bytes at that offset...
const description = byteStream.tee().skip(offset).readString(strLen);
const someOtherVal = byteStream.readNumber(4); // Bytes 8-11
```