pad.pub0.org/doc/api/changeset_library.md

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# Changeset Library
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The [changeset
library](https://github.com/ether/etherpad-lite/blob/develop/src/static/js/Changeset.js)
provides tools to create, read, and apply changesets.
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## Changeset
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```javascript
const Changeset = require('ep_etherpad-lite/static/js/Changeset');
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```
A changeset describes the difference between two revisions of a document. When a
user edits a pad, the browser generates and sends a changeset to the server,
which relays it to the other users and saves a copy (so that every past revision
is accessible).
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A transmitted changeset looks like this:
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```
'Z:z>1|2=m=b*0|1+1$\n'
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```
## Attribute Pool
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```javascript
const AttributePool = require('ep_etherpad-lite/static/js/AttributePool');
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```
Changesets do not include any attribute keyvalue pairs. Instead, they use
numeric identifiers that reference attributes kept in an [attribute
pool](https://github.com/ether/etherpad-lite/blob/develop/src/static/js/AttributePool.js).
This attribute interning reduces the transmission overhead of attributes that
are used many times.
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There is one attribute pool per pad, and it includes every current and
historical attribute used in the pad.
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## Further Reading
Detailed information about the changesets & Easysync protocol:
* [Easysync Protocol](https://github.com/ether/etherpad-lite/blob/develop/doc/easysync/easysync-notes.pdf)
* [Etherpad and EasySync Technical Manual](https://github.com/ether/etherpad-lite/blob/develop/doc/easysync/easysync-full-description.pdf)