git-blob-stream

git-blob-stream

WARNING This package is still under active development, I reserve the right to change anything until 0.1.0 is released. At that point I'll go all SemVer and everything.

This npm package makes it easy and efficient to read and write Git blob files using node.js Stream2 streams. It has no dependencies on command line git or native code git libraries; instead using crypto and compression libraries already built into node.js.

Installation

npm install git-blob-stream
 
# To run tests from within the package directory 
npm install && npm test

Usage

To read a blob file:

var fs = require('fs');
var gbs = require('git-blob-stream');
 
var input = fs.createReadStream("filename.blob");
var output = fs.createWriteStream("filename");
 
var headerFunc = function (err, ret) {
  // ret is an object:
  // { size: <blobDataLength>, type: <blobType> }
};
 
var xformStream = gbs.blobReader({
    noOutput: false    // Default, if true, no data will be readable
  },
  headerFunc);      // callback is optional
 
// Decode the file...
input.pipe(xformStream).pipe(output);
 
output.on('close', function () {
  // All done
});

To write a blob file:

var fs = require('fs');
var gbs = require('git-blob-stream');
 
var input = fs.createReadStream("filename");
var output = fs.createWriteStream("filename.blob");
 
var hashFunc = function (err, ret) {
  // ret is an object:
  // { size: <blobDataLength>, hash: <hashValue> }
  // hashValue is a hex string of the 20 byte SHA1 sum
}
 
// All options are manditory!
var xformStream = gbs.blobWriter({
  size: fs.statSync("filename").size,  // Optional, but more efficient if provided!
  type: "blob",                        // Default, or "tree", "tag" or "commit"
  noOutput: false                      // Default, if true, no data will be written
  },
  hashFunc); // callback is optional
 
// Write the file. hashCallback will be called when finished
input.pipe(xformStream).pipe(output);
 
output.on('close', function () {
  // All done
});

Higher level git objects

In addition to blobs, this package can also stream to/from js-git style tree, commit and tag objects.

To read a tree blob file:

var fs = require('fs');
var gbs = require('git-blob-stream');
var input = fs.createReadStream("tree.blob");
 
var callback = function (err, ret) {
  // ret is a tree object
}
 
var xformStream = gbs.treeReader(callback); // callback is optional
 
// Decode the file...
output = input.pipe(xformStream);
 
// If a callback is not provided to treeReader, then it writes its output
// as an object to the stream output
// output.on('data', function (data) {
//   // data is a tree object
//   // This will only be called once
// });
//
// output.on('end', function () {
//   // All done
// });

To write a tree blob file:

var fs = require('fs');
var gbs = require('git-blob-stream');
 
var output = fs.createWriteStream("tree.blob");
 
var hashFunc = function (ret) {
  // ret is an object:
  // { size: <blobDataLength>, hash: <hashValue>, tree: <normalizedTreeObj>}
  // hashValue is a hex string of the 20 byte SHA1 sum
  // normalizedTreeObj is the actual tree object that would be read back, as
  // normalized to git standard form (canonical sorting, missing fields added)
}
 
// All options are manditory!
var xformStream = gbs.treeWriter(
  {
    'greetings.txt' : { mode: gbs.gitModes.file, hash: fileHash }
  },
  hashFunc); // callback is optional
 
// Write the file. hashCallback will be called when finished
xformStream.pipe(output);
 
output.on('close', function () {
  // All done
});

Analogous calls for reading/writing commits and (annotated) tags also exist: commitReader, commitWriter, tagReader, tagWriter. All assume js-git style objects.

Enjoy!