replace-in-zipfile
v1.0.2
Published
Put a placeholder file into a zipfile and replace it with new content while streaming
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replace-in-zipfile
Put a placeholder file into a zipfile and replace it later. Supports streaming!
You can use any filename for your placeholder file. The matching is performed using the filesize and the file's CRC32. (Yes, there's a chance of checksum collision here!)
A tool called make-magic
is provided to create high entropy placeholder data.
Command line usage
# create a placeholder whith high entropy
make-magic 512 > data/magic
# and put it into a zipfile along with other files
echo "Stuff" > data/stuff
zip -r data data
# you can now replace the magic data with any other content
echo "HEY!" | replace-in-zipfile data.zip data/magic > unpack/new.zip
# Let's unpack the new zipfile to see if it worked!
cd unpack
unzip new.zip
cd data
cat magic # displays "Hey!"
Javascript usage
const fs = require('fs')
const concat = require('concat-stream')
const replaceFileInzip = require('../replace-file-in-zip')
if (process.argv.length<4) {
console.error(`usage: ${process.argv[1]} <zip-file> <magic-file>`)
console.error('(data read from stdin will replace magic file data in the zip-file)')
process.exit(1)
}
const zipFileName = process.argv[2]
const magicFileName = process.argv[3]
const magicData = fs.readFileSync(magicFileName)
process.stdin.pipe(concat(function (newContent) {
fs.createReadStream(zipFileName)
.pipe( replaceFileInzip(magicData, newContent) )
.pipe(process.stdout)
}))