// Generates an index from a reader
// This is mostly a utility function to avoid being overly verbose in tests that need
// an index to work, but don't want to construct one by hand in order to avoid the dependencies
// obviously this means that those tests are likely to fail if there are issues with any of the other
// modules, which is not ideal.
// TODO: move to util?
func BuildChecksumIndex(check *filechecksum.FileChecksumGenerator, r io.Reader) (
fcheck []byte,
i *index.ChecksumIndex,
lookup filechecksum.ChecksumLookup,
err error,
) {
b := bytes.NewBuffer(nil)
fcheck, err = check.GenerateChecksums(r, b)
if err != nil {
return
}
weakSize := check.WeakRollingHash.Size()
strongSize := check.GetStrongHash().Size()
readChunks, err := chunks.LoadChecksumsFromReader(b, weakSize, strongSize)
if err != nil {
return
}
i = index.MakeChecksumIndex(readChunks)
lookup = chunks.StrongChecksumGetter(readChunks)
return
}
func ExampleFileChecksumGenerator_LoadChecksumsFromReader() {
const BLOCKSIZE = 8096
checksum := NewFileChecksumGenerator(BLOCKSIZE)
// This could be any source that conforms to io.Reader
// sections of a file, or the body of an http response
file1, err := os.Open("fileChecksums.chk")
if err != nil {
return
}
defer file1.Close()
ws, ss := checksum.GetChecksumSizes()
checksums, err := chunks.LoadChecksumsFromReader(file1, ws, ss)
if err != nil {
return
}
// Make an index that we can use against our local
// checksums
i := index.MakeChecksumIndex(checksums)
// example checksum from a local file
// look for the chunk in the index
i.FindWeakChecksumInIndex([]byte("a"))
}
func readIndex(r io.Reader, blocksize uint) (
i *index.ChecksumIndex,
checksumLookup filechecksum.ChecksumLookup,
blockCount uint,
err error,
) {
generator := filechecksum.NewFileChecksumGenerator(blocksize)
readChunks, e := chunks.LoadChecksumsFromReader(
r,
generator.WeakRollingHash.Size(),
generator.StrongHash.Size(),
)
err = e
if err != nil {
return
}
checksumLookup = chunks.StrongChecksumGetter(readChunks)
i = index.MakeChecksumIndex(readChunks)
blockCount = uint(len(readChunks))
return
}