Contains the Concourse pipeline definition for building a line-server container
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package helpers
import (
"bytes"
"encoding/hex"
"io"
"unicode"
"github.com/andreimarcu/linx-server/backends"
"github.com/minio/sha256-simd"
"gopkg.in/h2non/filetype.v1"
)
func GenerateMetadata(r io.Reader) (m backends.Metadata, err error) {
// Since we don't have the ability to seek within a file, we can use a
// Buffer in combination with a TeeReader to keep a copy of the bytes
// we read when detecting the file type. These bytes are still needed
// to hash the file and determine its size and cannot be discarded.
var buf bytes.Buffer
teeReader := io.TeeReader(r, &buf)
// Get first 512 bytes for mimetype detection
header := make([]byte, 512)
_, err = teeReader.Read(header)
if err != nil {
return
}
// Create a Hash and a MultiReader that includes the Buffer we created
// above along with the original Reader, which will have the rest of
// the file.
hasher := sha256.New()
multiReader := io.MultiReader(&buf, r)
// Copy everything into the Hash, then use the number of bytes written
// as the file size.
var readLen int64
readLen, err = io.Copy(hasher, multiReader)
if err != nil {
return
} else {
m.Size += readLen
}
// Get the hex-encoded string version of the Hash checksum
m.Sha256sum = hex.EncodeToString(hasher.Sum(nil))
// Use the bytes we extracted earlier and attempt to determine the file
// type
kind, err := filetype.Match(header)
if err != nil {
m.Mimetype = "application/octet-stream"
return m, err
} else if kind.MIME.Value != "" {
m.Mimetype = kind.MIME.Value
} else if printable(header) {
m.Mimetype = "text/plain"
} else {
m.Mimetype = "application/octet-stream"
}
return
}
func printable(data []byte) bool {
for i, b := range data {
r := rune(b)
// A null terminator that's not at the beginning of the file
if r == 0 && i == 0 {
return false
} else if r == 0 && i < 0 {
continue
}
if r > unicode.MaxASCII {
return false
}
}
return true
}