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util.go
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util.go
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// Package util implements various utility functions used within ipfs
// that do not currently have a better place to live.
package util
import (
"errors"
"io"
"math/rand"
"os"
"path/filepath"
"runtime/debug"
"strings"
"time"
b58 "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-base58"
ds "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-datastore"
mh "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multihash"
"github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/mitchellh/go-homedir"
)
// Debug is a global flag for debugging.
var Debug bool
// ErrNotImplemented signifies a function has not been implemented yet.
var ErrNotImplemented = errors.New("Error: not implemented yet.")
// ErrTimeout implies that a timeout has been triggered
var ErrTimeout = errors.New("Error: Call timed out.")
// ErrSeErrSearchIncomplete implies that a search type operation didnt
// find the expected node, but did find 'a' node.
var ErrSearchIncomplete = errors.New("Error: Search Incomplete.")
// ErrNotFound is returned when a search fails to find anything
var ErrNotFound = ds.ErrNotFound
// TildeExpansion expands a filename, which may begin with a tilde.
func TildeExpansion(filename string) (string, error) {
return homedir.Expand(filename)
}
// ErrCast is returned when a cast fails AND the program should not panic.
func ErrCast() error {
debug.PrintStack()
return errCast
}
var errCast = errors.New("cast error")
// ExpandPathnames takes a set of paths and turns them into absolute paths
func ExpandPathnames(paths []string) ([]string, error) {
var out []string
for _, p := range paths {
abspath, err := filepath.Abs(p)
if err != nil {
return nil, err
}
out = append(out, abspath)
}
return out, nil
}
type randGen struct {
rand.Rand
}
func NewTimeSeededRand() io.Reader {
src := rand.NewSource(time.Now().UnixNano())
return &randGen{
Rand: *rand.New(src),
}
}
func NewSeededRand(seed int64) io.Reader {
src := rand.NewSource(seed)
return &randGen{
Rand: *rand.New(src),
}
}
func (r *randGen) Read(p []byte) (n int, err error) {
for i := 0; i < len(p); i++ {
p[i] = byte(r.Rand.Intn(255))
}
return len(p), nil
}
// GetenvBool is the way to check an env var as a boolean
func GetenvBool(name string) bool {
v := strings.ToLower(os.Getenv(name))
return v == "true" || v == "t" || v == "1"
}
// MultiErr is a util to return multiple errors
type MultiErr []error
func (m MultiErr) Error() string {
if len(m) == 0 {
return "no errors"
}
s := "Multiple errors: "
for i, e := range m {
if i != 0 {
s += ", "
}
s += e.Error()
}
return s
}
func Partition(subject string, sep string) (string, string, string) {
if i := strings.Index(subject, sep); i != -1 {
return subject[:i], subject[i : i+len(sep)], subject[i+len(sep):]
}
return subject, "", ""
}
func RPartition(subject string, sep string) (string, string, string) {
if i := strings.LastIndex(subject, sep); i != -1 {
return subject[:i], subject[i : i+len(sep)], subject[i+len(sep):]
}
return subject, "", ""
}
// Hash is the global IPFS hash function. uses multihash SHA2_256, 256 bits
func Hash(data []byte) mh.Multihash {
h, err := mh.Sum(data, mh.SHA2_256, -1)
if err != nil {
// this error can be safely ignored (panic) because multihash only fails
// from the selection of hash function. If the fn + length are valid, it
// won't error.
panic("multihash failed to hash using SHA2_256.")
}
return h
}
// IsValidHash checks whether a given hash is valid (b58 decodable, len > 0)
func IsValidHash(s string) bool {
out := b58.Decode(s)
if out == nil || len(out) == 0 {
return false
}
_, err := mh.Cast(out)
if err != nil {
return false
}
return true
}
// XOR takes two byte slices, XORs them together, returns the resulting slice.
func XOR(a, b []byte) []byte {
c := make([]byte, len(a))
for i := 0; i < len(a); i++ {
c[i] = a[i] ^ b[i]
}
return c
}