Bitcoin/address validation: Difference between revisions
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return 0;
}</lang>
=={{header|Go}}==
{{trans|C}}
<lang go>package main
import (
"bytes"
"crypto/sha256"
"errors"
"os"
)
// With at least one other bitcoin RC task, this source is styled more like
// a package to show how functions of the two tasks might be combined into
// a single package. It turns out there's not really that much shared code,
// just the A25 type and doubleSHA256 method, but it's enough to suggest how
// the code might be organized. Types, methods, and functions are capitalized
// where they might be exported from a package.
// A25 is a type for a 25 byte (not base58 encoded) bitcoin address.
type A25 [25]byte
func (a *A25) Version() byte {
return a[0]
}
func (a *A25) EmbeddedChecksum() (c [4]byte) {
copy(c[:], a[21:])
return
}
// DoubleSHA256 computes a double sha256 hash of the first 21 bytes of the
// address. This is the one function shared with the other bitcoin RC task.
// Returned is the full 32 byte sha256 hash. (The bitcoin checksum will be
// the first four bytes of the slice.)
func (a *A25) doubleSHA256() []byte {
h := sha256.New()
h.Write(a[:21])
d := h.Sum([]byte{})
h = sha256.New()
h.Write(d)
return h.Sum(d[:0])
}
// ComputeChecksum returns a four byte checksum computed from the first 21
// bytes of the address. The embedded checksum is not updated.
func (a *A25) ComputeChecksum() (c [4]byte) {
copy(c[:], a.doubleSHA256())
return
}
// Tmpl and Set58 are adapted from the C solution.
// Go has big integers but this techinique seems better.
var tmpl = []byte("123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz")
// Set58 takes a base58 encoded address and decodes it into the receiver.
// Errors are returned if the argument is not valid base58 or if the decoded
// value does not fit in the 25 byte address. The address is not otherwise
// checked for validity.
func (a *A25) Set58(s []byte) error {
for _, s1 := range s {
c := bytes.IndexByte(tmpl, s1)
if c < 0 {
return errors.New("bad char")
}
for j := 24; j >= 0; j-- {
c += 58 * int(a[j])
a[j] = byte(c % 256)
c /= 256
}
if c > 0 {
return errors.New("too long")
}
}
return nil
}
// ValidA58 validates a base58 encoded bitcoin address. An address is valid
// if it can be decoded into a 25 byte address, the version number is 0,
// and the checksum validates. Return value ok will be true for valid
// addresses. If ok is false, the address is invalid and the error value
// may indicate why.
func ValidA58(a58 []byte) (ok bool, err error) {
var a A25
if err := a.Set58(a58); err != nil {
return false, err
}
if a.Version() != 0 {
return false, errors.New("not version 0")
}
return a.EmbeddedChecksum() == a.ComputeChecksum(), nil
}
// Program returns exit code 0 with valid address and produces no output.
// Otherwise exit code is 1 and a message is written to stderr.
func main() {
if len(os.Args) != 2 {
errorExit("Usage: valid <base58 address>")
}
switch ok, err := ValidA58([]byte(os.Args[1])); {
case ok:
case err == nil:
errorExit("Invalid")
default:
errorExit(err.Error())
}
}
func errorExit(m string) {
os.Stderr.WriteString(m + "\n")
os.Exit(1)
}</lang>
{{out}}
Command line usage examples showing program exit status.
<pre>
> valid ; echo $status
Usage: valid <base58 address>
1
> valid 1 1 ; echo $status
Usage: valid <base58 address>
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62i ; echo $status
0
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62j ; echo $status
Invalid
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62! ; echo $status
bad char
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62iz ; echo $status
not version 0
1
> valid 1AGNa15ZQXAZUgFiqJ2i7Z2DPU2J6hW62izz ; echo $status
too long
1
</pre>
=={{header|Perl}}==
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