| // Copyright 2017 The Wuffs Authors. |
| // |
| // Licensed under the Apache License, Version 2.0 (the "License"); |
| // you may not use this file except in compliance with the License. |
| // You may obtain a copy of the License at |
| // |
| // https://www.apache.org/licenses/LICENSE-2.0 |
| // |
| // Unless required by applicable law or agreed to in writing, software |
| // distributed under the License is distributed on an "AS IS" BASIS, |
| // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| // See the License for the specific language governing permissions and |
| // limitations under the License. |
| |
| //go:build ignore |
| // +build ignore |
| |
| package main |
| |
| // checksum.go prints a checksum of stdin's bytes, or of the opening digits of |
| // π. Checksum algorithms include "adler32" and "crc32/ieee". |
| // |
| // Usage: go run checksum.go -algorithm=crc32/ieee < foo.bar |
| |
| import ( |
| "flag" |
| "fmt" |
| "hash" |
| "hash/adler32" |
| "hash/crc32" |
| "io" |
| "os" |
| "strings" |
| ) |
| |
| var ( |
| algorithm = flag.String("algorithm", "adler32", "checksum algorithm") |
| pi = flag.Bool("pi", false, "checksum the digits of pi instead of stdin") |
| ) |
| |
| func main() { |
| if err := main1(); err != nil { |
| os.Stderr.WriteString(err.Error() + "\n") |
| os.Exit(1) |
| } |
| } |
| |
| func main1() error { |
| flag.Parse() |
| |
| if *pi { |
| const digits = "3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170" |
| if len(digits) != 99 { |
| panic("bad len(digits)") |
| } |
| for i := 0; i < 100; i++ { |
| if err := do(strings.NewReader(digits[:i])); err != nil { |
| return err |
| } |
| fmt.Print(",") |
| if i&7 == 7 { |
| fmt.Println() |
| } |
| } |
| } else { |
| if err := do(os.Stdin); err != nil { |
| return err |
| } |
| fmt.Println() |
| } |
| return nil |
| } |
| |
| func do(r io.Reader) error { |
| h := io.Writer(nil) |
| switch *algorithm { |
| case "adler32": |
| h = adler32.New() |
| case "crc32/ieee": |
| h = crc32.NewIEEE() |
| default: |
| return fmt.Errorf("unknown algorithm %q", *algorithm) |
| } |
| |
| if _, err := io.Copy(h, r); err != nil { |
| return err |
| } |
| |
| switch h := h.(type) { |
| case hash.Hash32: |
| fmt.Printf("0x%08X", h.Sum32()) |
| case hash.Hash64: |
| fmt.Printf("0x%016X", h.Sum64()) |
| default: |
| return fmt.Errorf("algorithm %q is not a Hash32 or Hash64", *algorithm) |
| } |
| return nil |
| } |