add more algo

commands/crc32/crc32.go

@@ -0,0 +1,83 @@
+package crc32
+
+import (
+	"context"
+	"flag"
+	"fmt"
+	"hash/crc32"
+	"hash_utils/tools"
+	"os"
+
+	"github.com/google/subcommands"
+)
+
+type (
+	CRC32Cmd struct {
+		file  string
+		table string
+	}
+)
+
+func (*CRC32Cmd) Name() string     { return "crc32" }
+func (*CRC32Cmd) Synopsis() string { return "" }
+func (*CRC32Cmd) Usage() string {
+	return `Usage: hash_utils crc32
+
+Algorithm available:
+  - Castagnoli
+  - Koopman
+  - IEEE
+
+Options:
+`
+}
+
+func (p *CRC32Cmd) SetFlags(f *flag.FlagSet) {
+	f.StringVar(&p.file, "file", "", "get the checksum of a file")
+	f.StringVar(&p.table, "table", "IEEE", "Predefined CRC-32 algorithms")
+}
+
+func (p *CRC32Cmd) Execute(ctx context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	var err error
+	var param uint32 = crc32.IEEE
+	if len(p.table) > 0 {
+		param, err = parse(p.table)
+		if err != nil {
+			fmt.Printf("Available tables: IEEE Castagnoli Koopman")
+			return subcommands.ExitFailure
+		}
+	}
+
+	if len(p.file) > 0 {
+		b, err := os.ReadFile(p.file)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "error: failed to read file:", err)
+			return subcommands.ExitFailure
+		}
+
+		h := tools.CRC32(b, param)
+
+		fmt.Printf("%s: %s\n", f.Name(), h)
+
+		return subcommands.ExitSuccess
+	}
+
+	for _, arg := range f.Args() {
+		h := tools.CRC32([]byte(arg), param)
+		fmt.Printf("%s: %s\n", arg, h)
+	}
+
+	return subcommands.ExitSuccess
+}
+
+func parse(tableName string) (uint32, error) {
+	switch tableName {
+	case "Castagnoli":
+		return crc32.Castagnoli, nil
+	case "Koopman":
+		return crc32.Koopman, nil
+	case "IEEE":
+		return crc32.IEEE, nil
+	}
+	return 0, fmt.Errorf("invalid table name: %s", tableName)
+}