1 files changed, 143 insertions, 0 deletions
diff --git a/internal/slackware_com/checksums.go b/internal/slackware_com/checksums.go
new file mode 100644
index 0000000..643e204
--- /dev/null
+++ b/internal/slackware_com/checksums.go
@@ -0,0 +1,143 @@
+package slackware_com
+
+import (
+	"bufio"
+	"bytes"
+	"crypto/md5"
+	"errors"
+	"fmt"
+	"hash"
+	"io"
+	"os"
+	"path"
+	"strings"
+)
+
+var checksumsHeader = strings.TrimSpace(`
+These are the MD5 message digests for the files in this directory.
+If you want to test your files, use 'md5sum' and compare the values to
+the ones listed here.
+
+To test all these files, use this command:
+
+tail +13 CHECKSUMS.md5 | md5sum -c --quiet - | less
+
+'md5sum' can be found in the GNU coreutils package on ftp.gnu.org in
+/pub/gnu, or at any GNU mirror site.
+
+MD5 message digest                Filename
+`)
+
+type ChecksumsEntry struct {
+	MD5      string
+	Filename string
+}
+
+type Checksums struct {
+	Entries []ChecksumsEntry
+}
+
+func OpenChecksums(filePath string) (*Checksums, error) {
+	f, err := os.Open(filePath)
+	if err != nil {
+		return nil, err
+	}
+
+	buf, err := io.ReadAll(f)
+	if err != nil {
+		return nil, err
+	}
+
+	var checksums Checksums
+	err = checksums.UnmarshalText(buf)
+	if err != nil {
+		return nil, err
+	}
+
+	return &checksums, nil
+}
+
+func (c *Checksums) Hash() hash.Hash {
+	return md5.New()
+}
+
+func (c *Checksums) UnmarshalText(buf []byte) error {
+	r := bufio.NewReader(bytes.NewReader(buf))
+
+	for _, headerLine := range strings.Split(checksumsHeader, "\n") {
+		line, _, err := r.ReadLine()
+		if err != nil {
+			return err
+		}
+
+		if string(line) != headerLine {
+			println(string(line))
+			println(headerLine)
+			return errors.New("unexpected format")
+		}
+	}
+
+	for {
+		line, _, err := r.ReadLine()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+
+		fields := strings.Split(string(line), "  ")
+		if len(fields) != 2 {
+			return errors.New("unexpected format")
+		}
+		c.Entries = append(c.Entries, ChecksumsEntry{
+			MD5:      fields[0],
+			Filename: fields[1],
+		})
+	}
+
+	return nil
+}
+
+func (c *Checksums) HasFilePath(filePath string) bool {
+	filePath = path.Clean(filePath)
+	for _, entry := range c.Entries {
+		if entry.Filename == "./"+filePath {
+			return true
+		}
+	}
+	return false
+}
+
+func (c *Checksums) Files() []string {
+	var entries []string
+
+	for _, entry := range c.Entries {
+		entries = append(entries, entry.Filename)
+	}
+
+	return entries
+}
+
+func (c *Checksums) String() string {
+	str := strings.TrimSpace(checksumsHeader)
+
+	for _, entry := range c.Entries {
+		line := fmt.Sprintf("%s  %s", entry.MD5, entry.Filename)
+		str = str + "\n" + line
+	}
+
+	return str
+}
+
+func (c *Checksums) Verify(fileName string, sum []byte) (bool, error) {
+	fileName = path.Clean(fileName)
+	sumStr := fmt.Sprintf("%x", sum)
+
+	for _, entry := range c.Entries {
+		if entry.Filename == "./"+fileName {
+			return entry.MD5 == sumStr, nil
+		}
+	}
+
+	return false, errors.New("not found")
+}