go-dpkg/dpkg/reader.go

package dpkg

import (
	"archive/tar"
	"fmt"
	"io"
	"path"

	"sirherobrine23.com.br/sirherobrine23/go-dpkg/ar"
	"sirherobrine23.com.br/sirherobrine23/go-dpkg/internal/descompress"
)

func tarReader(r io.Reader) (*tar.Reader, io.Closer, error) {
	tarballFile, err := descompress.Descompress(r)
	if err != nil {
		return nil, nil, err
	}
	return tar.NewReader(tarballFile), tarballFile, nil
}

// Parse a dpkg file and return a Dpkg struct and data.tar reader without compression
func ParseDpkg(r io.Reader) (*Dpkg, io.ReadCloser, error) {
	dpkgFile, err := ar.NewReader(r)
	if err != nil {
		return nil, nil, err
	}

	head, err := dpkgFile.Next()
	if err != nil {
		return nil, nil, err
	} else if head.Filename != "debian-binary" {
		return nil, nil, ErrInvalidDebian
	}
	dpkgFile.Read(make([]byte, 4))

	if head, err = dpkgFile.Next(); err != nil {
		return nil, nil, fmt.Errorf("cannot get control.tar: %s", err)
	} else if head.Filename[:11] != "control.tar" {
		return nil, nil, ErrInvalidDebian
	}

	controller, closerDescompress, err := tarReader(dpkgFile)
	if err != nil {
		return nil, nil, fmt.Errorf("cannot extract control.tar file: %s", err)
	}
	defer closerDescompress.Close()

	dpkg := &Dpkg{Pkg: &Package{}}
	for {
		head, err := controller.Next()
		if err != nil && err == io.EOF {
			break
		} else if err != nil {
			return nil, nil, fmt.Errorf("cannot get file header from control.tar: %s", err)
		}

		switch path.Base(head.Name) {
		case "control":
			header, err := io.ReadAll(controller)
			if err != nil {
				return nil, nil, err
			} else if err = dpkg.Pkg.UnmarshalBinary(header); err != nil {
				return nil, nil, err
			}
		case "postinst", "preinst", "prerm", "postrm":
			script, err := io.ReadAll(controller)
			if err != nil {
				return nil, nil, err
			} else if dpkg.Scripts == nil {
				dpkg.Scripts = &Scripts{}
			}
			switch path.Base(head.Name) {
			case "postinst":
				dpkg.Scripts.PostInstall = script
			case "preinst":
				dpkg.Scripts.PreInstall = script
			case "prerm":
				dpkg.Scripts.PostRemove = script
			case "postrm":
				dpkg.Scripts.PostRemove = script
			}
		case "old-postinst", "old-preinst", "old-prerm", "old-postrm":
			script, err := io.ReadAll(controller)
			if err != nil {
				return nil, nil, err
			} else if dpkg.OldScripts == nil {
				dpkg.OldScripts = &Scripts{}
			}
			switch path.Base(head.Name) {
			case "old-postinst":
				dpkg.OldScripts.PostInstall = script
			case "old-preinst":
				dpkg.OldScripts.PreInstall = script
			case "old-prerm":
				dpkg.OldScripts.PostRemove = script
			case "old-postrm":
				dpkg.OldScripts.PostRemove = script
			}
		case "new-postinst", "new-preinst", "new-prerm", "new-postrm":
			script, err := io.ReadAll(controller)
			if err != nil {
				return nil, nil, err
			} else if dpkg.NewScripts == nil {
				dpkg.NewScripts = &Scripts{}
			}
			switch path.Base(head.Name) {
			case "new-postinst":
				dpkg.NewScripts.PostInstall = script
			case "new-preinst":
				dpkg.NewScripts.PreInstall = script
			case "new-prerm":
				dpkg.NewScripts.PostRemove = script
			case "new-postrm":
				dpkg.NewScripts.PostRemove = script
			}
		default:
			if !head.FileInfo().Mode().IsDir() {
				io.Copy(io.Discard, controller)
			}
		}
	}

	if head, err = dpkgFile.Next(); err != nil {
		if err != io.EOF {
			return nil, nil, fmt.Errorf("cannot get data.tar: %s", err)
		}
		io.Copy(io.Discard, dpkgFile) // Ignore the last byte if the size is odd
		if head, err = dpkgFile.Next(); err != nil {
			return nil, nil, fmt.Errorf("cannot get data.tar: %s", err)
		}
	}

	if head.Filename[:8] != "data.tar" {
		return nil, nil, ErrInvalidDebian
	}

	dpkg.Ext = path.Ext(head.Filename)
	dpkg.Size = head.Size
	data, err := descompress.Descompress(dpkgFile)
	return dpkg, data, err
}