Subversion Repositories openrisc

// Copyright 2010 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package zip

import (
        "bufio"
        "compress/flate"
        "encoding/binary"
        "errors"
        "hash"
        "hash/crc32"
        "io"
        "io/ioutil"
        "os"
)

var (
        ErrFormat    = errors.New("zip: not a valid zip file")
        ErrAlgorithm = errors.New("zip: unsupported compression algorithm")
        ErrChecksum  = errors.New("zip: checksum error")
)

type Reader struct {
        r       io.ReaderAt
        File    []*File
        Comment string
}

type ReadCloser struct {
        f *os.File
        Reader
}

type File struct {
        FileHeader
        zipr         io.ReaderAt
        zipsize      int64
        headerOffset int64
}

func (f *File) hasDataDescriptor() bool {
        return f.Flags&0x8 != 0
}

// OpenReader will open the Zip file specified by name and return a ReadCloser.
func OpenReader(name string) (*ReadCloser, error) {
        f, err := os.Open(name)
        if err != nil {
                return nil, err
        }
        fi, err := f.Stat()
        if err != nil {
                f.Close()
                return nil, err
        }
        r := new(ReadCloser)
        if err := r.init(f, fi.Size()); err != nil {
                f.Close()
                return nil, err
        }
        r.f = f
        return r, nil
}

// NewReader returns a new Reader reading from r, which is assumed to
// have the given size in bytes.
func NewReader(r io.ReaderAt, size int64) (*Reader, error) {
        zr := new(Reader)
        if err := zr.init(r, size); err != nil {
                return nil, err
        }
        return zr, nil
}

func (z *Reader) init(r io.ReaderAt, size int64) error {
        end, err := readDirectoryEnd(r, size)
        if err != nil {
                return err
        }
        z.r = r
        z.File = make([]*File, 0, end.directoryRecords)
        z.Comment = end.comment
        rs := io.NewSectionReader(r, 0, size)
        if _, err = rs.Seek(int64(end.directoryOffset), os.SEEK_SET); err != nil {
                return err
        }
        buf := bufio.NewReader(rs)

        // The count of files inside a zip is truncated to fit in a uint16.
        // Gloss over this by reading headers until we encounter
        // a bad one, and then only report a ErrFormat or UnexpectedEOF if
        // the file count modulo 65536 is incorrect.
        for {
                f := &File{zipr: r, zipsize: size}
                err = readDirectoryHeader(f, buf)
                if err == ErrFormat || err == io.ErrUnexpectedEOF {
                        break
                }
                if err != nil {
                        return err
                }
                z.File = append(z.File, f)
        }
        if uint16(len(z.File)) != end.directoryRecords {
                // Return the readDirectoryHeader error if we read
                // the wrong number of directory entries.
                return err
        }
        return nil
}

// Close closes the Zip file, rendering it unusable for I/O.
func (rc *ReadCloser) Close() error {
        return rc.f.Close()
}

// Open returns a ReadCloser that provides access to the File's contents.
// Multiple files may be read concurrently.
func (f *File) Open() (rc io.ReadCloser, err error) {
        bodyOffset, err := f.findBodyOffset()
        if err != nil {
                return
        }
        size := int64(f.CompressedSize)
        if size == 0 && f.hasDataDescriptor() {
                // permit SectionReader to see the rest of the file
                size = f.zipsize - (f.headerOffset + bodyOffset)
        }
        r := io.NewSectionReader(f.zipr, f.headerOffset+bodyOffset, size)
        switch f.Method {
        case Store: // (no compression)
                rc = ioutil.NopCloser(r)
        case Deflate:
                rc = flate.NewReader(r)
        default:
                err = ErrAlgorithm
        }
        if rc != nil {
                rc = &checksumReader{rc, crc32.NewIEEE(), f, r}
        }
        return
}

type checksumReader struct {
        rc   io.ReadCloser
        hash hash.Hash32
        f    *File
        zipr io.Reader // for reading the data descriptor
}

func (r *checksumReader) Read(b []byte) (n int, err error) {
        n, err = r.rc.Read(b)
        r.hash.Write(b[:n])
        if err != io.EOF {
                return
        }
        if r.f.hasDataDescriptor() {
                if err = readDataDescriptor(r.zipr, r.f); err != nil {
                        return
                }
        }
        if r.hash.Sum32() != r.f.CRC32 {
                err = ErrChecksum
        }
        return
}

func (r *checksumReader) Close() error { return r.rc.Close() }

func readFileHeader(f *File, r io.Reader) error {
        var b [fileHeaderLen]byte
        if _, err := io.ReadFull(r, b[:]); err != nil {
                return err
        }
        c := binary.LittleEndian
        if sig := c.Uint32(b[:4]); sig != fileHeaderSignature {
                return ErrFormat
        }
        f.ReaderVersion = c.Uint16(b[4:6])
        f.Flags = c.Uint16(b[6:8])
        f.Method = c.Uint16(b[8:10])
        f.ModifiedTime = c.Uint16(b[10:12])
        f.ModifiedDate = c.Uint16(b[12:14])
        f.CRC32 = c.Uint32(b[14:18])
        f.CompressedSize = c.Uint32(b[18:22])
        f.UncompressedSize = c.Uint32(b[22:26])
        filenameLen := int(c.Uint16(b[26:28]))
        extraLen := int(c.Uint16(b[28:30]))
        d := make([]byte, filenameLen+extraLen)
        if _, err := io.ReadFull(r, d); err != nil {
                return err
        }
        f.Name = string(d[:filenameLen])
        f.Extra = d[filenameLen:]
        return nil
}

// findBodyOffset does the minimum work to verify the file has a header
// and returns the file body offset.
func (f *File) findBodyOffset() (int64, error) {
        r := io.NewSectionReader(f.zipr, f.headerOffset, f.zipsize-f.headerOffset)
        var b [fileHeaderLen]byte
        if _, err := io.ReadFull(r, b[:]); err != nil {
                return 0, err
        }
        c := binary.LittleEndian
        if sig := c.Uint32(b[:4]); sig != fileHeaderSignature {
                return 0, ErrFormat
        }
        filenameLen := int(c.Uint16(b[26:28]))
        extraLen := int(c.Uint16(b[28:30]))
        return int64(fileHeaderLen + filenameLen + extraLen), nil
}

// readDirectoryHeader attempts to read a directory header from r.
// It returns io.ErrUnexpectedEOF if it cannot read a complete header,
// and ErrFormat if it doesn't find a valid header signature.
func readDirectoryHeader(f *File, r io.Reader) error {
        var b [directoryHeaderLen]byte
        if _, err := io.ReadFull(r, b[:]); err != nil {
                return err
        }
        c := binary.LittleEndian
        if sig := c.Uint32(b[:4]); sig != directoryHeaderSignature {
                return ErrFormat
        }
        f.CreatorVersion = c.Uint16(b[4:6])
        f.ReaderVersion = c.Uint16(b[6:8])
        f.Flags = c.Uint16(b[8:10])
        f.Method = c.Uint16(b[10:12])
        f.ModifiedTime = c.Uint16(b[12:14])
        f.ModifiedDate = c.Uint16(b[14:16])
        f.CRC32 = c.Uint32(b[16:20])
        f.CompressedSize = c.Uint32(b[20:24])
        f.UncompressedSize = c.Uint32(b[24:28])
        filenameLen := int(c.Uint16(b[28:30]))
        extraLen := int(c.Uint16(b[30:32]))
        commentLen := int(c.Uint16(b[32:34]))
        // startDiskNumber := c.Uint16(b[34:36])    // Unused
        // internalAttributes := c.Uint16(b[36:38]) // Unused
        f.ExternalAttrs = c.Uint32(b[38:42])
        f.headerOffset = int64(c.Uint32(b[42:46]))
        d := make([]byte, filenameLen+extraLen+commentLen)
        if _, err := io.ReadFull(r, d); err != nil {
                return err
        }
        f.Name = string(d[:filenameLen])
        f.Extra = d[filenameLen : filenameLen+extraLen]
        f.Comment = string(d[filenameLen+extraLen:])
        return nil
}

func readDataDescriptor(r io.Reader, f *File) error {
        var b [dataDescriptorLen]byte
        if _, err := io.ReadFull(r, b[:]); err != nil {
                return err
        }
        c := binary.LittleEndian
        f.CRC32 = c.Uint32(b[:4])
        f.CompressedSize = c.Uint32(b[4:8])
        f.UncompressedSize = c.Uint32(b[8:12])
        return nil
}

func readDirectoryEnd(r io.ReaderAt, size int64) (dir *directoryEnd, err error) {
        // look for directoryEndSignature in the last 1k, then in the last 65k
        var b []byte
        for i, bLen := range []int64{1024, 65 * 1024} {
                if bLen > size {
                        bLen = size
                }
                b = make([]byte, int(bLen))
                if _, err := r.ReadAt(b, size-bLen); err != nil && err != io.EOF {
                        return nil, err
                }
                if p := findSignatureInBlock(b); p >= 0 {
                        b = b[p:]
                        break
                }
                if i == 1 || bLen == size {
                        return nil, ErrFormat
                }
        }

        // read header into struct
        c := binary.LittleEndian
        d := new(directoryEnd)
        d.diskNbr = c.Uint16(b[4:6])
        d.dirDiskNbr = c.Uint16(b[6:8])
        d.dirRecordsThisDisk = c.Uint16(b[8:10])
        d.directoryRecords = c.Uint16(b[10:12])
        d.directorySize = c.Uint32(b[12:16])
        d.directoryOffset = c.Uint32(b[16:20])
        d.commentLen = c.Uint16(b[20:22])
        d.comment = string(b[22 : 22+int(d.commentLen)])
        return d, nil
}

func findSignatureInBlock(b []byte) int {
        for i := len(b) - directoryEndLen; i >= 0; i-- {
                // defined from directoryEndSignature in struct.go
                if b[i] == 'P' && b[i+1] == 'K' && b[i+2] == 0x05 && b[i+3] == 0x06 {
                        // n is length of comment
                        n := int(b[i+directoryEndLen-2]) | int(b[i+directoryEndLen-1])<<8
                        if n+directoryEndLen+i == len(b) {
                                return i
                        }
                }
        }
        return -1
}