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read.go
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/*
Copyright 2018 The pdfcpu 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
http://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.
*/
package pdfcpu
import (
"bufio"
"bytes"
"context"
"io"
"os"
"sort"
"strconv"
"strings"
"github.com/pdfcpu/pdfcpu/pkg/filter"
"github.com/pdfcpu/pdfcpu/pkg/log"
"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/model"
"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/scan"
"github.com/pdfcpu/pdfcpu/pkg/pdfcpu/types"
"github.com/pkg/errors"
)
const (
defaultBufSize = 1024
)
var (
ErrWrongPassword = errors.New("pdfcpu: please provide the correct password")
ErrCorruptHeader = errors.New("pdfcpu: no header version available")
ErrReferenceDoesNotExist = errors.New("pdfcpu: referenced object does not exist")
zero int64 = 0
)
// ReadFile reads in a PDF file and builds an internal structure holding its cross reference table aka the PDF model context.
func ReadFile(inFile string, conf *model.Configuration) (*model.Context, error) {
return ReadFileWithContext(context.Background(), inFile, conf)
}
// ReadFileContext reads in a PDF file and builds an internal structure holding its cross reference table aka the PDF model context.
// If the passed Go context is cancelled, reading will be interrupted.
func ReadFileWithContext(c context.Context, inFile string, conf *model.Configuration) (*model.Context, error) {
if log.InfoEnabled() {
log.Info.Printf("reading %s..\n", inFile)
}
f, err := os.Open(inFile)
if err != nil {
return nil, errors.Wrapf(err, "can't open %q", inFile)
}
defer func() {
f.Close()
}()
return ReadWithContext(c, f, conf)
}
// Read takes a readSeeker and generates a PDF model context,
// an in-memory representation containing a cross reference table.
func Read(rs io.ReadSeeker, conf *model.Configuration) (*model.Context, error) {
return ReadWithContext(context.Background(), rs, conf)
}
// Read takes a readSeeker and generates a PDF model context,
// an in-memory representation containing a cross reference table.
// If the passed Go context is cancelled, reading will be interrupted.
func ReadWithContext(c context.Context, rs io.ReadSeeker, conf *model.Configuration) (*model.Context, error) {
if log.ReadEnabled() {
log.Read.Println("Read: begin")
}
ctx, err := model.NewContext(rs, conf)
if err != nil {
return nil, err
}
if log.InfoEnabled() {
if ctx.Reader15 {
log.Info.Println("PDF Version 1.5 conforming reader")
} else {
log.Info.Println("PDF Version 1.4 conforming reader - no object streams or xrefstreams allowed")
}
}
// Populate xRefTable.
if err = readXRefTable(c, ctx); err != nil {
return nil, errors.Wrap(err, "Read: xRefTable failed")
}
// Make all objects explicitly available (load into memory) in corresponding xRefTable entries.
// Also decode any involved object streams.
if err = dereferenceXRefTable(c, ctx, conf); err != nil {
return nil, err
}
// Some PDFWriters write an incorrect Size into trailer.
if *ctx.XRefTable.Size < len(ctx.XRefTable.Table) {
*ctx.XRefTable.Size = len(ctx.XRefTable.Table)
}
if log.ReadEnabled() {
log.Read.Println("Read: end")
}
return ctx, nil
}
// fillBuffer reads from r until buf is full or read returns an error.
// Unlike io.ReadAtLeast fillBuffer does not return ErrUnexpectedEOF
// if an EOF happens after reading some but not all the bytes.
// Special thanks go to Rene Kaufmann.
func fillBuffer(r io.Reader, buf []byte) (int, error) {
var n int
var err error
for n < len(buf) && err == nil {
var nn int
nn, err = r.Read(buf[n:])
n += nn
}
if n > 0 && err == io.EOF {
return n, nil
}
return n, err
}
func newPositionedReader(rs io.ReadSeeker, offset *int64) (*bufio.Reader, error) {
if _, err := rs.Seek(*offset, io.SeekStart); err != nil {
return nil, err
}
if log.ReadEnabled() {
log.Read.Printf("newPositionedReader: positioned to offset: %d\n", *offset)
}
return bufio.NewReader(rs), nil
}
// Get the file offset of the last XRefSection.
// Go to end of file and search backwards for the first occurrence of startxref {offset} %%EOF
func offsetLastXRefSection(ctx *model.Context, skip int64) (*int64, error) {
rs := ctx.Read.RS
var (
prevBuf, workBuf []byte
bufSize int64 = 512
offset int64
)
if ctx.Read.FileSize < bufSize {
bufSize = ctx.Read.FileSize
}
for i := 1; offset == 0; i++ {
off, err := rs.Seek(-int64(i)*bufSize-skip, io.SeekEnd)
if err != nil {
return nil, errors.New("pdfcpu: can't find last xref section")
}
if log.ReadEnabled() {
log.Read.Printf("scanning for offsetLastXRefSection starting at %d\n", off)
}
curBuf := make([]byte, bufSize)
if _, err = fillBuffer(rs, curBuf); err != nil {
return nil, err
}
workBuf = curBuf
if prevBuf != nil {
workBuf = append(curBuf, prevBuf...)
}
j := strings.LastIndex(string(workBuf), "startxref")
if j == -1 {
prevBuf = curBuf
continue
}
p := workBuf[j+len("startxref"):]
posEOF := strings.Index(string(p), "%%EOF")
if posEOF == -1 {
return nil, errors.New("pdfcpu: no matching %%EOF for startxref")
}
p = p[:posEOF]
offset, err = strconv.ParseInt(strings.TrimSpace(string(p)), 10, 64)
if err != nil || offset >= ctx.Read.FileSize {
return nil, errors.New("pdfcpu: corrupted last xref section")
}
}
if log.ReadEnabled() {
log.Read.Printf("Offset last xrefsection: %d\n", offset)
}
return &offset, nil
}
func createXRefTableEntry(entryType string, objNr int, offset, offExtra int64, generation int) (model.XRefTableEntry, bool) {
entry := model.XRefTableEntry{Offset: &offset, Generation: &generation}
if entryType == "n" {
// in use object
if log.ReadEnabled() {
log.Read.Printf("createXRefTableEntry: Object #%d is in use at offset=%d, generation=%d\n", objNr, offset, generation)
}
if offset == 0 {
if log.InfoEnabled() {
log.Info.Printf("createXRefTableEntry: Skip entry for in use object #%d with offset 0\n", objNr)
}
return entry, false
}
*entry.Offset += offExtra
return entry, true
}
// free object
if log.ReadEnabled() {
log.Read.Printf("createXRefTableEntry: Object #%d is unused, next free is object#%d, generation=%d\n", objNr, offset, generation)
}
entry.Free = true
return entry, true
}
func decodeSubsection(fields []string, repairOff int) (int64, int, string, error) {
offset, err := strconv.ParseInt(fields[0], 10, 64)
if err != nil {
return 0, 0, "", err
}
offset += int64(repairOff)
generation, err := strconv.Atoi(fields[1])
if err != nil {
return 0, 0, "", err
}
entryType := fields[2]
if entryType != "f" && entryType != "n" {
return 0, 0, "", errors.New("pdfcpu: decodeSubsection: corrupt xref subsection entryType")
}
return offset, generation, entryType, nil
}
// Read next subsection entry and generate corresponding xref table entry.
func parseXRefTableEntry(xRefTable *model.XRefTable, s *bufio.Scanner, objNr int, offExtra int64, repairOff int) error {
if log.ReadEnabled() {
log.Read.Println("parseXRefTableEntry: begin")
}
line, err := scanLine(s)
if err != nil {
return err
}
if xRefTable.Exists(objNr) {
if log.ReadEnabled() {
log.Read.Printf("parseXRefTableEntry: end - Skip entry %d - already assigned\n", objNr)
}
return nil
}
fields := strings.Fields(line)
if len(fields) != 3 ||
len(fields[0]) != 10 || len(fields[1]) != 5 || len(fields[2]) != 1 {
return errors.New("pdfcpu: parseXRefTableEntry: corrupt xref subsection header")
}
offset, generation, entryType, err := decodeSubsection(fields, repairOff)
if err != nil {
return err
}
entry, ok := createXRefTableEntry(entryType, objNr, offset, offExtra, generation)
if !ok {
return nil
}
if log.ReadEnabled() {
log.Read.Printf("parseXRefTableEntry: Insert new xreftable entry for Object %d\n", objNr)
}
xRefTable.Table[objNr] = &entry
if log.ReadEnabled() {
log.Read.Println("parseXRefTableEntry: end")
}
return nil
}
// Process xRef table subsection and create corrresponding xRef table entries.
func parseXRefTableSubSection(xRefTable *model.XRefTable, s *bufio.Scanner, fields []string, offExtra int64, repairOff int) error {
if log.ReadEnabled() {
log.Read.Println("parseXRefTableSubSection: begin")
}
startObjNumber, err := strconv.Atoi(fields[0])
if err != nil {
return err
}
objCount, err := strconv.Atoi(fields[1])
if err != nil {
return err
}
if log.ReadEnabled() {
log.Read.Printf("detected xref subsection, startObj=%d length=%d\n", startObjNumber, objCount)
}
// Process all entries of this subsection into xRefTable entries.
for i := 0; i < objCount; i++ {
if err = parseXRefTableEntry(xRefTable, s, startObjNumber+i, offExtra, repairOff); err != nil {
return err
}
}
if log.ReadEnabled() {
log.Read.Println("parseXRefTableSubSection: end")
}
return nil
}
// Parse compressed object.
func compressedObject(c context.Context, s string) (types.Object, error) {
if log.ReadEnabled() {
log.Read.Println("compressedObject: begin")
}
o, err := model.ParseObjectContext(c, &s)
if err != nil {
return nil, err
}
d, ok := o.(types.Dict)
if !ok {
// return trivial Object: Integer, Array, etc.
if log.ReadEnabled() {
log.Read.Println("compressedObject: end, any other than dict")
}
return o, nil
}
streamLength, streamLengthRef := d.Length()
if streamLength == nil && streamLengthRef == nil {
// return Dict
if log.ReadEnabled() {
log.Read.Println("compressedObject: end, dict")
}
return d, nil
}
return nil, errors.New("pdfcpu: compressedObject: stream objects are not to be stored in an object stream")
}
// Parse all objects of an object stream and save them into objectStreamDict.ObjArray.
func parseObjectStream(c context.Context, osd *types.ObjectStreamDict) error {
if log.ReadEnabled() {
log.Read.Printf("parseObjectStream begin: decoding %d objects.\n", osd.ObjCount)
}
decodedContent := osd.Content
if decodedContent == nil {
// The actual content will be decoded lazily, only decode the prolog here.
var err error
decodedContent, err = osd.DecodeLength(int64(osd.FirstObjOffset))
if err != nil {
return err
}
}
prolog := decodedContent[:osd.FirstObjOffset]
// The separator used in the prolog shall be white space
// but some PDF writers use 0x00.
prolog = bytes.ReplaceAll(prolog, []byte{0x00}, []byte{0x20})
objs := strings.Fields(string(prolog))
if len(objs)%2 > 0 {
return errors.New("pdfcpu: parseObjectStream: corrupt object stream dict")
}
// e.g., 10 0 11 25 = 2 Objects: #10 @ offset 0, #11 @ offset 25
var objArray types.Array
var offsetOld int
for i := 0; i < len(objs); i += 2 {
if err := c.Err(); err != nil {
return err
}
offset, err := strconv.Atoi(objs[i+1])
if err != nil {
return err
}
offset += osd.FirstObjOffset
if i > 0 {
o := types.NewLazyObjectStreamObject(osd, offsetOld, offset, compressedObject)
objArray = append(objArray, o)
}
if i == len(objs)-2 {
o := types.NewLazyObjectStreamObject(osd, offset, -1, compressedObject)
objArray = append(objArray, o)
}
offsetOld = offset
}
osd.ObjArray = objArray
if log.ReadEnabled() {
log.Read.Println("parseObjectStream end")
}
return nil
}
func createXRefTableEntryFromXRefStream(entry byte, objNr int, c2, c3, offExtra int64, objStreams types.IntSet) model.XRefTableEntry {
var xRefTableEntry model.XRefTableEntry
switch entry {
case 0x00:
// free object
if log.ReadEnabled() {
log.Read.Printf("createXRefTableEntryFromXRefStream: Object #%d is unused, next free is object#%d, generation=%d\n", objNr, c2, c3)
}
g := int(c3)
xRefTableEntry =
model.XRefTableEntry{
Free: true,
Compressed: false,
Offset: &c2,
Generation: &g}
case 0x01:
// in use object
if log.ReadEnabled() {
log.Read.Printf("createXRefTableEntryFromXRefStream: Object #%d is in use at offset=%d, generation=%d\n", objNr, c2, c3)
}
g := int(c3)
c2 += offExtra
xRefTableEntry =
model.XRefTableEntry{
Free: false,
Compressed: false,
Offset: &c2,
Generation: &g}
case 0x02:
// compressed object
// generation always 0.
if log.ReadEnabled() {
log.Read.Printf("createXRefTableEntryFromXRefStream: Object #%d is compressed at obj %5d[%d]\n", objNr, c2, c3)
}
objNumberRef := int(c2)
objIndex := int(c3)
xRefTableEntry =
model.XRefTableEntry{
Free: false,
Compressed: true,
ObjectStream: &objNumberRef,
ObjectStreamInd: &objIndex}
objStreams[objNumberRef] = true
}
return xRefTableEntry
}
// For each object embedded in this xRefStream create the corresponding xRef table entry.
func extractXRefTableEntriesFromXRefStream(buf []byte, offExtra int64, xsd *types.XRefStreamDict, ctx *model.Context) error {
if log.ReadEnabled() {
log.Read.Printf("extractXRefTableEntriesFromXRefStream begin")
}
// Note:
// A value of zero for an element in the W array indicates that the corresponding field shall not be present in the stream,
// and the default value shall be used, if there is one.
// If the first element is zero, the type field shall not be present, and shall default to type 1.
i1 := xsd.W[0]
i2 := xsd.W[1]
i3 := xsd.W[2]
xrefEntryLen := i1 + i2 + i3
if log.ReadEnabled() {
log.Read.Printf("extractXRefTableEntriesFromXRefStream: begin xrefEntryLen = %d\n", xrefEntryLen)
}
if len(buf)%xrefEntryLen > 0 {
return errors.New("pdfcpu: extractXRefTableEntriesFromXRefStream: corrupt xrefstream")
}
objCount := len(xsd.Objects)
if log.ReadEnabled() {
log.Read.Printf("extractXRefTableEntriesFromXRefStream: objCount:%d %v\n", objCount, xsd.Objects)
log.Read.Printf("extractXRefTableEntriesFromXRefStream: len(buf):%d objCount*xrefEntryLen:%d\n", len(buf), objCount*xrefEntryLen)
}
if len(buf) < objCount*xrefEntryLen {
// Sometimes there is an additional xref entry not accounted for by "Index".
// We ignore such entries and do not treat this as an error.
return errors.New("pdfcpu: extractXRefTableEntriesFromXRefStream: corrupt xrefstream")
}
j := 0
// bufToInt64 interprets the content of buf as an int64.
bufToInt64 := func(buf []byte) (i int64) {
for _, b := range buf {
i <<= 8
i |= int64(b)
}
return
}
for i := 0; i < len(buf) && j < len(xsd.Objects); i += xrefEntryLen {
objNr := xsd.Objects[j]
i2Start := i + i1
c2 := bufToInt64(buf[i2Start : i2Start+i2])
c3 := bufToInt64(buf[i2Start+i2 : i2Start+i2+i3])
entry := createXRefTableEntryFromXRefStream(buf[i], objNr, c2, c3, offExtra, ctx.Read.ObjectStreams)
if ctx.XRefTable.Exists(objNr) {
if log.ReadEnabled() {
log.Read.Printf("extractXRefTableEntriesFromXRefStream: Skip entry %d - already assigned\n", objNr)
}
} else {
ctx.Table[objNr] = &entry
}
j++
}
if log.ReadEnabled() {
log.Read.Println("extractXRefTableEntriesFromXRefStream: end")
}
return nil
}
func xRefStreamDict(c context.Context, ctx *model.Context, o types.Object, objNr int, streamOffset int64) (*types.XRefStreamDict, error) {
d, ok := o.(types.Dict)
if !ok {
return nil, errors.New("pdfcpu: xRefStreamDict: no dict")
}
// Parse attributes for stream object.
streamLength, streamLengthObjNr := d.Length()
if streamLength == nil && streamLengthObjNr == nil {
return nil, errors.New("pdfcpu: xRefStreamDict: no \"Length\" entry")
}
filterPipeline, err := pdfFilterPipeline(c, ctx, d)
if err != nil {
return nil, err
}
// We have a stream object.
if log.ReadEnabled() {
log.Read.Printf("xRefStreamDict: streamobject #%d\n", objNr)
}
sd := types.NewStreamDict(d, streamOffset, streamLength, streamLengthObjNr, filterPipeline)
if err = loadEncodedStreamContent(c, ctx, &sd, false); err != nil {
return nil, err
}
// Decode xrefstream content
if err = saveDecodedStreamContent(nil, &sd, 0, 0, true); err != nil {
return nil, errors.Wrapf(err, "xRefStreamDict: cannot decode stream for obj#:%d\n", objNr)
}
return model.ParseXRefStreamDict(&sd)
}
func processXRefStream(ctx *model.Context, xsd *types.XRefStreamDict, objNr, genNr *int, offset *int64, offExtra int64) (prevOffset *int64, err error) {
if log.ReadEnabled() {
log.Read.Println("processXRefStream: begin")
}
if err = parseTrailer(ctx.XRefTable, xsd.Dict); err != nil {
return nil, err
}
// Parse xRefStream and create xRefTable entries for embedded objects.
if err = extractXRefTableEntriesFromXRefStream(xsd.Content, offExtra, xsd, ctx); err != nil {
return nil, err
}
*offset += offExtra
entry :=
model.XRefTableEntry{
Free: false,
Offset: offset,
Generation: genNr,
Object: *xsd}
if log.ReadEnabled() {
log.Read.Printf("processXRefStream: Insert new xRefTable entry for Object %d\n", *objNr)
}
ctx.Table[*objNr] = &entry
ctx.Read.XRefStreams[*objNr] = true
prevOffset = xsd.PreviousOffset
if log.ReadEnabled() {
log.Read.Println("processXRefStream: end")
}
return prevOffset, nil
}
// Parse xRef stream and setup xrefTable entries for all embedded objects and the xref stream dict.
func parseXRefStream(c context.Context, ctx *model.Context, rd io.Reader, offset *int64, offExtra int64) (prevOffset *int64, err error) {
if log.ReadEnabled() {
log.Read.Printf("parseXRefStream: begin at offset %d\n", *offset)
}
buf, endInd, streamInd, streamOffset, err := buffer(c, rd)
if err != nil {
return nil, err
}
if log.ReadEnabled() {
log.Read.Printf("parseXRefStream: endInd=%[1]d(%[1]x) streamInd=%[2]d(%[2]x)\n", endInd, streamInd)
}
line := string(buf)
// We expect a stream and therefore "stream" before "endobj" if "endobj" within buffer.
// There is no guarantee that "endobj" is contained in this buffer for large streams!
if streamInd < 0 || (endInd > 0 && endInd < streamInd) {
return nil, errors.New("pdfcpu: parseXRefStream: corrupt pdf file")
}
// Init object parse buf.
l := line[:streamInd]
objNr, genNr, err := model.ParseObjectAttributes(&l)
if err != nil {
return nil, err
}
// parse this object
if log.ReadEnabled() {
log.Read.Printf("parseXRefStream: xrefstm obj#:%d gen:%d\n", *objNr, *genNr)
log.Read.Printf("parseXRefStream: dereferencing object %d\n", *objNr)
}
o, err := model.ParseObjectContext(c, &l)
if err != nil {
return nil, errors.Wrapf(err, "parseXRefStream: no object")
}
if log.ReadEnabled() {
log.Read.Printf("parseXRefStream: we have an object: %s\n", o)
}
streamOffset += *offset
xsd, err := xRefStreamDict(c, ctx, o, *objNr, streamOffset)
if err != nil {
return nil, err
}
return processXRefStream(ctx, xsd, objNr, genNr, offset, offExtra)
}
// Parse an xRefStream for a hybrid PDF file.
func parseHybridXRefStream(c context.Context, ctx *model.Context, offset *int64, offExtra int64) error {
if log.ReadEnabled() {
log.Read.Println("parseHybridXRefStream: begin")
}
rd, err := newPositionedReader(ctx.Read.RS, offset)
if err != nil {
return err
}
if _, err = parseXRefStream(c, ctx, rd, offset, offExtra); err != nil {
return err
}
if log.ReadEnabled() {
log.Read.Println("parseHybridXRefStream: end")
}
return nil
}
func parseTrailerSize(xRefTable *model.XRefTable, d types.Dict) error {
i := d.Size()
if i == nil {
return errors.New("pdfcpu: parseTrailerSize: missing entry \"Size\"")
}
// Not reliable!
// Patched after all read in.
xRefTable.Size = i
return nil
}
func parseTrailerRoot(xRefTable *model.XRefTable, d types.Dict) error {
indRef := d.IndirectRefEntry("Root")
if indRef == nil {
return errors.New("pdfcpu: parseTrailerRoot: missing entry \"Root\"")
}
xRefTable.Root = indRef
if log.ReadEnabled() {
log.Read.Printf("parseTrailerRoot: Root object: %s\n", *xRefTable.Root)
}
return nil
}
func parseTrailerInfo(xRefTable *model.XRefTable, d types.Dict) error {
indRef := d.IndirectRefEntry("Info")
if indRef != nil {
xRefTable.Info = indRef
if log.ReadEnabled() {
log.Read.Printf("parseTrailerInfo: Info object: %s\n", *xRefTable.Info)
}
}
return nil
}
func parseTrailerID(xRefTable *model.XRefTable, d types.Dict) error {
arr := d.ArrayEntry("ID")
if arr != nil {
xRefTable.ID = arr
if log.ReadEnabled() {
log.Read.Printf("parseTrailerID: ID object: %s\n", xRefTable.ID)
}
return nil
}
if xRefTable.Encrypt != nil {
return errors.New("pdfcpu: parseTrailerID: missing entry \"ID\"")
}
return nil
}
// Parse trailer dict and return any offset of a previous xref section.
func parseTrailer(xRefTable *model.XRefTable, d types.Dict) error {
if log.ReadEnabled() {
log.Read.Println("parseTrailer begin")
}
if indRef := d.IndirectRefEntry("Encrypt"); indRef != nil {
xRefTable.Encrypt = indRef
if log.ReadEnabled() {
log.Read.Printf("parseTrailer: Encrypt object: %s\n", *xRefTable.Encrypt)
}
}
if xRefTable.Size == nil {
if err := parseTrailerSize(xRefTable, d); err != nil {
return err
}
}
if xRefTable.Root == nil {
if err := parseTrailerRoot(xRefTable, d); err != nil {
return err
}
}
if xRefTable.Info == nil {
if err := parseTrailerInfo(xRefTable, d); err != nil {
return err
}
}
if xRefTable.ID == nil {
if err := parseTrailerID(xRefTable, d); err != nil {
return err
}
}
if log.ReadEnabled() {
log.Read.Println("parseTrailerf end")
}
return nil
}
func scanForPreviousXref(ctx *model.Context, offset *int64) *int64 {
var (
prevBuf, workBuf []byte
bufSize int64 = 512
off int64
match1 []byte = []byte("startxref")
match2 []byte = []byte("xref")
)
m := match1
for i := int64(1); ; i++ {
off = *offset - i*bufSize
rd, err := newPositionedReader(ctx.Read.RS, &off)
if err != nil {
return nil
}
curBuf := make([]byte, bufSize)
n, err := fillBuffer(rd, curBuf)
if err != nil {
return nil
}
workBuf = curBuf
if prevBuf != nil {
workBuf = append(curBuf, prevBuf...)
}
j := bytes.LastIndex(workBuf, m)
if j == -1 {
if int64(n) < bufSize {
return nil
}
prevBuf = curBuf
continue
}
if bytes.Equal(m, match1) {
m = match2
continue
}
off += int64(j)
break
}
return &off
}
func handleAdditionalStreams(trailerDict types.Dict, xRefTable *model.XRefTable) {
arr := trailerDict.ArrayEntry("AdditionalStreams")
if arr == nil {
return
}
if log.ReadEnabled() {
log.Read.Printf("found AdditionalStreams: %s\n", arr)
}
a := types.Array{}
for _, value := range arr {
if indRef, ok := value.(types.IndirectRef); ok {
a = append(a, indRef)
}
}
xRefTable.AdditionalStreams = &a
}
func offsetPrev(ctx *model.Context, trailerDict types.Dict, offCurXRef *int64) *int64 {
offset := trailerDict.Prev()
if offset != nil {
if log.ReadEnabled() {
log.Read.Printf("offsetPrev: previous xref table section offset:%d\n", *offset)
}
if *offset == 0 {
offset = nil
if offCurXRef != nil {
if off := scanForPreviousXref(ctx, offCurXRef); off != nil {
offset = off
}
}
}
}
return offset
}
func parseTrailerDict(c context.Context, ctx *model.Context, trailerDict types.Dict, offCurXRef *int64, offExtra int64) (*int64, error) {
if log.ReadEnabled() {
log.Read.Println("parseTrailerDict begin")
}
xRefTable := ctx.XRefTable
if err := parseTrailer(xRefTable, trailerDict); err != nil {
return nil, err
}
handleAdditionalStreams(trailerDict, xRefTable)
offset := offsetPrev(ctx, trailerDict, offCurXRef)
offsetXRefStream := trailerDict.Int64Entry("XRefStm")
if offsetXRefStream == nil {
// No cross reference stream.
if !ctx.Reader15 && xRefTable.Version() >= model.V14 && !ctx.Read.Hybrid {
return nil, errors.Errorf("parseTrailerDict: PDF1.4 conformant reader: found incompatible version: %s", xRefTable.VersionString())
}
if log.ReadEnabled() {
log.Read.Println("parseTrailerDict end")
}
// continue to parse previous xref section, if there is any.
return offset, nil
}
// This file is using cross reference streams.
if !ctx.Read.Hybrid {
ctx.Read.Hybrid = true
ctx.Read.UsingXRefStreams = true
}
// 1.5 conformant readers process hidden objects contained
// in XRefStm before continuing to process any previous XRefSection.
// Previous XRefSection is expected to have free entries for hidden entries.
// May appear in XRefSections only.
if ctx.Reader15 {
if err := parseHybridXRefStream(c, ctx, offsetXRefStream, offExtra); err != nil {
return nil, err
}
}
if log.ReadEnabled() {
log.Read.Println("parseTrailerDict end")
}
return offset, nil
}
func scanLineRaw(s *bufio.Scanner) (string, error) {
if ok := s.Scan(); !ok {
if s.Err() != nil {
return "", s.Err()
}
return "", errors.New("pdfcpu: scanLineRaw: returning nothing")
}
return s.Text(), nil
}
func scanLine(s *bufio.Scanner) (s1 string, err error) {
for i := 0; i <= 1; i++ {
s1, err = scanLineRaw(s)
if err != nil {
return "", err
}
if len(s1) > 0 {
break
}
}
return s1, nil
}
func isDict(s string) (bool, error) {
o, err := model.ParseObject(&s)
if err != nil {
return false, err
}
_, ok := o.(types.Dict)
return ok, nil
}