forked from jung-kurt/gofpdf
/
load.go
388 lines (344 loc) · 8.54 KB
/
load.go
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/*
* Copyright (c) 2017 Jerry Caligiure (Gmail: caligiure.ja)
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
package gofpdf
import (
"bytes"
"errors"
"fmt"
"io"
"os"
"strconv"
)
//Load takes in a pdf at path filePath and returns a *Fpdf
//
// filePath can be either an absolute file path or relative to the running
// program.
//
// *Fpdf is as close to the original pdf as possible. Probably needs more real
// world testing to get everything right. Feel free to improve this or propose
// improvements on the github.
func Load(filePath string) (f *Fpdf, err error) {
var reader pdfReader
if err = reader.openFile(filePath); err != nil {
return nil, err
}
if err = reader.parseXRefTable(); err != nil {
return nil, err
}
f, err = reader.buildFpdf()
if err != nil {
return nil, err
}
if err = reader.closeFile(); err != nil {
return nil, err
}
return f, nil
}
type pdfReader struct {
file *os.File
recentReading []byte
cursorAt int64
recentDict map[string]interface{}
pdfVersion byte
inStrEsc bool
xrefOffset int64
xrefTable xref
}
var whiteSpaceChars = []byte{0, //Null
9, //Horizontal Tab
10, //Line Feed
12, //Form Feed
13, //Carriage return
32} //Space
var delimiterChars = []byte{40, //left parenthesis
41, //right parenthesis
60, //less than sign
62, //greater than sign
91, //left square bracket
93, //right square bracket
123, //left curly brace
125, //right curly brace
47, //Solidus
37} //percent
func (r *pdfReader) openFile(filePath string) error {
f, err := os.Open(filePath)
if err != nil {
return err
}
r.file = f
if err = r.pdfReadAt(0, false, true); err != nil {
return err
}
if !bytes.HasPrefix(r.recentReading, []byte("%PDF-1.")) {
return errors.New("malformed PDF header")
}
r.pdfVersion = r.recentReading[7]
if r.pdfVersion < '0' || r.pdfVersion > '7' {
return errors.New("version incompatible with this reader")
}
if err = r.pdfReadAt(r.pdfSize(), true, true); err != nil {
return err
}
if !bytes.HasPrefix(r.recentReading, []byte("FOE%%")) {
fmt.Println(r.recentReading)
return errors.New("malformed PDF footer")
}
if err = r.pdfReadAt(r.cursorAt, true, false); err != nil {
return err
}
r.xrefOffset, err = strconv.ParseInt(string(reverseByteSlice(r.recentReading)),
10, 64)
if err != nil {
return err
}
r.recentDict = make(map[string]interface{})
return nil
}
type xref struct {
objStart, objEnd int
objTable []xrefObjData
trailer map[string]interface{}
}
type xrefObjData struct {
offset, generationNumber, objNum int
inUse bool
}
type objReference struct {
objNum, generationNum int
}
func (r *pdfReader) closeFile() error {
return r.file.Close()
}
func (r *pdfReader) pdfSize() int64 {
fileInfo, _ := r.file.Stat()
return fileInfo.Size()
}
func (r *pdfReader) pdfReadAt(readOffset int64, readBackwards, headfoot bool) error {
var reading []byte
r.cursorAt = readOffset
buf := make([]byte, 1)
for {
_, err := r.file.ReadAt(buf, r.cursorAt)
if err != nil && err != io.EOF {
return err
}
ck := isInByteArr(buf[0], delimiterChars)
if !headfoot {
if ck && len(reading) != 0 {
r.recentReading = reading
return nil
}
}
if readBackwards {
r.cursorAt--
} else {
r.cursorAt++
}
ck = isInByteArr(buf[0], whiteSpaceChars)
if ck && len(reading) == 0 {
continue
}
if ck {
r.recentReading = reading
return nil
}
reading = append(reading, buf[0])
if err == io.EOF {
r.recentReading = reading
return nil
}
}
}
func isInByteArr(b byte, arr []byte) bool {
for _, val := range arr {
if b == val {
return true
}
}
return false
}
func reverseByteSlice(in []byte) []byte {
for i := 0; i < len(in)/2; i++ {
j := len(in) - i - 1
in[i], in[j] = in[j], in[i]
}
return in
}
const (
objNumStart int = iota
objNumEnd
objTabCol1
objTabCol2
objTabCol3
trailerPart
)
func (r *pdfReader) parseXRefTable() error {
err := r.pdfReadAt(r.xrefOffset, false, false)
if err != nil {
return err
}
if bytes.Compare(r.recentReading, []byte("xref")) != 0 {
errors.New("malformed pdf: xref offset was incorrect")
}
part := objNumStart
var objRow xrefObjData
var objNum int
for bytes.Compare(r.recentReading, []byte("startxref")) != 0 {
err = r.pdfReadAt(r.cursorAt, false, false)
if err != nil {
return err
}
if bytes.Compare(r.recentReading, []byte("trailer")) == 0 {
part = trailerPart
}
switch part {
case objNumStart:
start, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return err
}
r.xrefTable.objStart = start
objNum = r.xrefTable.objStart
part = objNumEnd
case objNumEnd:
end, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return err
}
r.xrefTable.objEnd = end
part = objTabCol1
case objTabCol1:
objRow = xrefObjData{}
objRow.objNum = objNum
objNum++
offset, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return err
}
objRow.offset = offset
part = objTabCol2
case objTabCol2:
genNum, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return err
}
objRow.generationNumber = genNum
part = objTabCol3
case objTabCol3:
if bytes.Compare(r.recentReading, []byte("f")) == 0 {
objRow.inUse = false
} else if bytes.Compare(r.recentReading, []byte("n")) == 0 {
objRow.inUse = true
} else {
return errors.New("malformed xref table third col can be only f or n")
}
r.xrefTable.objTable = append(r.xrefTable.objTable, objRow)
part = objTabCol1
case trailerPart:
r.pdfReadAt(r.cursorAt, false, false)
err := r.parsePDFDict()
if err != nil {
return err
}
r.xrefTable.trailer = r.recentDict
}
}
return nil
}
func (r *pdfReader) parsePDFDict() error {
if !bytes.HasPrefix(r.recentReading, []byte("<")) {
return errors.New("expected pdf dictionary")
}
r.pdfReadAt(r.cursorAt, false, false)
if !bytes.HasPrefix(r.recentReading, []byte("<")) {
return errors.New("expected pdf dictionary")
}
r.pdfReadAt(r.cursorAt, false, false)
atKey := true
cK := ""
for !bytes.HasSuffix(r.recentReading, []byte(">")) {
if atKey {
key, err := r.parsePDFObject()
if err != nil {
return err
}
cK = key.(string)
atKey = false
} else {
val, err := r.parsePDFObject()
if err != nil {
return err
}
r.recentDict[cK] = val
atKey = true
}
r.pdfReadAt(r.cursorAt, false, false)
}
r.pdfReadAt(r.cursorAt, false, false)
if !bytes.HasPrefix(r.recentReading, []byte(">")) {
return errors.New("pdf dictionary ending malformed")
}
r.pdfReadAt(r.cursorAt, false, false)
return nil
}
func (r *pdfReader) parsePDFObject() (interface{}, error) {
switch {
case bytes.HasPrefix(r.recentReading, []byte("/")):
return string(r.recentReading[1:len(r.recentReading)]), nil
case byte('0') <= r.recentReading[0] && byte('9') >= r.recentReading[0]:
peek, err := r.peek()
if err != nil {
return nil, err
}
if isInByteArr(peek[0], delimiterChars) {
if bytes.ContainsRune(r.recentReading, '.') {
return strconv.ParseFloat(string(r.recentReading), 32)
}
return strconv.Atoi(string(r.recentReading))
}
var retObj objReference
num, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return nil, err
}
retObj.objNum = num
r.pdfReadAt(r.cursorAt, false, false)
gen, err := strconv.Atoi(string(r.recentReading))
if err != nil {
return nil, err
}
retObj.generationNum = gen
r.pdfReadAt(r.cursorAt, false, false)
return retObj, nil
}
return nil, nil
}
func (r *pdfReader) peek() ([]byte, error) {
saveLoc := r.cursorAt
saveRead := r.recentReading
err := r.pdfReadAt(r.cursorAt, false, false)
if err != nil {
return nil, err
}
retRead := r.recentReading
r.cursorAt = saveLoc
r.recentReading = saveRead
return retRead, nil
}
func (r *pdfReader) buildFpdf() (f *Fpdf, err error) {
fmt.Println(r.xrefTable)
return f, err
}