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path: root/compare.go
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/*
 * Copyright (c) 2015 Kurt Jung (Gmail: kurt.w.jung)
 *
 * 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"
	"fmt"
	"io"
	"io/ioutil"
)

func writeBytes(leadStr string, startPos int, sl []byte) {
	var pos, max int
	var b byte
	fmt.Printf("%s %07x", leadStr, startPos)
	max = len(sl)
	for pos < max {
		fmt.Printf(" ")
		for k := 0; k < 8; k++ {
			if pos < max {
				fmt.Printf(" %02x", sl[pos])
			} else {
				fmt.Printf("   ")
			}
			pos++
		}
	}
	fmt.Printf("  |")
	pos = 0
	for pos < max {
		b = sl[pos]
		if b < 32 || b >= 128 {
			b = '.'
		}
		fmt.Printf("%c", b)
		pos++
	}
	fmt.Printf("|\n")
}

func checkBytes(pos int, sl1, sl2 []byte) (eq bool) {
	eq = bytes.Equal(sl1, sl2)
	if !eq {
		writeBytes("<", pos, sl1)
		writeBytes(">", pos, sl2)
	}
	return
}

// compareBytes compares the bytes referred to by sl1 with those referred to by
// sl2. Nil is returned if the buffers are equal, otherwise an error.
func compareBytes(sl1, sl2 []byte) (err error) {
	var posStart, posEnd, len1, len2, length int
	var diffs bool

	len1 = len(sl1)
	len2 = len(sl2)
	length = len1
	if length > len2 {
		length = len2
	}
	for posStart < length-1 {
		posEnd = posStart + 16
		if posEnd > length {
			posEnd = length
		}
		if !checkBytes(posStart, sl1[posStart:posEnd], sl2[posStart:posEnd]) {
			diffs = true
		}
		posStart = posEnd
	}
	if diffs {
		err = fmt.Errorf("documents are different")
	}
	return
}

// ComparePDFs reads and compares the full contents of the two specified
// readers. The comparison is done byte-for-byte with the exception of the
// CreationDate fields which are effectively ignored. Nil is returned if the
// buffers are equal, otherwise an error.
func ComparePDFs(rdr1, rdr2 io.Reader) (err error) {
	var b1, b2 *bytes.Buffer
	_, err = b1.ReadFrom(rdr1)
	if err == nil {
		_, err = b2.ReadFrom(rdr2)
		if err == nil {
			err = compareBytes(b1.Bytes(), b2.Bytes())
		}
	}
	return
}

// ComparePDFFiles reads and compares the full contents of the two specified
// files. The comparison is done byte-for-byte with the exception of the
// CreationDate fields which are effectively ignored. Nil is returned if the
// file contents are equal, or if the second file is missing, otherwise an
// error.
func ComparePDFFiles(file1Str, file2Str string) (err error) {
	var sl1, sl2 []byte
	sl1, err = ioutil.ReadFile(file1Str)
	if err == nil {
		sl2, err = ioutil.ReadFile(file2Str)
		if err == nil {
			err = compareBytes(sl1, sl2)
		} else {
			// Second file is missing; treat this as success
			err = nil
		}
	}
	return
}