Implement PDF comparison with rudimentary byte-difference display. If a reference file exists, it will be compared with its associated example file. If the reference file is missing, the associated example file is considered to be without differences. PDF files in any subdirectory named reference are not deleted when the test begins. This commit is broken -- it illustrates how the use of maps for fonts, images and other resources lead to different dictionary tables in the PDF document.

1 files changed, 144 insertions, 0 deletions

diff --git a/compare.go b/compare.go
new file mode 100644
index 0000000..dadf5eb
--- /dev/null
+++ b/compare.go
@@ -0,0 +1,144 @@
+/*
+ * 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"
+	"regexp"
+)
+
+var (
+	// 00000230  44 46 20 31 2e 37 29 0a  2f 43 72 65 61 74 69 6f  |DF 1.7)./Creatio|
+	// 00000240  6e 44 61 74 65 20 28 44  3a 32 30 31 35 31 30 30  |nDate (D:2015100|
+	// 00000250  38 31 32 33 30 34 35 29  0a 3e 3e 0a 65 6e 64 6f  |8123045).>>.endo|
+	creationDateRe = regexp.MustCompile("/CreationDate \\(D:\\d{14}\\)")
+	fixDate        = []byte("/CreationDate (D:20000101000000)")
+)
+
+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 {
+		// 		fmt.Printf("< %v\n", sl1)
+		// 		fmt.Printf("> %v\n", sl2)
+		writeBytes("<", pos, sl1)
+		writeBytes(">", pos, sl2)
+	}
+	return
+}
+
+// compareBytes compares the bytes referred to by sl1 with those referred to by
+// sl2. 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 compareBytes(sl1, sl2 []byte) (err error) {
+	var posStart, posEnd, len1, len2, length int
+	var diffs bool
+
+	sl1 = creationDateRe.ReplaceAll(sl1, fixDate)
+	sl2 = creationDateRe.ReplaceAll(sl2, fixDate)
+	len1 = len(sl1)
+	len2 = len(sl2)
+	length = len1
+	if length > len2 {
+		length = len2
+	}
+	// fmt.Printf("Len 1 %d, Len 2 %d, Len %d\n", len1, len2, length)
+	for posStart < length-1 {
+		posEnd = posStart + 16
+		if posEnd > length {
+			posEnd = length
+		}
+		// fmt.Printf("%d to %d\n", posStart, posEnd)
+		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
+	// fmt.Printf("Comparing [%s] with [%s]\n", file1Str, file2Str)
+	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
+}