1 files changed, 149 insertions, 0 deletions
diff --git a/compare.go b/compare.go
new file mode 100644
index 0000000..64cad1f
--- /dev/null
+++ b/compare.go
@@ -0,0 +1,149 @@
+/*
+ * 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"
+	"sort"
+)
+
+type sortType struct {
+	length int
+	less   func(int, int) bool
+	swap   func(int, int)
+}
+
+func (s *sortType) Len() int {
+	return s.length
+}
+
+func (s *sortType) Less(i, j int) bool {
+	return s.less(i, j)
+}
+
+func (s *sortType) Swap(i, j int) {
+	s.swap(i, j)
+}
+
+func gensort(Len int, Less func(int, int) bool, Swap func(int, int)) {
+	sort.Sort(&sortType{length: Len, less: Less, swap: Swap})
+}
+
+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
+}