Compare bytes of PDFs generated as examples with reference copies. Differences in the CreationDate values are effectively ignored in the comparison.

1 files changed, 55 insertions, 0 deletions

diff --git a/internal/example/example.go b/internal/example/example.go
index d6a114c..3a60a1e 100644
--- a/internal/example/example.go
+++ b/internal/example/example.go
@@ -18,9 +18,12 @@
 package example
 
 import (
+	"bytes"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"path/filepath"
+	"regexp"
 	"strings"
 )
 
@@ -87,12 +90,64 @@ func Filename(baseStr string) string {
 	return PdfFile(baseStr + ".pdf")
 }
 
+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.Regexp = regexp.MustCompile("/CreationDate \\(D:\\d{14}\\)")
+	fixDate        []byte         = []byte("/CreationDate (D:20000101000000)")
+)
+
+// referenceCompare compares the specified file with the file's reference copy
+// located in the 'reference' subdirectory. All bytes of the two files are
+// compared except for the value of the /CreationDate field in the PDF. An
+// error is returned if the two files do not match. If the file does not exist,
+// a copy of the specified file is made and a non-nil error is returned only if
+// this copy fails.
+func referenceCompare(fileStr string) (err error) {
+	var fileBuf, refFileBuf []byte
+	var refFileStr, refDirStr, dirStr, baseFileStr string
+	dirStr, baseFileStr = filepath.Split(fileStr)
+	refDirStr = filepath.Join(dirStr, "reference")
+	err = os.MkdirAll(refDirStr, 0755)
+	if err == nil {
+		refFileStr = filepath.Join(refDirStr, baseFileStr)
+		fileBuf, err = ioutil.ReadFile(fileStr)
+		if err == nil {
+			// Replace the creation timestamp of this PDF with a fixed value
+			fileBuf = creationDateRe.ReplaceAll(fileBuf, fixDate)
+			refFileBuf, err = ioutil.ReadFile(refFileStr)
+			if err == nil {
+				if len(fileBuf) == len(refFileBuf) {
+					if bytes.Equal(fileBuf, refFileBuf) {
+						// Files match
+					} else {
+						err = fmt.Errorf("%s differs from %s", fileStr, refFileStr)
+					}
+				} else {
+					err = fmt.Errorf("size of %s (%d) does not match size of %s (%d)",
+						fileStr, len(fileBuf), refFileStr, len(refFileBuf))
+				}
+			} else {
+				// Reference file is missing. Create it with a copy of the newly produced
+				// file in which the creation date has been fixed. Overwrite error with copy
+				// error.
+				err = ioutil.WriteFile(refFileStr, fileBuf, 0644)
+			}
+		}
+	}
+	return
+}
+
 // Summary generates a predictable report for use by test examples. If the
 // specified error is nil, the filename delimiters are normalized and the
 // filename printed to standard output with a success message. If the specified
 // error is not nil, its String() value is printed to standard output.
 func Summary(err error, fileStr string) {
 	if err == nil {
+		err = referenceCompare(fileStr)
+	}
+	if err == nil {
 		fileStr = filepath.ToSlash(fileStr)
 		fmt.Printf("Successfully generated %s\n", fileStr)
 	} else {