Fix #539 Fixed error opening excel file created in encoding d… (#540)

* Fixed issue #539 Fixed error opening excel file created in encoding different from UTF-8, added logging of possible errors when decoding XML if the function does not provide exit with an error

* Added test for CharsetReader

* Fixed #discussion_r359397878

Discussion: https://github.com/360EntSecGroup-Skylar/excelize/pull/540#discussion_r359397878

* Fixed go fmt

* go mod tidy and removed unused imports

* The code has been refactored

1 files changed, 53 insertions, 25 deletions

diff --git a/sheet.go b/sheet.go
index 951baf9..42fd6b3 100644
--- a/sheet.go
+++ b/sheet.go
@@ -15,7 +15,9 @@ import (
 	"encoding/xml"
 	"errors"
 	"fmt"
+	"io"
 	"io/ioutil"
+	"log"
 	"os"
 	"path"
 	"reflect"
@@ -61,11 +63,16 @@ func (f *File) NewSheet(name string) int {
 // contentTypesReader provides a function to get the pointer to the
 // [Content_Types].xml structure after deserialization.
 func (f *File) contentTypesReader() *xlsxTypes {
+	var err error
+
 	if f.ContentTypes == nil {
-		var content xlsxTypes
-		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("[Content_Types].xml")), &content)
-		f.ContentTypes = &content
+		f.ContentTypes = new(xlsxTypes)
+		if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readXML("[Content_Types].xml")))).
+			Decode(f.ContentTypes); err != nil && err != io.EOF {
+			log.Printf("xml decode error: %s", err)
+		}
 	}
+
 	return f.ContentTypes
 }
 
@@ -81,11 +88,16 @@ func (f *File) contentTypesWriter() {
 // workbookReader provides a function to get the pointer to the xl/workbook.xml
 // structure after deserialization.
 func (f *File) workbookReader() *xlsxWorkbook {
+	var err error
+
 	if f.WorkBook == nil {
-		var content xlsxWorkbook
-		_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML("xl/workbook.xml")), &content)
-		f.WorkBook = &content
+		f.WorkBook = new(xlsxWorkbook)
+		if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readXML("xl/workbook.xml")))).
+			Decode(f.WorkBook); err != nil && err != io.EOF {
+			log.Printf("xml decode error: %s", err)
+		}
 	}
+
 	return f.WorkBook
 }
 
@@ -679,42 +691,51 @@ func (f *File) GetSheetVisible(name string) bool {
 //
 //    result, err := f.SearchSheet("Sheet1", "[0-9]", true)
 //
-func (f *File) SearchSheet(sheet, value string, reg ...bool) ([]string, error) {
+func (f *File) SearchSheet(sheet, value string, reg ...bool) (result []string, err error) {
 	var (
-		regSearch bool
-		result    []string
+		xlsx             *xlsxWorksheet
+		regSearch, r, ok bool
+		name             string
+		output           []byte
 	)
-	for _, r := range reg {
+
+	for _, r = range reg {
 		regSearch = r
 	}
-	xlsx, err := f.workSheetReader(sheet)
-	if err != nil {
-		return result, err
+	if xlsx, err = f.workSheetReader(sheet); err != nil {
+		return
 	}
-	name, ok := f.sheetMap[trimSheetName(sheet)]
-	if !ok {
-		return result, nil
+	if name, ok = f.sheetMap[trimSheetName(sheet)]; !ok {
+		return
 	}
 	if xlsx != nil {
-		output, _ := xml.Marshal(f.Sheet[name])
+		if output, err = xml.Marshal(f.Sheet[name]); err != nil {
+			return
+		}
 		f.saveFileList(name, replaceWorkSheetsRelationshipsNameSpaceBytes(output))
 	}
+
 	return f.searchSheet(name, value, regSearch)
 }
 
 // searchSheet provides a function to get coordinates by given worksheet name,
 // cell value, and regular expression.
-func (f *File) searchSheet(name, value string, regSearch bool) ([]string, error) {
+func (f *File) searchSheet(name, value string, regSearch bool) (result []string, err error) {
 	var (
+		d         *xlsxSST
+		decoder   *xml.Decoder
 		inElement string
-		result    []string
 		r         xlsxRow
+		token     xml.Token
 	)
-	d := f.sharedStringsReader()
-	decoder := xml.NewDecoder(bytes.NewReader(f.readXML(name)))
+
+	d = f.sharedStringsReader()
+	decoder = f.xmlNewDecoder(bytes.NewReader(f.readXML(name)))
 	for {
-		token, _ := decoder.Token()
-		if token == nil {
+		if token, err = decoder.Token(); err != nil || token == nil {
+			if err == io.EOF {
+				err = nil
+			}
 			break
 		}
 		switch startElement := token.(type) {
@@ -750,7 +771,8 @@ func (f *File) searchSheet(name, value string, regSearch bool) ([]string, error)
 		default:
 		}
 	}
-	return result, nil
+
+	return
 }
 
 // SetHeaderFooter provides a function to set headers and footers by given
@@ -1360,14 +1382,20 @@ func (f *File) UngroupSheets() error {
 // relsReader provides a function to get the pointer to the structure
 // after deserialization of xl/worksheets/_rels/sheet%d.xml.rels.
 func (f *File) relsReader(path string) *xlsxRelationships {
+	var err error
+
 	if f.Relationships[path] == nil {
 		_, ok := f.XLSX[path]
 		if ok {
 			c := xlsxRelationships{}
-			_ = xml.Unmarshal(namespaceStrictToTransitional(f.readXML(path)), &c)
+			if err = f.xmlNewDecoder(bytes.NewReader(namespaceStrictToTransitional(f.readXML(path)))).
+				Decode(&c); err != nil && err != io.EOF {
+				log.Printf("xml decode error: %s", err)
+			}
 			f.Relationships[path] = &c
 		}
 	}
+
 	return f.Relationships[path]
 }