This closes #971, closes #972 and closes #974

- Escape XML character in the drop list
- Fix incorrect character count limit in the drop list
- Fix Excel time parse issue in some case
- Fix custom number format month parse issue in some case
- Fix corrupted file generated caused by concurrency adding pictures

6 files changed, 25 insertions, 28 deletions

diff --git a/col.go b/col.go
index 5171f34..088fac9 100644
--- a/col.go
+++ b/col.go
@@ -439,10 +439,10 @@ func (f *File) SetColStyle(sheet, columns string, styleID int) error {
 		for col := start; col <= end; col++ {
 			from, _ := CoordinatesToCellName(col, 1)
 			to, _ := CoordinatesToCellName(col, rows)
-			f.SetCellStyle(sheet, from, to, styleID)
+			err = f.SetCellStyle(sheet, from, to, styleID)
 		}
 	}
-	return nil
+	return err
 }
 
 // SetColWidth provides a function to set the width of a single column or
diff --git a/datavalidation.go b/datavalidation.go
index 0f8508b..a95f4d0 100644
--- a/datavalidation.go
+++ b/datavalidation.go
@@ -14,6 +14,7 @@ package excelize
 import (
 	"fmt"
 	"strings"
+	"unicode/utf16"
 )
 
 // DataValidationType defined the type of data validation.
@@ -111,10 +112,10 @@ func (dd *DataValidation) SetInput(title, msg string) {
 // SetDropList data validation list.
 func (dd *DataValidation) SetDropList(keys []string) error {
 	formula := "\"" + strings.Join(keys, ",") + "\""
-	if dataValidationFormulaStrLen < len(formula) {
+	if dataValidationFormulaStrLen < len(utf16.Encode([]rune(formula))) {
 		return fmt.Errorf(dataValidationFormulaStrLenErr)
 	}
-	dd.Formula1 = fmt.Sprintf("<formula1>%s</formula1>", formula)
+	dd.Formula1 = formula
 	dd.Type = convDataValidationType(typeList)
 	return nil
 }
@@ -123,12 +124,12 @@ func (dd *DataValidation) SetDropList(keys []string) error {
 func (dd *DataValidation) SetRange(f1, f2 float64, t DataValidationType, o DataValidationOperator) error {
 	formula1 := fmt.Sprintf("%f", f1)
 	formula2 := fmt.Sprintf("%f", f2)
-	if dataValidationFormulaStrLen+21 < len(dd.Formula1) || dataValidationFormulaStrLen+21 < len(dd.Formula2) {
+	if dataValidationFormulaStrLen < len(utf16.Encode([]rune(dd.Formula1))) || dataValidationFormulaStrLen < len(utf16.Encode([]rune(dd.Formula2))) {
 		return fmt.Errorf(dataValidationFormulaStrLenErr)
 	}
 
-	dd.Formula1 = fmt.Sprintf("<formula1>%s</formula1>", formula1)
-	dd.Formula2 = fmt.Sprintf("<formula2>%s</formula2>", formula2)
+	dd.Formula1 = formula1
+	dd.Formula2 = formula2
 	dd.Type = convDataValidationType(t)
 	dd.Operator = convDataValidationOperatior(o)
 	return nil
@@ -148,7 +149,7 @@ func (dd *DataValidation) SetRange(f1, f2 float64, t DataValidationType, o DataV
 //
 func (dd *DataValidation) SetSqrefDropList(sqref string, isCurrentSheet bool) error {
 	if isCurrentSheet {
-		dd.Formula1 = fmt.Sprintf("<formula1>%s</formula1>", sqref)
+		dd.Formula1 = sqref
 		dd.Type = convDataValidationType(typeList)
 		return nil
 	}
diff --git a/date.go b/date.go
index 0531b6c..a5edcf8 100644
--- a/date.go
+++ b/date.go
@@ -17,11 +17,14 @@ import (
 )
 
 const (
+	nanosInADay    = float64((24 * time.Hour) / time.Nanosecond)
 	dayNanoseconds = 24 * time.Hour
 	maxDuration    = 290 * 364 * dayNanoseconds
 )
 
 var (
+	excel1900Epoc         = time.Date(1899, time.December, 30, 0, 0, 0, 0, time.UTC)
+	excel1904Epoc         = time.Date(1904, time.January, 1, 0, 0, 0, 0, time.UTC)
 	excelMinTime1900      = time.Date(1899, time.December, 31, 0, 0, 0, 0, time.UTC)
 	excelBuggyPeriodStart = time.Date(1900, time.March, 1, 0, 0, 0, 0, time.UTC).Add(-time.Nanosecond)
 )
@@ -131,12 +134,11 @@ func doTheFliegelAndVanFlandernAlgorithm(jd int) (day, month, year int) {
 // timeFromExcelTime provides a function to convert an excelTime
 // representation (stored as a floating point number) to a time.Time.
 func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
-	const MDD int64 = 106750 // Max time.Duration Days, aprox. 290 years
 	var date time.Time
-	var intPart = int64(excelTime)
+	var wholeDaysPart = int(excelTime)
 	// Excel uses Julian dates prior to March 1st 1900, and Gregorian
 	// thereafter.
-	if intPart <= 61 {
+	if wholeDaysPart <= 61 {
 		const OFFSET1900 = 15018.0
 		const OFFSET1904 = 16480.0
 		const MJD0 float64 = 2400000.5
@@ -148,23 +150,14 @@ func timeFromExcelTime(excelTime float64, date1904 bool) time.Time {
 		}
 		return date
 	}
-	var floatPart = excelTime - float64(intPart)
-	var dayNanoSeconds float64 = 24 * 60 * 60 * 1000 * 1000 * 1000
+	var floatPart = excelTime - float64(wholeDaysPart)
 	if date1904 {
-		date = time.Date(1904, 1, 1, 0, 0, 0, 0, time.UTC)
+		date = excel1904Epoc
 	} else {
-		date = time.Date(1899, 12, 30, 0, 0, 0, 0, time.UTC)
+		date = excel1900Epoc
 	}
-
-	// Duration is limited to aprox. 290 years
-	for intPart > MDD {
-		durationDays := time.Duration(MDD) * time.Hour * 24
-		date = date.Add(durationDays)
-		intPart = intPart - MDD
-	}
-	durationDays := time.Duration(intPart) * time.Hour * 24
-	durationPart := time.Duration(dayNanoSeconds * floatPart)
-	return date.Add(durationDays).Add(durationPart)
+	durationPart := time.Duration(nanosInADay * floatPart)
+	return date.AddDate(0, 0, wholeDaysPart).Add(durationPart)
 }
 
 // ExcelDateToTime converts a float-based excel date representation to a time.Time.
diff --git a/sheet.go b/sheet.go
index 7a1fff3..756eb81 100644
--- a/sheet.go
+++ b/sheet.go
@@ -72,12 +72,13 @@ func (f *File) contentTypesReader() *xlsxTypes {
 
 	if f.ContentTypes == nil {
 		f.ContentTypes = new(xlsxTypes)
+		f.ContentTypes.Lock()
+		defer f.ContentTypes.Unlock()
 		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
 }
 
diff --git a/styles.go b/styles.go
index 07ccab1..2a99a4d 100644
--- a/styles.go
+++ b/styles.go
@@ -996,6 +996,7 @@ func parseTime(v string, format string) string {
 		{"mm", "01"},
 		{"am/pm", "pm"},
 		{"m/", "1/"},
+		{"m", "1"},
 		{"%%%%", "January"},
 		{"&&&&", "Monday"},
 	}
@@ -1005,6 +1006,7 @@ func parseTime(v string, format string) string {
 		{"\\ ", " "},
 		{"\\.", "."},
 		{"\\", ""},
+		{"\"", ""},
 	}
 	// It is the presence of the "am/pm" indicator that determines if this is
 	// a 12 hour or 24 hours time format, not the number of 'h' characters.
diff --git a/xmlWorksheet.go b/xmlWorksheet.go
index 4499546..a54d51b 100644
--- a/xmlWorksheet.go
+++ b/xmlWorksheet.go
@@ -436,8 +436,8 @@ type DataValidation struct {
 	ShowInputMessage bool    `xml:"showInputMessage,attr,omitempty"`
 	Sqref            string  `xml:"sqref,attr"`
 	Type             string  `xml:"type,attr,omitempty"`
-	Formula1         string  `xml:",innerxml"`
-	Formula2         string  `xml:",innerxml"`
+	Formula1         string  `xml:"formula1,omitempty"`
+	Formula2         string  `xml:"formula2,omitempty"`
 }
 
 // xlsxC collection represents a cell in the worksheet. Information about the