excelize/lib.go

// Copyright 2016 - 2018 The excelize Authors. All rights reserved. Use of
// this source code is governed by a BSD-style license that can be found in
// the LICENSE file.
//
// Package excelize providing a set of functions that allow you to write to
// and read from XLSX files. Support reads and writes XLSX file generated by
// Microsoft Excel™ 2007 and later. Support save file without losing original
// charts of XLSX. This library needs Go version 1.8 or later.

package excelize

import (
	"archive/zip"
	"bytes"
	"io"
	"log"
	"math"
	"strconv"
	"strings"
	"unicode"
)

// ReadZipReader can be used to read an XLSX in memory without touching the
// filesystem.
func ReadZipReader(r *zip.Reader) (map[string][]byte, int, error) {
	fileList := make(map[string][]byte)
	worksheets := 0
	for _, v := range r.File {
		fileList[v.Name] = readFile(v)
		if len(v.Name) > 18 {
			if v.Name[0:19] == "xl/worksheets/sheet" {
				worksheets++
			}
		}
	}
	return fileList, worksheets, nil
}

// readXML provides a function to read XML content as string.
func (f *File) readXML(name string) []byte {
	if content, ok := f.XLSX[name]; ok {
		return content
	}
	return []byte{}
}

// saveFileList provides a function to update given file content in file list
// of XLSX.
func (f *File) saveFileList(name string, content []byte) {
	newContent := make([]byte, 0, len(XMLHeader)+len(content))
	newContent = append(newContent, []byte(XMLHeader)...)
	newContent = append(newContent, content...)
	f.XLSX[name] = newContent
}

// Read file content as string in a archive file.
func readFile(file *zip.File) []byte {
	rc, err := file.Open()
	if err != nil {
		log.Fatal(err)
	}
	buff := bytes.NewBuffer(nil)
	_, _ = io.Copy(buff, rc)
	rc.Close()
	return buff.Bytes()
}

// ToAlphaString provides a function to convert integer to Excel sheet column
// title. For example convert 36 to column title AK:
//
//     excelize.ToAlphaString(36)
//
func ToAlphaString(value int) string {
	if value < 0 {
		return ""
	}
	var ans string
	i := value + 1
	for i > 0 {
		ans = string((i-1)%26+65) + ans
		i = (i - 1) / 26
	}
	return ans
}

// TitleToNumber provides a function to convert Excel sheet column title to
// int (this function doesn't do value check currently). For example convert
// AK and ak to column title 36:
//
//    excelize.TitleToNumber("AK")
//    excelize.TitleToNumber("ak")
//
func TitleToNumber(s string) int {
	weight := 0.0
	sum := 0
	for i := len(s) - 1; i >= 0; i-- {
		ch := int(s[i])
		if int(s[i]) >= int('a') && int(s[i]) <= int('z') {
			ch = int(s[i]) - 32
		}
		sum = sum + (ch-int('A')+1)*int(math.Pow(26, weight))
		weight++
	}
	return sum - 1
}

// letterOnlyMapF is used in conjunction with strings.Map to return only the
// characters A-Z and a-z in a string.
func letterOnlyMapF(rune rune) rune {
	switch {
	case 'A' <= rune && rune <= 'Z':
		return rune
	case 'a' <= rune && rune <= 'z':
		return rune - 32
	}
	return -1
}

// intOnlyMapF is used in conjunction with strings.Map to return only the
// numeric portions of a string.
func intOnlyMapF(rune rune) rune {
	if rune >= 48 && rune < 58 {
		return rune
	}
	return -1
}

// boolPtr returns a pointer to a bool with the given value.
func boolPtr(b bool) *bool { return &b }

// defaultTrue returns true if b is nil, or the pointed value.
func defaultTrue(b *bool) bool {
	if b == nil {
		return true
	}
	return *b
}

// axisLowerOrEqualThan returns true if axis1 <= axis2 axis1/axis2 can be
// either a column or a row axis, e.g. "A", "AAE", "42", "1", etc.
//
// For instance, the following comparisons are all true:
//
// "A" <= "B"
// "A" <= "AA"
// "B" <= "AA"
// "BC" <= "ABCD" (in a XLSX sheet, the BC col comes before the ABCD col)
// "1" <= "2"
// "2" <= "11" (in a XLSX sheet, the row 2 comes before the row 11)
// and so on
func axisLowerOrEqualThan(axis1, axis2 string) bool {
	if len(axis1) < len(axis2) {
		return true
	} else if len(axis1) > len(axis2) {
		return false
	} else {
		return axis1 <= axis2
	}
}

// getCellColRow returns the two parts of a cell identifier (its col and row)
// as strings
//
// For instance:
//
// "C220" => "C", "220"
// "aaef42" => "aaef", "42"
// "" => "", ""
func getCellColRow(cell string) (col, row string) {
	for index, rune := range cell {
		if unicode.IsDigit(rune) {
			return cell[:index], cell[index:]
		}

	}

	return cell, ""
}

// parseFormatSet provides a method to convert format string to []byte and
// handle empty string.
func parseFormatSet(formatSet string) []byte {
	if formatSet != "" {
		return []byte(formatSet)
	}
	return []byte("{}")
}

// namespaceStrictToTransitional provides a method to convert Strict and
// Transitional namespaces.
func namespaceStrictToTransitional(content []byte) []byte {
	var namespaceTranslationDic = map[string]string{
		StrictSourceRelationship:         SourceRelationship,
		StrictSourceRelationshipChart:    SourceRelationshipChart,
		StrictSourceRelationshipComments: SourceRelationshipComments,
		StrictSourceRelationshipImage:    SourceRelationshipImage,
		StrictNameSpaceSpreadSheet:       NameSpaceSpreadSheet,
	}
	for s, n := range namespaceTranslationDic {
		content = bytes.Replace(content, []byte(s), []byte(n), -1)
	}
	return content
}

// genSheetPasswd provides a method to generate password for worksheet
// protection by given plaintext. When an Excel sheet is being protected with
// a password, a 16-bit (two byte) long hash is generated. To verify a
// password, it is compared to the hash. Obviously, if the input data volume
// is great, numerous passwords will match the same hash. Here is the
// algorithm to create the hash value:
//
// take the ASCII values of all characters shift left the first character 1 bit, the second 2 bits and so on (use only the lower 15 bits and rotate all higher bits, the highest bit of the 16-bit value is always 0 [signed short])
// XOR all these values
// XOR the count of characters
// XOR the constant 0xCE4B
func genSheetPasswd(plaintext string) string {
	var password int64 = 0x0000
	var charPos uint = 1
	for _, v := range plaintext {
		value := int64(v) << charPos
		charPos++
		rotatedBits := value >> 15 // rotated bits beyond bit 15
		value &= 0x7fff            // first 15 bits
		password ^= (value | rotatedBits)
	}
	password ^= int64(len(plaintext))
	password ^= 0xCE4B
	return strings.ToUpper(strconv.FormatInt(password, 16))
}