一. Linux xxd -i功能
Linux系統xxd指令使用二進位或十六進位格式顯示檔案內容。若未指定outfile參數，則將結果顯示在終端機畫面上；否則輸出至outfile中。詳細的用法可參考linux指令xxd。
本文主要關注xxd指令-i選項。使用此選項可輸出以inputfile為名的C語言陣列定義。例如，執行echo 12345 > test和xxd -i test指令後，輸出為：
unsigned char test[] = {
0x31, 0x32, 0x33, 0x34, 0x35, 0x0a
};
unsigned int test_len = 6;可見，陣列名稱即輸入檔名(若有後綴名則點號替換為底線)。請注意，0x0a表示換行符LF，即'\n'。
二. xxd -i常見用途
#當裝置沒有檔案系統或不支援動態記憶體管理時，有時會將二進位檔案(如引導程式和韌體)內容儲存在C程式碼靜態數組內。此時，借助xxd指令就可自動產生版本陣列。舉例如下：
1) 使用Linux指令xdd將二進位檔案VdslBooter.bin轉換為16進位檔案DslBooter.txt：
xxd -i < VdslBooter.bin > DslBooter.txt
其中，'-i'選項表示輸出為C包含檔案的風格(陣列方式)。重定向符號'<'將VdslBooter.bin檔案內容重定向到標準輸入，該處理可剔除陣列宣告和長度變數定義，使輸出僅包含16進位數值。
2) 在C程式碼原始檔內定義對應的靜態陣列：
static const uint8 bootImageArray[] = {
#include " ../../DslBooter.txt"
};
TargetImage bootImage = {
(uint8 *) bootImageArray,
sizeof(bootImageArray) / sizeof(bootImageArray[0])
};編譯原始碼時，DslBooter.txt檔案的內容會自動展開到上述數組內。透過巧用#include預處理指令，可免去手工拷貝數組內容的麻煩。
三. 類別xxd -i功能的Python實作
#本節將使用Python2.7語言實作類似xxd -i的功能。
因為作者處於學習階段，程式碼中存在許多寫法不同但功能相同或相近的地方，旨在提供不同的語法參考，敬請諒解。
首先，請看一段短小卻完整的程式(保存為xddi.py)：
##!/usr/bin/python
#coding=utf-8
#判断是否C语言关键字
CKeywords = ("auto", "break", "case", "char", "const", "continue", "default",
"do","double","else","enum","extern","float","for",
"goto","if","int","long","register","return","short",
"signed","static","sizeof","struct","switch","typedef","union",
"unsigned","void","volatile","while", "_Bool") #_Bool为C99新关键字
def IsCKeywords(name):
for x in CKeywords:
if cmp(x, name) == 0:
return True
return False
if __name__ == '__main__':
print IsCKeywords('const')
#Xxdi()import re
def GenerateCArrayName(inFile):
#字母数字下划线以外的字符均转为下划线
#'int $=5;'的定义在Gcc 4.1.2可编译通过，但此处仍视为非法标识符
inFile = re.sub('[^0-9a-zA-Z\_]', '_', inFile) #'_'改为''可剔除非法字符
#数字开头加双下划线
if inFile[0].isdigit() == True:
inFile = '__' + inFile
#若输入文件名为C语言关键字，则将其大写并加下划线后缀作为数组名
#不能仅仅大写或加下划线前，否则易于用户自定义名冲突
if IsCKeywords(inFile) is True:
inFile = '%s_' %inFile.upper()
return inFile#def ParseOption(base, cols, strip, inFile, outFile):
def ParseOption(base = 16, cols = 12, strip = False, inFile = '', outFile = None):
from optparse import OptionParser
custUsage = '\n xxdi(.py) [options] inFile [outFile]'
parser = OptionParser(usage=custUsage)
parser.add_option('-b', '--base', dest='base',
help='represent values according to BASE(default:16)')
parser.add_option('-c', '--column', dest='col',
help='COL octets per line(default:12)')
parser.add_option('-s', '--strip', action='store_true', dest='strip',
help='only output C array elements')
(options, args) = parser.parse_args()
if options.base is not None:
base = int(options.base)
if options.col is not None:
cols = int(options.col)
if options.strip is not None:
strip = True
if len(args) == 0:
print 'No argument, at least one(inFile)!\nUsage:%s' %custUsage
if len(args) >= 1:
inFile = args[0]
if len(args) >= 2:
outFile = args[1]
return ([base, cols, strip], [inFile, outFile])base = 16; cols = 12; strip = False; inFile = ''; outFile = '' ([base, cols, strip], [inFile, outFile]) = ParseOption(base, cols, strip, inFile, outFile)
E:\PyTest>python xxdi.py -h Usage: xxdi(.py) [options] inFile [outFile] Options: -h, --help show this help message and exit -b BASE, --base=BASE represent values according to BASE(default:16) -c COL, --column=COL COL octets per line(default:12) -s, --strip only output C array elements
def Xxdi():
#解析命令行选项及参数
([base, cols, strip], [inFile, outFile]) = ParseOption()
import os
if os.path.isfile(inFile) is False:
print ''''%s' is not a file!''' %inFile
return
with open(inFile, 'rb') as file: #必须以'b'模式访问二进制文件
#file = open(inFile, 'rb') #Python2.5以下版本不支持with...as语法
#if True:
#不用for line in file或readline(s)，以免遇'0x0a'换行
content = file.read()
#将文件内容"打散"为字节数组
if base is 16: #Hexadecimal
content = map(lambda x: hex(ord(x)), content)
elif base is 10: #Decimal
content = map(lambda x: str(ord(x)), content)
elif base is 8: #Octal
content = map(lambda x: oct(ord(x)), content)
else:
print '[%s]: Invalid base or radix for C language!' %base
return
#构造数组定义头及长度变量
cArrayName = GenerateCArrayName(inFile)
if strip is False:
cArrayHeader = 'unsigned char %s[] = {' %cArrayName
else:
cArrayHeader = ''
cArrayTailer = '};\nunsigned int %s_len = %d;' %(cArrayName, len(content))
if strip is True: cArrayTailer = ''
#print会在每行输出后自动换行
if outFile is None:
print cArrayHeader
for i in range(0, len(content), cols):
line = ', '.join(content[i:i+cols])
print ' ' + line + ','
print cArrayTailer
return
with open(outFile, 'w') as file:
#file = open(outFile, 'w') #Python2.5以下版本不支持with...as语法
#if True:
file.write(cArrayHeader + '\n')
for i in range(0, len(content), cols):
line = reduce(lambda x,y: ', '.join([x,y]), content[i:i+cols])
file.write(' %s,\n' %line)
file.flush()
file.write(cArrayTailer)import platform
#判断Python是否为major.minor及以上版本
def IsForwardPyVersion(major, minor):
#python_version()返回'major.minor.patchlevel'，如'2.7.11'
ver = platform.python_version().split('.')
if int(ver[0]) >= major and int(ver[1]) >= minor:
return True
return False再以稍大的二級製檔為例，執行python xxdi.py VdslBooter.bin booter.c後，booter.c檔內容如下(截取首尾)：
E:\PyTest>python xxdi.py -c 5 -b 2 -s 123456789ABCDEF.txt
[2]: Invalid base or radix for C language!
E:\Pytest>python xxdi.py -c 5 -b 10 -s 123456789ABCDEF.txt
49, 50, 51, 52, 53,
54, 55, 56, 57, 65,
66, 67, 68, 69, 70,
E:\PyTest>python xxdi.py -c 5 -b 10 123456789ABCDEF.txt
unsigned char __123456789ABCDEF_txt[] = {
49, 50, 51, 52, 53,
54, 55, 56, 57, 65,
66, 67, 68, 69, 70,
};
unsigned int __123456789ABCDEF_txt_len = 15;
E:\PyTest>python xxdi.py -c 5 -b 8 123456789ABCDEF.txt
unsigned char __123456789ABCDEF_txt[] = {
061, 062, 063, 064, 065,
066, 067, 070, 071, 0101,
0102, 0103, 0104, 0105, 0106,
};
unsigned int __123456789ABCDEF_txt_len = 15;
E:\PyTest>python xxdi.py 123456789ABCDEF.txt
unsigned char __123456789ABCDEF_txt[] = {
0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38, 0x39, 0x41, 0x42, 0x43,
0x44, 0x45, 0x46,
};
unsigned int __123456789ABCDEF_txt_len = 15;綜上可見，作者實現的xxdi模組與Linux xxd -i功能非常接近，且各有優劣。 xxdi優點在於對陣列名合法性校驗更充分(關鍵字檢查)，陣列內容表現形式更豐富(8進位和10進位)；缺點在於不支援重定向，且數值寬度不固定(如0xb和0xff)。當然，這些缺點並不難消除。例如，以'0x%02x'%val取代hex(val)即可控制輸出位寬。只是，再加完善難免提高程式碼複雜度，也許會事倍功半。
以上所述是小編給大家介紹的Python實作Linux指令xxd -i功能，希望對大家以上幫忙！
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