/*#####################################################################
#
#   文件          : unpack_update.c
#   作者          : Michellgaby(vincent.18023962826@gmail.com)
#   說明          : 解壓縮華為的'UPDATA.APP'官方系統包.
#
#   創建時間      : 2013年1月22號 -Michellgaby
#
#####################################################################*/
#include<stdio.h>
#include<stdlib.h>
#include<string.h>

#define MAXLEN 10240

void usage();
int main(int argc,char *argv[])
{
    int count,packetLength,dataLength,olddataLength,datasum,line,remainder,*Length;
    char *FILENAME,*OUTNAME;
    char int2char[10];
    unsigned char buffer[MAXLEN];
    FILE *INFILE,*OUTFILE;

    //獲取輸入的參數
    if(argc == 1)
        FILENAME="UPDATE.APP";
    else
        FILENAME=argv[1];

    //用二進制打開輸入文件
    if((INFILE = fopen(FILENAME, "rb")) == NULL) usage();

    //創建文件夾并進入目錄
    mkdir("output");
    chdir("output");

    //跳過92空字節
    fseek(INFILE, 92, 0);

    for(count=1;INFILE != NULL;count++)
    {
        //判斷是否為華為固件索引頭
        fread(buffer, 4, 1, INFILE);
        if(buffer[0] != 0x55) break;
        if(buffer[1] != 0XAA) break;
        if(buffer[2] != 0x5A) break;
        if(buffer[3] != 0xA5) break;

        //獲取頭文件長度
        fread(buffer, 4, 1, INFILE);
        Length = (int *)buffer;
        packetLength=*Length;

        //跳過16字節
        fseek(INFILE, 16, 1);

        //獲取內容長度
        fread(buffer, 4, 1, INFILE);
        Length = (int *) buffer;
        dataLength=*Length;

        //把整數和字符串連接并復制給文件名
        itoa(count, int2char, 10);
        OUTNAME=strcat(int2char, ".img");

        //跳到頭文件末尾
        fseek(INFILE, packetLength-28, 1);

        //創建文件
        if((OUTFILE = fopen(OUTNAME, "wb")) == NULL)
        {
            printf("Unrecognised file format. Wrong identifier./n");
            return -1;
        } else printf("Extracted output/%s/n",OUTNAME);

        //把內容數據分成多個部分
        datasum=dataLength/MAXLEN;

        for(line=0;line <= datasum;line++)
        {
            //獲取內容數據
            if(datasum == line)
                fread(buffer, dataLength % MAXLEN, 1, INFILE);
            else
            fread(buffer, MAXLEN, 1, INFILE);

            //輸出文件
            if(datasum == line)
                fwrite(buffer, dataLength % MAXLEN, 1, OUTFILE);
            else
            fwrite(buffer, MAXLEN, 1, OUTFILE);
        }

        //關閉輸出文件
        fclose(OUTFILE);

        //指針取整，4的倍數
        remainder = 4 - (ftell(INFILE) % 4);
        if (remainder < 4)
        {
            //進行填充剩余的字節
            fseek(INFILE, remainder, 1);
        }
    }
    //關閉輸入文件
    fclose(INFILE);
    return 0;
}

void usage()
{
    //幫助函數
    printf("uasge: unpack_update.exe [UPDATE.APP|UPDATA.APP]/n");
    exit(0);
}