讀mp3文件ID3V2信息，文字編碼轉換…

提取mp3文件ID3V2信息，通過curl命令發送請求，發佈微博。ID3V2信息爲UTF-16編碼，需要在發送curl命令之前先轉碼成UTF-8

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>

typedef struct id3_v2_head
{
    char Header[3];    //必須爲"ID3"否則認爲標籤不存在
    unsigned char Ver;    //版本號ID3V2.3就記錄3
    unsigned char Revision;    //副版本號此版本記錄爲0
    unsigned char Flag;    //存放標誌的字節，這個版本只定義了三位，稍後詳細解說
    unsigned char Size[4];    //標籤大小，包括標籤頭的10個字節和所有的標籤幀的大小
}id3_v2_head_t;

typedef struct id3_v2_frame
{
    char FrameID[4];  //用四個字符標識一個幀，說明其內容，稍後有常用的標識對照表
    unsigned char Size[4];   //幀內容的大小，不包括幀頭，不得小於1
    unsigned char Flags[2];   //存放標誌，只定義了6位，稍後詳細解說
}id3_v2_frame_t;

int get_id3_v2_info(char *string);
int publish_weibo(const char* hdr, const int info_idx[3][2]);
int convert_UTF16toUTF8(const char *input, int *insize, char *output, int *outsize);

int main(int argc,char **argv)
{
    char *filename;
    if(argc!=2) {
        return -1;
    }
    filename = argv[1];
    get_id3_v2_info(filename);
    return 0;
}

int get_id3_v2_info(char *string)
{
    int info_idx[3][2] = {0};
    char *filename=NULL;
    int ret = 0;
    id3_v2_head_t * id3_v2_head=NULL;
    id3_v2_frame_t* id3_v2_frame=NULL;
    int fd;
    char *hdr = NULL;
    long int id3_v2_head_length=0;
    long int id3_v2_frame_length=0;
    long int total_read=0;
    struct stat sb;
    char *info = NULL;
    filename=string;
    fd = open(filename, O_RDONLY);
    if(fd==-1)
    {
        return -1;
    }
    fstat(fd,&sb);
    hdr=(char*)mmap(NULL,sb.st_size,PROT_READ,MAP_PRIVATE,fd,0);
    if(hdr== MAP_FAILED)
    {
        return 0;
        close(fd);
    }
    id3_v2_head=(id3_v2_head_t *)malloc(sizeof(id3_v2_head_t));
    if(id3_v2_head==NULL)
    {
        munmap(hdr,sb.st_size);
        close(fd);
        return -1;
    }
    memcpy(id3_v2_head,hdr,sizeof(id3_v2_head_t));
    if(strncmp(id3_v2_head->Header, "ID3", 3))
    {
        printf("have no id3 v2 info\n");
        munmap(hdr,sb.st_size);
        close(fd);
        return -1;
    }
    printf("have  id3 v2.%d.%d info\n",id3_v2_head->Ver,id3_v2_head->Revision);
    id3_v2_head_length = (id3_v2_head->Size[0]&0x7F)*0x200000+(id3_v2_head->Size[1]&0x7F)*0x400+(id3_v2_head->Size[2]&0x7F)*0x80+(id3_v2_head->Size[3]&0x7F);
    printf("head length:%ld\n",id3_v2_head_length);
    total_read += sizeof(id3_v2_head_t);
        id3_v2_frame = (id3_v2_frame_t *)malloc(sizeof(id3_v2_frame_t));