why iconv read more bytes than i specified

I use

size_t iconv(i开发者_开发问答conv_t cd,   char **inbuf, size_t *inbytesleft, char **outbuf, size_t *outbytesleft);

to convert UTF-16BE to GB2312.

inbytesleft is bytes number to be convert. After conversion, inbytesleft is bytes number of not converted.

After one call, I found inbytesleft is -2, according to iconv man page this function should read at most inbytesleft. Who can tell my why and how to fix this?

code to be convert is

"保单验证"

Thanks

---

How are you getting the input data into your program?

I've tested the situation using this code and it seems to work:

#include <stdio.h>
#include <iconv.h>
#include <errno.h>

int main(){
    char data[10] = {0x4f,0xdd,0x53,0x55,0x9a,0x8c,0x8b,0xc1, 0, 0};
    char outdata[20];
    char *dataptr;
    char *outdataptr;
    iconv_t cd;
    size_t result;
    size_t inbytesleft = 8;
    size_t outbytesleft = 20;
    int i;

    cd = iconv_open("GB2312", "UTF-16BE");
    dataptr = data;
    outdataptr = outdata;
    result = iconv(cd, &dataptr, &inbytesleft, &outdataptr, &outbytesleft);
    if(result == -1)
        printf("Error: %d\n", errno);
    printf("      result: %zd\n", result);
    printf(" inbytesleft: %zd\n", inbytesleft);
    printf("outbytesleft: %zd\n", outbytesleft);

    for(i = 20; i > outbytesleft; i--){
        if(i != 20)
            printf(",");
        printf("0x%02x", *((unsigned char *)&(outdata[20-i])));
    }
    printf("\n");

    return 0;
}

It prints

      result: 0
 inbytesleft: 0
outbytesleft: 12
0xb1,0xa3,0xb5,0xa5,0xd1,0xe9,0xd6,0xa4

Which appears to be correct.

The array of items in the variable data is the UTF-16BE encoding of 保单验证

If this doesn't help, could you post your code for analysis?