C to Java

[dreamz]

Hello,
I was just wondering if you guys would kindly help me out converting the following code to java. I tried it myself but I am not very good at C or C++. trying to learn it.
Thank you.

---Code Starts ---

typedef unsigned char byte;
typedef unsigned int uint;

static byte decode_hex[257]={0};
#define hex_none 0x10
#define hex_eofc 0x20
#define sgetc(s) (*((s)++))


int
sreadhex(str, rlen, nread, odd_digit, s)
    byte *str;
    uint rlen;
    uint *nread;
    int *odd_digit;

    register byte *s;
    {     
        byte *ptr=str;
        byte *limit = ptr+rlen;
        byte val1 = (byte)*odd_digit;
        byte val2;
        register char *decoder = (char*)(decode_hex+1);          
        if (decoder[-1]==0)
        {   
            static char hex_chars[]= "0123456789ABCDEFabcdef";
            int i;
            memset(decoder-1, hex_none, 257);
            for (i=0; i<16+6; i++)
            decoder[hex_chars[i]] = (i>=16? i-6: i);
            decoder[0] = hex_eofc; 
        }
        if (val1<=0xf) goto d2;

d1:   while ((val1=decoder[sgetc(s)])>0xf)
{ if (val1==hex_eofc) {*odd_digit=-1; goto ended;}
}

d2:   while ((val2=decoder[sgetc(s)])>0xf)
{ if (val2==hex_eofc) {*odd_digit=val1; goto ended;}
}

        *ptr++ = (val1<<4) +val2;
        if (ptr<limit) goto d1;
        *nread = rlen;
        return 0;

ended: *nread = ptr - str;

return 1;

}

[Wraithan]

Sorry you didn't read the FAQs and if you don't feel like putting forth that small bit of effort then why should we help you?

[Salem]

Maybe start with a proper description of what the code actually does, then write the Java version from scratch.

That code looks like it's about 20 years old. The function is written in K&R style, and is riddled with gotos and non-standard array hackery. Definitely looks like something tuned for performance rather than readability.

[SKeane]

FWIW ...

sreadhex is a function that takes a string of characters that represent hexadecimal digits. Each character in the string represents a hexadecimal number. All such numbers can be represented in 4 bits:

'3' -> 3 -> 0011
'4' -> 4 -> 0100
'A' -> 10 -> 1010
'B' -> 11 -> 1011

Thus the values of two characters can be packed into a single byte, and a whole string can be packed into about half its length.

Example 1: "34AB" is packed into:
Byte 1: 00110100 Byte 2: 10101011

Example 2: There is an odd number of characters - "34ABF"
Byte 1: 00110100 Byte 2: 10101011

'F' (0xf) as the extra return value, which is typically used in the next call to sreadhex.

Example 3: sreadhex completely ignores characters in the source string that do not represent hexadecimal digits.
"34AB", "3 4 A B", "3G4GAMB-" will yield the same result.

sreadhex(str, rlen, nread, odd_digit, s)

where,

str is a byte array to fill. It is the destination.

rlen is the maximum number of bytes to be filled in str.
nread is a pointer to an integer. When the routine finishes, it leaves the number of bytes it used in that integer.

odd_digit is a pointer to an integer. The caller uses it to pass in the first digit (if the last call used an odd number of digits; the routine leaves either -1 or the extra digit in it after return. (The ‘odd’ in odd_digit refers to its being set when there are an odd number of hexadecimal characters to be placed in str)

s is a null-terminated string. It is the source of hexadecimal characters.

sreadhex returns 0 or 1.

1 means sreadhex ran out of characters before filling str.

[dreamz]

Thnx guys, I converted it.


Cheerz