method
sum
ruby latest stable - Class:
String
sum(p1 = v1)public
Returns a basic n-bit checksum of the characters in str, where n is the optional Integer parameter, defaulting to 16. The result is simply the sum of the binary value of each byte in str modulo 2**n - 1. This is not a particularly good checksum.
static VALUE
rb_str_sum(int argc, VALUE *argv, VALUE str)
{
VALUE vbits;
int bits;
char *ptr, *p, *pend;
long len;
VALUE sum = INT2FIX(0);
unsigned long sum0 = 0;
if (argc == 0) {
bits = 16;
}
else {
rb_scan_args(argc, argv, "01", &vbits);
bits = NUM2INT(vbits);
if (bits < 0)
bits = 0;
}
ptr = p = RSTRING_PTR(str);
len = RSTRING_LEN(str);
pend = p + len;
while (p < pend) {
if (FIXNUM_MAX - UCHAR_MAX < sum0) {
sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
str_mod_check(str, ptr, len);
sum0 = 0;
}
sum0 += (unsigned char)*p;
p++;
}
if (bits == 0) {
if (sum0) {
sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
}
}
else {
if (sum == INT2FIX(0)) {
if (bits < (int)sizeof(long)*CHAR_BIT) {
sum0 &= (((unsigned long)1)<<bits)-1;
}
sum = LONG2FIX(sum0);
}
else {
VALUE mod;
if (sum0) {
sum = rb_funcall(sum, '+', 1, LONG2FIX(sum0));
}
mod = rb_funcall(INT2FIX(1), idLTLT, 1, INT2FIX(bits));
mod = rb_funcall(mod, '-', 1, INT2FIX(1));
sum = rb_funcall(sum, '&', 1, mod);
}
}
return sum;
}