ref: df1f2fb3daa1acd25c88510f259d5535fb482126
dir: /internal/adler32/adler32_generic.go/
package adler32
const (
// mod is the largest prime that is less than 65536.
mod = 65521
// nmax is the largest n such that
// 255 * n * (n+1) / 2 + (n+1) * (mod-1) <= 2^32-1.
// It is mentioned in RFC 1950 (search for "5552").
nmax = 5552
// binary representation compatible with standard library.
magic = "adl\x01"
marshaledSize = len(magic) + 4
)
// Add p to the running checksum d.
func update(d uint32, p []byte) uint32 {
s1, s2 := d&0xffff, d>>16
for len(p) > 0 {
var q []byte
if len(p) > nmax {
p, q = p[:nmax], p[nmax:]
}
for len(p) >= 4 {
s1 += uint32(p[0])
s2 += s1
s1 += uint32(p[1])
s2 += s1
s1 += uint32(p[2])
s2 += s1
s1 += uint32(p[3])
s2 += s1
p = p[4:]
}
for _, x := range p {
s1 += uint32(x)
s2 += s1
}
s1 %= mod
s2 %= mod
p = q
}
return s2<<16 | s1
}