mirror of
https://github.com/golang/go
synced 2024-11-25 21:57:57 -07:00
document hash
R=rsc DELTA=50 (33 added, 4 deleted, 13 changed) OCL=25878 CL=25887
This commit is contained in:
Rob Pike
parent
c5560d3aaa
commit
1910a7c595
@ -2,41 +2,44 @@
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
// Adler-32 checksum.
|
||||
// This package implements the Adler-32 checksum.
|
||||
// Defined in RFC 1950:
|
||||
// Adler-32 is composed of two sums accumulated per byte: s1 is
|
||||
// the sum of all bytes, s2 is the sum of all s1 values. Both sums
|
||||
// are done modulo 65521. s1 is initialized to 1, s2 to zero. The
|
||||
// Adler-32 checksum is stored as s2*65536 + s1 in most-
|
||||
// significant-byte first (network) order.
|
||||
|
||||
package adler32
|
||||
|
||||
import "os"
|
||||
|
||||
// Digest represents the partial evaluation of a checksum.
|
||||
type Digest struct {
|
||||
a, b uint32;
|
||||
n int;
|
||||
}
|
||||
|
||||
const (
|
||||
_Mod = 65521;
|
||||
_MaxIter = 5552; // max mod-free iterations before would overflow uint32
|
||||
mod = 65521;
|
||||
maxIter = 5552; // max mod-free iterations before would overflow uint32
|
||||
)
|
||||
|
||||
// NewDigest creates a new Digest.
|
||||
func NewDigest() *Digest {
|
||||
return &Digest{1, 0, 0};
|
||||
}
|
||||
|
||||
// Write updates the Digest with the incremental checksum generated by p.
|
||||
// It returns the number of bytes written; err is always nil.
|
||||
func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
a, b, n := d.a, d.b, d.n;
|
||||
for i := 0; i < len(p); i++ {
|
||||
a += uint32(p[i]);
|
||||
b += a;
|
||||
n++;
|
||||
if n == _MaxIter {
|
||||
a %= _Mod;
|
||||
b %= _Mod;
|
||||
if n == maxIter {
|
||||
a %= mod;
|
||||
b %= mod;
|
||||
n = 0;
|
||||
}
|
||||
}
|
||||
@ -44,15 +47,18 @@ func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
return len(p), nil
|
||||
}
|
||||
|
||||
// Sum32 returns the 32-bit Adler-32 checksum of the data written to the Digest.
|
||||
func (d *Digest) Sum32() uint32 {
|
||||
a, b := d.a, d.b;
|
||||
if a >= _Mod || b >= _Mod {
|
||||
a %= _Mod;
|
||||
b %= _Mod;
|
||||
if a >= mod || b >= mod {
|
||||
a %= mod;
|
||||
b %= mod;
|
||||
}
|
||||
return b<<16 | a;
|
||||
}
|
||||
|
||||
// Sum returns the 32-bit Adler-32 checksum of the data written to the Digest
|
||||
// in the form of an array of 4 bytes in big-endian order.
|
||||
func (d *Digest) Sum() []byte {
|
||||
p := make([]byte, 4);
|
||||
s := d.Sum32();
|
||||
|
||||
@ -2,13 +2,13 @@
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
// CRC-32 checksum.
|
||||
// http://en.wikipedia.org/wiki/Cyclic_redundancy_check for links
|
||||
|
||||
// This package implements the 32-bit cyclic redundancy check, or CRC-32, checksum.
|
||||
// See http://en.wikipedia.org/wiki/Cyclic_redundancy_check for information.
|
||||
package crc32
|
||||
|
||||
import "os"
|
||||
|
||||
// Predefined polynomials.
|
||||
const (
|
||||
// Far and away the most common CRC-32 polynomial.
|
||||
// Used by ethernet (IEEE 802.3), v.42, fddi, gzip, zip, png, mpeg-2, ...
|
||||
@ -25,9 +25,11 @@ const (
|
||||
Koopman = 0xeb31d82e;
|
||||
)
|
||||
|
||||
// Table is a 256-word table representing the polynomial for efficient processing.
|
||||
// TODO(rsc): Change to [256]uint32 once 6g can handle it.
|
||||
type Table []uint32
|
||||
|
||||
// MakeTable returns the Table constructed from the specified polynomial.
|
||||
func MakeTable(poly uint32) Table {
|
||||
t := make(Table, 256);
|
||||
for i := 0; i < 256; i++ {
|
||||
@ -44,21 +46,29 @@ func MakeTable(poly uint32) Table {
|
||||
return t;
|
||||
}
|
||||
|
||||
// IEEETable is the table for the IEEE polynomial.
|
||||
var IEEETable = MakeTable(IEEE);
|
||||
|
||||
// Digest represents the partial evaluation of a checksum.
|
||||
type Digest struct {
|
||||
crc uint32;
|
||||
tab Table;
|
||||
}
|
||||
|
||||
// NewDigest creates a new Digest for the checksum based on
|
||||
// the polynomial represented by the Table.
|
||||
func NewDigest(tab Table) *Digest {
|
||||
return &Digest{0, tab};
|
||||
}
|
||||
|
||||
// NewIEEEDigest creates a new Digest for the checksum based on
|
||||
// the IEEE polynomial.
|
||||
func NewIEEEDigest() *Digest {
|
||||
return NewDigest(IEEETable);
|
||||
}
|
||||
|
||||
// Write updates the Digest with the incremental checksum generated by p.
|
||||
// It returns the number of bytes written; err is always nil.
|
||||
func (d *Digest) Write(p []byte) (n int, err *os.Error) {
|
||||
crc := d.crc ^ 0xFFFFFFFF;
|
||||
tab := d.tab;
|
||||
@ -69,10 +79,13 @@ func (d *Digest) Write(p []byte) (n int, err *os.Error) {
|
||||
return len(p), nil;
|
||||
}
|
||||
|
||||
// Sum32 returns the CRC-32 checksum of the data written to the Digest.
|
||||
func (d *Digest) Sum32() uint32 {
|
||||
return d.crc
|
||||
}
|
||||
|
||||
// Sum returns the CRC-32 checksum of the data written to the Digest
|
||||
// in the form of an array of 4 bytes in big-endian order.
|
||||
func (d *Digest) Sum() []byte {
|
||||
p := make([]byte, 4);
|
||||
s := d.Sum32();
|
||||
|
||||
@ -2,8 +2,7 @@
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
// MD5 hash algorithm. See RFC 1321.
|
||||
|
||||
// This package implements the MD5 hash algorithm as defined in RFC 1321.
|
||||
package md5
|
||||
|
||||
import "os"
|
||||
@ -17,6 +16,7 @@ const (
|
||||
_Init3 = 0x10325476;
|
||||
)
|
||||
|
||||
// Digest represents the partial evaluation of a checksum.
|
||||
type Digest struct {
|
||||
s [4]uint32;
|
||||
x [_Chunk]byte;
|
||||
@ -24,6 +24,7 @@ type Digest struct {
|
||||
len uint64;
|
||||
}
|
||||
|
||||
// NewDigest creates a new Digest.
|
||||
func NewDigest() *Digest {
|
||||
d := new(Digest);
|
||||
d.s[0] = _Init0;
|
||||
@ -35,6 +36,8 @@ func NewDigest() *Digest {
|
||||
|
||||
func _Block(dig *Digest, p []byte) int
|
||||
|
||||
// Write updates the Digest with the incremental checksum generated by p.
|
||||
// It returns the number of bytes written; err is always nil.
|
||||
func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
nn = len(p);
|
||||
d.len += uint64(nn);
|
||||
@ -64,6 +67,8 @@ func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
return;
|
||||
}
|
||||
|
||||
// Sum returns the MD5 checksum of the data written to the Digest
|
||||
// in the form of an array of 16 bytes in big-endian order.
|
||||
func (d *Digest) Sum() []byte {
|
||||
// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
|
||||
len := d.len;
|
||||
|
||||
@ -2,8 +2,7 @@
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
// SHA1 hash algorithm. See RFC 3174.
|
||||
|
||||
// This package implements the SHA1 hash algorithm as defined in RFC 3174.
|
||||
package sha1
|
||||
|
||||
import "os"
|
||||
@ -18,6 +17,7 @@ const (
|
||||
_Init4 = 0xC3D2E1F0;
|
||||
)
|
||||
|
||||
// Digest represents the partial evaluation of a checksum.
|
||||
type Digest struct {
|
||||
h [5]uint32;
|
||||
x [_Chunk]byte;
|
||||
@ -25,6 +25,7 @@ type Digest struct {
|
||||
len uint64;
|
||||
}
|
||||
|
||||
// NewDigest creates a new Digest.
|
||||
func NewDigest() *Digest {
|
||||
d := new(Digest);
|
||||
d.h[0] = _Init0;
|
||||
@ -37,6 +38,8 @@ func NewDigest() *Digest {
|
||||
|
||||
func _Block(dig *Digest, p []byte) int
|
||||
|
||||
// Write updates the Digest with the incremental checksum generated by p.
|
||||
// It returns the number of bytes written; err is always nil.
|
||||
func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
nn = len(p);
|
||||
d.len += uint64(nn);
|
||||
@ -66,6 +69,8 @@ func (d *Digest) Write(p []byte) (nn int, err *os.Error) {
|
||||
return;
|
||||
}
|
||||
|
||||
// Sum returns the SHA-1 checksum of the data written to the Digest
|
||||
// in the form of an array of 20 bytes in big-endian order.
|
||||
func (d *Digest) Sum() []byte {
|
||||
// Padding. Add a 1 bit and 0 bits until 56 bytes mod 64.
|
||||
len := d.len;
|
||||
|
||||
Loading…
Reference in New Issue
Block a user