Overview
| Comment: | encoding/mtf optimizations |
|---|---|
| Downloads: | Tarball | ZIP archive | SQL archive |
| Timelines: | family | ancestors | descendants | both | trunk |
| Files: | files | file ages | folders |
| SHA1: | 5c9c0a2164ec08b6bb7d2f5fa5ca42dc45a6588a |
| User & Date: | spaskalev on 2015-01-10 21:28:17 |
| Other Links: | manifest | tags |
Context
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2015-01-11
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| 08:44 | Switched encoding/fibonacci.Encoder back to using a 2-bytes array as a preallocated write buffer. It seems that it otherwise escapes everytime and calls a causes a lot of allocations and subsequent gc work. check-in: 90877fa64f user: spaskalev tags: trunk | |
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2015-01-10
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| 21:28 | encoding/mtf optimizations check-in: 5c9c0a2164 user: spaskalev tags: trunk | |
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2015-01-04
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| 16:45 | Use a lookup table for fibonacci's encoding of bytes. check-in: 9ded78a659 user: spaskalev tags: trunk | |
Changes
Modified src/0dev.org/encoding/mtf/mtf.go from [cebf1719c8] to [76460f96cb].
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type context struct {
table [256]byte
}
// Encodes data in place
func (c *context) encode(data []byte) {
for index, value := range data {
// Shortcut for sequential, equal values
if c.table[0] == value {
data[index] = 0
continue
}
// Loop over the MTF table
for j := byte(1); j != 0; j++ {
if c.table[j] == value {
// Output the value
data[index] = j
// Shift the table
copy(c.table[1:], c.table[:j])
// Restore the value in front and break
c.table[0] = value
break
}
}
}
................................................................................
}
// Decode data in place
func (c *context) decode(data []byte) {
for index, value := range data {
position := value
// Shortcut for sequential, equal values
if position == 0 {
data[index] = c.table[0]
continue
}
// Output the value
data[index] = c.table[position]
// Shift the table and restore the value in front
copy(c.table[1:], c.table[:position])
c.table[0] = data[index]
}
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type context struct {
table [256]byte
}
// Encodes data in place
func (c *context) encode(data []byte) {
for index, value := range data {
// Loop over the MTF table
for i := byte(0); i <= 255; i++ {
if c.table[i] == value {
// Output the value
data[index] = i
// Shift the table
copy(c.table[1:], c.table[:i])
// Restore the value in front and break
c.table[0] = value
break
}
}
}
................................................................................
}
// Decode data in place
func (c *context) decode(data []byte) {
for index, value := range data {
position := value
// Output the value
data[index] = c.table[position]
// Shift the table and restore the value in front
copy(c.table[1:], c.table[:position])
c.table[0] = data[index]
}
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