From 31dbd21c02b62f9899e802579f3ca0e507faab38 Mon Sep 17 00:00:00 2001
From: Per Hedbor <ph@opera.com>
Date: Wed, 9 Mar 2011 14:05:16 +0100
Subject: [PATCH] Optimization of the BitBuffer class
This made our usage of it about 20% faster.
This is done mainly by avoiding making (shorter) copies of the buffer
string when reading.
---
lib/modules/ADT.pmod/BitBuffer.pike | 25 +++++++++++++++++--------
1 file changed, 17 insertions(+), 8 deletions(-)
diff --git a/lib/modules/ADT.pmod/BitBuffer.pike b/lib/modules/ADT.pmod/BitBuffer.pike
index 5d167b561a..04926af18b 100644
--- a/lib/modules/ADT.pmod/BitBuffer.pike
+++ b/lib/modules/ADT.pmod/BitBuffer.pike
@@ -32,13 +32,20 @@ protected void create(void|string data) {
this_program feed( string x ) {
if(String.width(x)!=8) error("Only eight bits wide characters allowed.\n");
if(bob)
- foreach(x; int p; int c)
+ foreach(x;; int c)
put(c,8);
else
- data += x;
+ {
+ if(dptr) {
+ data = data[dptr..];
+ dptr = 0;
+ }
+ data += x;
+ }
return this;
}
+
//! Drains the buffer of all full (8-bits wide) bytes.
string drain() {
if(_sizeof()<8)
@@ -59,6 +66,8 @@ string drain() {
protected int out_buffer, bib;
+#define pow2(X) (1<<(X))
+
//! Get @[bits] from the buffer.
//!
//! @throws
@@ -79,18 +88,14 @@ int get( int bits ) {
if(bob<n) error("BitBuffer undeflow.\n");
out_buffer = (out_buffer<<n) | (in_buffer>>(bob-n));
bib += n;
- in_buffer &= pow(2,bob-n)-1;
+ in_buffer &= pow2(bob-n)-1;
bob -= n;
}
int res = out_buffer>>(bib-bits);
- out_buffer &= pow(2,bib-bits)-1;
+ out_buffer &= pow2(bib-bits)-1;
bib-=bits;
- if(dptr>64) {
- data = data[dptr..];
- dptr = 0;
- }
return res;
}
@@ -122,6 +127,10 @@ protected int in_buffer, bob;
//! bit first.
this_program put( int value, int bits ) {
// werror("\n%O %O %O\n", bob, bib, bits);
+ if(dptr) {
+ data = data[dptr..];
+ dptr = 0;
+ }
if(!bits) return this;
bob += bits;
in_buffer <<= bits;
--
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