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76 lines
2.3 KiB
C++
76 lines
2.3 KiB
C++
/*
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Copyright 2007 nVidia, Inc.
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Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License.
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You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and limitations under the License.
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*/
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#ifndef _AVPCL_BITS_H
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#define _AVPCL_BITS_H
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// read/write a bitstream
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#include "nvcore/Debug.h"
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namespace AVPCL {
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class Bits
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{
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public:
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Bits(char *data, int maxdatabits) { nvAssert (data && maxdatabits > 0); bptr = bend = 0; bits = data; maxbits = maxdatabits; readonly = 0;}
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Bits(const char *data, int availdatabits) { nvAssert (data && availdatabits > 0); bptr = 0; bend = availdatabits; cbits = data; maxbits = availdatabits; readonly = 1;}
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void write(int value, int nbits) {
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nvAssert (nbits >= 0 && nbits < 32);
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nvAssert (sizeof(int)>= 4);
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for (int i=0; i<nbits; ++i)
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writeone(value>>i);
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}
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int read(int nbits) {
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nvAssert (nbits >= 0 && nbits < 32);
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nvAssert (sizeof(int)>= 4);
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int out = 0;
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for (int i=0; i<nbits; ++i)
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out |= readone() << i;
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return out;
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}
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int getptr() { return bptr; }
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void setptr(int ptr) { nvAssert (ptr >= 0 && ptr < maxbits); bptr = ptr; }
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int getsize() { return bend; }
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private:
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int bptr; // next bit to read
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int bend; // last written bit + 1
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char *bits; // ptr to user bit stream
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const char *cbits; // ptr to const user bit stream
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int maxbits; // max size of user bit stream
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char readonly; // 1 if this is a read-only stream
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int readone() {
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nvAssert (bptr < bend);
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if (bptr >= bend) return 0;
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int bit = (readonly ? cbits[bptr>>3] : bits[bptr>>3]) & (1 << (bptr & 7));
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++bptr;
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return bit != 0;
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}
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void writeone(int bit) {
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nvAssert (!readonly); // "Writing a read-only bit stream"
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nvAssert (bptr < maxbits);
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if (bptr >= maxbits) return;
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if (bit&1)
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bits[bptr>>3] |= 1 << (bptr & 7);
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else
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bits[bptr>>3] &= ~(1 << (bptr & 7));
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if (bptr++ >= bend) bend = bptr;
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}
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};
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}
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#endif |