mirror of https://github.com/status-im/qzxing.git
75 lines
2.1 KiB
C++
75 lines
2.1 KiB
C++
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/*
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* BitSource.cpp
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* zxing
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*
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* Created by Christian Brunschen on 09/05/2008.
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* Copyright 2008 Google UK. All rights reserved.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* 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
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* 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
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* limitations under the License.
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*/
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#include <zxing/common/BitSource.h>
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#include <zxing/common/IllegalArgumentException.h>
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namespace zxing {
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int BitSource::readBits(int numBits) {
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if (numBits < 0 || numBits > 32) {
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throw IllegalArgumentException("cannot read <1 or >32 bits");
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} else if (numBits > available()) {
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throw IllegalArgumentException("reading more bits than are available");
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}
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int result = 0;
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// First, read remainder from current byte
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if (bitOffset_ > 0) {
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int bitsLeft = 8 - bitOffset_;
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int toRead = numBits < bitsLeft ? numBits : bitsLeft;
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int bitsToNotRead = bitsLeft - toRead;
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int mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
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result = (bytes_[byteOffset_] & mask) >> bitsToNotRead;
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numBits -= toRead;
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bitOffset_ += toRead;
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if (bitOffset_ == 8) {
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bitOffset_ = 0;
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byteOffset_++;
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}
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}
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// Next read whole bytes
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if (numBits > 0) {
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while (numBits >= 8) {
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result = (result << 8) | (bytes_[byteOffset_] & 0xFF);
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byteOffset_++;
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numBits -= 8;
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}
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// Finally read a partial byte
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if (numBits > 0) {
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int bitsToNotRead = 8 - numBits;
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int mask = (0xFF >> bitsToNotRead) << bitsToNotRead;
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result = (result << numBits) | ((bytes_[byteOffset_] & mask) >> bitsToNotRead);
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bitOffset_ += numBits;
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}
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}
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return result;
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}
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int BitSource::available() {
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return 8 * (bytes_.size() - byteOffset_) - bitOffset_;
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}
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}
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