@zxing/library
Version:
TypeScript port of ZXing multi-format 1D/2D barcode image processing library.
107 lines (106 loc) • 4.09 kB
JavaScript
;
/*
* Copyright 2007 ZXing authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
Object.defineProperty(exports, "__esModule", { value: true });
/*namespace com.google.zxing.common {*/
var IllegalArgumentException_1 = require("../IllegalArgumentException");
/**
* <p>This provides an easy abstraction to read bits at a time from a sequence of bytes, where the
* number of bits read is not often a multiple of 8.</p>
*
* <p>This class is thread-safe but not reentrant -- unless the caller modifies the bytes array
* it passed in, in which case all bets are off.</p>
*
* @author Sean Owen
*/
var BitSource = /** @class */ (function () {
/**
* @param bytes bytes from which this will read bits. Bits will be read from the first byte first.
* Bits are read within a byte from most-significant to least-significant bit.
*/
function BitSource(bytes) {
this.bytes = bytes;
this.byteOffset = 0;
this.bitOffset = 0;
}
/**
* @return index of next bit in current byte which would be read by the next call to {@link #readBits(int)}.
*/
BitSource.prototype.getBitOffset = function () {
return this.bitOffset;
};
/**
* @return index of next byte in input byte array which would be read by the next call to {@link #readBits(int)}.
*/
BitSource.prototype.getByteOffset = function () {
return this.byteOffset;
};
/**
* @param numBits number of bits to read
* @return int representing the bits read. The bits will appear as the least-significant
* bits of the int
* @throws IllegalArgumentException if numBits isn't in [1,32] or more than is available
*/
BitSource.prototype.readBits = function (numBits /*int*/) {
if (numBits < 1 || numBits > 32 || numBits > this.available()) {
throw new IllegalArgumentException_1.default('' + numBits);
}
var result = 0;
var bitOffset = this.bitOffset;
var byteOffset = this.byteOffset;
var bytes = this.bytes;
// First, read remainder from current byte
if (bitOffset > 0) {
var bitsLeft = 8 - bitOffset;
var toRead = numBits < bitsLeft ? numBits : bitsLeft;
var bitsToNotRead = bitsLeft - toRead;
var mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
result = (bytes[byteOffset] & mask) >> bitsToNotRead;
numBits -= toRead;
bitOffset += toRead;
if (bitOffset === 8) {
bitOffset = 0;
byteOffset++;
}
}
// Next read whole bytes
if (numBits > 0) {
while (numBits >= 8) {
result = (result << 8) | (bytes[byteOffset] & 0xFF);
byteOffset++;
numBits -= 8;
}
// Finally read a partial byte
if (numBits > 0) {
var bitsToNotRead = 8 - numBits;
var mask = (0xFF >> bitsToNotRead) << bitsToNotRead;
result = (result << numBits) | ((bytes[byteOffset] & mask) >> bitsToNotRead);
bitOffset += numBits;
}
}
this.bitOffset = bitOffset;
this.byteOffset = byteOffset;
return result;
};
/**
* @return number of bits that can be read successfully
*/
BitSource.prototype.available = function () {
return 8 * (this.bytes.length - this.byteOffset) - this.bitOffset;
};
return BitSource;
}());
exports.default = BitSource;