New C# port from Suraj Supekar

[zxing.git] / csharp / common / BitSource.cs

diff --git a/csharp/common/BitSource.cs b/csharp/common/BitSource.cs
new file mode 100755 (executable)
index 0000000..983caa7
--- /dev/null
+++ b/csharp/common/BitSource.cs
@@ -0,0 +1,109 @@
+/*\r
+* Copyright 2007 ZXing authors\r
+*\r
+* Licensed under the Apache License, Version 2.0 (the "License");\r
+* you may not use this file except in compliance with the License.\r
+* You may obtain a copy of the License at\r
+*\r
+*      http://www.apache.org/licenses/LICENSE-2.0\r
+*\r
+* Unless required by applicable law or agreed to in writing, software\r
+* distributed under the License is distributed on an "AS IS" BASIS,\r
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\r
+* See the License for the specific language governing permissions and\r
+* limitations under the License.\r
+*/\r
+using System;\r
+namespace com.google.zxing.common\r
+{\r
+       \r
+       /// <summary> <p>This provides an easy abstraction to read bits at a time from a sequence of bytes, where the\r
+       /// number of bits read is not often a multiple of 8.</p>\r
+       /// \r
+       /// <p>This class is thread-safe but not reentrant. Unless the caller modifies the bytes array\r
+       /// it passed in, in which case all bets are off.</p>\r
+       /// \r
+       /// </summary>\r
+       /// <author>  Sean Owen\r
+       /// </author>\r
+       /// <author>www.Redivivus.in (suraj.supekar@redivivus.in) - Ported from ZXING Java Source \r
+       /// </author>\r
+       public sealed class BitSource\r
+       {\r
+               \r
+               //UPGRADE_NOTE: Final was removed from the declaration of 'bytes '. "ms-help://MS.VSCC.v80/dv_commoner/local/redirect.htm?index='!DefaultContextWindowIndex'&keyword='jlca1003'"\r
+               private sbyte[] bytes;\r
+               private int byteOffset;\r
+               private int bitOffset;\r
+               \r
+               /// <param name="bytes">bytes from which this will read bits. Bits will be read from the first byte first.\r
+               /// Bits are read within a byte from most-significant to least-significant bit.\r
+               /// </param>\r
+               public BitSource(sbyte[] bytes)\r
+               {\r
+                       this.bytes = bytes;\r
+               }\r
+               \r
+               /// <param name="numBits">number of bits to read\r
+               /// </param>\r
+               /// <returns> int representing the bits read. The bits will appear as the least-significant\r
+               /// bits of the int\r
+               /// </returns>\r
+               /// <throws>  IllegalArgumentException if numBits isn't in [1,32] </throws>\r
+               public int readBits(int numBits)\r
+               {\r
+                       if (numBits < 1 || numBits > 32)\r
+                       {\r
+                               throw new System.ArgumentException();\r
+                       }\r
+                       \r
+                       int result = 0;\r
+                       \r
+                       // First, read remainder from current byte\r
+                       if (bitOffset > 0)\r
+                       {\r
+                               int bitsLeft = 8 - bitOffset;\r
+                               int toRead = numBits < bitsLeft?numBits:bitsLeft;\r
+                               int bitsToNotRead = bitsLeft - toRead;\r
+                               int mask = (0xFF >> (8 - toRead)) << bitsToNotRead;\r
+                               result = (bytes[byteOffset] & mask) >> bitsToNotRead;\r
+                               numBits -= toRead;\r
+                               bitOffset += toRead;\r
+                               if (bitOffset == 8)\r
+                               {\r
+                                       bitOffset = 0;\r
+                                       byteOffset++;\r
+                               }\r
+                       }\r
+                       \r
+                       // Next read whole bytes\r
+                       if (numBits > 0)\r
+                       {\r
+                               while (numBits >= 8)\r
+                               {\r
+                                       result = (result << 8) | (bytes[byteOffset] & 0xFF);\r
+                                       byteOffset++;\r
+                                       numBits -= 8;\r
+                               }\r
+                               \r
+                               // Finally read a partial byte\r
+                               if (numBits > 0)\r
+                               {\r
+                                       int bitsToNotRead = 8 - numBits;\r
+                                       int mask = (0xFF >> bitsToNotRead) << bitsToNotRead;\r
+                                       result = (result << numBits) | ((bytes[byteOffset] & mask) >> bitsToNotRead);\r
+                                       bitOffset += numBits;\r
+                               }\r
+                       }\r
+                       \r
+                       return result;\r
+               }\r
+               \r
+               /// <returns> number of bits that can be read successfully\r
+               /// </returns>\r
+               public int available()\r
+               {\r
+                       return 8 * (bytes.Length - byteOffset) - bitOffset;\r
+               }\r
+       }\r
+}
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