Committed C# port from Mohamad

[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..91df66e
--- /dev/null
+++ b/csharp/common/BitSource.cs
@@ -0,0 +1,102 @@
+/*\r
+* Copyright 2008 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
+namespace com.google.zxing.common\r
+{\r
+    using System;\r
+    using System.Text;\r
+\r
+    /// <summary> A class which wraps a 2D array of bytes. The default usage is signed. If you want to use it as a\r
+    /// unsigned container, it's up to you to do byteValue & 0xff at each location.\r
+    /// *\r
+    /// JAVAPORT: I'm not happy about the argument ordering throughout the file, as I always like to have\r
+    /// the horizontal component first, but this is for compatibility with the C++ code. The original\r
+    /// code was a 2D array of ints, but since it only ever gets assigned -1, 0, and 1, I'm going to use\r
+    /// less memory and go with bytes.\r
+    /// *\r
+    /// </summary>\r
+    /// <author>  dswitkin@google.com (Daniel Switkin)\r
+    /// \r
+    /// </author>\r
+    public sealed class BitSource\r
+    { \r
+          private sbyte[] bytes;\r
+          private int byteOffset;\r
+          private int bitOffset;\r
+\r
+          /**\r
+           * @param 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
+           */\r
+          public BitSource(sbyte[] bytes) {\r
+            this.bytes = bytes;\r
+          }\r
+\r
+          /**\r
+           * @param numBits number of bits to read\r
+           * @return int representing the bits read. The bits will appear as the least-significant\r
+           *         bits of the int\r
+           * @throws IllegalArgumentException if numBits isn't in [1,32]\r
+           */\r
+          public int readBits(int numBits) {\r
+            if (numBits < 1 || numBits > 32) {\r
+              throw new Exception();\r
+            }\r
+\r
+            int result = 0;\r
+\r
+            // First, read remainder from current byte\r
+            if (bitOffset > 0) {\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
+                bitOffset = 0;\r
+                byteOffset++;\r
+              }\r
+            }\r
+\r
+            // Next read whole bytes\r
+            if (numBits > 0) {\r
+              while (numBits >= 8) {\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
+                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
+          /**\r
+           * @return number of bits that can be read successfully\r
+           */\r
+          public int available() {\r
+            return 8 * (bytes.Length - byteOffset) - bitOffset;\r
+          }\r
+    }\r
+}
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