break out many mods

src/common/bit_source.rs

@@ -0,0 +1,125 @@
+
+/*
+ * 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.
+ */
+
+//package com.google.zxing.common;
+
+use std::cmp;
+
+use crate::Exceptions;
+
+/**
+ * <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
+ */
+pub struct BitSource {
+    bytes: Vec<u8>,
+    byte_offset: usize,
+    bit_offset: usize,
+}
+
+impl BitSource {
+    /**
+     * @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.
+     */
+    pub fn new(bytes: Vec<u8>) -> Self {
+        Self {
+            bytes,
+            byte_offset: 0,
+            bit_offset: 0,
+        }
+    }
+
+    /**
+     * @return index of next bit in current byte which would be read by the next call to {@link #readBits(int)}.
+     */
+    pub fn getBitOffset(&self) -> usize {
+        return self.bit_offset;
+    }
+
+    /**
+     * @return index of next byte in input byte array which would be read by the next call to {@link #readBits(int)}.
+     */
+    pub fn getByteOffset(&self) -> usize {
+        return self.byte_offset;
+    }
+
+    /**
+     * @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
+     */
+    pub fn readBits(&mut self, numBits: usize) -> Result<u32, Exceptions> {
+        if numBits < 1 || numBits > 32 || numBits > self.available() {
+            return Err(Exceptions::IllegalArgumentException(numBits.to_string()));
+        }
+
+        let mut result: u32 = 0;
+
+        let mut num_bits = numBits;
+
+        // First, read remainder from current byte
+        if self.bit_offset > 0 {
+            let bitsLeft = 8 - self.bit_offset;
+            let toRead = cmp::min(num_bits, bitsLeft);
+            let bitsToNotRead = bitsLeft - toRead;
+            let mask = (0xFF >> (8 - toRead)) << bitsToNotRead;
+
+            result = (self.bytes[self.byte_offset] & mask) as u32 >> bitsToNotRead;
+            num_bits -= toRead;
+            self.bit_offset += toRead;
+            if self.bit_offset == 8 {
+                self.bit_offset = 0;
+                self.byte_offset += 1;
+            }
+        }
+
+        // Next read whole bytes
+        if num_bits > 0 {
+            while num_bits >= 8 {
+                result = (result << 8) | (self.bytes[self.byte_offset] & 0xFF) as u32;
+                // result = ((result as u16) << 8) as u8 | (self.bytes[self.byte_offset]);
+                self.byte_offset += 1;
+                num_bits -= 8;
+            }
+
+            // Finally read a partial byte
+            if num_bits > 0 {
+                let bits_to_not_read = 8 - num_bits;
+                let mask = (0xFF >> bits_to_not_read) << bits_to_not_read;
+                result = (result << num_bits)
+                    | ((self.bytes[self.byte_offset] & mask) as u32 >> bits_to_not_read);
+                self.bit_offset += num_bits;
+            }
+        }
+
+        return Ok(result);
+    }
+
+    /**
+     * @return number of bits that can be read successfully
+     */
+    pub fn available(&self) -> usize {
+        return 8 * (self.bytes.len() - self.byte_offset) - self.bit_offset;
+    }
+}