1 files changed, 98 insertions, 0 deletions
diff --git a/media/libstagefright/foundation/ABitReader.cpp b/media/libstagefright/foundation/ABitReader.cpp
new file mode 100644
index 0000000..24c8df8
--- /dev/null
+++ b/media/libstagefright/foundation/ABitReader.cpp
@@ -0,0 +1,98 @@
+/*
+ * Copyright (C) 2010 The Android Open Source Project
+ *
+ * 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.
+ */
+
+#include "ABitReader.h"
+
+#include <media/stagefright/foundation/ADebug.h>
+
+namespace android {
+
+ABitReader::ABitReader(const uint8_t *data, size_t size)
+    : mData(data),
+      mSize(size),
+      mReservoir(0),
+      mNumBitsLeft(0) {
+}
+
+void ABitReader::fillReservoir() {
+    CHECK_GT(mSize, 0u);
+
+    mReservoir = 0;
+    size_t i;
+    for (i = 0; mSize > 0 && i < 4; ++i) {
+        mReservoir = (mReservoir << 8) | *mData;
+
+        ++mData;
+        --mSize;
+    }
+
+    mNumBitsLeft = 8 * i;
+    mReservoir <<= 32 - mNumBitsLeft;
+}
+
+uint32_t ABitReader::getBits(size_t n) {
+    CHECK_LE(n, 32u);
+
+    uint32_t result = 0;
+    while (n > 0) {
+        if (mNumBitsLeft == 0) {
+            fillReservoir();
+        }
+
+        size_t m = n;
+        if (m > mNumBitsLeft) {
+            m = mNumBitsLeft;
+        }
+
+        result = (result << m) | (mReservoir >> (32 - m));
+        mReservoir <<= m;
+        mNumBitsLeft -= m;
+
+        n -= m;
+    }
+
+    return result;
+}
+
+void ABitReader::skipBits(size_t n) {
+    while (n > 32) {
+        getBits(32);
+        n -= 32;
+    }
+
+    if (n > 0) {
+        getBits(n);
+    }
+}
+
+void ABitReader::putBits(uint32_t x, size_t n) {
+    CHECK_LE(mNumBitsLeft + n, 32u);
+
+    mReservoir = (mReservoir >> n) | (x << (32 - n));
+    mNumBitsLeft += n;
+}
+
+size_t ABitReader::numBitsLeft() const {
+    return mSize * 8 + mNumBitsLeft;
+}
+
+const uint8_t *ABitReader::data() const {
+    CHECK_EQ(mNumBitsLeft % 8, 0u);
+
+    return mData - mNumBitsLeft / 8;
+}
+
+}  // namespace android