1 files changed, 108 insertions, 0 deletions
diff --git a/media/libstagefright/webm/EbmlUtil.cpp b/media/libstagefright/webm/EbmlUtil.cpp
new file mode 100644
index 0000000..449fec6
--- /dev/null
+++ b/media/libstagefright/webm/EbmlUtil.cpp
@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2014 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 <stdint.h>
+
+namespace {
+
+// Table for Seal's algorithm for Number of Trailing Zeros. Hacker's Delight
+// online, Figure 5-18 (http://www.hackersdelight.org/revisions.pdf)
+// The entries whose value is -1 are never referenced.
+int NTZ_TABLE[] = {
+    32,  0,  1, 12,  2,  6, -1, 13,   3, -1,  7, -1, -1, -1, -1, 14,
+    10,  4, -1, -1,  8, -1, -1, 25,  -1, -1, -1, -1, -1, 21, 27, 15,
+    31, 11,  5, -1, -1, -1, -1, -1,   9, -1, -1, 24, -1, -1, 20, 26,
+    30, -1, -1, -1, -1, 23, -1, 19,  29, -1, 22, 18, 28, 17, 16, -1
+};
+
+int numberOfTrailingZeros32(int32_t i) {
+    uint32_t u = (i & -i) * 0x0450FBAF;
+    return NTZ_TABLE[(u) >> 26];
+}
+
+uint64_t highestOneBit(uint64_t n) {
+    n |= (n >> 1);
+    n |= (n >> 2);
+    n |= (n >> 4);
+    n |= (n >> 8);
+    n |= (n >> 16);
+    n |= (n >> 32);
+    return n - (n >> 1);
+}
+
+uint64_t _powerOf2(uint64_t u) {
+    uint64_t powerOf2 = highestOneBit(u);
+    return powerOf2 ? powerOf2 : 1;
+}
+
+// Based on Long.numberOfTrailingZeros in Long.java
+int numberOfTrailingZeros(uint64_t u) {
+    int32_t low = u;
+    return low !=0 ? numberOfTrailingZeros32(low)
+                   : 32 + numberOfTrailingZeros32((int32_t) (u >> 32));
+}
+}
+
+namespace webm {
+
+// Encode the id and/or size of an EBML element bytes by setting a leading length descriptor bit:
+//
+//   1xxxxxxx                                                                - 1-byte values
+//   01xxxxxx xxxxxxxx                                                       -
+//   001xxxxx xxxxxxxx xxxxxxxx                                              -
+//   0001xxxx xxxxxxxx xxxxxxxx xxxxxxxx                                     - ...
+//   00001xxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx                            -
+//   000001xx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx                   -
+//   0000001x xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx          -
+//   00000001 xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx xxxxxxxx - 8-byte values
+//
+// This function uses the least the number of bytes possible.
+uint64_t encodeUnsigned(uint64_t u) {
+    uint64_t powerOf2 = _powerOf2(u);
+    if (u + 1 == powerOf2 << 1)
+        powerOf2 <<= 1;
+    int shiftWidth = (7 + numberOfTrailingZeros(powerOf2)) / 7 * 7;
+    long lengthDescriptor = 1 << shiftWidth;
+    return lengthDescriptor | u;
+}
+
+// Like above but pads the input value with leading zeros up to the specified width. The length
+// descriptor is calculated based on width.
+uint64_t encodeUnsigned(uint64_t u, int width) {
+    int shiftWidth = 7 * width;
+    uint64_t lengthDescriptor = 1;
+    lengthDescriptor <<= shiftWidth;
+    return lengthDescriptor | u;
+}
+
+// Calculate the length of an EBML coded id or size from its length descriptor.
+int sizeOf(uint64_t u) {
+    uint64_t powerOf2 = _powerOf2(u);
+    int unsignedLength = numberOfTrailingZeros(powerOf2) / 8 + 1;
+    return unsignedLength;
+}
+
+// Serialize an EBML coded id or size in big-endian order.
+int serializeCodedUnsigned(uint64_t u, uint8_t* bary) {
+    int unsignedLength = sizeOf(u);
+    for (int i = unsignedLength - 1; i >= 0; i--) {
+        bary[i] = u & 0xff;
+        u >>= 8;
+    }
+    return unsignedLength;
+}
+
+}