c97e3e7d60
See http://wiki.webmproject.org/encryption/webm-subsample-encryption for the format. Change-Id: Ia5d6f3566b92c46911704108d3e86cd0fac9ee34
86 lines
2.3 KiB
C++
86 lines
2.3 KiB
C++
// Copyright (c) 2012 The WebM project authors. All Rights Reserved.
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//
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// Use of this source code is governed by a BSD-style license
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// that can be found in the LICENSE file in the root of the source
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// tree. An additional intellectual property rights grant can be found
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// in the file PATENTS. All contributing project authors may
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// be found in the AUTHORS file in the root of the source tree.
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#include "common/webm_endian.h"
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#include <stdint.h>
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namespace {
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// Swaps unsigned 32 bit values to big endian if needed. Returns |value|
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// unmodified if architecture is big endian. Returns swapped bytes of |value|
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// if architecture is little endian. Returns 0 otherwise.
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uint32_t swap32_check_little_endian(uint32_t value) {
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// Check endianness.
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union {
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uint32_t val32;
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uint8_t c[4];
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} check;
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check.val32 = 0x01234567U;
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// Check for big endian.
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if (check.c[3] == 0x67)
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return value;
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// Check for not little endian.
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if (check.c[0] != 0x67)
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return 0;
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return value << 24 | ((value << 8) & 0x0000FF00U) |
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((value >> 8) & 0x00FF0000U) | value >> 24;
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}
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// Swaps unsigned 64 bit values to big endian if needed. Returns |value|
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// unmodified if architecture is big endian. Returns swapped bytes of |value|
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// if architecture is little endian. Returns 0 otherwise.
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uint64_t swap64_check_little_endian(uint64_t value) {
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// Check endianness.
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union {
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uint64_t val64;
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uint8_t c[8];
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} check;
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check.val64 = 0x0123456789ABCDEFULL;
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// Check for big endian.
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if (check.c[7] == 0xEF)
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return value;
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// Check for not little endian.
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if (check.c[0] != 0xEF)
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return 0;
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return value << 56 | ((value << 40) & 0x00FF000000000000ULL) |
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((value << 24) & 0x0000FF0000000000ULL) |
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((value << 8) & 0x000000FF00000000ULL) |
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((value >> 8) & 0x00000000FF000000ULL) |
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((value >> 24) & 0x0000000000FF0000ULL) |
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((value >> 40) & 0x000000000000FF00ULL) | value >> 56;
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}
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} // namespace
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namespace libwebm {
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uint32_t host_to_bigendian(uint32_t value) {
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return swap32_check_little_endian(value);
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}
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uint32_t bigendian_to_host(uint32_t value) {
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return swap32_check_little_endian(value);
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}
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uint64_t host_to_bigendian(uint64_t value) {
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return swap64_check_little_endian(value);
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}
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uint64_t bigendian_to_host(uint64_t value) {
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return swap64_check_little_endian(value);
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}
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} // namespace libwebm
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