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Add CRC-8 method in Util

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PiperOrigin-RevId: 279911378
This commit is contained in:
kimvde 2019-11-12 09:33:59 +00:00 committed by Oliver Woodman
parent 6df92fdd3f
commit 2faef48302
3 changed files with 108 additions and 43 deletions
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2
library/core/src/main/java/com/google/android/exoplayer2/extractor/ts/SectionReader.java
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@ -114,7 +114,7 @@ public final class SectionReader implements TsPayloadReader {
if (bytesRead == totalSectionLength) {
if (sectionSyntaxIndicator) {
// This section has common syntax as defined in ISO/IEC 13818-1, section 2.4.4.11.
if (Util.crc(sectionData.data, 0, totalSectionLength, 0xFFFFFFFF) != 0) {
if (Util.crc32(sectionData.data, 0, totalSectionLength, 0xFFFFFFFF) != 0) {
// The CRC is invalid so discard the section.
waitingForPayloadStart = true;
return;

51
library/core/src/main/java/com/google/android/exoplayer2/util/Util.java
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@ -1719,8 +1719,8 @@ public final class Util {
}
/**
* Returns the result of updating a CRC with the specified bytes in a "most significant bit first"
* order.
* Returns the result of updating a CRC-32 with the specified bytes in a "most significant bit
* first" order.
*
* @param bytes Array containing the bytes to update the crc value with.
* @param start The index to the first byte in the byte range to update the crc with.
@ -1728,7 +1728,7 @@ public final class Util {
* @param initialValue The initial value for the crc calculation.
* @return The result of updating the initial value with the specified bytes.
*/
public static int crc(byte[] bytes, int start, int end, int initialValue) {
public static int crc32(byte[] bytes, int start, int end, int initialValue) {
for (int i = start; i < end; i++) {
initialValue = (initialValue << 8)
^ CRC32_BYTES_MSBF[((initialValue >>> 24) ^ (bytes[i] & 0xFF)) & 0xFF];
@ -1736,6 +1736,23 @@ public final class Util {
return initialValue;
}
/**
* Returns the result of updating a CRC-8 with the specified bytes in a "most significant bit
* first" order.
*
* @param bytes Array containing the bytes to update the crc value with.
* @param start The index to the first byte in the byte range to update the crc with.
* @param end The index after the last byte in the byte range to update the crc with.
* @param initialValue The initial value for the crc calculation.
* @return The result of updating the initial value with the specified bytes.
*/
public static int crc8(byte[] bytes, int start, int end, int initialValue) {
for (int i = start; i < end; i++) {
initialValue = CRC8_BYTES_MSBF[initialValue ^ (bytes[i] & 0xFF)];
}
return initialValue;
}
/**
* Returns the {@link C.NetworkType} of the current network connection.
*
@ -2096,8 +2113,8 @@ public final class Util {
};
/**
* Allows the CRC calculation to be done byte by byte instead of bit per bit being the order
* "most significant bit first".
* Allows the CRC-32 calculation to be done byte by byte instead of bit per bit in the order "most
* significant bit first".
*/
private static final int[] CRC32_BYTES_MSBF = {
0X00000000, 0X04C11DB7, 0X09823B6E, 0X0D4326D9, 0X130476DC, 0X17C56B6B, 0X1A864DB2,
@ -2139,4 +2156,28 @@ public final class Util {
0XBCB4666D, 0XB8757BDA, 0XB5365D03, 0XB1F740B4
};
/**
* Allows the CRC-8 calculation to be done byte by byte instead of bit per bit in the order "most
* significant bit first".
*/
private static final int[] CRC8_BYTES_MSBF = {
0x00, 0x07, 0x0E, 0x09, 0x1C, 0x1B, 0x12, 0x15, 0x38, 0x3F, 0x36, 0x31, 0x24, 0x23, 0x2A,
0x2D, 0x70, 0x77, 0x7E, 0x79, 0x6C, 0x6B, 0x62, 0x65, 0x48, 0x4F, 0x46, 0x41, 0x54, 0x53,
0x5A, 0x5D, 0xE0, 0xE7, 0xEE, 0xE9, 0xFC, 0xFB, 0xF2, 0xF5, 0xD8, 0xDF, 0xD6, 0xD1, 0xC4,
0xC3, 0xCA, 0xCD, 0x90, 0x97, 0x9E, 0x99, 0x8C, 0x8B, 0x82, 0x85, 0xA8, 0xAF, 0xA6, 0xA1,
0xB4, 0xB3, 0xBA, 0xBD, 0xC7, 0xC0, 0xC9, 0xCE, 0xDB, 0xDC, 0xD5, 0xD2, 0xFF, 0xF8, 0xF1,
0xF6, 0xE3, 0xE4, 0xED, 0xEA, 0xB7, 0xB0, 0xB9, 0xBE, 0xAB, 0xAC, 0xA5, 0xA2, 0x8F, 0x88,
0x81, 0x86, 0x93, 0x94, 0x9D, 0x9A, 0x27, 0x20, 0x29, 0x2E, 0x3B, 0x3C, 0x35, 0x32, 0x1F,
0x18, 0x11, 0x16, 0x03, 0x04, 0x0D, 0x0A, 0x57, 0x50, 0x59, 0x5E, 0x4B, 0x4C, 0x45, 0x42,
0x6F, 0x68, 0x61, 0x66, 0x73, 0x74, 0x7D, 0x7A, 0x89, 0x8E, 0x87, 0x80, 0x95, 0x92, 0x9B,
0x9C, 0xB1, 0xB6, 0xBF, 0xB8, 0xAD, 0xAA, 0xA3, 0xA4, 0xF9, 0xFE, 0xF7, 0xF0, 0xE5, 0xE2,
0xEB, 0xEC, 0xC1, 0xC6, 0xCF, 0xC8, 0xDD, 0xDA, 0xD3, 0xD4, 0x69, 0x6E, 0x67, 0x60, 0x75,
0x72, 0x7B, 0x7C, 0x51, 0x56, 0x5F, 0x58, 0x4D, 0x4A, 0x43, 0x44, 0x19, 0x1E, 0x17, 0x10,
0x05, 0x02, 0x0B, 0x0C, 0x21, 0x26, 0x2F, 0x28, 0x3D, 0x3A, 0x33, 0x34, 0x4E, 0x49, 0x40,
0x47, 0x52, 0x55, 0x5C, 0x5B, 0x76, 0x71, 0x78, 0x7F, 0x6A, 0x6D, 0x64, 0x63, 0x3E, 0x39,
0x30, 0x37, 0x22, 0x25, 0x2C, 0x2B, 0x06, 0x01, 0x08, 0x0F, 0x1A, 0x1D, 0x14, 0x13, 0xAE,
0xA9, 0xA0, 0xA7, 0xB2, 0xB5, 0xBC, 0xBB, 0x96, 0x91, 0x98, 0x9F, 0x8A, 0x8D, 0x84, 0x83,
0xDE, 0xD9, 0xD0, 0xD7, 0xC2, 0xC5, 0xCC, 0xCB, 0xE6, 0xE1, 0xE8, 0xEF, 0xFA, 0xFD, 0xF4,
0xF3
};
}

24
library/core/src/test/java/com/google/android/exoplayer2/util/UtilTest.java
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@ -266,6 +266,30 @@ public class UtilTest {
}
}
@Test
public void testCrc32() {
byte[] bytes = {0x5F, 0x78, 0x04, 0x7B, 0x5F};
int start = 1;
int end = 4;
int initialValue = 0xFFFFFFFF;
int result = Util.crc32(bytes, start, end, initialValue);
assertThat(result).isEqualTo(0x67CE9747);
}
@Test
public void testCrc8() {
byte[] bytes = {0x5F, 0x78, 0x04, 0x7B, 0x5F};
int start = 1;
int end = 4;
int initialValue = 0;
int result = Util.crc8(bytes, start, end, initialValue);
assertThat(result).isEqualTo(0x4);
}
@Test
public void testInflate() {
byte[] testData = TestUtil.buildTestData(/*arbitrary test data size*/ 256 * 1024);