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Co-authored-by: Alejandro Perez <alejandro.perez@scanoss.com>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,136 @@ | ||
| package com.scanoss.utils; | ||
|
|
||
| import java.nio.charset.StandardCharsets; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
|
|
||
| /** | ||
| * SCANOSS Hpsm Class | ||
| * <p> | ||
| * The Hpsm class provides all the necessary implementations to generate HPSM fingerprint for a given file or contents. | ||
| * </p> | ||
| */ | ||
| public class Hpsm { | ||
| private static final int CRC8_MAXIM_DOW_TABLE_SIZE = 0x100; | ||
| private static final int CRC8_MAXIM_DOW_POLYNOMIAL = 0x8C; // 0x31 reflected | ||
| private static final int CRC8_MAXIM_DOW_INITIAL = 0x00; // 0x00 reflected | ||
| private static final int CRC8_MAXIM_DOW_FINAL = 0x00; // 0x00 reflected | ||
| private static int[] crc8MaximDowTable = new int[CRC8_MAXIM_DOW_TABLE_SIZE]; | ||
|
|
||
| private static final byte[] HEX_ARRAY = "0123456789ABCDEF".getBytes(StandardCharsets.US_ASCII); | ||
|
|
||
| public static String calcHpsm(byte[] content) { | ||
| List<Integer> listNormalized = new ArrayList<>(); | ||
| List<Integer> crcLines = new ArrayList<>(); | ||
|
|
||
| int lastLine = 0; | ||
| crc8MaximDowGenerateTable(); | ||
|
|
||
| for (int i = 0; i < content.length ; i++) { | ||
| char c = (char) content[i]; | ||
| if (c == '\n') { // When there is a new line | ||
| if (!listNormalized.isEmpty()) { | ||
| crcLines.add(crc8MaximDowBuffer(convertListToByteArray(listNormalized))); | ||
| listNormalized.clear(); | ||
| } else if (lastLine + 1 == i) { | ||
| crcLines.add(0xFF); | ||
| } else if (i - lastLine > 1) { | ||
| crcLines.add(0x00); | ||
| } | ||
| lastLine = i; | ||
| } else { | ||
| int cNormalized = WinnowingUtils.normalize(c); | ||
| if (cNormalized != 0) listNormalized.add(cNormalized); | ||
| } | ||
| } | ||
|
|
||
| return convertToHex(convertListToByteArray(crcLines)); | ||
| } | ||
|
|
||
| /** | ||
| * Calculates CRC-8 using the Maxim/Dallas polynomial without using a lookup table. | ||
| * This method is suitable for applications where memory constraints are critical | ||
| * and a lookup table cannot be afforded. | ||
| * | ||
| * @param crc The current CRC value. | ||
| * @param b The byte to be processed. | ||
| * @return The updated CRC value after processing the byte. | ||
| */ | ||
| private static int crc8MaximDowByteNoTable(int crc, int b) { | ||
| crc ^= b; | ||
| for (int count = 0; count < 8; count++) { | ||
| boolean isSet = (crc & 0x01) != 0; | ||
| crc >>= 1; | ||
| if (isSet) crc ^= CRC8_MAXIM_DOW_POLYNOMIAL; | ||
| } | ||
| return crc; | ||
| } | ||
|
|
||
| /** | ||
| * Generates a lookup table for CRC-8 using the Maxim/Dallas polynomial. | ||
| * The generated table is used for faster CRC calculations. | ||
| */ | ||
| private static void crc8MaximDowGenerateTable() { | ||
| for (int i = 0; i < CRC8_MAXIM_DOW_TABLE_SIZE; i++) { | ||
| crc8MaximDowTable[i] = crc8MaximDowByteNoTable(0, i); | ||
| } | ||
| } | ||
|
|
||
| /** | ||
| * Calculates CRC-8 using the Maxim/Dow polynomial with a lookup table. | ||
| * This method utilizes a pre-generated lookup table for faster CRC calculations. | ||
| * | ||
| * @param crc The current CRC value. | ||
| * @param b The byte to be processed. | ||
| * @return The updated CRC value after processing the byte. | ||
| */ | ||
| private static int crc8MaximDowByte(int crc, int b) { | ||
| int index = b ^ crc; | ||
| return crc8MaximDowTable[index] ^ (crc >> 8); | ||
| } | ||
|
|
||
| /** | ||
| * Calculates CRC-8 for a buffer of bytes using the Maxim/Dallas polynomial. | ||
| * | ||
| * @param buffer The buffer containing bytes for CRC calculation. | ||
| * @return The CRC-8 value for the given buffer. | ||
| */ | ||
| private static int crc8MaximDowBuffer(byte[] buffer) { | ||
| int crc = CRC8_MAXIM_DOW_INITIAL; | ||
| for (byte b : buffer) { | ||
| crc = crc8MaximDowByte(crc, b & 0xFF); // Convert byte to unsigned integer | ||
| } | ||
| crc ^= CRC8_MAXIM_DOW_FINAL; | ||
| return crc; | ||
| } | ||
|
|
||
| /** | ||
| * Converts a list of integers to a byte array. | ||
| * | ||
| * @param integerList The list of integers to be converted. | ||
| * @return The byte array representing the converted integers. | ||
| */ | ||
| private static byte[] convertListToByteArray(List<Integer> integerList) { | ||
| byte[] byteArray = new byte[integerList.size()]; | ||
| for (int i = 0; i < integerList.size(); i++) { | ||
| byteArray[i] = integerList.get(i).byteValue(); | ||
| } | ||
| return byteArray; | ||
| } | ||
|
|
||
| /** | ||
| * Converts an array of bytes to its hexadecimal representation. | ||
| * | ||
| * @param bytes the array of bytes to be converted | ||
| * @return the hexadecimal representation of the input byte array | ||
| */ | ||
| private static String convertToHex(byte [] bytes) { | ||
| byte[] hexChars = new byte[bytes.length * 2]; | ||
| for (int j = 0; j < bytes.length; j++) { | ||
| int v = bytes[j] & 0xFF; | ||
| hexChars[j * 2] = HEX_ARRAY[v >>> 4]; | ||
| hexChars[j * 2 + 1] = HEX_ARRAY[v & 0x0F]; | ||
| } | ||
| return new String(hexChars, StandardCharsets.UTF_8).toLowerCase(); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,22 @@ | ||
| package com.scanoss.utils; | ||
|
|
||
| public class WinnowingUtils { | ||
|
|
||
| /** | ||
| * Normalise the given character | ||
| * | ||
| * @param c character to normalise | ||
| * @return normalised character | ||
| */ | ||
| public static char normalize(char c) { | ||
| if (c < '0' || c > 'z') { | ||
| return 0; | ||
| } else if (c <= '9' || c >= 'a') { | ||
| return c; | ||
| } else if (c >= 'A' && c <= 'Z') { | ||
| return (char) (c + 32); | ||
| } else { | ||
| return 0; | ||
| } | ||
| } | ||
| } |
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