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feat: Add delta compression support (#74)
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191 changes: 191 additions & 0 deletions
191
centrifuge/src/main/java/io/github/centrifugal/centrifuge/Fossil.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,191 @@ | ||
| package io.github.centrifugal.centrifuge; | ||
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| import java.io.ByteArrayOutputStream; | ||
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| public class Fossil { | ||
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| private static final int[] zValue = new int[] { | ||
| -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, | ||
| -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, | ||
| -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, | ||
| 8, 9, -1, -1, -1, -1, -1, -1, -1, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, | ||
| 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, -1, -1, -1, | ||
| -1, 36, -1, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, | ||
| 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, -1, -1, -1, 63, -1, | ||
| }; | ||
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| // Reader class | ||
| static class Reader { | ||
| private byte[] a; | ||
| private int pos; | ||
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| public Reader(byte[] array) { | ||
| this.a = array; | ||
| this.pos = 0; | ||
| } | ||
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| public boolean haveBytes() { | ||
| return this.pos < this.a.length; | ||
| } | ||
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| public int getByte() { | ||
| if (this.pos >= this.a.length) { | ||
| throw new IndexOutOfBoundsException("out of bounds"); | ||
| } | ||
| int b = this.a[this.pos++] & 0xFF; | ||
| return b; | ||
| } | ||
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| public char getChar() { | ||
| return (char) getByte(); | ||
| } | ||
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| public int getInt() { | ||
| int v = 0; | ||
| int c; | ||
| while (haveBytes() && (c = zValue[getByte() & 0x7F]) >= 0) { | ||
| v = (v << 6) + c; | ||
| } | ||
| this.pos--; | ||
| return v; | ||
| } | ||
| } | ||
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| // Writer class | ||
| static class Writer { | ||
| private ByteArrayOutputStream a = new ByteArrayOutputStream(); | ||
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| public byte[] toByteArray() { | ||
| return a.toByteArray(); | ||
| } | ||
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| // Copy from array 'arr' from 'start' to 'end' (exclusive) | ||
| public void putArray(byte[] arr, int start, int end) { | ||
| if (start < 0 || end > arr.length || start > end) { | ||
| throw new IndexOutOfBoundsException("Invalid start or end index"); | ||
| } | ||
| a.write(arr, start, end - start); | ||
| } | ||
| } | ||
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| // Checksum function | ||
| public static long checksum(byte[] arr) { | ||
| int sum0 = 0, sum1 = 0, sum2 = 0, sum3 = 0; | ||
| int z = 0; | ||
| int N = arr.length; | ||
| while (N >= 16) { | ||
| sum0 += (arr[z + 0] & 0xFF); | ||
| sum1 += (arr[z + 1] & 0xFF); | ||
| sum2 += (arr[z + 2] & 0xFF); | ||
| sum3 += (arr[z + 3] & 0xFF); | ||
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| sum0 += (arr[z + 4] & 0xFF); | ||
| sum1 += (arr[z + 5] & 0xFF); | ||
| sum2 += (arr[z + 6] & 0xFF); | ||
| sum3 += (arr[z + 7] & 0xFF); | ||
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| sum0 += (arr[z + 8] & 0xFF); | ||
| sum1 += (arr[z + 9] & 0xFF); | ||
| sum2 += (arr[z + 10] & 0xFF); | ||
| sum3 += (arr[z + 11] & 0xFF); | ||
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| sum0 += (arr[z + 12] & 0xFF); | ||
| sum1 += (arr[z + 13] & 0xFF); | ||
| sum2 += (arr[z + 14] & 0xFF); | ||
| sum3 += (arr[z + 15] & 0xFF); | ||
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| z += 16; | ||
| N -= 16; | ||
| } | ||
| while (N >= 4) { | ||
| sum0 += (arr[z + 0] & 0xFF); | ||
| sum1 += (arr[z + 1] & 0xFF); | ||
| sum2 += (arr[z + 2] & 0xFF); | ||
| sum3 += (arr[z + 3] & 0xFF); | ||
| z += 4; | ||
| N -= 4; | ||
| } | ||
| sum3 += (sum2 << 8) + (sum1 << 16) + (sum0 << 24); | ||
| switch (N) { | ||
| case 3: | ||
| sum3 += (arr[z + 2] & 0xFF) << 8; | ||
| case 2: | ||
| sum3 += (arr[z + 1] & 0xFF) << 16; | ||
| case 1: | ||
| sum3 += (arr[z + 0] & 0xFF) << 24; | ||
| break; | ||
| default: | ||
| break; | ||
| } | ||
| return sum3 & 0xFFFFFFFFL; | ||
| } | ||
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| /** | ||
| * Apply a delta byte array to a source byte array, returning the target byte array. | ||
| */ | ||
| public static byte[] applyDelta(byte[] source, byte[] delta) throws Exception { | ||
| int total = 0; | ||
| Reader zDelta = new Reader(delta); | ||
| int lenSrc = source.length; | ||
| int lenDelta = delta.length; | ||
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| int limit = zDelta.getInt(); | ||
| char c = zDelta.getChar(); | ||
| if (c != '\n') { | ||
| throw new Exception("size integer not terminated by '\\n'"); | ||
| } | ||
| Writer zOut = new Writer(); | ||
| while (zDelta.haveBytes()) { | ||
| int cnt = zDelta.getInt(); | ||
| int ofst; | ||
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| c = zDelta.getChar(); | ||
| switch (c) { | ||
| case '@': | ||
| ofst = zDelta.getInt(); | ||
| if (zDelta.haveBytes() && zDelta.getChar() != ',') { | ||
| throw new Exception("copy command not terminated by ','"); | ||
| } | ||
| total += cnt; | ||
| if (total > limit) { | ||
| throw new Exception("copy exceeds output file size"); | ||
| } | ||
| if (ofst + cnt > lenSrc) { | ||
| throw new Exception("copy extends past end of input"); | ||
| } | ||
| zOut.putArray(source, ofst, ofst + cnt); | ||
| break; | ||
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| case ':': | ||
| total += cnt; | ||
| if (total > limit) { | ||
| throw new Exception("insert command gives an output larger than predicted"); | ||
| } | ||
| if (cnt > lenDelta - zDelta.pos) { | ||
| throw new Exception("insert count exceeds size of delta"); | ||
| } | ||
| zOut.putArray(zDelta.a, zDelta.pos, zDelta.pos + cnt); | ||
| zDelta.pos += cnt; | ||
| break; | ||
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| case ';': | ||
| byte[] out = zOut.toByteArray(); | ||
| long checksumValue = checksum(out); | ||
| if (cnt != (int) checksumValue) { | ||
| throw new Exception("bad checksum"); | ||
| } | ||
| if (total != limit) { | ||
| throw new Exception("generated size does not match predicted size"); | ||
| } | ||
| return out; | ||
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| default: | ||
| System.out.println(c); | ||
| throw new Exception("unknown delta operator"); | ||
| } | ||
| } | ||
| throw new Exception("unterminated delta"); | ||
| } | ||
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| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -23,7 +23,6 @@ void setInfo(ClientInfo info) { | |
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| private ClientInfo info; | ||
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| public long getOffset() { | ||
| return offset; | ||
| } | ||
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