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Unified Diff: courgette/third_party/qsufsort.h

Issue 1961963003: Move //courgette/third_party to subfolder. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Fixes according to comments Created 4 years, 7 months ago
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Index: courgette/third_party/qsufsort.h
diff --git a/courgette/third_party/qsufsort.h b/courgette/third_party/qsufsort.h
deleted file mode 100644
index 7bb46dfc7365caa156bdbea0551d4de3790bea54..0000000000000000000000000000000000000000
--- a/courgette/third_party/qsufsort.h
+++ /dev/null
@@ -1,226 +0,0 @@
-/*
- qsufsort.h -- Suffix array generation.
-
- Copyright 2003 Colin Percival
-
- For the terms under which this work may be distributed, please see
- the adjoining file "LICENSE".
-
- ChangeLog:
- 2005-05-05 - Use the modified header struct from bspatch.h; use 32-bit
- values throughout.
- --Benjamin Smedberg <benjamin@smedbergs.us>
- 2010-05-26 - Use a paged array for V and I. The address space may be too
- fragmented for these big arrays to be contiguous.
- --Stephen Adams <sra@chromium.org>
- 2015-08-03 - Extract QSufSort to a separate file as template.
- --Samuel Huang <huangs@chromium.org>
- 2015-08-19 - Optimize split() and search(), add comments.
- --Samuel Huang <huangs@chromium.org>
- 2016-04-27 - Change split() to use Bentley & McIlroy's pivot selection
- algorithm, which QSufSort originally used. Reference:
- http://www.larsson.dogma.net/qsufsort.c
- --Samuel Huang <huangs@chromium.org>
-*/
-
-#include <algorithm>
-#include <cstring>
-
-namespace courgette {
-namespace qsuf {
-
-// ------------------------------------------------------------------------
-//
-// The following code is taken verbatim from 'bsdiff.c'. Please keep all the
-// code formatting and variable names. The changes from the original are:
-// (1) replacing tabs with spaces,
-// (2) indentation,
-// (3) using 'const',
-// (4) changing the V and I parameters from int* to template <typename T>.
-// (5) optimizing split() and search(); fix styles.
-//
-// The code appears to be a rewritten version of the suffix array algorithm
-// presented in "Faster Suffix Sorting" by N. Jesper Larsson and Kunihiko
-// Sadakane, special cased for bytes.
-
-namespace {
-
-template <typename T> T median3(const T& a, const T& b, const T& c) {
- if (a < b)
- return b < c ? b : (a < c ? c : a);
- return b > c ? b : (a > c ? c : a);
-}
-
-} // namespace
-
-template <typename T> void split(T I, T V, int start, int end, int h) {
- // For small interval, apply selection sort.
- if (end - start < 16) {
- for (int i = start; i < end; ) {
- int skip = 1;
- int best = V[I[i] + h];
- for (int j = i + 1; j < end; j++) {
- int cur = V[I[j] + h];
- if (best > cur) {
- best = cur;
- int tmp = I[i];
- I[i] = I[j];
- I[j] = tmp;
- skip = 1;
- } else if (best == cur) {
- int tmp = I[i + skip];
- I[i + skip] = I[j];
- I[j] = tmp;
- ++skip;
- }
- }
- if (skip == 1) {
- V[I[i]] = i;
- I[i] = -1;
- } else {
- for (int j = i, jend = i + skip; j < jend; j++)
- V[I[j]] = jend - 1;
- }
- i += skip;
- }
- return;
- }
-
- // Select pivot, algorithm by Bentley & McIlroy.
- int n = end - start;
- int mid = start + (n >> 1);
- int pivot = V[I[mid] + h];
- int p1 = V[I[start] + h];
- int p2 = V[I[end - 1] + h];
- if (n > 40) { // Big array: Pseudomedian of 9.
- int s = n >> 3;
- pivot = median3(pivot, V[I[mid - s] + h], V[I[mid + s] + h]);
- p1 = median3(p1, V[I[start + s] + h], V[I[start + s + s] + h]);
- p2 = median3(p2, V[I[end - 1 - s] + h], V[I[end - 1 - s - s] + h]);
- } // Else medium array: Pseudomedian of 3.
- pivot = median3(pivot, p1, p2);
-
- // Split [start, end) into 3 intervals:
- // [start, j) with secondary keys < pivot,
- // [j, k) with secondary keys == pivot,
- // [k, end) with secondary keys > pivot.
- int j = start;
- int k = end;
- for (int i = start; i < k; ) {
- int cur = V[I[i] + h];
- if (cur < pivot) {
- if (i != j) {
- int tmp = I[i];
- I[i] = I[j];
- I[j] = tmp;
- }
- ++i;
- ++j;
- } else if (cur > pivot) {
- --k;
- int tmp = I[i];
- I[i] = I[k];
- I[k] = tmp;
- } else {
- ++i;
- }
- }
-
- // Recurse on the "< pivot" piece.
- if (start < j)
- split<T>(I, V, start, j, h);
-
- // Update the "== pivot" piece.
- if (j == k - 1) {
- V[I[j]] = j;
- I[j] = -1;
- } else {
- for (int i = j; i < k; ++i)
- V[I[i]] = k - 1;
- }
-
- // Recurse on the "> pivot" piece.
- if (k < end)
- split<T>(I, V, k, end, h);
-}
-
-template <class T>
-static void
-qsufsort(T I, T V,const unsigned char *old,int oldsize)
-{
- int buckets[256];
- int i,h,len;
-
- for(i=0;i<256;i++) buckets[i]=0;
- for(i=0;i<oldsize;i++) buckets[old[i]]++;
- for(i=1;i<256;i++) buckets[i]+=buckets[i-1];
- for(i=255;i>0;i--) buckets[i]=buckets[i-1];
- buckets[0]=0;
-
- for(i=0;i<oldsize;i++) I[++buckets[old[i]]]=i;
- I[0]=oldsize;
- for(i=0;i<oldsize;i++) V[i]=buckets[old[i]];
- V[oldsize]=0;
- for(i=1;i<256;i++) if(buckets[i]==buckets[i-1]+1) I[buckets[i]]=-1;
- I[0]=-1;
-
- for(h=1;I[0]!=-(oldsize+1);h+=h) {
- len=0;
- for(i=0;i<oldsize+1;) {
- if(I[i]<0) {
- len-=I[i];
- i-=I[i];
- } else {
- if(len) I[i-len]=-len;
- len=V[I[i]]+1-i;
- split<T>(I,V,i,i+len,h);
- i+=len;
- len=0;
- };
- };
- if(len) I[i-len]=-len;
- };
-
- for(i=0;i<oldsize+1;i++) I[V[i]]=i;
-}
-
-static int
-matchlen(const unsigned char *old,int oldsize,const unsigned char *newbuf,int newsize)
-{
- int i;
-
- for(i=0;(i<oldsize)&&(i<newsize);i++)
- if(old[i]!=newbuf[i]) break;
-
- return i;
-}
-
-template <class T>
-static int search(T I, const unsigned char *old, int oldsize,
- const unsigned char *newbuf, int newsize, int *pos) {
- int lo = 0;
- int hi = oldsize;
- while (hi - lo >= 2) {
- int mid = (lo + hi) / 2;
- if(memcmp(old+I[mid],newbuf,std::min(oldsize-I[mid],newsize))<0) {
- lo = mid;
- } else {
- hi = mid;
- }
- }
-
- int x = matchlen(old + I[lo], oldsize - I[lo], newbuf, newsize);
- int y = matchlen(old + I[hi], oldsize - I[hi], newbuf, newsize);
- if(x > y) {
- *pos = I[lo];
- return x;
- }
- *pos = I[hi];
- return y;
-}
-
-// End of 'verbatim' code.
-// ------------------------------------------------------------------------
-
-} // namespace qsuf
-} // namespace courgette
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