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git/kwset.c
Ben Walton 189c860c9e kwset: use unsigned char to store values with high-bit set 
Sun Studio on Solaris issues warnings about improper initialization
values being used when defining tolower_trans_tbl[] in ctype.c.  The
array wants to store values with high-bit set and treat them as
values between 128 to 255.  Unlike the rest of the Git codebase
where we explicitly specify 'unsigned char' for such variables and
arrays, however, kwset code we borrowed from elsewhere uses 'char'
for this and other variables.

Fix the declarations to explicitly use 'unsigned char' where
necessary to bring it in line with the rest of the Git.

Signed-off-by: Ben Walton <bdwalton@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-02 12:32:24 -08:00

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/*
* This file has been copied from commit e7ac713d^ in the GNU grep git
* repository. A few small changes have been made to adapt the code to
* Git.
*/
/* kwset.c - search for any of a set of keywords.
Copyright 1989, 1998, 2000, 2005 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2, or (at your option)
any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA
02110-1301, USA. */
/* Written August 1989 by Mike Haertel.
The author may be reached (Email) at the address mike@ai.mit.edu,
or (US mail) as Mike Haertel c/o Free Software Foundation. */
/* The algorithm implemented by these routines bears a startling resemblance
to one discovered by Beate Commentz-Walter, although it is not identical.
See "A String Matching Algorithm Fast on the Average," Technical Report,
IBM-Germany, Scientific Center Heidelberg, Tiergartenstrasse 15, D-6900
Heidelberg, Germany. See also Aho, A.V., and M. Corasick, "Efficient
String Matching: An Aid to Bibliographic Search," CACM June 1975,
Vol. 18, No. 6, which describes the failure function used below. */
#include "cache.h"
#include "kwset.h"
#include "compat/obstack.h"
#define NCHAR (UCHAR_MAX + 1)
#define obstack_chunk_alloc xmalloc
#define obstack_chunk_free free
#define U(c) ((unsigned char) (c))
/* Balanced tree of edges and labels leaving a given trie node. */
struct tree
{
struct tree *llink; /* Left link; MUST be first field. */
struct tree *rlink; /* Right link (to larger labels). */
struct trie *trie; /* Trie node pointed to by this edge. */
unsigned char label; /* Label on this edge. */
char balance; /* Difference in depths of subtrees. */
};
/* Node of a trie representing a set of reversed keywords. */
struct trie
{
unsigned int accepting; /* Word index of accepted word, or zero. */
struct tree *links; /* Tree of edges leaving this node. */
struct trie *parent; /* Parent of this node. */
struct trie *next; /* List of all trie nodes in level order. */
struct trie *fail; /* Aho-Corasick failure function. */
int depth; /* Depth of this node from the root. */
int shift; /* Shift function for search failures. */
int maxshift; /* Max shift of self and descendants. */
};
/* Structure returned opaquely to the caller, containing everything. */
struct kwset
{
struct obstack obstack; /* Obstack for node allocation. */
int words; /* Number of words in the trie. */
struct trie *trie; /* The trie itself. */
int mind; /* Minimum depth of an accepting node. */
int maxd; /* Maximum depth of any node. */
unsigned char delta[NCHAR]; /* Delta table for rapid search. */
struct trie *next[NCHAR]; /* Table of children of the root. */
char *target; /* Target string if there's only one. */
int mind2; /* Used in Boyer-Moore search for one string. */
unsigned char const *trans; /* Character translation table. */
};
/* Allocate and initialize a keyword set object, returning an opaque
pointer to it. Return NULL if memory is not available. */
kwset_t
kwsalloc (unsigned char const *trans)
{
struct kwset *kwset;
kwset = (struct kwset *) xmalloc(sizeof (struct kwset));
obstack_init(&kwset->obstack);
kwset->words = 0;
kwset->trie
= (struct trie *) obstack_alloc(&kwset->obstack, sizeof (struct trie));
if (!kwset->trie)
{
kwsfree((kwset_t) kwset);
return NULL;
}
kwset->trie->accepting = 0;
kwset->trie->links = NULL;
kwset->trie->parent = NULL;
kwset->trie->next = NULL;
kwset->trie->fail = NULL;
kwset->trie->depth = 0;
kwset->trie->shift = 0;
kwset->mind = INT_MAX;
kwset->maxd = -1;
kwset->target = NULL;
kwset->trans = trans;
return (kwset_t) kwset;
}
/* This upper bound is valid for CHAR_BIT >= 4 and
exact for CHAR_BIT in { 4..11, 13, 15, 17, 19 }. */
#define DEPTH_SIZE (CHAR_BIT + CHAR_BIT/2)
/* Add the given string to the contents of the keyword set. Return NULL
for success, an error message otherwise. */
const char *
kwsincr (kwset_t kws, char const *text, size_t len)
{
struct kwset *kwset;
register struct trie *trie;
register unsigned char label;
register struct tree *link;
register int depth;
struct tree *links[DEPTH_SIZE];
enum { L, R } dirs[DEPTH_SIZE];
struct tree *t, *r, *l, *rl, *lr;
kwset = (struct kwset *) kws;
trie = kwset->trie;
text += len;
/* Descend the trie (built of reversed keywords) character-by-character,
installing new nodes when necessary. */
while (len--)
{
label = kwset->trans ? kwset->trans[U(*--text)] : *--text;
/* Descend the tree of outgoing links for this trie node,
looking for the current character and keeping track
of the path followed. */
link = trie->links;
links[0] = (struct tree *) &trie->links;
dirs[0] = L;
depth = 1;
while (link && label != link->label)
{
links[depth] = link;
if (label < link->label)
dirs[depth++] = L, link = link->llink;
else
dirs[depth++] = R, link = link->rlink;
}
/* The current character doesn't have an outgoing link at
this trie node, so build a new trie node and install
a link in the current trie node's tree. */
if (!link)
{
link = (struct tree *) obstack_alloc(&kwset->obstack,
sizeof (struct tree));
if (!link)
return "memory exhausted";
link->llink = NULL;
link->rlink = NULL;
link->trie = (struct trie *) obstack_alloc(&kwset->obstack,
sizeof (struct trie));
if (!link->trie)
{
obstack_free(&kwset->obstack, link);
return "memory exhausted";
}
link->trie->accepting = 0;
link->trie->links = NULL;
link->trie->parent = trie;
link->trie->next = NULL;
link->trie->fail = NULL;
link->trie->depth = trie->depth + 1;
link->trie->shift = 0;
link->label = label;
link->balance = 0;
/* Install the new tree node in its parent. */
if (dirs[--depth] == L)
links[depth]->llink = link;
else
links[depth]->rlink = link;
/* Back up the tree fixing the balance flags. */
while (depth && !links[depth]->balance)
{
if (dirs[depth] == L)
--links[depth]->balance;
else
++links[depth]->balance;
--depth;
}
/* Rebalance the tree by pointer rotations if necessary. */
if (depth && ((dirs[depth] == L && --links[depth]->balance)
|| (dirs[depth] == R && ++links[depth]->balance)))
{
switch (links[depth]->balance)
{
case (char) -2:
switch (dirs[depth + 1])
{
case L:
r = links[depth], t = r->llink, rl = t->rlink;
t->rlink = r, r->llink = rl;
t->balance = r->balance = 0;
break;
case R:
r = links[depth], l = r->llink, t = l->rlink;
rl = t->rlink, lr = t->llink;
t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
l->balance = t->balance != 1 ? 0 : -1;
r->balance = t->balance != (char) -1 ? 0 : 1;
t->balance = 0;
break;
default:
abort ();
}
break;
case 2:
switch (dirs[depth + 1])
{
case R:
l = links[depth], t = l->rlink, lr = t->llink;
t->llink = l, l->rlink = lr;
t->balance = l->balance = 0;
break;
case L:
l = links[depth], r = l->rlink, t = r->llink;
lr = t->llink, rl = t->rlink;
t->llink = l, l->rlink = lr, t->rlink = r, r->llink = rl;
l->balance = t->balance != 1 ? 0 : -1;
r->balance = t->balance != (char) -1 ? 0 : 1;
t->balance = 0;
break;
default:
abort ();
}
break;
default:
abort ();
}
if (dirs[depth - 1] == L)
links[depth - 1]->llink = t;
else
links[depth - 1]->rlink = t;
}
}
trie = link->trie;
}
/* Mark the node we finally reached as accepting, encoding the
index number of this word in the keyword set so far. */
if (!trie->accepting)
trie->accepting = 1 + 2 * kwset->words;
++kwset->words;
/* Keep track of the longest and shortest string of the keyword set. */
if (trie->depth < kwset->mind)
kwset->mind = trie->depth;
if (trie->depth > kwset->maxd)
kwset->maxd = trie->depth;
return NULL;
}
/* Enqueue the trie nodes referenced from the given tree in the
given queue. */
static void
enqueue (struct tree *tree, struct trie **last)
{
if (!tree)
return;
enqueue(tree->llink, last);
enqueue(tree->rlink, last);
(*last) = (*last)->next = tree->trie;
}
/* Compute the Aho-Corasick failure function for the trie nodes referenced
from the given tree, given the failure function for their parent as
well as a last resort failure node. */
static void
treefails (register struct tree const *tree, struct trie const *fail,
struct trie *recourse)
{
register struct tree *link;
if (!tree)
return;
treefails(tree->llink, fail, recourse);
treefails(tree->rlink, fail, recourse);
/* Find, in the chain of fails going back to the root, the first
node that has a descendant on the current label. */
while (fail)
{
link = fail->links;
while (link && tree->label != link->label)
if (tree->label < link->label)
link = link->llink;
else
link = link->rlink;
if (link)
{
tree->trie->fail = link->trie;
return;
}
fail = fail->fail;
}
tree->trie->fail = recourse;
}
/* Set delta entries for the links of the given tree such that
the preexisting delta value is larger than the current depth. */
static void
treedelta (register struct tree const *tree,
register unsigned int depth,
unsigned char delta[])
{
if (!tree)
return;
treedelta(tree->llink, depth, delta);
treedelta(tree->rlink, depth, delta);
if (depth < delta[tree->label])
delta[tree->label] = depth;
}
/* Return true if A has every label in B. */
static int
hasevery (register struct tree const *a, register struct tree const *b)
{
if (!b)
return 1;
if (!hasevery(a, b->llink))
return 0;
if (!hasevery(a, b->rlink))
return 0;
while (a && b->label != a->label)
if (b->label < a->label)
a = a->llink;
else
a = a->rlink;
return !!a;
}
/* Compute a vector, indexed by character code, of the trie nodes
referenced from the given tree. */
static void
treenext (struct tree const *tree, struct trie *next[])
{
if (!tree)
return;
treenext(tree->llink, next);
treenext(tree->rlink, next);
next[tree->label] = tree->trie;
}
/* Compute the shift for each trie node, as well as the delta
table and next cache for the given keyword set. */
const char *
kwsprep (kwset_t kws)
{
register struct kwset *kwset;
register int i;
register struct trie *curr;
register unsigned char const *trans;
unsigned char delta[NCHAR];
kwset = (struct kwset *) kws;
/* Initial values for the delta table; will be changed later. The
delta entry for a given character is the smallest depth of any
node at which an outgoing edge is labeled by that character. */
memset(delta, kwset->mind < UCHAR_MAX ? kwset->mind : UCHAR_MAX, NCHAR);
/* Check if we can use the simple boyer-moore algorithm, instead
of the hairy commentz-walter algorithm. */
if (kwset->words == 1 && kwset->trans == NULL)
{
char c;
/* Looking for just one string. Extract it from the trie. */
kwset->target = obstack_alloc(&kwset->obstack, kwset->mind);
if (!kwset->target)
return "memory exhausted";
for (i = kwset->mind - 1, curr = kwset->trie; i >= 0; --i)
{
kwset->target[i] = curr->links->label;
curr = curr->links->trie;
}
/* Build the Boyer Moore delta. Boy that's easy compared to CW. */
for (i = 0; i < kwset->mind; ++i)
delta[U(kwset->target[i])] = kwset->mind - (i + 1);
/* Find the minimal delta2 shift that we might make after
a backwards match has failed. */
c = kwset->target[kwset->mind - 1];
for (i = kwset->mind - 2; i >= 0; --i)
if (kwset->target[i] == c)
break;
kwset->mind2 = kwset->mind - (i + 1);
}
else
{
register struct trie *fail;
struct trie *last, *next[NCHAR];
/* Traverse the nodes of the trie in level order, simultaneously
computing the delta table, failure function, and shift function. */
for (curr = last = kwset->trie; curr; curr = curr->next)
{
/* Enqueue the immediate descendants in the level order queue. */
enqueue(curr->links, &last);
curr->shift = kwset->mind;
curr->maxshift = kwset->mind;
/* Update the delta table for the descendants of this node. */
treedelta(curr->links, curr->depth, delta);
/* Compute the failure function for the descendants of this node. */
treefails(curr->links, curr->fail, kwset->trie);
/* Update the shifts at each node in the current node's chain
of fails back to the root. */
for (fail = curr->fail; fail; fail = fail->fail)
{
/* If the current node has some outgoing edge that the fail
doesn't, then the shift at the fail should be no larger
than the difference of their depths. */
if (!hasevery(fail->links, curr->links))
if (curr->depth - fail->depth < fail->shift)
fail->shift = curr->depth - fail->depth;
/* If the current node is accepting then the shift at the
fail and its descendants should be no larger than the
difference of their depths. */
if (curr->accepting && fail->maxshift > curr->depth - fail->depth)
fail->maxshift = curr->depth - fail->depth;
}
}
/* Traverse the trie in level order again, fixing up all nodes whose
shift exceeds their inherited maxshift. */
for (curr = kwset->trie->next; curr; curr = curr->next)
{
if (curr->maxshift > curr->parent->maxshift)
curr->maxshift = curr->parent->maxshift;
if (curr->shift > curr->maxshift)
curr->shift = curr->maxshift;
}
/* Create a vector, indexed by character code, of the outgoing links
from the root node. */
for (i = 0; i < NCHAR; ++i)
next[i] = NULL;
treenext(kwset->trie->links, next);
if ((trans = kwset->trans) != NULL)
for (i = 0; i < NCHAR; ++i)
kwset->next[i] = next[U(trans[i])];
else
memcpy(kwset->next, next, NCHAR * sizeof(struct trie *));
}
/* Fix things up for any translation table. */
if ((trans = kwset->trans) != NULL)
for (i = 0; i < NCHAR; ++i)
kwset->delta[i] = delta[U(trans[i])];
else
memcpy(kwset->delta, delta, NCHAR);
return NULL;
}
/* Fast boyer-moore search. */
static size_t
bmexec (kwset_t kws, char const *text, size_t size)
{
struct kwset const *kwset;
register unsigned char const *d1;
register char const *ep, *sp, *tp;
register int d, gc, i, len, md2;
kwset = (struct kwset const *) kws;
len = kwset->mind;
if (len == 0)
return 0;
if (len > size)
return -1;
if (len == 1)
{
tp = memchr (text, kwset->target[0], size);
return tp ? tp - text : -1;
}
d1 = kwset->delta;
sp = kwset->target + len;
gc = U(sp[-2]);
md2 = kwset->mind2;
tp = text + len;
/* Significance of 12: 1 (initial offset) + 10 (skip loop) + 1 (md2). */
if (size > 12 * len)
/* 11 is not a bug, the initial offset happens only once. */
for (ep = text + size - 11 * len;;)
{
while (tp <= ep)
{
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
if (d == 0)
goto found;
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
if (d == 0)
goto found;
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
if (d == 0)
goto found;
d = d1[U(tp[-1])], tp += d;
d = d1[U(tp[-1])], tp += d;
}
break;
found:
if (U(tp[-2]) == gc)
{
for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
;
if (i > len)
return tp - len - text;
}
tp += md2;
}
/* Now we have only a few characters left to search. We
carefully avoid ever producing an out-of-bounds pointer. */
ep = text + size;
d = d1[U(tp[-1])];
while (d <= ep - tp)
{
d = d1[U((tp += d)[-1])];
if (d != 0)
continue;
if (U(tp[-2]) == gc)
{
for (i = 3; i <= len && U(tp[-i]) == U(sp[-i]); ++i)
;
if (i > len)
return tp - len - text;
}
d = md2;
}
return -1;
}
/* Hairy multiple string search. */
static size_t
cwexec (kwset_t kws, char const *text, size_t len, struct kwsmatch *kwsmatch)
{
struct kwset const *kwset;
struct trie * const *next;
struct trie const *trie;
struct trie const *accept;
char const *beg, *lim, *mch, *lmch;
register unsigned char c;
register unsigned char const *delta;
register int d;
register char const *end, *qlim;
register struct tree const *tree;
register unsigned char const *trans;
accept = NULL;
/* Initialize register copies and look for easy ways out. */
kwset = (struct kwset *) kws;
if (len < kwset->mind)
return -1;
next = kwset->next;
delta = kwset->delta;
trans = kwset->trans;
lim = text + len;
end = text;
if ((d = kwset->mind) != 0)
mch = NULL;
else
{
mch = text, accept = kwset->trie;
goto match;
}
if (len >= 4 * kwset->mind)
qlim = lim - 4 * kwset->mind;
else
qlim = NULL;
while (lim - end >= d)
{
if (qlim && end <= qlim)
{
end += d - 1;
while ((d = delta[c = *end]) && end < qlim)
{
end += d;
end += delta[U(*end)];
end += delta[U(*end)];
}
++end;
}
else
d = delta[c = (end += d)[-1]];
if (d)
continue;
beg = end - 1;
trie = next[c];
if (trie->accepting)
{
mch = beg;
accept = trie;
}
d = trie->shift;
while (beg > text)
{
c = trans ? trans[U(*--beg)] : *--beg;
tree = trie->links;
while (tree && c != tree->label)
if (c < tree->label)
tree = tree->llink;
else
tree = tree->rlink;
if (tree)
{
trie = tree->trie;
if (trie->accepting)
{
mch = beg;
accept = trie;
}
}
else
break;
d = trie->shift;
}
if (mch)
goto match;
}
return -1;
match:
/* Given a known match, find the longest possible match anchored
at or before its starting point. This is nearly a verbatim
copy of the preceding main search loops. */
if (lim - mch > kwset->maxd)
lim = mch + kwset->maxd;
lmch = NULL;
d = 1;
while (lim - end >= d)
{
if ((d = delta[c = (end += d)[-1]]) != 0)
continue;
beg = end - 1;
if (!(trie = next[c]))
{
d = 1;
continue;
}
if (trie->accepting && beg <= mch)
{
lmch = beg;
accept = trie;
}
d = trie->shift;
while (beg > text)
{
c = trans ? trans[U(*--beg)] : *--beg;
tree = trie->links;
while (tree && c != tree->label)
if (c < tree->label)
tree = tree->llink;
else
tree = tree->rlink;
if (tree)
{
trie = tree->trie;
if (trie->accepting && beg <= mch)
{
lmch = beg;
accept = trie;
}
}
else
break;
d = trie->shift;
}
if (lmch)
{
mch = lmch;
goto match;
}
if (!d)
d = 1;
}
if (kwsmatch)
{
kwsmatch->index = accept->accepting / 2;
kwsmatch->offset[0] = mch - text;
kwsmatch->size[0] = accept->depth;
}
return mch - text;
}
/* Search through the given text for a match of any member of the
given keyword set. Return a pointer to the first character of
the matching substring, or NULL if no match is found. If FOUNDLEN
is non-NULL store in the referenced location the length of the
matching substring. Similarly, if FOUNDIDX is non-NULL, store
in the referenced location the index number of the particular
keyword matched. */
size_t
kwsexec (kwset_t kws, char const *text, size_t size,
struct kwsmatch *kwsmatch)
{
struct kwset const *kwset = (struct kwset *) kws;
if (kwset->words == 1 && kwset->trans == NULL)
{
size_t ret = bmexec (kws, text, size);
if (kwsmatch != NULL && ret != (size_t) -1)
{
kwsmatch->index = 0;
kwsmatch->offset[0] = ret;
kwsmatch->size[0] = kwset->mind;
}
return ret;
}
else
return cwexec(kws, text, size, kwsmatch);
}
/* Free the components of the given keyword set. */
void
kwsfree (kwset_t kws)
{
struct kwset *kwset;
kwset = (struct kwset *) kws;
obstack_free(&kwset->obstack, NULL);
free(kws);
}
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