Revision 56d7c27af1f8aa7519f165f6c022732e64db3716 authored by Jeff King on 26 May 2011, 16:30:27 UTC, committed by Junio C Hamano on 26 May 2011, 20:54:18 UTC
The read_in_full function repeatedly calls read() to fill a
buffer. If the first read() returns an error, we notify the
caller by returning the error. However, if we read some data
and then get an error on a subsequent read, we simply return
the amount of data that we did read, and the caller is
unaware of the error.
This makes the tradeoff that seeing the partial data is more
important than the fact that an error occurred. In practice,
this is generally not the case; we care more if an error
occurred, and should throw away any partial data.
I audited the current callers. In most cases, this will make
no difference at all, as they do:
if (read_in_full(fd, buf, size) != size)
error("short read");
However, it will help in a few cases:
1. In sha1_file.c:index_stream, we would fail to notice
errors in the incoming stream.
2. When reading symbolic refs in resolve_ref, we would
fail to notice errors and potentially use a truncated
ref name.
3. In various places, we will get much better error
messages. For example, callers of safe_read would
erroneously print "the remote end hung up unexpectedly"
instead of showing the read error.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 09ffc70
xprepare.c
/*
* LibXDiff by Davide Libenzi ( File Differential Library )
* Copyright (C) 2003 Davide Libenzi
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library 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
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Davide Libenzi <davidel@xmailserver.org>
*
*/
#include "xinclude.h"
#define XDL_KPDIS_RUN 4
#define XDL_MAX_EQLIMIT 1024
#define XDL_SIMSCAN_WINDOW 100
typedef struct s_xdlclass {
struct s_xdlclass *next;
unsigned long ha;
char const *line;
long size;
long idx;
} xdlclass_t;
typedef struct s_xdlclassifier {
unsigned int hbits;
long hsize;
xdlclass_t **rchash;
chastore_t ncha;
long count;
long flags;
} xdlclassifier_t;
static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags);
static void xdl_free_classifier(xdlclassifier_t *cf);
static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
xrecord_t *rec);
static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
xdlclassifier_t *cf, xdfile_t *xdf);
static void xdl_free_ctx(xdfile_t *xdf);
static int xdl_clean_mmatch(char const *dis, long i, long s, long e);
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2);
static int xdl_init_classifier(xdlclassifier_t *cf, long size, long flags) {
long i;
cf->flags = flags;
cf->hbits = xdl_hashbits((unsigned int) size);
cf->hsize = 1 << cf->hbits;
if (xdl_cha_init(&cf->ncha, sizeof(xdlclass_t), size / 4 + 1) < 0) {
return -1;
}
if (!(cf->rchash = (xdlclass_t **) xdl_malloc(cf->hsize * sizeof(xdlclass_t *)))) {
xdl_cha_free(&cf->ncha);
return -1;
}
for (i = 0; i < cf->hsize; i++)
cf->rchash[i] = NULL;
cf->count = 0;
return 0;
}
static void xdl_free_classifier(xdlclassifier_t *cf) {
xdl_free(cf->rchash);
xdl_cha_free(&cf->ncha);
}
static int xdl_classify_record(xdlclassifier_t *cf, xrecord_t **rhash, unsigned int hbits,
xrecord_t *rec) {
long hi;
char const *line;
xdlclass_t *rcrec;
line = rec->ptr;
hi = (long) XDL_HASHLONG(rec->ha, cf->hbits);
for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
if (rcrec->ha == rec->ha &&
xdl_recmatch(rcrec->line, rcrec->size,
rec->ptr, rec->size, cf->flags))
break;
if (!rcrec) {
if (!(rcrec = xdl_cha_alloc(&cf->ncha))) {
return -1;
}
rcrec->idx = cf->count++;
rcrec->line = line;
rcrec->size = rec->size;
rcrec->ha = rec->ha;
rcrec->next = cf->rchash[hi];
cf->rchash[hi] = rcrec;
}
rec->ha = (unsigned long) rcrec->idx;
hi = (long) XDL_HASHLONG(rec->ha, hbits);
rec->next = rhash[hi];
rhash[hi] = rec;
return 0;
}
static int xdl_prepare_ctx(mmfile_t *mf, long narec, xpparam_t const *xpp,
xdlclassifier_t *cf, xdfile_t *xdf) {
unsigned int hbits;
long i, nrec, hsize, bsize;
unsigned long hav;
char const *blk, *cur, *top, *prev;
xrecord_t *crec;
xrecord_t **recs, **rrecs;
xrecord_t **rhash;
unsigned long *ha;
char *rchg;
long *rindex;
if (xdl_cha_init(&xdf->rcha, sizeof(xrecord_t), narec / 4 + 1) < 0) {
return -1;
}
if (!(recs = (xrecord_t **) xdl_malloc(narec * sizeof(xrecord_t *)))) {
xdl_cha_free(&xdf->rcha);
return -1;
}
hbits = xdl_hashbits((unsigned int) narec);
hsize = 1 << hbits;
if (!(rhash = (xrecord_t **) xdl_malloc(hsize * sizeof(xrecord_t *)))) {
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
for (i = 0; i < hsize; i++)
rhash[i] = NULL;
nrec = 0;
if ((cur = blk = xdl_mmfile_first(mf, &bsize)) != NULL) {
for (top = blk + bsize;;) {
if (cur >= top) {
if (!(cur = blk = xdl_mmfile_next(mf, &bsize)))
break;
top = blk + bsize;
}
prev = cur;
hav = xdl_hash_record(&cur, top, xpp->flags);
if (nrec >= narec) {
narec *= 2;
if (!(rrecs = (xrecord_t **) xdl_realloc(recs, narec * sizeof(xrecord_t *)))) {
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
recs = rrecs;
}
if (!(crec = xdl_cha_alloc(&xdf->rcha))) {
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
crec->ptr = prev;
crec->size = (long) (cur - prev);
crec->ha = hav;
recs[nrec++] = crec;
if (xdl_classify_record(cf, rhash, hbits, crec) < 0) {
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
}
}
if (!(rchg = (char *) xdl_malloc((nrec + 2) * sizeof(char)))) {
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
memset(rchg, 0, (nrec + 2) * sizeof(char));
if (!(rindex = (long *) xdl_malloc((nrec + 1) * sizeof(long)))) {
xdl_free(rchg);
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
if (!(ha = (unsigned long *) xdl_malloc((nrec + 1) * sizeof(unsigned long)))) {
xdl_free(rindex);
xdl_free(rchg);
xdl_free(rhash);
xdl_free(recs);
xdl_cha_free(&xdf->rcha);
return -1;
}
xdf->nrec = nrec;
xdf->recs = recs;
xdf->hbits = hbits;
xdf->rhash = rhash;
xdf->rchg = rchg + 1;
xdf->rindex = rindex;
xdf->nreff = 0;
xdf->ha = ha;
xdf->dstart = 0;
xdf->dend = nrec - 1;
return 0;
}
static void xdl_free_ctx(xdfile_t *xdf) {
xdl_free(xdf->rhash);
xdl_free(xdf->rindex);
xdl_free(xdf->rchg - 1);
xdl_free(xdf->ha);
xdl_free(xdf->recs);
xdl_cha_free(&xdf->rcha);
}
int xdl_prepare_env(mmfile_t *mf1, mmfile_t *mf2, xpparam_t const *xpp,
xdfenv_t *xe) {
long enl1, enl2;
xdlclassifier_t cf;
enl1 = xdl_guess_lines(mf1) + 1;
enl2 = xdl_guess_lines(mf2) + 1;
if (xdl_init_classifier(&cf, enl1 + enl2 + 1, xpp->flags) < 0) {
return -1;
}
if (xdl_prepare_ctx(mf1, enl1, xpp, &cf, &xe->xdf1) < 0) {
xdl_free_classifier(&cf);
return -1;
}
if (xdl_prepare_ctx(mf2, enl2, xpp, &cf, &xe->xdf2) < 0) {
xdl_free_ctx(&xe->xdf1);
xdl_free_classifier(&cf);
return -1;
}
xdl_free_classifier(&cf);
if (!(xpp->flags & XDF_PATIENCE_DIFF) &&
xdl_optimize_ctxs(&xe->xdf1, &xe->xdf2) < 0) {
xdl_free_ctx(&xe->xdf2);
xdl_free_ctx(&xe->xdf1);
return -1;
}
return 0;
}
void xdl_free_env(xdfenv_t *xe) {
xdl_free_ctx(&xe->xdf2);
xdl_free_ctx(&xe->xdf1);
}
static int xdl_clean_mmatch(char const *dis, long i, long s, long e) {
long r, rdis0, rpdis0, rdis1, rpdis1;
/*
* Limits the window the is examined during the similar-lines
* scan. The loops below stops when dis[i - r] == 1 (line that
* has no match), but there are corner cases where the loop
* proceed all the way to the extremities by causing huge
* performance penalties in case of big files.
*/
if (i - s > XDL_SIMSCAN_WINDOW)
s = i - XDL_SIMSCAN_WINDOW;
if (e - i > XDL_SIMSCAN_WINDOW)
e = i + XDL_SIMSCAN_WINDOW;
/*
* Scans the lines before 'i' to find a run of lines that either
* have no match (dis[j] == 0) or have multiple matches (dis[j] > 1).
* Note that we always call this function with dis[i] > 1, so the
* current line (i) is already a multimatch line.
*/
for (r = 1, rdis0 = 0, rpdis0 = 1; (i - r) >= s; r++) {
if (!dis[i - r])
rdis0++;
else if (dis[i - r] == 2)
rpdis0++;
else
break;
}
/*
* If the run before the line 'i' found only multimatch lines, we
* return 0 and hence we don't make the current line (i) discarded.
* We want to discard multimatch lines only when they appear in the
* middle of runs with nomatch lines (dis[j] == 0).
*/
if (rdis0 == 0)
return 0;
for (r = 1, rdis1 = 0, rpdis1 = 1; (i + r) <= e; r++) {
if (!dis[i + r])
rdis1++;
else if (dis[i + r] == 2)
rpdis1++;
else
break;
}
/*
* If the run after the line 'i' found only multimatch lines, we
* return 0 and hence we don't make the current line (i) discarded.
*/
if (rdis1 == 0)
return 0;
rdis1 += rdis0;
rpdis1 += rpdis0;
return rpdis1 * XDL_KPDIS_RUN < (rpdis1 + rdis1);
}
/*
* Try to reduce the problem complexity, discard records that have no
* matches on the other file. Also, lines that have multiple matches
* might be potentially discarded if they happear in a run of discardable.
*/
static int xdl_cleanup_records(xdfile_t *xdf1, xdfile_t *xdf2) {
long i, nm, rhi, nreff, mlim;
unsigned long hav;
xrecord_t **recs;
xrecord_t *rec;
char *dis, *dis1, *dis2;
if (!(dis = (char *) xdl_malloc(xdf1->nrec + xdf2->nrec + 2))) {
return -1;
}
memset(dis, 0, xdf1->nrec + xdf2->nrec + 2);
dis1 = dis;
dis2 = dis1 + xdf1->nrec + 1;
if ((mlim = xdl_bogosqrt(xdf1->nrec)) > XDL_MAX_EQLIMIT)
mlim = XDL_MAX_EQLIMIT;
for (i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart]; i <= xdf1->dend; i++, recs++) {
hav = (*recs)->ha;
rhi = (long) XDL_HASHLONG(hav, xdf2->hbits);
for (nm = 0, rec = xdf2->rhash[rhi]; rec; rec = rec->next)
if (rec->ha == hav && ++nm == mlim)
break;
dis1[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
}
if ((mlim = xdl_bogosqrt(xdf2->nrec)) > XDL_MAX_EQLIMIT)
mlim = XDL_MAX_EQLIMIT;
for (i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart]; i <= xdf2->dend; i++, recs++) {
hav = (*recs)->ha;
rhi = (long) XDL_HASHLONG(hav, xdf1->hbits);
for (nm = 0, rec = xdf1->rhash[rhi]; rec; rec = rec->next)
if (rec->ha == hav && ++nm == mlim)
break;
dis2[i] = (nm == 0) ? 0: (nm >= mlim) ? 2: 1;
}
for (nreff = 0, i = xdf1->dstart, recs = &xdf1->recs[xdf1->dstart];
i <= xdf1->dend; i++, recs++) {
if (dis1[i] == 1 ||
(dis1[i] == 2 && !xdl_clean_mmatch(dis1, i, xdf1->dstart, xdf1->dend))) {
xdf1->rindex[nreff] = i;
xdf1->ha[nreff] = (*recs)->ha;
nreff++;
} else
xdf1->rchg[i] = 1;
}
xdf1->nreff = nreff;
for (nreff = 0, i = xdf2->dstart, recs = &xdf2->recs[xdf2->dstart];
i <= xdf2->dend; i++, recs++) {
if (dis2[i] == 1 ||
(dis2[i] == 2 && !xdl_clean_mmatch(dis2, i, xdf2->dstart, xdf2->dend))) {
xdf2->rindex[nreff] = i;
xdf2->ha[nreff] = (*recs)->ha;
nreff++;
} else
xdf2->rchg[i] = 1;
}
xdf2->nreff = nreff;
xdl_free(dis);
return 0;
}
/*
* Early trim initial and terminal matching records.
*/
static int xdl_trim_ends(xdfile_t *xdf1, xdfile_t *xdf2) {
long i, lim;
xrecord_t **recs1, **recs2;
recs1 = xdf1->recs;
recs2 = xdf2->recs;
for (i = 0, lim = XDL_MIN(xdf1->nrec, xdf2->nrec); i < lim;
i++, recs1++, recs2++)
if ((*recs1)->ha != (*recs2)->ha)
break;
xdf1->dstart = xdf2->dstart = i;
recs1 = xdf1->recs + xdf1->nrec - 1;
recs2 = xdf2->recs + xdf2->nrec - 1;
for (lim -= i, i = 0; i < lim; i++, recs1--, recs2--)
if ((*recs1)->ha != (*recs2)->ha)
break;
xdf1->dend = xdf1->nrec - i - 1;
xdf2->dend = xdf2->nrec - i - 1;
return 0;
}
static int xdl_optimize_ctxs(xdfile_t *xdf1, xdfile_t *xdf2) {
if (xdl_trim_ends(xdf1, xdf2) < 0 ||
xdl_cleanup_records(xdf1, xdf2) < 0) {
return -1;
}
return 0;
}
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