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Make cmp work by mmapping chunks of a file, rather than the whole

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file at one time.

PR:		24732
Submitted by:	Andrew L. Neporada <andr@dgap.mipt.ru>
MFC after:	2 weeks
This commit is contained in:
David Malone 2001-11-04 21:31:16 +00:00
parent b1f214cf5f
commit 60b49f05fa
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=86044
1 changed files with 52 additions and 14 deletions
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66
usr.bin/cmp/regular.c
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@ -51,6 +51,9 @@ static const char sccsid[] = "@(#)regular.c 8.3 (Berkeley) 4/2/94";
#include "extern.h"
static u_char *remmap __P((u_char *, int, off_t));
#define MMAP_CHUNK (8*1024*1024)
#define ROUNDPAGE(i) ((i) & ~pagemask)
void
@ -59,7 +62,7 @@ c_regular(fd1, file1, skip1, len1, fd2, file2, skip2, len2)
char *file1, *file2;
off_t skip1, len1, skip2, len2;
{
u_char ch, *p1, *p2;
u_char ch, *p1, *p2, *m1, *m2, *e1, *e2;
off_t byte, length, line;
int dfound;
off_t pagemask, off1, off2;
@ -81,23 +84,25 @@ c_regular(fd1, file1, skip1, len1, fd2, file2, skip2, len2)
off2 = ROUNDPAGE(skip2);
length = MIN(len1, len2);
if (length > SIZE_T_MAX)
return (c_special(fd1, file1, skip1, fd2, file2, skip2));
if ((p1 = (u_char *)mmap(NULL, (size_t)len1 + skip1 % pagesize,
PROT_READ, MAP_SHARED, fd1, off1)) == (u_char *)MAP_FAILED)
err(ERR_EXIT, "%s", file1);
if ((m1 = remmap(NULL, fd1, off1)) == NULL) {
c_special(fd1, file1, skip1, fd2, file2, skip2);
return;
}
madvise(p1, len1 + skip1 % pagesize, MADV_SEQUENTIAL);
if ((p2 = (u_char *)mmap(NULL, (size_t)len2 + skip2 % pagesize,
PROT_READ, MAP_SHARED, fd2, off2)) == (u_char *)MAP_FAILED)
err(ERR_EXIT, "%s", file2);
madvise(p2, len2 + skip2 % pagesize, MADV_SEQUENTIAL);
if ((m2 = remmap(NULL, fd2, off2)) == NULL) {
munmap(m1, MMAP_CHUNK);
c_special(fd1, file1, skip1, fd2, file2, skip2);
return;
}
dfound = 0;
p1 += skip1 - off1;
p2 += skip2 - off2;
for (byte = line = 1; length--; ++p1, ++p2, ++byte) {
e1 = m1 + MMAP_CHUNK;
e2 = m2 + MMAP_CHUNK;
p1 = m1 + (skip1 - off1);
p2 = m2 + (skip2 - off2);
for (byte = line = 1; length--; ++byte) {
if ((ch = *p1) != *p2) {
if (xflag) {
dfound = 1;
@ -111,10 +116,43 @@ c_regular(fd1, file1, skip1, len1, fd2, file2, skip2, len2)
}
if (ch == '\n')
++line;
if (++p1 == e1) {
off1 += MMAP_CHUNK;
if ((p1 = m1 = remmap(m1, fd1, off1)) == NULL) {
munmap(m2, MMAP_CHUNK);
err(ERR_EXIT, "remmap %s", file1);
}
e1 = m1 + MMAP_CHUNK;
}
if (++p2 == e2) {
off2 += MMAP_CHUNK;
if ((p2 = m2 = remmap(m2, fd2, off2)) == NULL) {
munmap(m1, MMAP_CHUNK);
err(ERR_EXIT, "remmap %s", file2);
}
e2 = m2 + MMAP_CHUNK;
}
}
munmap(m1, MMAP_CHUNK);
munmap(m2, MMAP_CHUNK);
if (len1 != len2)
eofmsg (len1 > len2 ? file2 : file1);
if (dfound)
exit(DIFF_EXIT);
}
static u_char *
remmap(mem, fd, offset)
u_char *mem;
int fd;
off_t offset;
{
if (mem != NULL)
munmap(mem, MMAP_CHUNK);
mem = mmap(NULL, MMAP_CHUNK, PROT_READ, MAP_SHARED, fd, offset);
if (mem == MAP_FAILED)
return (NULL);
madvise(mem, MMAP_CHUNK, MADV_SEQUENTIAL);
return (mem);
}