From: Jim Beveridge <ji...@chromium.org>
The original code is by Jim Beveridge working on Fuchsia. I merged it
with slight changes.
Time to tar two 1GB files:
Before patch:
real 0m6.428s
user 0m0.245s
sys 0m4.881s
real 0m6.454s
user 0m0.239s
sys 0m4.883s
real 0m6.515s
user 0m0.259s
sys 0m4.839s
After patch:
real 0m4.755s
user 0m0.026s
sys 0m1.598s
real 0m4.788s
user 0m0.063s
sys 0m1.578s
real 0m4.822s
user 0m0.007s
sys 0m1.662s
A similar speedup can be observed for untaring.
In addition to the buffer size increase we change the code to only create
directories for non-compliant tar files and we check for st to be NULL
in the recursive copy function.
---
tar.c | 72 +++++++++++++++++++++++++++++++++++++++++++++++++++----------------
1 file changed, 55 insertions(+), 17 deletions(-)
diff --git a/tar.c b/tar.c
index 53a737c..8cd1abe 100644
--- a/tar.c
+++ b/tar.c
@@ -16,6 +16,8 @@
#include "util.h"
#define BLKSIZ 512
+// COPY_CHUNK_SIZE must be a power of 2
+#define COPY_CHUNK_SIZE 8192
enum Type {
REG = '0',
@@ -236,10 +238,13 @@ archive(const char *path)
ewrite(tarfd, b, BLKSIZ);
if (fd != -1) {
- while ((l = eread(fd, b, BLKSIZ)) > 0) {
- if (l < BLKSIZ)
- memset(b + l, 0, BLKSIZ - l);
- ewrite(tarfd, b, BLKSIZ);
+ char chunk[COPY_CHUNK_SIZE];
+ while ((l = eread(fd, chunk, COPY_CHUNK_SIZE)) > 0) {
+ // Ceiling to BLKSIZ boundary
+ int ceilsize = (l + (BLKSIZ-1)) & ~(BLKSIZ-1);
+ if (l < ceilsize)
+ memset(chunk + l, 0, ceilsize - l);
+ ewrite(tarfd, chunk, ceilsize);
}
close(fd);
}
@@ -250,7 +255,7 @@ archive(const char *path)
static int
unarchive(char *fname, ssize_t l, char b[BLKSIZ])
{
- char lname[101], *tmp, *p;
+ char lname[101], *p;
long mode, major, minor, type, mtime, uid, gid;
struct header *h = (struct header *)b;
int fd = -1;
@@ -261,9 +266,13 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
if (remove(fname) < 0 && errno != ENOENT)
weprintf("remove %s:", fname);
- tmp = estrdup(fname);
- mkdirp(dirname(tmp), 0777, 0777);
- free(tmp);
+ // tar files normally create the directory chain. This is a fallback
+ // for noncompliant tar files.
+ if (h->type != DIRECTORY) {
+ char* tmp = estrdup(fname);
+ mkdirp(dirname(tmp), 0777, 0777);
+ free(tmp);
+ }
switch (h->type) {
case REG:
@@ -319,9 +328,25 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
eprintf("strtol %s: invalid number\n", h->gid);
if (fd != -1) {
- for (; l > 0; l -= BLKSIZ)
- if (eread(tarfd, b, BLKSIZ) > 0)
- ewrite(fd, b, MIN(l, BLKSIZ));
+ // Ceiling to BLKSIZ boundary
+ int readsize = (l + (BLKSIZ-1)) & ~(BLKSIZ-1);
+ char chunk[COPY_CHUNK_SIZE];
+ int lastread = 0;
+
+ for (; readsize > 0; l -= lastread, readsize -= lastread) {
+ int chunk_size = MIN(readsize, COPY_CHUNK_SIZE);
+ // Short reads are legal, so don't expect to read
+ // everything that was requested.
+ lastread = eread(tarfd, chunk, chunk_size);
+ if (lastread == 0) {
+ close(fd);
+ remove(fname);
+ eprintf("unexpected end of file reading %s.\n",
+ fname);
+ }
+
+ ewrite(fd, chunk, MIN(l, lastread));
+ }
close(fd);
}
@@ -331,7 +356,7 @@ unarchive(char *fname, ssize_t l, char b[BLKSIZ])
times[0].tv_sec = times[1].tv_sec = mtime;
times[0].tv_nsec = times[1].tv_nsec = 0;
if (!mflag && utimensat(AT_FDCWD, fname, times, AT_SYMLINK_NOFOLLOW) <
0)
- weprintf("utimensat %s:\n", fname);
+ weprintf("utimensat %s %d:\n", fname, errno);
if (h->type == SYMLINK) {
if (!getuid() && lchown(fname, uid, gid))
weprintf("lchown %s:\n", fname);
@@ -349,10 +374,23 @@ static void
skipblk(ssize_t l)
{
char b[BLKSIZ];
-
- for (; l > 0; l -= BLKSIZ)
- if (!eread(tarfd, b, BLKSIZ))
- break;
+ int lastread = 0;
+ // Ceiling to BLKSIZ boundary
+ int ceilsize = (l + (BLKSIZ-1)) & ~(BLKSIZ-1);
+
+ off_t offset = lseek(tarfd, ceilsize, SEEK_CUR);
+ if (offset >= ceilsize)
+ return;
+ if (errno != ESPIPE)
+ eprintf("unexpected end of file.\n");
+
+ // This is a pipe, socket or FIFO. Fall back to a sequential read.
+ for (; ceilsize > 0; ceilsize -= lastread) {
+ int chunk_size = MIN(ceilsize, BLKSIZ);
+ lastread = eread(tarfd, b, chunk_size);
+ if (lastread == 0)
+ eprintf("unexpected end of file %d.\n", errno);
+ }
}
static int
@@ -370,7 +408,7 @@ c(const char *path, struct stat *st, void *data, struct
recursor *r)
if (vflag)
puts(path);
- if (S_ISDIR(st->st_mode))
+ if (st && S_ISDIR(st->st_mode))
recurse(path, NULL, r);
}
--
2.7.4
