Don't use buffered IO (fread) when not appropriate

fread reads the entire requested size (BUFSIZ), which causes tools to
block if only small amounts of data are available at a time. At best,
this causes unnecessary copies and inefficiency, at worst, tools like
tee and cat are almost unusable in some cases since they only display
large chunks of data at a time.
master
Michael Forney 6 years ago committed by Anselm R Garbe
parent 5cb3a1eba1
commit 9a3b12525b

@ -1,7 +1,9 @@
/* See LICENSE file for copyright and license details. */
#include <fcntl.h>
#include <inttypes.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "util.h"
@ -61,19 +63,20 @@ static const unsigned long crctab[] = { 0x00000000,
};
static void
cksum(FILE *fp, const char *s)
cksum(int fd, const char *s)
{
size_t len = 0, i, n;
ssize_t n;
size_t len = 0, i;
uint32_t ck = 0;
unsigned char buf[BUFSIZ];
while ((n = fread(buf, 1, sizeof(buf), fp))) {
while ((n = read(fd, buf, sizeof(buf))) > 0) {
for (i = 0; i < n; i++)
ck = (ck << 8) ^ crctab[(ck >> 24) ^ buf[i]];
len += n;
}
if (ferror(fp)) {
weprintf("fread %s:", s ? s : "<stdin>");
if (n < 0) {
weprintf("read %s:", s ? s : "<stdin>");
ret = 1;
return;
}
@ -92,29 +95,29 @@ cksum(FILE *fp, const char *s)
int
main(int argc, char *argv[])
{
FILE *fp;
int fd;
argv0 = argv[0], argc--, argv++;
if (!argc) {
cksum(stdin, NULL);
cksum(0, NULL);
} else {
for (; *argv; argc--, argv++) {
if (!strcmp(*argv, "-")) {
*argv = "<stdin>";
fp = stdin;
} else if (!(fp = fopen(*argv, "r"))) {
weprintf("fopen %s:", *argv);
fd = 0;
} else if ((fd = open(*argv, O_RDONLY)) < 0) {
weprintf("open %s:", *argv);
ret = 1;
continue;
}
cksum(fp, *argv);
if (fp != stdin && fshut(fp, *argv))
ret = 1;
cksum(fd, *argv);
if (fd != 0)
close(fd);
}
}
ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
ret |= fshut(stdout, "<stdout>");
return ret;
}

@ -8,5 +8,5 @@ struct crypt_ops {
int cryptcheck(int, char **, struct crypt_ops *, uint8_t *, size_t);
int cryptmain(int, char **, struct crypt_ops *, uint8_t *, size_t);
int cryptsum(struct crypt_ops *, FILE *, const char *, uint8_t *);
int cryptsum(struct crypt_ops *, int, const char *, uint8_t *);
void mdprint(const uint8_t *, const char *, size_t);

@ -1,8 +1,10 @@
/* See LICENSE file for copyright and license details. */
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "../crypt.h"
#include "../text.h"
@ -41,7 +43,7 @@ static void
mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
int *formatsucks, int *noread, int *nonmatch)
{
FILE *fp;
int fd;
size_t bufsiz = 0;
int r;
char *line = NULL, *file, *p;
@ -59,12 +61,12 @@ mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
file += 2;
for (p = file; *p && *p != '\n' && *p != '\r'; p++); /* strip newline */
*p = '\0';
if (!(fp = fopen(file, "r"))) {
weprintf("fopen %s:", file);
if ((fd = open(file, O_RDONLY)) < 0) {
weprintf("open %s:", file);
(*noread)++;
continue;
}
if (cryptsum(ops, fp, file, md)) {
if (cryptsum(ops, fd, file, md)) {
(*noread)++;
continue;
}
@ -77,7 +79,7 @@ mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
} else {
(*formatsucks)++;
}
fclose(fp);
close(fd);
}
free(line);
}
@ -124,11 +126,11 @@ cryptcheck(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz
int
cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
{
FILE *fp;
int fd;
int ret = 0;
if (argc == 0) {
if (cryptsum(ops, stdin, "<stdin>", md))
if (cryptsum(ops, 0, "<stdin>", md))
ret = 1;
else
mdprint(md, "<stdin>", sz);
@ -136,18 +138,18 @@ cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
for (; *argv; argc--, argv++) {
if ((*argv)[0] == '-' && !(*argv)[1]) {
*argv = "<stdin>";
fp = stdin;
} else if (!(fp = fopen(*argv, "r"))) {
weprintf("fopen %s:", *argv);
fd = 0;
} else if ((fd = open(*argv, O_RDONLY)) < 0) {
weprintf("open %s:", *argv);
ret = 1;
continue;
}
if (cryptsum(ops, fp, *argv, md))
if (cryptsum(ops, fd, *argv, md))
ret = 1;
else
mdprint(md, *argv, sz);
if (fp != stdin && fshut(fp, *argv))
ret = 1;
if (fd != 0)
close(fd);
}
}
@ -155,16 +157,15 @@ cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
}
int
cryptsum(struct crypt_ops *ops, FILE *fp, const char *f,
uint8_t *md)
cryptsum(struct crypt_ops *ops, int fd, const char *f, uint8_t *md)
{
uint8_t buf[BUFSIZ];
size_t n;
ssize_t n;
ops->init(ops->s);
while ((n = fread(buf, 1, sizeof(buf), fp)) > 0)
while ((n = read(fd, buf, sizeof(buf))) > 0)
ops->update(ops->s, buf, n);
if (ferror(fp)) {
if (n < 0) {
weprintf("%s: read error:", f);
return 1;
}

43
od.c

@ -1,8 +1,10 @@
/* See LICENSE file for copyright and license details. */
#include <fcntl.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include "queue.h"
#include "util.h"
@ -124,20 +126,23 @@ once:
}
}
static void
od(FILE *fp, char *fname, int last)
static int
od(int fd, char *fname, int last)
{
static unsigned char *line;
static size_t lineoff;
static off_t addr;
unsigned char buf[BUFSIZ];
size_t i, n, size = sizeof(buf);
size_t i, size = sizeof(buf);
ssize_t n;
while (skip - addr > 0) {
n = fread(buf, 1, MIN(skip - addr, sizeof(buf)), fp);
n = read(fd, buf, MIN(skip - addr, sizeof(buf)));
if (n < 0)
weprintf("read %s:", fname);
if (n <= 0)
return n;
addr += n;
if (feof(fp) || ferror(fp))
return;
}
if (!line)
line = emalloc(linelen);
@ -145,7 +150,7 @@ od(FILE *fp, char *fname, int last)
for (;;) {
if (max >= 0)
size = MIN(max - (addr - skip), size);
if (!(n = fread(buf, 1, size, fp)))
if ((n = read(fd, buf, size)) <= 0)
break;
for (i = 0; i < n; i++, addr++) {
line[lineoff++] = buf[i];
@ -155,10 +160,15 @@ od(FILE *fp, char *fname, int last)
}
}
}
if (n < 0) {
weprintf("read %s:", fname);
return n;
}
if (lineoff && last)
printline(line, lineoff, addr - lineoff);
if (last)
printline((unsigned char *)"", 0, addr);
return 0;
}
static int
@ -196,7 +206,7 @@ usage(void)
int
main(int argc, char *argv[])
{
FILE *fp;
int fd;
struct type *t;
int ret = 0, len;
char *s;
@ -293,25 +303,26 @@ main(int argc, char *argv[])
linelen *= 2;
if (!argc) {
od(stdin, "<stdin>", 1);
if (od(0, "<stdin>", 1) < 0)
ret = 1;
} else {
for (; *argv; argc--, argv++) {
if (!strcmp(*argv, "-")) {
*argv = "<stdin>";
fp = stdin;
} else if (!(fp = fopen(*argv, "r"))) {
weprintf("fopen %s:", *argv);
fd = 0;
} else if ((fd = open(*argv, O_RDONLY)) < 0) {
weprintf("open %s:", *argv);
ret = 1;
continue;
}
od(fp, *argv, (!*(argv + 1)));
if (fp != stdin && fshut(fp, *argv))
if (od(fd, *argv, (!*(argv + 1))) < 0)
ret = 1;
if (fd != 0)
close(fd);
}
}
ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>") |
fshut(stderr, "<stderr>");
ret |= fshut(stdout, "<stdout>") | fshut(stderr, "<stderr>");
return ret;
}

39
tee.c

@ -1,6 +1,7 @@
/* See LICENSE file for copyright and license details. */
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
#include "util.h"
@ -13,14 +14,15 @@ usage(void)
int
main(int argc, char *argv[])
{
FILE **fps = NULL;
size_t i, n, nfps;
int ret = 0, aflag = 0, iflag = 0;
int *fds = NULL;
size_t i, nfds;
ssize_t n;
int ret = 0, aflag = O_TRUNC, iflag = 0;
char buf[BUFSIZ];
ARGBEGIN {
case 'a':
aflag = 1;
aflag = O_APPEND;
break;
case 'i':
iflag = 1;
@ -31,31 +33,28 @@ main(int argc, char *argv[])
if (iflag && signal(SIGINT, SIG_IGN) == SIG_ERR)
eprintf("signal:");
nfps = argc + 1;
fps = ecalloc(nfps, sizeof(*fps));
nfds = argc + 1;
fds = ecalloc(nfds, sizeof(*fds));
for (i = 0; i < argc; i++) {
if (!(fps[i] = fopen(argv[i], aflag ? "a" : "w"))) {
weprintf("fopen %s:", argv[i]);
if ((fds[i] = open(argv[i], O_WRONLY|O_CREAT|aflag, 0666)) < 0) {
weprintf("open %s:", argv[i]);
ret = 1;
}
}
fps[i] = stdout;
fds[i] = 1;
while ((n = fread(buf, 1, sizeof(buf), stdin))) {
for (i = 0; i < nfps; i++) {
if (fps[i] && fwrite(buf, 1, n, fps[i]) != n) {
fshut(fps[i], (i != argc) ? argv[i] : "<stdout>");
fps[i] = NULL;
while ((n = read(0, buf, sizeof(buf))) > 0) {
for (i = 0; i < nfds; i++) {
if (fds[i] >= 0 && writeall(fds[i], buf, n) < 0) {
weprintf("write %s:", (i != argc) ? argv[i] : "<stdout>");
fds[i] = -1;
ret = 1;
}
}
}
ret |= fshut(stdin, "<stdin>");
for (i = 0; i < nfps; i++)
if (fps[i])
ret |= fshut(fps[i], (i != argc) ? argv[i] : "<stdout>");
if (n < 0)
eprintf("read <stdin>:");
return ret;
}

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