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.
This commit is contained in:
Michael Forney
Anselm R Garbe
parent
5cb3a1eba1
commit
9a3b12525b
31
cksum.c
31
cksum.c
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@ -1,7 +1,9 @@
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/* See LICENSE file for copyright and license details. */
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#include <fcntl.h>
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#include <inttypes.h>
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#include <stdio.h>
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#include <string.h>
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#include <unistd.h>
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#include "util.h"
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@ -61,19 +63,20 @@ static const unsigned long crctab[] = { 0x00000000,
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};
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static void
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cksum(FILE *fp, const char *s)
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cksum(int fd, const char *s)
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{
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size_t len = 0, i, n;
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ssize_t n;
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size_t len = 0, i;
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uint32_t ck = 0;
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unsigned char buf[BUFSIZ];
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while ((n = fread(buf, 1, sizeof(buf), fp))) {
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while ((n = read(fd, buf, sizeof(buf))) > 0) {
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for (i = 0; i < n; i++)
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ck = (ck << 8) ^ crctab[(ck >> 24) ^ buf[i]];
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len += n;
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}
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if (ferror(fp)) {
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weprintf("fread %s:", s ? s : "<stdin>");
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if (n < 0) {
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weprintf("read %s:", s ? s : "<stdin>");
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ret = 1;
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return;
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}
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@ -92,29 +95,29 @@ cksum(FILE *fp, const char *s)
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int
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main(int argc, char *argv[])
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{
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FILE *fp;
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int fd;
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argv0 = argv[0], argc--, argv++;
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if (!argc) {
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cksum(stdin, NULL);
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cksum(0, NULL);
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} else {
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for (; *argv; argc--, argv++) {
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if (!strcmp(*argv, "-")) {
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*argv = "<stdin>";
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fp = stdin;
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} else if (!(fp = fopen(*argv, "r"))) {
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weprintf("fopen %s:", *argv);
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fd = 0;
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} else if ((fd = open(*argv, O_RDONLY)) < 0) {
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weprintf("open %s:", *argv);
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ret = 1;
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continue;
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}
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cksum(fp, *argv);
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if (fp != stdin && fshut(fp, *argv))
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ret = 1;
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cksum(fd, *argv);
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if (fd != 0)
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close(fd);
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}
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}
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ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>");
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ret |= fshut(stdout, "<stdout>");
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return ret;
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}
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2
crypt.h
2
crypt.h
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@ -8,5 +8,5 @@ struct crypt_ops {
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int cryptcheck(int, char **, struct crypt_ops *, uint8_t *, size_t);
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int cryptmain(int, char **, struct crypt_ops *, uint8_t *, size_t);
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int cryptsum(struct crypt_ops *, FILE *, const char *, uint8_t *);
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int cryptsum(struct crypt_ops *, int, const char *, uint8_t *);
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void mdprint(const uint8_t *, const char *, size_t);
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@ -1,8 +1,10 @@
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/* See LICENSE file for copyright and license details. */
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#include <fcntl.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "../crypt.h"
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#include "../text.h"
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@ -41,7 +43,7 @@ static void
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mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
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int *formatsucks, int *noread, int *nonmatch)
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{
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FILE *fp;
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int fd;
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size_t bufsiz = 0;
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int r;
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char *line = NULL, *file, *p;
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@ -59,12 +61,12 @@ mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
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file += 2;
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for (p = file; *p && *p != '\n' && *p != '\r'; p++); /* strip newline */
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*p = '\0';
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if (!(fp = fopen(file, "r"))) {
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weprintf("fopen %s:", file);
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if ((fd = open(file, O_RDONLY)) < 0) {
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weprintf("open %s:", file);
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(*noread)++;
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continue;
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}
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if (cryptsum(ops, fp, file, md)) {
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if (cryptsum(ops, fd, file, md)) {
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(*noread)++;
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continue;
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}
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@ -77,7 +79,7 @@ mdchecklist(FILE *listfp, struct crypt_ops *ops, uint8_t *md, size_t sz,
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} else {
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(*formatsucks)++;
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}
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fclose(fp);
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close(fd);
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}
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free(line);
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}
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@ -124,11 +126,11 @@ cryptcheck(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz
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int
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cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
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{
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FILE *fp;
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int fd;
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int ret = 0;
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if (argc == 0) {
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if (cryptsum(ops, stdin, "<stdin>", md))
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if (cryptsum(ops, 0, "<stdin>", md))
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ret = 1;
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else
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mdprint(md, "<stdin>", sz);
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@ -136,18 +138,18 @@ cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
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for (; *argv; argc--, argv++) {
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if ((*argv)[0] == '-' && !(*argv)[1]) {
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*argv = "<stdin>";
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fp = stdin;
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} else if (!(fp = fopen(*argv, "r"))) {
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weprintf("fopen %s:", *argv);
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fd = 0;
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} else if ((fd = open(*argv, O_RDONLY)) < 0) {
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weprintf("open %s:", *argv);
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ret = 1;
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continue;
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}
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if (cryptsum(ops, fp, *argv, md))
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if (cryptsum(ops, fd, *argv, md))
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ret = 1;
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else
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mdprint(md, *argv, sz);
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if (fp != stdin && fshut(fp, *argv))
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ret = 1;
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if (fd != 0)
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close(fd);
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}
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}
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@ -155,16 +157,15 @@ cryptmain(int argc, char *argv[], struct crypt_ops *ops, uint8_t *md, size_t sz)
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}
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int
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cryptsum(struct crypt_ops *ops, FILE *fp, const char *f,
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uint8_t *md)
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cryptsum(struct crypt_ops *ops, int fd, const char *f, uint8_t *md)
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{
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uint8_t buf[BUFSIZ];
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size_t n;
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ssize_t n;
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ops->init(ops->s);
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while ((n = fread(buf, 1, sizeof(buf), fp)) > 0)
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while ((n = read(fd, buf, sizeof(buf))) > 0)
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ops->update(ops->s, buf, n);
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if (ferror(fp)) {
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if (n < 0) {
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weprintf("%s: read error:", f);
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return 1;
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}
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43
od.c
43
od.c
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@ -1,8 +1,10 @@
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/* See LICENSE file for copyright and license details. */
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#include <fcntl.h>
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#include <stdint.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include "queue.h"
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#include "util.h"
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@ -124,20 +126,23 @@ once:
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}
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}
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static void
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od(FILE *fp, char *fname, int last)
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static int
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od(int fd, char *fname, int last)
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{
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static unsigned char *line;
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static size_t lineoff;
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static off_t addr;
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unsigned char buf[BUFSIZ];
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size_t i, n, size = sizeof(buf);
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size_t i, size = sizeof(buf);
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ssize_t n;
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while (skip - addr > 0) {
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n = fread(buf, 1, MIN(skip - addr, sizeof(buf)), fp);
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n = read(fd, buf, MIN(skip - addr, sizeof(buf)));
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if (n < 0)
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weprintf("read %s:", fname);
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if (n <= 0)
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return n;
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addr += n;
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if (feof(fp) || ferror(fp))
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return;
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}
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if (!line)
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line = emalloc(linelen);
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@ -145,7 +150,7 @@ od(FILE *fp, char *fname, int last)
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for (;;) {
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if (max >= 0)
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size = MIN(max - (addr - skip), size);
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if (!(n = fread(buf, 1, size, fp)))
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if ((n = read(fd, buf, size)) <= 0)
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break;
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for (i = 0; i < n; i++, addr++) {
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line[lineoff++] = buf[i];
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@ -155,10 +160,15 @@ od(FILE *fp, char *fname, int last)
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}
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}
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}
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if (n < 0) {
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weprintf("read %s:", fname);
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return n;
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}
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if (lineoff && last)
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printline(line, lineoff, addr - lineoff);
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if (last)
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printline((unsigned char *)"", 0, addr);
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return 0;
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}
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static int
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@ -196,7 +206,7 @@ usage(void)
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int
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main(int argc, char *argv[])
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{
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FILE *fp;
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int fd;
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struct type *t;
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int ret = 0, len;
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char *s;
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@ -293,25 +303,26 @@ main(int argc, char *argv[])
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linelen *= 2;
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if (!argc) {
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od(stdin, "<stdin>", 1);
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if (od(0, "<stdin>", 1) < 0)
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ret = 1;
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} else {
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for (; *argv; argc--, argv++) {
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if (!strcmp(*argv, "-")) {
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*argv = "<stdin>";
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fp = stdin;
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} else if (!(fp = fopen(*argv, "r"))) {
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weprintf("fopen %s:", *argv);
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fd = 0;
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} else if ((fd = open(*argv, O_RDONLY)) < 0) {
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weprintf("open %s:", *argv);
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ret = 1;
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continue;
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}
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od(fp, *argv, (!*(argv + 1)));
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if (fp != stdin && fshut(fp, *argv))
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if (od(fd, *argv, (!*(argv + 1))) < 0)
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ret = 1;
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if (fd != 0)
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close(fd);
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}
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}
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ret |= fshut(stdin, "<stdin>") | fshut(stdout, "<stdout>") |
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fshut(stderr, "<stderr>");
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ret |= fshut(stdout, "<stdout>") | fshut(stderr, "<stderr>");
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return ret;
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}
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39
tee.c
39
tee.c
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@ -1,6 +1,7 @@
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/* See LICENSE file for copyright and license details. */
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#include <fcntl.h>
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#include <signal.h>
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#include <stdio.h>
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#include <unistd.h>
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#include "util.h"
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@ -13,14 +14,15 @@ usage(void)
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int
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main(int argc, char *argv[])
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{
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FILE **fps = NULL;
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size_t i, n, nfps;
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int ret = 0, aflag = 0, iflag = 0;
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int *fds = NULL;
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size_t i, nfds;
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ssize_t n;
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int ret = 0, aflag = O_TRUNC, iflag = 0;
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char buf[BUFSIZ];
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ARGBEGIN {
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case 'a':
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aflag = 1;
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aflag = O_APPEND;
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break;
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case 'i':
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iflag = 1;
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@ -31,31 +33,28 @@ main(int argc, char *argv[])
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if (iflag && signal(SIGINT, SIG_IGN) == SIG_ERR)
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eprintf("signal:");
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nfps = argc + 1;
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fps = ecalloc(nfps, sizeof(*fps));
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nfds = argc + 1;
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fds = ecalloc(nfds, sizeof(*fds));
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for (i = 0; i < argc; i++) {
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if (!(fps[i] = fopen(argv[i], aflag ? "a" : "w"))) {
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weprintf("fopen %s:", argv[i]);
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if ((fds[i] = open(argv[i], O_WRONLY|O_CREAT|aflag, 0666)) < 0) {
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weprintf("open %s:", argv[i]);
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ret = 1;
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}
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}
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fps[i] = stdout;
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fds[i] = 1;
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while ((n = fread(buf, 1, sizeof(buf), stdin))) {
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for (i = 0; i < nfps; i++) {
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if (fps[i] && fwrite(buf, 1, n, fps[i]) != n) {
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fshut(fps[i], (i != argc) ? argv[i] : "<stdout>");
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fps[i] = NULL;
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while ((n = read(0, buf, sizeof(buf))) > 0) {
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for (i = 0; i < nfds; i++) {
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if (fds[i] >= 0 && writeall(fds[i], buf, n) < 0) {
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weprintf("write %s:", (i != argc) ? argv[i] : "<stdout>");
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fds[i] = -1;
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ret = 1;
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}
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}
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}
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ret |= fshut(stdin, "<stdin>");
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for (i = 0; i < nfps; i++)
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if (fps[i])
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ret |= fshut(fps[i], (i != argc) ? argv[i] : "<stdout>");
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if (n < 0)
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eprintf("read <stdin>:");
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return ret;
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}
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Block a user