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tar,smemcap: commonalyze checksumming code for tar header

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function                                             old     new   delta
chksum_and_xwrite_tar_header                           -      99     +99
writeheader                                          280     199     -81
chksum_and_xwrite                                    102       -    -102
------------------------------------------------------------------------------
(add/remove: 2/1 grow/shrink: 0/1 up/down: 99/-183)           Total: -84 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko
2021-08-20 17:58:49 +02:00
parent 38e9c8c95b
commit 62d5a1e56f
4 changed files with 39 additions and 44 deletions
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35
archival/chksum_and_xwrite_tar_header.c Normal file
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@@ -0,0 +1,35 @@
/*
* Copyright (C) 2021 Denys Vlasenko <vda.linux@googlemail.com>
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
//kbuild:lib-$(CONFIG_FEATURE_TAR_CREATE) += chksum_and_xwrite_tar_header.o
//kbuild:lib-$(CONFIG_SMEMCAP) += chksum_and_xwrite_tar_header.o
#include "libbb.h"
#include "bb_archive.h"
void FAST_FUNC chksum_and_xwrite_tar_header(int fd, struct tar_header_t *hp)
{
/* POSIX says that checksum is done on unsigned bytes
* (Sun and HP-UX gets it wrong... more details in
* GNU tar source) */
const unsigned char *cp;
int chksum, size;
strcpy(hp->magic, "ustar ");
/* Calculate and store the checksum (the sum of all of the bytes of
* the header). The checksum field must be filled with blanks for the
* calculation. The checksum field is formatted differently from the
* other fields: it has 6 digits, a NUL, then a space -- rather than
* digits, followed by a NUL like the other fields... */
memset(hp->chksum, ' ', sizeof(hp->chksum));
cp = (const unsigned char *) hp;
chksum = 0;
size = sizeof(*hp);
do { chksum += *cp++; } while (--size);
sprintf(hp->chksum, "%06o", chksum);
xwrite(fd, hp, sizeof(*hp));
}

31
archival/tar.c
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@@ -254,32 +254,6 @@ static void putOctal(char *cp, int len, off_t value)
}
#define PUT_OCTAL(a, b) putOctal((a), sizeof(a), (b))
static void chksum_and_xwrite(int fd, struct tar_header_t* hp)
{
/* POSIX says that checksum is done on unsigned bytes
* (Sun and HP-UX gets it wrong... more details in
* GNU tar source) */
const unsigned char *cp;
int chksum, size;
strcpy(hp->magic, "ustar ");
/* Calculate and store the checksum (i.e., the sum of all of the bytes of
* the header). The checksum field must be filled with blanks for the
* calculation. The checksum field is formatted differently from the
* other fields: it has 6 digits, a null, then a space -- rather than
* digits, followed by a null like the other fields... */
memset(hp->chksum, ' ', sizeof(hp->chksum));
cp = (const unsigned char *) hp;
chksum = 0;
size = sizeof(*hp);
do { chksum += *cp++; } while (--size);
putOctal(hp->chksum, sizeof(hp->chksum)-1, chksum);
/* Now write the header out to disk */
xwrite(fd, hp, sizeof(*hp));
}
# if ENABLE_FEATURE_TAR_GNU_EXTENSIONS
static void writeLongname(int fd, int type, const char *name, int dir)
{
@@ -310,7 +284,7 @@ static void writeLongname(int fd, int type, const char *name, int dir)
/* + dir: account for possible '/' */
PUT_OCTAL(header.size, size);
chksum_and_xwrite(fd, &header);
chksum_and_xwrite_tar_header(fd, &header);
/* Write filename[/] and pad the block. */
/* dir=0: writes 'name<NUL>', pads */
@@ -441,8 +415,7 @@ static int writeTarHeader(struct TarBallInfo *tbInfo,
header_name, S_ISDIR(statbuf->st_mode));
# endif
/* Now write the header out to disk */
chksum_and_xwrite(tbInfo->tarFd, &header);
chksum_and_xwrite_tar_header(tbInfo->tarFd, &header);
/* Now do the verbose thing (or not) */
if (tbInfo->verboseFlag) {

1
include/bb_archive.h
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@@ -167,6 +167,7 @@ typedef struct tar_header_t { /* byte offset */
struct BUG_tar_header {
char c[sizeof(tar_header_t) == TAR_BLOCK_SIZE ? 1 : -1];
};
void chksum_and_xwrite_tar_header(int fd, struct tar_header_t *hp) FAST_FUNC;
extern const char cpio_TRAILER[];

16
procps/smemcap.c
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@@ -29,7 +29,6 @@ struct fileblock {
static void writeheader(const char *path, struct stat *sb, int type)
{
struct tar_header_t header;
int i, sum;
memset(&header, 0, TAR_BLOCK_SIZE);
strcpy(header.name, path);
@@ -40,20 +39,7 @@ static void writeheader(const char *path, struct stat *sb, int type)
sprintf(header.size, "%o", (unsigned)sb->st_size);
sprintf(header.mtime, "%llo", sb->st_mtime & 077777777777LL);
header.typeflag = type;
strcpy(header.magic, "ustar "); /* like GNU tar */
/* Calculate and store the checksum (the sum of all of the bytes of
* the header). The checksum field must be filled with blanks for the
* calculation. The checksum field is formatted differently from the
* other fields: it has 6 digits, a NUL, then a space -- rather than
* digits, followed by a NUL like the other fields... */
header.chksum[7] = ' ';
sum = ' ' * 7;
for (i = 0; i < TAR_BLOCK_SIZE; i++)
sum += ((unsigned char*)&header)[i];
sprintf(header.chksum, "%06o", sum);
xwrite(STDOUT_FILENO, &header, TAR_BLOCK_SIZE);
chksum_and_xwrite_tar_header(STDOUT_FILENO, &header);
}
static void archivefile(const char *path)