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tar: store negative mtime as 0; pack very large files using base-256 encoding

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function                                             old     new   delta
writeTarHeader                                       841     979    +138

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Denys Vlasenko 2011-05-04 21:14:12 +02:00
parent 882062915d
commit 9180c6045e
2 changed files with 33 additions and 5 deletions
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36
archival/tar.c
View File

@ -264,7 +264,8 @@ static int writeTarHeader(struct TarBallInfo *tbInfo,
PUT_OCTAL(header.uid, statbuf->st_uid);
PUT_OCTAL(header.gid, statbuf->st_gid);
memset(header.size, '0', sizeof(header.size)-1); /* Regular file size is handled later */
PUT_OCTAL(header.mtime, statbuf->st_mtime);
/* users report that files with negative st_mtime cause trouble, so: */
PUT_OCTAL(header.mtime, statbuf->st_mtime >= 0 ? statbuf->st_mtime : 0);
/* Enter the user and group names */
safe_strncpy(header.uname, get_cached_username(statbuf->st_uid), sizeof(header.uname));
@ -316,15 +317,42 @@ static int writeTarHeader(struct TarBallInfo *tbInfo,
} else if (S_ISFIFO(statbuf->st_mode)) {
header.typeflag = FIFOTYPE;
} else if (S_ISREG(statbuf->st_mode)) {
if (sizeof(statbuf->st_size) > 4
&& statbuf->st_size > (off_t)0777777777777LL
/* header.size field is 12 bytes long */
/* Does octal-encoded size fit? */
uoff_t filesize = statbuf->st_size;
if (sizeof(filesize) <= 4
|| filesize <= (uoff_t)0777777777777LL
) {
PUT_OCTAL(header.size, filesize);
}
/* Does base256-encoded size fit?
* It always does unless off_t is wider than 64 bits.
*/
else if (ENABLE_FEATURE_TAR_GNU_EXTENSIONS
#if ULLONG_MAX > 0xffffffffffffffffLL /* 2^64-1 */
&& (filesize <= 0x3fffffffffffffffffffffffLL)
#endif
) {
/* GNU tar uses "base-256 encoding" for very large numbers.
* Encoding is binary, with highest bit always set as a marker
* and sign in next-highest bit:
* 80 00 .. 00 - zero
* bf ff .. ff - largest positive number
* ff ff .. ff - minus 1
* c0 00 .. 00 - smallest negative number
*/
char *p8 = header.size + sizeof(header.size);
do {
*--p8 = (uint8_t)filesize;
filesize >>= 8;
} while (p8 != header.size);
*p8 |= 0x80;
} else {
bb_error_msg_and_die("can't store file '%s' "
"of size %"OFF_FMT"u, aborting",
fileName, statbuf->st_size);
}
header.typeflag = REGTYPE;
PUT_OCTAL(header.size, statbuf->st_size);
} else {
bb_error_msg("%s: unknown file type", fileName);
return FALSE;

2
include/archive.h
View File

@ -125,7 +125,7 @@ typedef struct archive_handle_t {
#define TAR_BLOCK_SIZE 512
#define NAME_SIZE 100
#define NAME_SIZE_STR "100"
typedef struct tar_header_t { /* byte offset */
typedef struct tar_header_t { /* byte offset */
char name[NAME_SIZE]; /* 0-99 */
char mode[8]; /* 100-107 */
char uid[8]; /* 108-115 */