git/tar-tree.c
Rene Scharfe 87fec8fc9e [PATCH] GIT: Create tar archives of tree on the fly
Write commit ID to global extended pax header at the beginning of the tar
file, if possible.  get-tar-commit-id.c is an example program to get the
ID back out of such a tar archive.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-04-29 19:51:04 -07:00

371 lines
8.9 KiB
C

#include <time.h>
#include "cache.h"
#define RECORDSIZE (512)
#define BLOCKSIZE (RECORDSIZE * 20)
static const char *tar_tree_usage = "tar-tree <key> [basedir]";
static char block[BLOCKSIZE];
static unsigned long offset;
static const char *basedir;
static time_t archive_time;
struct path_prefix {
struct path_prefix *prev;
const char *name;
};
/* tries hard to write, either succeeds or dies in the attempt */
static void reliable_write(void *buf, unsigned long size)
{
while (size > 0) {
long ret = write(1, buf, size);
if (ret < 0) {
if (errno == EAGAIN)
continue;
if (errno == EPIPE)
exit(0);
die("tar-tree: %s", strerror(errno));
} else if (!ret) {
die("tar-tree: disk full?");
}
size -= ret;
buf += ret;
}
}
/* writes out the whole block, but only if it is full */
static void write_if_needed(void)
{
if (offset == BLOCKSIZE) {
reliable_write(block, BLOCKSIZE);
offset = 0;
}
}
/*
* The end of tar archives is marked by 1024 nul bytes and after that
* follows the rest of the block (if any).
*/
static void write_trailer(void)
{
memset(block + offset, 0, RECORDSIZE);
offset += RECORDSIZE;
write_if_needed();
memset(block + offset, 0, RECORDSIZE);
offset += RECORDSIZE;
write_if_needed();
if (offset) {
memset(block + offset, 0, BLOCKSIZE - offset);
reliable_write(block, BLOCKSIZE);
offset = 0;
}
}
/*
* queues up writes, so that all our write(2) calls write exactly one
* full block; pads writes to RECORDSIZE
*/
static void write_blocked(void *buf, unsigned long size)
{
unsigned long tail;
if (offset) {
unsigned long chunk = BLOCKSIZE - offset;
if (size < chunk)
chunk = size;
memcpy(block + offset, buf, chunk);
size -= chunk;
offset += chunk;
buf += chunk;
write_if_needed();
}
while (size >= BLOCKSIZE) {
reliable_write(buf, BLOCKSIZE);
size -= BLOCKSIZE;
buf += BLOCKSIZE;
}
if (size) {
memcpy(block + offset, buf, size);
buf += size;
offset += size;
}
tail = offset % RECORDSIZE;
if (tail) {
memset(block + offset, 0, RECORDSIZE - tail);
offset += RECORDSIZE - tail;
}
write_if_needed();
}
static void append_string(char **p, const char *s)
{
unsigned int len = strlen(s);
memcpy(*p, s, len);
*p += len;
}
static void append_char(char **p, char c)
{
**p = c;
*p += 1;
}
static void append_long(char **p, long n)
{
int len = sprintf(*p, "%ld", n);
*p += len;
}
static void append_path_prefix(char **buffer, struct path_prefix *prefix)
{
if (!prefix)
return;
append_path_prefix(buffer, prefix->prev);
append_string(buffer, prefix->name);
append_char(buffer, '/');
}
static unsigned int path_prefix_len(struct path_prefix *prefix)
{
if (!prefix)
return 0;
return path_prefix_len(prefix->prev) + strlen(prefix->name) + 1;
}
static void append_path(char **p, int is_dir, const char *basepath,
struct path_prefix *prefix, const char *path)
{
if (basepath) {
append_string(p, basepath);
append_char(p, '/');
}
append_path_prefix(p, prefix);
append_string(p, path);
if (is_dir)
append_char(p, '/');
}
static unsigned int path_len(int is_dir, const char *basepath,
struct path_prefix *prefix, const char *path)
{
unsigned int len = 0;
if (basepath)
len += strlen(basepath) + 1;
len += path_prefix_len(prefix) + strlen(path);
if (is_dir)
len++;
return len;
}
static void write_header(const char *, char, const char *, struct path_prefix *,
const char *, unsigned int, unsigned long);
/* stores a pax extended header directly in the block buffer */
static void write_extended_header(const char *headerfilename, int is_dir,
const char *basepath,
struct path_prefix *prefix,
const char *path, unsigned int namelen)
{
char *p;
unsigned int size = 1 + 6 + namelen + 1;
if (size > 9)
size++;
if (size > 99)
size++;
if (size > RECORDSIZE)
die("tar-tree: extended header too big, wtf?");
write_header(NULL, 'x', NULL, NULL, headerfilename, 0100600, size);
p = block + offset;
memset(p, 0, RECORDSIZE);
offset += RECORDSIZE;
append_long(&p, size);
append_string(&p, " path=");
append_path(&p, is_dir, basepath, prefix, path);
append_char(&p, '\n');
write_if_needed();
}
static void write_global_extended_header(const char *sha1)
{
char *p;
write_header(NULL, 'g', NULL, NULL, "pax_global_header", 0, 52);
p = block + offset;
memset(p, 0, RECORDSIZE);
offset += RECORDSIZE;
append_long(&p, 52); /* 2 + 9 + 40 + 1 */
append_string(&p, " comment=");
append_string(&p, sha1_to_hex(sha1));
append_char(&p, '\n');
write_if_needed();
}
/* stores a ustar header directly in the block buffer */
static void write_header(const char *sha1, char typeflag, const char *basepath,
struct path_prefix *prefix, const char *path,
unsigned int mode, unsigned long size)
{
unsigned int namelen;
char *p, *header = NULL;
unsigned int checksum = 0;
int i;
namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
if (namelen > 500) {
die("tar-tree: name too log of object %s\n", sha1_to_hex(sha1));
} else if (namelen > 100) {
char *sha1_hex = sha1_to_hex(sha1);
char headerfilename[51];
sprintf(headerfilename, "%s.paxheader", sha1_hex);
/* the extended header must be written before the normal one */
write_extended_header(headerfilename, S_ISDIR(mode), basepath,
prefix, path, namelen);
header = block + offset;
memset(header, 0, RECORDSIZE);
offset += RECORDSIZE;
sprintf(header, "%s.data", sha1_hex);
} else {
header = block + offset;
memset(header, 0, RECORDSIZE);
offset += RECORDSIZE;
p = header;
append_path(&p, S_ISDIR(mode), basepath, prefix, path);
}
if (S_ISDIR(mode))
mode |= 0755; /* GIT doesn't store permissions of dirs */
sprintf(&header[100], "%07o", mode & 07777);
/* XXX: should we provide more meaningful info here? */
sprintf(&header[108], "%07o", 0); /* uid */
sprintf(&header[116], "%07o", 0); /* gid */
strncpy(&header[265], "git", 31); /* uname */
strncpy(&header[297], "git", 31); /* gname */
sprintf(&header[124], "%011lo", S_ISDIR(mode) ? 0 : size);
sprintf(&header[136], "%011lo", archive_time);
header[156] = typeflag;
memcpy(&header[257], "ustar", 6);
memcpy(&header[263], "00", 2);
printf(&header[329], "%07o", 0); /* devmajor */
printf(&header[337], "%07o", 0); /* devminor */
memset(&header[148], ' ', 8);
for (i = 0; i < RECORDSIZE; i++)
checksum += header[i];
sprintf(&header[148], "%07o", checksum & 0x1fffff);
write_if_needed();
}
static void traverse_tree(void *buffer, unsigned long size,
struct path_prefix *prefix)
{
struct path_prefix this_prefix;
this_prefix.prev = prefix;
while (size) {
int namelen = strlen(buffer)+1;
void *eltbuf;
char elttype[20];
unsigned long eltsize;
unsigned char *sha1 = buffer + namelen;
char *path = strchr(buffer, ' ') + 1;
unsigned int mode;
if (size < namelen + 20 || sscanf(buffer, "%o", &mode) != 1)
die("corrupt 'tree' file");
buffer = sha1 + 20;
size -= namelen + 20;
eltbuf = read_sha1_file(sha1, elttype, &eltsize);
if (!eltbuf)
die("cannot read %s", sha1_to_hex(sha1));
write_header(sha1, S_ISDIR(mode) ? '5' : '0', basedir,
prefix, path, mode, eltsize);
if (!strcmp(elttype, "tree")) {
this_prefix.name = path;
traverse_tree(eltbuf, eltsize, &this_prefix);
} else if (!strcmp(elttype, "blob")) {
write_blocked(eltbuf, eltsize);
}
free(eltbuf);
}
}
/* get commit time from committer line of commit object */
time_t commit_time(void * buffer, unsigned long size)
{
time_t result = 0;
char *p = buffer;
while (size > 0) {
char *endp = memchr(p, '\n', size);
if (!endp || endp == p)
break;
*endp = '\0';
if (endp - p > 10 && !memcmp(p, "committer ", 10)) {
char *nump = strrchr(p, '>');
if (!nump)
break;
nump++;
result = strtoul(nump, &endp, 10);
if (*endp != ' ')
result = 0;
break;
}
size -= endp - p - 1;
p = endp + 1;
}
return result;
}
int main(int argc, char **argv)
{
unsigned char sha1[20];
unsigned char commit_sha1[20];
void *buffer;
unsigned long size;
switch (argc) {
case 3:
basedir = argv[2];
/* FALLTHROUGH */
case 2:
if (get_sha1_hex(argv[1], sha1) < 0)
usage(tar_tree_usage);
break;
default:
usage(tar_tree_usage);
}
sha1_file_directory = getenv(DB_ENVIRONMENT);
if (!sha1_file_directory)
sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
buffer = read_object_with_reference(sha1, "commit", &size, commit_sha1);
if (buffer) {
write_global_extended_header(commit_sha1);
archive_time = commit_time(buffer, size);
free(buffer);
}
buffer = read_object_with_reference(sha1, "tree", &size, NULL);
if (!buffer)
die("not a reference to a tag, commit or tree object: %s",
sha1_to_hex(sha1));
if (!archive_time)
archive_time = time(NULL);
if (basedir)
write_header("0", '5', NULL, NULL, basedir, 040755, 0);
traverse_tree(buffer, size, NULL);
free(buffer);
write_trailer();
return 0;
}