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ae64bbc18c
git/tar-tree.c
Rene Scharfe ae64bbc18c tar-tree: Introduce write_entry() 
... and use it initially to write global extended header records.
Improvements compared to the old write_header():

  - Uses a struct ustar_header instead of hardcoded offsets.
  - Takes one struct strbuf as path argument instead of a (basedir,
    prefix, name) tuple.
  - Not only writes the tar header, but also the contents of the
    file, if any.
  - Does not write directly into the ring buffer.  This allows the
    code to be layed out more naturally, because there is no more
    ordering constraint.  Before we had to first finish writing the
    extended header, now we can construct the extended and normal
    headers in parallel.
  - The typeflag parameter has been replaced by (reasonable) magic
    values.  path == NULL indicates an extended header, additionally
    sha1 == NULL means it is a global extended header.

Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <junkio@cox.net>
2006-03-25 16:35:43 -08:00

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/*
* Copyright (c) 2005, 2006 Rene Scharfe
*/
#include <time.h>
#include "cache.h"
#include "diff.h"
#include "commit.h"
#include "strbuf.h"
#include "tar.h"
#define RECORDSIZE (512)
#define BLOCKSIZE (RECORDSIZE * 20)
#define EXT_HEADER_PATH 1
#define EXT_HEADER_LINKPATH 2
static const char tar_tree_usage[] = "git-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 = xwrite(1, buf, size);
if (ret < 0) {
if (errno == EPIPE)
exit(0);
die("git-tar-tree: %s", strerror(errno));
} else if (!ret) {
die("git-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;
}
}
/* acquire the next record from the buffer; user must call write_if_needed() */
static char *get_record(void)
{
char *p = block + offset;
memset(p, 0, RECORDSIZE);
offset += RECORDSIZE;
return p;
}
/*
* 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)
{
get_record();
write_if_needed();
get_record();
write_if_needed();
while (offset) {
get_record();
write_if_needed();
}
}
/*
* 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();
}
/*
* pax extended header records have the format "%u %s=%s\n". %u contains
* the size of the whole string (including the %u), the first %s is the
* keyword, the second one is the value. This function constructs such a
* string and appends it to a struct strbuf.
*/
static void strbuf_append_ext_header(struct strbuf *sb, const char *keyword,
const char *value, unsigned int valuelen)
{
char *p;
int len, total, tmp;
/* "%u %s=%s\n" */
len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
for (tmp = len; tmp > 9; tmp /= 10)
len++;
total = sb->len + len;
if (total > sb->alloc) {
sb->buf = xrealloc(sb->buf, total);
sb->alloc = total;
}
p = sb->buf;
p += sprintf(p, "%u %s=", len, keyword);
memcpy(p, value, valuelen);
p += valuelen;
*p = '\n';
sb->len = total;
}
static unsigned int ustar_header_chksum(const struct ustar_header *header)
{
char *p = (char *)header;
unsigned int chksum = 0;
while (p < header->chksum)
chksum += *p++;
chksum += sizeof(header->chksum) * ' ';
p += sizeof(header->chksum);
while (p < (char *)header + sizeof(struct ustar_header))
chksum += *p++;
return chksum;
}
static void write_entry(const unsigned char *sha1, struct strbuf *path,
unsigned int mode, void *buffer, unsigned long size)
{
struct ustar_header header;
struct strbuf ext_header;
memset(&header, 0, sizeof(header));
ext_header.buf = NULL;
ext_header.len = ext_header.alloc = 0;
if (!sha1) {
*header.typeflag = TYPEFLAG_GLOBAL_HEADER;
mode = 0100666;
strcpy(header.name, "pax_global_header");
} else if (!path) {
*header.typeflag = TYPEFLAG_EXT_HEADER;
mode = 0100666;
sprintf(header.name, "%s.paxheader", sha1_to_hex(sha1));
} else {
if (S_ISDIR(mode)) {
*header.typeflag = TYPEFLAG_DIR;
mode |= 0777;
} else if (S_ISLNK(mode)) {
*header.typeflag = TYPEFLAG_LNK;
mode |= 0777;
} else if (S_ISREG(mode)) {
*header.typeflag = TYPEFLAG_REG;
mode |= (mode & 0100) ? 0777 : 0666;
} else {
error("unsupported file mode: 0%o (SHA1: %s)",
mode, sha1_to_hex(sha1));
return;
}
if (path->len > sizeof(header.name)) {
sprintf(header.name, "%s.data", sha1_to_hex(sha1));
strbuf_append_ext_header(&ext_header, "path",
path->buf, path->len);
} else
memcpy(header.name, path->buf, path->len);
}
if (S_ISLNK(mode) && buffer) {
if (size > sizeof(header.linkname)) {
sprintf(header.linkname, "see %s.paxheader",
sha1_to_hex(sha1));
strbuf_append_ext_header(&ext_header, "linkpath",
buffer, size);
} else
memcpy(header.linkname, buffer, size);
}
sprintf(header.mode, "%07o", mode & 07777);
sprintf(header.size, "%011lo", S_ISREG(mode) ? size : 0);
sprintf(header.mtime, "%011lo", archive_time);
/* XXX: should we provide more meaningful info here? */
sprintf(header.uid, "%07o", 0);
sprintf(header.gid, "%07o", 0);
strncpy(header.uname, "git", 31);
strncpy(header.gname, "git", 31);
sprintf(header.devmajor, "%07o", 0);
sprintf(header.devminor, "%07o", 0);
memcpy(header.magic, "ustar", 6);
memcpy(header.version, "00", 2);
sprintf(header.chksum, "%07o", ustar_header_chksum(&header));
if (ext_header.len > 0) {
write_entry(sha1, NULL, 0, ext_header.buf, ext_header.len);
free(ext_header.buf);
}
write_blocked(&header, sizeof(header));
if (S_ISREG(mode) && buffer && size > 0)
write_blocked(buffer, size);
}
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_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 append_extended_header_prefix(char **p, unsigned int size,
const char *keyword)
{
int len = sprintf(*p, "%u %s=", size, keyword);
*p += len;
}
static unsigned int extended_header_len(const char *keyword,
unsigned int valuelen)
{
/* "%u %s=%s\n" */
unsigned int len = 1 + 1 + strlen(keyword) + 1 + valuelen + 1;
if (len > 9)
len++;
if (len > 99)
len++;
return len;
}
static void append_extended_header(char **p, const char *keyword,
const char *value, unsigned int len)
{
unsigned int size = extended_header_len(keyword, len);
append_extended_header_prefix(p, size, keyword);
memcpy(*p, value, len);
*p += len;
append_char(p, '\n');
}
static void write_header(const unsigned char *, char, const char *, struct path_prefix *,
const char *, unsigned int, void *, unsigned long);
/* stores a pax extended header directly in the block buffer */
static void write_extended_header(const char *headerfilename, int is_dir,
unsigned int flags, const char *basepath,
struct path_prefix *prefix,
const char *path, unsigned int namelen,
void *content, unsigned int contentsize)
{
char *buffer, *p;
unsigned int pathlen, size, linkpathlen = 0;
size = pathlen = extended_header_len("path", namelen);
if (flags & EXT_HEADER_LINKPATH) {
linkpathlen = extended_header_len("linkpath", contentsize);
size += linkpathlen;
}
write_header(NULL, TYPEFLAG_EXT_HEADER, NULL, NULL, headerfilename,
0100600, NULL, size);
buffer = p = malloc(size);
if (!buffer)
die("git-tar-tree: %s", strerror(errno));
append_extended_header_prefix(&p, pathlen, "path");
append_path(&p, is_dir, basepath, prefix, path);
append_char(&p, '\n');
if (flags & EXT_HEADER_LINKPATH)
append_extended_header(&p, "linkpath", content, contentsize);
write_blocked(buffer, size);
free(buffer);
}
static void write_global_extended_header(const unsigned char *sha1)
{
struct strbuf ext_header;
ext_header.buf = NULL;
ext_header.len = ext_header.alloc = 0;
strbuf_append_ext_header(&ext_header, "comment", sha1_to_hex(sha1), 40);
write_entry(NULL, NULL, 0, ext_header.buf, ext_header.len);
free(ext_header.buf);
}
/* stores a ustar header directly in the block buffer */
static void write_header(const unsigned char *sha1, char typeflag, const char *basepath,
struct path_prefix *prefix, const char *path,
unsigned int mode, void *buffer, unsigned long size)
{
unsigned int namelen;
char *header = NULL;
unsigned int checksum = 0;
int i;
unsigned int ext_header = 0;
if (typeflag == TYPEFLAG_AUTO) {
if (S_ISDIR(mode))
typeflag = TYPEFLAG_DIR;
else if (S_ISLNK(mode))
typeflag = TYPEFLAG_LNK;
else
typeflag = TYPEFLAG_REG;
}
namelen = path_len(S_ISDIR(mode), basepath, prefix, path);
if (namelen > 100)
ext_header |= EXT_HEADER_PATH;
if (typeflag == TYPEFLAG_LNK && size > 100)
ext_header |= EXT_HEADER_LINKPATH;
/* the extended header must be written before the normal one */
if (ext_header) {
char headerfilename[51];
sprintf(headerfilename, "%s.paxheader", sha1_to_hex(sha1));
write_extended_header(headerfilename, S_ISDIR(mode),
ext_header, basepath, prefix, path,
namelen, buffer, size);
}
header = get_record();
if (ext_header) {
sprintf(header, "%s.data", sha1_to_hex(sha1));
} else {
char *p = header;
append_path(&p, S_ISDIR(mode), basepath, prefix, path);
}
if (typeflag == TYPEFLAG_LNK) {
if (ext_header & EXT_HEADER_LINKPATH) {
sprintf(&header[157], "see %s.paxheader",
sha1_to_hex(sha1));
} else {
if (buffer)
strncpy(&header[157], buffer, size);
}
}
if (S_ISDIR(mode))
mode |= 0777;
else if (S_ISREG(mode))
mode |= (mode & 0100) ? 0777 : 0666;
else if (S_ISLNK(mode))
mode |= 0777;
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 */
if (S_ISDIR(mode) || S_ISLNK(mode))
size = 0;
sprintf(&header[124], "%011lo", size);
sprintf(&header[136], "%011lo", archive_time);
header[156] = typeflag;
memcpy(&header[257], "ustar", 6);
memcpy(&header[263], "00", 2);
sprintf(&header[329], "%07o", 0); /* devmajor */
sprintf(&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(struct tree_desc *tree,
struct path_prefix *prefix)
{
struct path_prefix this_prefix;
this_prefix.prev = prefix;
while (tree->size) {
const char *name;
const unsigned char *sha1;
unsigned mode;
void *eltbuf;
char elttype[20];
unsigned long eltsize;
sha1 = tree_entry_extract(tree, &name, &mode);
update_tree_entry(tree);
eltbuf = read_sha1_file(sha1, elttype, &eltsize);
if (!eltbuf)
die("cannot read %s", sha1_to_hex(sha1));
write_header(sha1, TYPEFLAG_AUTO, basedir,
prefix, name, mode, eltbuf, eltsize);
if (S_ISDIR(mode)) {
struct tree_desc subtree;
subtree.buf = eltbuf;
subtree.size = eltsize;
this_prefix.name = name;
traverse_tree(&subtree, &this_prefix);
} else if (!S_ISLNK(mode)) {
write_blocked(eltbuf, eltsize);
}
free(eltbuf);
}
}
int main(int argc, char **argv)
{
unsigned char sha1[20], tree_sha1[20];
struct commit *commit;
struct tree_desc tree;
setup_git_directory();
switch (argc) {
case 3:
basedir = argv[2];
/* FALLTHROUGH */
case 2:
if (get_sha1(argv[1], sha1) < 0)
usage(tar_tree_usage);
break;
default:
usage(tar_tree_usage);
}
commit = lookup_commit_reference_gently(sha1, 1);
if (commit) {
write_global_extended_header(commit->object.sha1);
archive_time = commit->date;
}
tree.buf = read_object_with_reference(sha1, "tree", &tree.size,
tree_sha1);
if (!tree.buf)
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(tree_sha1, TYPEFLAG_DIR, NULL, NULL,
basedir, 040777, NULL, 0);
traverse_tree(&tree, NULL);
write_trailer();
return 0;
}
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