git/sha1_file.c

611 строки
14 KiB
C

/*
* GIT - The information manager from hell
*
* Copyright (C) Linus Torvalds, 2005
*
* This handles basic git sha1 object files - packing, unpacking,
* creation etc.
*/
#include "cache.h"
#include "delta.h"
#ifndef O_NOATIME
#if defined(__linux__) && (defined(__i386__) || defined(__PPC__))
#define O_NOATIME 01000000
#else
#define O_NOATIME 0
#endif
#endif
static unsigned int sha1_file_open_flag = O_NOATIME;
static unsigned hexval(char c)
{
if (c >= '0' && c <= '9')
return c - '0';
if (c >= 'a' && c <= 'f')
return c - 'a' + 10;
if (c >= 'A' && c <= 'F')
return c - 'A' + 10;
return ~0;
}
int get_sha1_hex(const char *hex, unsigned char *sha1)
{
int i;
for (i = 0; i < 20; i++) {
unsigned int val = (hexval(hex[0]) << 4) | hexval(hex[1]);
if (val & ~0xff)
return -1;
*sha1++ = val;
hex += 2;
}
return 0;
}
static int get_sha1_file(const char *path, unsigned char *result)
{
char buffer[60];
int fd = open(path, O_RDONLY);
int len;
if (fd < 0)
return -1;
len = read(fd, buffer, sizeof(buffer));
close(fd);
if (len < 40)
return -1;
return get_sha1_hex(buffer, result);
}
static char *git_dir, *git_object_dir, *git_index_file;
static void setup_git_env(void)
{
git_dir = gitenv(GIT_DIR_ENVIRONMENT);
if (!git_dir)
git_dir = DEFAULT_GIT_DIR_ENVIRONMENT;
git_object_dir = gitenv(DB_ENVIRONMENT);
if (!git_object_dir) {
git_object_dir = xmalloc(strlen(git_dir) + 9);
sprintf(git_object_dir, "%s/objects", git_dir);
}
git_index_file = gitenv(INDEX_ENVIRONMENT);
if (!git_index_file) {
git_index_file = xmalloc(strlen(git_dir) + 7);
sprintf(git_index_file, "%s/index", git_dir);
}
}
char *get_object_directory(void)
{
if (!git_object_dir)
setup_git_env();
return git_object_dir;
}
char *get_index_file(void)
{
if (!git_index_file)
setup_git_env();
return git_index_file;
}
int get_sha1(const char *str, unsigned char *sha1)
{
static char pathname[PATH_MAX];
static const char *prefix[] = {
"",
"refs",
"refs/tags",
"refs/heads",
"refs/snap",
NULL
};
const char **p;
if (!get_sha1_hex(str, sha1))
return 0;
if (!git_dir)
setup_git_env();
for (p = prefix; *p; p++) {
snprintf(pathname, sizeof(pathname), "%s/%s/%s",
git_dir, *p, str);
if (!get_sha1_file(pathname, sha1))
return 0;
}
return -1;
}
char * sha1_to_hex(const unsigned char *sha1)
{
static char buffer[50];
static const char hex[] = "0123456789abcdef";
char *buf = buffer;
int i;
for (i = 0; i < 20; i++) {
unsigned int val = *sha1++;
*buf++ = hex[val >> 4];
*buf++ = hex[val & 0xf];
}
return buffer;
}
static void fill_sha1_path(char *pathbuf, const unsigned char *sha1)
{
int i;
for (i = 0; i < 20; i++) {
static char hex[] = "0123456789abcdef";
unsigned int val = sha1[i];
char *pos = pathbuf + i*2 + (i > 0);
*pos++ = hex[val >> 4];
*pos = hex[val & 0xf];
}
}
/*
* NOTE! This returns a statically allocated buffer, so you have to be
* careful about using it. Do a "strdup()" if you need to save the
* filename.
*
* Also note that this returns the location for creating. Reading
* SHA1 file can happen from any alternate directory listed in the
* DB_ENVIRONMENT environment variable if it is not found in
* the primary object database.
*/
char *sha1_file_name(const unsigned char *sha1)
{
static char *name, *base;
if (!base) {
const char *sha1_file_directory = get_object_directory();
int len = strlen(sha1_file_directory);
base = xmalloc(len + 60);
memcpy(base, sha1_file_directory, len);
memset(base+len, 0, 60);
base[len] = '/';
base[len+3] = '/';
name = base + len + 1;
}
fill_sha1_path(name, sha1);
return base;
}
static struct alternate_object_database {
char *base;
char *name;
} *alt_odb;
/*
* Prepare alternate object database registry.
* alt_odb points at an array of struct alternate_object_database.
* This array is terminated with an element that has both its base
* and name set to NULL. alt_odb[n] comes from n'th non-empty
* element from colon separated ALTERNATE_DB_ENVIRONMENT environment
* variable, and its base points at a statically allocated buffer
* that contains "/the/directory/corresponding/to/.git/objects/...",
* while its name points just after the slash at the end of
* ".git/objects/" in the example above, and has enough space to hold
* 40-byte hex SHA1, an extra slash for the first level indirection,
* and the terminating NUL.
* This function allocates the alt_odb array and all the strings
* pointed by base fields of the array elements with one xmalloc();
* the string pool immediately follows the array.
*/
static void prepare_alt_odb(void)
{
int pass, totlen, i;
const char *cp, *last;
char *op = NULL;
const char *alt = gitenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
/* The first pass counts how large an area to allocate to
* hold the entire alt_odb structure, including array of
* structs and path buffers for them. The second pass fills
* the structure and prepares the path buffers for use by
* fill_sha1_path().
*/
for (totlen = pass = 0; pass < 2; pass++) {
last = alt;
i = 0;
do {
cp = strchr(last, ':') ? : last + strlen(last);
if (last != cp) {
/* 43 = 40-byte + 2 '/' + terminating NUL */
int pfxlen = cp - last;
int entlen = pfxlen + 43;
if (pass == 0)
totlen += entlen;
else {
alt_odb[i].base = op;
alt_odb[i].name = op + pfxlen + 1;
memcpy(op, last, pfxlen);
op[pfxlen] = op[pfxlen + 3] = '/';
op[entlen-1] = 0;
op += entlen;
}
i++;
}
while (*cp && *cp == ':')
cp++;
last = cp;
} while (*cp);
if (pass)
break;
alt_odb = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
alt_odb[i].base = alt_odb[i].name = NULL;
op = (char*)(&alt_odb[i+1]);
}
}
static char *find_sha1_file(const unsigned char *sha1, struct stat *st)
{
int i;
char *name = sha1_file_name(sha1);
if (!stat(name, st))
return name;
if (!alt_odb)
prepare_alt_odb();
for (i = 0; (name = alt_odb[i].name) != NULL; i++) {
fill_sha1_path(name, sha1);
if (!stat(alt_odb[i].base, st))
return alt_odb[i].base;
}
return NULL;
}
int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, const char *type)
{
char header[100];
unsigned char real_sha1[20];
SHA_CTX c;
SHA1_Init(&c);
SHA1_Update(&c, header, 1+sprintf(header, "%s %lu", type, size));
SHA1_Update(&c, map, size);
SHA1_Final(real_sha1, &c);
return memcmp(sha1, real_sha1, 20) ? -1 : 0;
}
void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
{
struct stat st;
void *map;
int fd;
char *filename = find_sha1_file(sha1, &st);
if (!filename) {
error("cannot map sha1 file %s", sha1_to_hex(sha1));
return NULL;
}
fd = open(filename, O_RDONLY | sha1_file_open_flag);
if (fd < 0) {
/* See if it works without O_NOATIME */
switch (sha1_file_open_flag) {
default:
fd = open(filename, O_RDONLY);
if (fd >= 0)
break;
/* Fallthrough */
case 0:
perror(filename);
return NULL;
}
/* If it failed once, it will probably fail again. Stop using O_NOATIME */
sha1_file_open_flag = 0;
}
map = mmap(NULL, st.st_size, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
if (-1 == (int)(long)map)
return NULL;
*size = st.st_size;
return map;
}
void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size)
{
int ret, bytes;
z_stream stream;
char buffer[8192];
unsigned char *buf;
/* Get the data stream */
memset(&stream, 0, sizeof(stream));
stream.next_in = map;
stream.avail_in = mapsize;
stream.next_out = (unsigned char *)buffer;
stream.avail_out = sizeof(buffer);
inflateInit(&stream);
ret = inflate(&stream, 0);
if (ret < Z_OK)
return NULL;
if (sscanf(buffer, "%10s %lu", type, size) != 2)
return NULL;
bytes = strlen(buffer) + 1;
buf = xmalloc(1+*size);
memcpy(buf, buffer + bytes, stream.total_out - bytes);
bytes = stream.total_out - bytes;
if (bytes < *size && ret == Z_OK) {
stream.next_out = buf + bytes;
stream.avail_out = *size - bytes;
while (inflate(&stream, Z_FINISH) == Z_OK)
/* nothing */;
}
buf[*size] = 0;
inflateEnd(&stream);
return buf;
}
void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size)
{
unsigned long mapsize;
void *map, *buf;
map = map_sha1_file(sha1, &mapsize);
if (map) {
buf = unpack_sha1_file(map, mapsize, type, size);
munmap(map, mapsize);
if (buf && !strcmp(type, "delta")) {
void *ref = NULL, *delta = buf;
unsigned long ref_size, delta_size = *size;
buf = NULL;
if (delta_size > 20)
ref = read_sha1_file(delta, type, &ref_size);
if (ref)
buf = patch_delta(ref, ref_size,
delta+20, delta_size-20,
size);
free(delta);
free(ref);
}
return buf;
}
return NULL;
}
void *read_object_with_reference(const unsigned char *sha1,
const char *required_type,
unsigned long *size,
unsigned char *actual_sha1_return)
{
char type[20];
void *buffer;
unsigned long isize;
unsigned char actual_sha1[20];
memcpy(actual_sha1, sha1, 20);
while (1) {
int ref_length = -1;
const char *ref_type = NULL;
buffer = read_sha1_file(actual_sha1, type, &isize);
if (!buffer)
return NULL;
if (!strcmp(type, required_type)) {
*size = isize;
if (actual_sha1_return)
memcpy(actual_sha1_return, actual_sha1, 20);
return buffer;
}
/* Handle references */
else if (!strcmp(type, "commit"))
ref_type = "tree ";
else if (!strcmp(type, "tag"))
ref_type = "object ";
else {
free(buffer);
return NULL;
}
ref_length = strlen(ref_type);
if (memcmp(buffer, ref_type, ref_length) ||
get_sha1_hex(buffer + ref_length, actual_sha1)) {
free(buffer);
return NULL;
}
/* Now we have the ID of the referred-to object in
* actual_sha1. Check again. */
}
}
int write_sha1_file(void *buf, unsigned long len, const char *type, unsigned char *returnsha1)
{
int size;
unsigned char *compressed;
z_stream stream;
unsigned char sha1[20];
SHA_CTX c;
char *filename;
static char tmpfile[PATH_MAX];
unsigned char hdr[50];
int fd, hdrlen, ret;
/* Generate the header */
hdrlen = sprintf((char *)hdr, "%s %lu", type, len)+1;
/* Sha1.. */
SHA1_Init(&c);
SHA1_Update(&c, hdr, hdrlen);
SHA1_Update(&c, buf, len);
SHA1_Final(sha1, &c);
if (returnsha1)
memcpy(returnsha1, sha1, 20);
filename = sha1_file_name(sha1);
fd = open(filename, O_RDONLY);
if (fd >= 0) {
/*
* FIXME!!! We might do collision checking here, but we'd
* need to uncompress the old file and check it. Later.
*/
close(fd);
return 0;
}
if (errno != ENOENT) {
fprintf(stderr, "sha1 file %s: %s", filename, strerror(errno));
return -1;
}
snprintf(tmpfile, sizeof(tmpfile), "%s/obj_XXXXXX", get_object_directory());
fd = mkstemp(tmpfile);
if (fd < 0) {
fprintf(stderr, "unable to create temporary sha1 filename %s: %s", tmpfile, strerror(errno));
return -1;
}
/* Set it up */
memset(&stream, 0, sizeof(stream));
deflateInit(&stream, Z_BEST_COMPRESSION);
size = deflateBound(&stream, len+hdrlen);
compressed = xmalloc(size);
/* Compress it */
stream.next_out = compressed;
stream.avail_out = size;
/* First header.. */
stream.next_in = hdr;
stream.avail_in = hdrlen;
while (deflate(&stream, 0) == Z_OK)
/* nothing */;
/* Then the data itself.. */
stream.next_in = buf;
stream.avail_in = len;
while (deflate(&stream, Z_FINISH) == Z_OK)
/* nothing */;
deflateEnd(&stream);
size = stream.total_out;
if (write(fd, compressed, size) != size)
die("unable to write file");
fchmod(fd, 0444);
close(fd);
free(compressed);
ret = link(tmpfile, filename);
if (ret < 0) {
ret = errno;
/*
* Coda hack - coda doesn't like cross-directory links,
* so we fall back to a rename, which will mean that it
* won't be able to check collisions, but that's not a
* big deal.
*
* When this succeeds, we just return 0. We have nothing
* left to unlink.
*/
if (ret == EXDEV && !rename(tmpfile, filename))
return 0;
}
unlink(tmpfile);
if (ret) {
if (ret != EEXIST) {
fprintf(stderr, "unable to write sha1 filename %s: %s", filename, strerror(ret));
return -1;
}
/* FIXME!!! Collision check here ? */
}
return 0;
}
int write_sha1_from_fd(const unsigned char *sha1, int fd)
{
char *filename = sha1_file_name(sha1);
int local;
z_stream stream;
unsigned char real_sha1[20];
unsigned char buf[4096];
unsigned char discard[4096];
int ret;
SHA_CTX c;
local = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
if (local < 0)
return error("Couldn't open %s\n", filename);
memset(&stream, 0, sizeof(stream));
inflateInit(&stream);
SHA1_Init(&c);
do {
ssize_t size;
size = read(fd, buf, 4096);
if (size <= 0) {
close(local);
unlink(filename);
if (!size)
return error("Connection closed?");
perror("Reading from connection");
return -1;
}
write(local, buf, size);
stream.avail_in = size;
stream.next_in = buf;
do {
stream.next_out = discard;
stream.avail_out = sizeof(discard);
ret = inflate(&stream, Z_SYNC_FLUSH);
SHA1_Update(&c, discard, sizeof(discard) -
stream.avail_out);
} while (stream.avail_in && ret == Z_OK);
} while (ret == Z_OK);
inflateEnd(&stream);
close(local);
SHA1_Final(real_sha1, &c);
if (ret != Z_STREAM_END) {
unlink(filename);
return error("File %s corrupted", sha1_to_hex(sha1));
}
if (memcmp(sha1, real_sha1, 20)) {
unlink(filename);
return error("File %s has bad hash\n", sha1_to_hex(sha1));
}
return 0;
}
int has_sha1_file(const unsigned char *sha1)
{
struct stat st;
return !!find_sha1_file(sha1, &st);
}
int index_fd(unsigned char *sha1, int fd, struct stat *st)
{
unsigned long size = st->st_size;
void *buf;
int ret;
buf = "";
if (size)
buf = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
close(fd);
if ((int)(long)buf == -1)
return -1;
ret = write_sha1_file(buf, size, "blob", sha1);
if (size)
munmap(buf, size);
return ret;
}