read-cache.c

/*
 * GIT - The information manager from hell
 *
 * Copyright (C) Linus Torvalds, 2005
 */
#include <stdarg.h>
#include "cache.h"

const char *sha1_file_directory = NULL;
struct cache_entry **active_cache = NULL;
unsigned int active_nr = 0, active_alloc = 0;

void usage(const char *err)
{
	fprintf(stderr, "usage: %s\n", err);
	exit(1);
}

static void report(const char *prefix, const char *err, va_list params)
{
	fputs(prefix, stderr);
	vfprintf(stderr, err, params);
	fputs("\n", stderr);
}

void die(const char *err, ...)
{
	va_list params;

	va_start(params, err);
	report("fatal: ", err, params);
	va_end(params);
	exit(1);
}

int error(const char *err, ...)
{
	va_list params;

	va_start(params, err);
	report("error: ", err, params);
	va_end(params);
	return -1;
}


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;
}

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;
}

/*
 * 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.
 */
char *sha1_file_name(const unsigned char *sha1)
{
	int i;
	static char *name, *base;

	if (!base) {
		char *sha1_file_directory = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
		int len = strlen(sha1_file_directory);
		base = malloc(len + 60);
		memcpy(base, sha1_file_directory, len);
		memset(base+len, 0, 60);
		base[len] = '/';
		base[len+3] = '/';
		name = base + len + 1;
	}
	for (i = 0; i < 20; i++) {
		static char hex[] = "0123456789abcdef";
		unsigned int val = sha1[i];
		char *pos = name + i*2 + (i > 0);
		*pos++ = hex[val >> 4];
		*pos = hex[val & 0xf];
	}
	return base;
}

int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size)
{
	unsigned char real_sha1[20];
	SHA_CTX c;

	SHA1_Init(&c);
	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)
{
	char *filename = sha1_file_name(sha1);
	int fd = open(filename, O_RDONLY);
	struct stat st;
	void *map;

	if (fd < 0) {
		perror(filename);
		return NULL;
	}
	if (fstat(fd, &st) < 0) {
		close(fd);
		return NULL;
	}
	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];
	char *buf;

	/* Get the data stream */
	memset(&stream, 0, sizeof(stream));
	stream.next_in = map;
	stream.avail_in = mapsize;
	stream.next_out = buffer;
	stream.avail_out = sizeof(buffer);

	inflateInit(&stream);
	ret = inflate(&stream, 0);
	if (sscanf(buffer, "%10s %lu", type, size) != 2)
		return NULL;

	bytes = strlen(buffer) + 1;
	buf = malloc(*size);
	if (!buf)
		return NULL;

	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 */;
	}
	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);
		return buf;
	}
	return NULL;
}

int write_sha1_file(char *buf, unsigned len, unsigned char *returnsha1)
{
	int size;
	char *compressed;
	z_stream stream;
	unsigned char sha1[20];
	SHA_CTX c;

	/* Set it up */
	memset(&stream, 0, sizeof(stream));
	deflateInit(&stream, Z_BEST_COMPRESSION);
	size = deflateBound(&stream, len);
	compressed = malloc(size);

	/* Compress it */
	stream.next_in = buf;
	stream.avail_in = len;
	stream.next_out = compressed;
	stream.avail_out = size;
	while (deflate(&stream, Z_FINISH) == Z_OK)
		/* nothing */;
	deflateEnd(&stream);
	size = stream.total_out;

	/* Sha1.. */
	SHA1_Init(&c);
	SHA1_Update(&c, compressed, size);
	SHA1_Final(sha1, &c);

	if (write_sha1_buffer(sha1, compressed, size) < 0)
		return -1;
	if (returnsha1)
		memcpy(returnsha1, sha1, 20);
	return 0;
}

static inline int collision_check(char *filename, void *buf, unsigned int size)
{
#ifdef COLLISION_CHECK
	void *map;
	int fd = open(filename, O_RDONLY);
	struct stat st;
	int cmp;

	/* Unreadable object, or object went away? Strange. */
	if (fd < 0)
		return -1;

	if (fstat(fd, &st) < 0 || size != st.st_size)
		return -1;

	map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
	close(fd);
	if (map == MAP_FAILED)
		return -1;
	cmp = memcmp(buf, map, size);
	munmap(map, size);
	if (cmp)
		return -1;
#endif
	return 0;
}

int write_sha1_buffer(const unsigned char *sha1, void *buf, unsigned int size)
{
	char *filename = sha1_file_name(sha1);
	int fd;

	fd = open(filename, O_WRONLY | O_CREAT | O_EXCL, 0666);
	if (fd < 0) {
		if (errno != EEXIST)
			return -1;
		if (collision_check(filename, buf, size))
			return error("SHA1 collision detected!"
					" This is bad, bad, BAD!\a\n");
		return 0;
	}
	write(fd, buf, size);
	close(fd);
	return 0;
}

int cache_match_stat(struct cache_entry *ce, struct stat *st)
{
	unsigned int changed = 0;

	if (ce->ce_mtime.sec != htonl(st->st_mtime))
		changed |= MTIME_CHANGED;
	if (ce->ce_ctime.sec != htonl(st->st_ctime))
		changed |= CTIME_CHANGED;

#ifdef NSEC
	/*
	 * nsec seems unreliable - not all filesystems support it, so
	 * as long as it is in the inode cache you get right nsec
	 * but after it gets flushed, you get zero nsec.
	 */
	if (ce->ce_mtime.nsec != htonl(st->st_mtim.tv_nsec)
		changed |= MTIME_CHANGED;
	if (ce->ce_ctime.nsec != htonl(st->st_ctim.tv_nsec)
		changed |= CTIME_CHANGED;
#endif	

	if (ce->ce_uid != htonl(st->st_uid) ||
	    ce->ce_gid != htonl(st->st_gid))
		changed |= OWNER_CHANGED;
	if (ce->ce_mode != htonl(st->st_mode))
		changed |= MODE_CHANGED;
	if (ce->ce_dev != htonl(st->st_dev) ||
	    ce->ce_ino != htonl(st->st_ino))
		changed |= INODE_CHANGED;
	if (ce->ce_size != htonl(st->st_size))
		changed |= DATA_CHANGED;
	return changed;
}

int cache_name_compare(const char *name1, int flags1, const char *name2, int flags2)
{
	int len1 = flags1 & CE_NAMEMASK;
	int len2 = flags2 & CE_NAMEMASK;
	int len = len1 < len2 ? len1 : len2;
	int cmp;

	cmp = memcmp(name1, name2, len);
	if (cmp)
		return cmp;
	if (len1 < len2)
		return -1;
	if (len1 > len2)
		return 1;
	if (flags1 < flags2)
		return -1;
	if (flags1 > flags2)
		return 1;
	return 0;
}

int cache_name_pos(const char *name, int namelen)
{
	int first, last;

	first = 0;
	last = active_nr;
	while (last > first) {
		int next = (last + first) >> 1;
		struct cache_entry *ce = active_cache[next];
		int cmp = cache_name_compare(name, namelen, ce->name, htons(ce->ce_flags));
		if (!cmp)
			return next;
		if (cmp < 0) {
			last = next;
			continue;
		}
		first = next+1;
	}
	return -first-1;
}

int remove_file_from_cache(char *path)
{
	int pos = cache_name_pos(path, strlen(path));
	if (pos >= 0) {
		active_nr--;
		if (pos < active_nr)
			memmove(active_cache + pos, active_cache + pos + 1, (active_nr - pos) * sizeof(struct cache_entry *));
	}
	return 0;
}

int add_cache_entry(struct cache_entry *ce, int ok_to_add)
{
	int pos;

	pos = cache_name_pos(ce->name, htons(ce->ce_flags));

	/* existing match? Just replace it */
	if (pos >= 0) {
		active_cache[pos] = ce;
		return 0;
	}
	pos = -pos-1;

	if (!ok_to_add)
		return -1;

	/* Make sure the array is big enough .. */
	if (active_nr == active_alloc) {
		active_alloc = alloc_nr(active_alloc);
		active_cache = realloc(active_cache, active_alloc * sizeof(struct cache_entry *));
	}

	/* Add it in.. */
	active_nr++;
	if (active_nr > pos)
		memmove(active_cache + pos + 1, active_cache + pos, (active_nr - pos - 1) * sizeof(ce));
	active_cache[pos] = ce;
	return 0;
}

static int verify_hdr(struct cache_header *hdr, unsigned long size)
{
	SHA_CTX c;
	unsigned char sha1[20];

	if (hdr->hdr_signature != htonl(CACHE_SIGNATURE))
		return error("bad signature");
	if (hdr->hdr_version != htonl(1))
		return error("bad version");
	SHA1_Init(&c);
	SHA1_Update(&c, hdr, offsetof(struct cache_header, sha1));
	SHA1_Update(&c, hdr+1, size - sizeof(*hdr));
	SHA1_Final(sha1, &c);
	if (memcmp(sha1, hdr->sha1, 20))
		return error("bad header sha1");
	return 0;
}

int read_cache(void)
{
	int fd, i;
	struct stat st;
	unsigned long size, offset;
	void *map;
	struct cache_header *hdr;

	errno = EBUSY;
	if (active_cache)
		return error("more than one cachefile");
	errno = ENOENT;
	sha1_file_directory = getenv(DB_ENVIRONMENT);
	if (!sha1_file_directory)
		sha1_file_directory = DEFAULT_DB_ENVIRONMENT;
	if (access(sha1_file_directory, X_OK) < 0)
		return error("no access to SHA1 file directory");
	fd = open(".git/index", O_RDONLY);
	if (fd < 0)
		return (errno == ENOENT) ? 0 : error("open failed");

	size = 0; // avoid gcc warning
	map = (void *)-1;
	if (!fstat(fd, &st)) {
		size = st.st_size;
		errno = EINVAL;
		if (size >= sizeof(struct cache_header))
			map = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
	}
	close(fd);
	if (-1 == (int)(long)map)
		return error("mmap failed");

	hdr = map;
	if (verify_hdr(hdr, size) < 0)
		goto unmap;

	active_nr = ntohl(hdr->hdr_entries);
	active_alloc = alloc_nr(active_nr);
	active_cache = calloc(active_alloc, sizeof(struct cache_entry *));

	offset = sizeof(*hdr);
	for (i = 0; i < active_nr; i++) {
		struct cache_entry *ce = map + offset;
		offset = offset + ce_size(ce);
		active_cache[i] = ce;
	}
	return active_nr;

unmap:
	munmap(map, size);
	errno = EINVAL;
	return error("verify header failed");
}

int write_cache(int newfd, struct cache_entry **cache, int entries)
{
	SHA_CTX c;
	struct cache_header hdr;
	int i;

	hdr.hdr_signature = htonl(CACHE_SIGNATURE);
	hdr.hdr_version = htonl(1);
	hdr.hdr_entries = htonl(entries);

	SHA1_Init(&c);
	SHA1_Update(&c, &hdr, offsetof(struct cache_header, sha1));
	for (i = 0; i < entries; i++) {
		struct cache_entry *ce = cache[i];
		int size = ce_size(ce);
		SHA1_Update(&c, ce, size);
	}
	SHA1_Final(hdr.sha1, &c);

	if (write(newfd, &hdr, sizeof(hdr)) != sizeof(hdr))
		return -1;

	for (i = 0; i < entries; i++) {
		struct cache_entry *ce = cache[i];
		int size = ce_size(ce);
		if (write(newfd, ce, size) != size)
			return -1;
	}
	return 0;
}