aac1794132
Make it much safer: we write to a temporary file, and then link that temporary file to the final destination. This avoids all the nasty races if several people write the same object at the same time. It should also result in nicer on-disk layout, since it means that objects all get created in the same subdirectory. That makes a lot of block allocation algorithms happier, since the objects will now be allocated from the same zone.
183 lines
5.4 KiB
C
183 lines
5.4 KiB
C
#ifndef CACHE_H
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#define CACHE_H
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#include <unistd.h>
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#include <stdio.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stddef.h>
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#include <stdlib.h>
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#include <stdarg.h>
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#include <string.h>
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#include <errno.h>
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#include <sys/mman.h>
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#include <sys/param.h>
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#include <netinet/in.h>
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#include SHA1_HEADER
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#include <zlib.h>
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#if ZLIB_VERNUM < 0x1200
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#define deflateBound(c,s) ((s) + (((s) + 7) >> 3) + (((s) + 63) >> 6) + 11)
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#endif
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#ifdef DT_UNKNOWN
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#define DTYPE(de) ((de)->d_type)
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#else
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#define DT_UNKNOWN 0
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#define DT_DIR 1
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#define DT_REG 2
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#define DTYPE(de) DT_UNKNOWN
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#endif
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/*
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* Basic data structures for the directory cache
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*
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* NOTE NOTE NOTE! This is all in the native CPU byte format. It's
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* not even trying to be portable. It's trying to be efficient. It's
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* just a cache, after all.
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*/
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#define CACHE_SIGNATURE 0x44495243 /* "DIRC" */
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struct cache_header {
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unsigned int hdr_signature;
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unsigned int hdr_version;
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unsigned int hdr_entries;
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};
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/*
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* The "cache_time" is just the low 32 bits of the
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* time. It doesn't matter if it overflows - we only
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* check it for equality in the 32 bits we save.
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*/
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struct cache_time {
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unsigned int sec;
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unsigned int nsec;
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};
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/*
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* dev/ino/uid/gid/size are also just tracked to the low 32 bits
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* Again - this is just a (very strong in practice) heuristic that
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* the inode hasn't changed.
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*
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* We save the fields in big-endian order to allow using the
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* index file over NFS transparently.
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*/
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struct cache_entry {
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struct cache_time ce_ctime;
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struct cache_time ce_mtime;
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unsigned int ce_dev;
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unsigned int ce_ino;
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unsigned int ce_mode;
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unsigned int ce_uid;
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unsigned int ce_gid;
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unsigned int ce_size;
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unsigned char sha1[20];
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unsigned short ce_flags;
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char name[0];
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};
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#define CE_NAMEMASK (0x0fff)
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#define CE_STAGEMASK (0x3000)
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#define CE_STAGESHIFT 12
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#define create_ce_flags(len, stage) htons((len) | ((stage) << CE_STAGESHIFT))
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#define ce_namelen(ce) (CE_NAMEMASK & ntohs((ce)->ce_flags))
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#define ce_size(ce) cache_entry_size(ce_namelen(ce))
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#define ce_stage(ce) ((CE_STAGEMASK & ntohs((ce)->ce_flags)) >> CE_STAGESHIFT)
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#define ce_permissions(mode) (((mode) & 0100) ? 0755 : 0644)
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#define create_ce_mode(mode) htonl(S_IFREG | ce_permissions(mode))
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#define cache_entry_size(len) ((offsetof(struct cache_entry,name) + (len) + 8) & ~7)
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const char *sha1_file_directory;
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struct cache_entry **active_cache;
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unsigned int active_nr, active_alloc;
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#define DB_ENVIRONMENT "SHA1_FILE_DIRECTORY"
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#define DEFAULT_DB_ENVIRONMENT ".git/objects"
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#define get_object_directory() (getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT)
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#define INDEX_ENVIRONMENT "GIT_INDEX_FILE"
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#define DEFAULT_INDEX_ENVIRONMENT ".git/index"
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#define get_index_file() (getenv(INDEX_ENVIRONMENT) ? : DEFAULT_INDEX_ENVIRONMENT)
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#define alloc_nr(x) (((x)+16)*3/2)
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/* Initialize and use the cache information */
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extern int read_cache(void);
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extern int write_cache(int newfd, struct cache_entry **cache, int entries);
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extern int cache_name_pos(const char *name, int namelen);
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extern int add_cache_entry(struct cache_entry *ce, int ok_to_add);
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extern int remove_entry_at(int pos);
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extern int remove_file_from_cache(char *path);
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extern int same_name(struct cache_entry *a, struct cache_entry *b);
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extern int cache_match_stat(struct cache_entry *ce, struct stat *st);
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extern int index_fd(unsigned char *sha1, int fd, struct stat *st);
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#define MTIME_CHANGED 0x0001
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#define CTIME_CHANGED 0x0002
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#define OWNER_CHANGED 0x0004
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#define MODE_CHANGED 0x0008
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#define INODE_CHANGED 0x0010
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#define DATA_CHANGED 0x0020
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/* Return a statically allocated filename matching the sha1 signature */
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extern char *sha1_file_name(const unsigned char *sha1);
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/* Read and unpack a sha1 file into memory, write memory to a sha1 file */
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extern void * map_sha1_file(const unsigned char *sha1, unsigned long *size);
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extern void * unpack_sha1_file(void *map, unsigned long mapsize, char *type, unsigned long *size);
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extern void * read_sha1_file(const unsigned char *sha1, char *type, unsigned long *size);
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extern int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned char *return_sha1);
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extern int check_sha1_signature(unsigned char *sha1, void *buf, unsigned long size, const char *type);
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/* Read a tree into the cache */
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extern int read_tree(void *buffer, unsigned long size, int stage);
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extern int write_sha1_from_fd(const unsigned char *sha1, int fd);
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extern int has_sha1_file(const unsigned char *sha1);
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/* Convert to/from hex/sha1 representation */
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extern int get_sha1(const char *str, unsigned char *sha1);
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extern int get_sha1_hex(const char *hex, unsigned char *sha1);
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extern char *sha1_to_hex(const unsigned char *sha1); /* static buffer result! */
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/* General helper functions */
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extern void usage(const char *err);
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extern void die(const char *err, ...);
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extern int error(const char *err, ...);
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extern int cache_name_compare(const char *name1, int len1, const char *name2, int len2);
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extern void *read_object_with_reference(const unsigned char *sha1,
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const unsigned char *required_type,
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unsigned long *size,
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unsigned char *sha1_ret);
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void parse_date(char *date, char *buf, int bufsize);
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void datestamp(char *buf, int bufsize);
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static inline void *xmalloc(int size)
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{
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void *ret = malloc(size);
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if (!ret)
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die("Out of memory, malloc failed");
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return ret;
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}
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static inline void *xrealloc(void *ptr, int size)
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{
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void *ret = realloc(ptr, size);
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if (!ret)
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die("Out of memory, realloc failed");
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return ret;
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}
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#endif /* CACHE_H */
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