Introduce SHA1_FILE_DIRECTORIES to support multiple object databases.

SHA1_FILE_DIRECTORIES environment variable is a colon separated paths
used when looking for SHA1 files not found in the usual place for
reading.  Creating a new SHA1 file does not use this alternate object
database location mechanism.  This is useful to archive older, rarely
used objects into separate directories.

Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/cache.h b/cache.h
index 1dba405..314ee0d 100644 (file)
--- a/cache.h
+++ b/cache.h
@@ -101,6 +101,7 @@ unsigned int active_nr, active_alloc, active_cache_changed;
 
 #define DB_ENVIRONMENT "SHA1_FILE_DIRECTORY"
 #define DEFAULT_DB_ENVIRONMENT ".git/objects"
+#define ALTERNATE_DB_ENVIRONMENT "SHA1_FILE_DIRECTORIES"
 
 #define get_object_directory() (getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT)
 

diff --git a/fsck-cache.c b/fsck-cache.c
index abdec92..d59d57e 100644 (file)
--- a/fsck-cache.c
+++ b/fsck-cache.c
@@ -306,7 +306,7 @@ int main(int argc, char **argv)
                        usage("fsck-cache [--tags] [[--unreachable] [--cache] <head-sha1>*]");
        }
 
-       sha1_dir = getenv(DB_ENVIRONMENT) ? : DEFAULT_DB_ENVIRONMENT;
+       sha1_dir = get_object_directory();
        for (i = 0; i < 256; i++) {
                static char dir[4096];
                sprintf(dir, "%s/%02x", sha1_dir, i);

diff --git a/sha1_file.c b/sha1_file.c
index f1c1c70..bd68783 100644 (file)
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -100,18 +100,34 @@ char * sha1_to_hex(const unsigned char *sha1)
        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
+ * SHA1_FILE_DIRECTORIES environment variable if it is not found in
+ * the primary object database.
  */
 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;
+               char *sha1_file_directory = get_object_directory();
                int len = strlen(sha1_file_directory);
                base = xmalloc(len + 60);
                memcpy(base, sha1_file_directory, len);
@@ -120,16 +136,74 @@ char *sha1_file_name(const unsigned char *sha1)
                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];
-       }
+       fill_sha1_path(name, sha1);
        return base;
 }
 
+static struct alternate_object_database
+{
+       char *base;
+       char *name;
+} *alt_odb;
+
+static void prepare_alt_odb(void)
+{
+       int pass, totlen, i;
+       void *buf;
+       const char *cp, *last;
+       char *op = 0;
+       const char *alt = getenv(ALTERNATE_DB_ENVIRONMENT) ? : "";
+
+       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 = buf = xmalloc(sizeof(*alt_odb) * (i + 1) + totlen);
+               alt_odb[i].base = alt_odb[i].name = 0;
+               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];
@@ -145,10 +219,15 @@ int check_sha1_signature(unsigned char *sha1, void *map, unsigned long size, con
 
 void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
 {
-       char *filename = sha1_file_name(sha1);
        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) {
@@ -167,10 +246,6 @@ void *map_sha1_file(const unsigned char *sha1, unsigned long *size)
                /* If it failed once, it will probably fail again. Stop using O_NOATIME */
                sha1_file_open_flag = 0;
        }
-       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)
@@ -315,6 +390,7 @@ int write_sha1_file(char *buf, unsigned long len, const char *type, unsigned cha
        }
 
        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));
@@ -442,12 +518,8 @@ int write_sha1_from_fd(const unsigned char *sha1, int fd)
 
 int has_sha1_file(const unsigned char *sha1)
 {
-       char *filename = sha1_file_name(sha1);
        struct stat st;
-
-       if (!stat(filename, &st))
-               return 1;
-       return 0;
+       return !!find_sha1_file(sha1, &st);
 }
 
 int index_fd(unsigned char *sha1, int fd, struct stat *st)