[PATCH] Add support for alternates in HTTP

This tries .../objects/info/http-alternates and then
.../objects/info/alternates, looking for a file which specifies where
else to download objects and packs from.

It currently only supports absolute paths, and doesn't support full URLs.

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/http-fetch.c b/http-fetch.c
index 1a433a9..17051fe 100644 (file)
--- a/http-fetch.c
+++ b/http-fetch.c
@@ -16,7 +16,17 @@
 static CURL *curl;
 static struct curl_slist *no_pragma_header;
 
-static char *base;
+static char *initial_base;
+
+struct alt_base
+{
+       char *base;
+       int got_indices;
+       struct packed_git *packs;
+       struct alt_base *next;
+};
+
+struct alt_base *alt = NULL;
 
 static SHA_CTX c;
 static z_stream stream;
@@ -72,11 +82,9 @@ void prefetch(unsigned char *sha1)
 {
 }
 
-static int got_indices = 0;
-
-static struct packed_git *packs = NULL;
+static int got_alternates = 0;
 
-static int fetch_index(unsigned char *sha1)
+static int fetch_index(struct alt_base *repo, unsigned char *sha1)
 {
        char *filename;
        char *url;
@@ -90,9 +98,9 @@ static int fetch_index(unsigned char *sha1)
                fprintf(stderr, "Getting index for pack %s\n",
                        sha1_to_hex(sha1));
        
-       url = xmalloc(strlen(base) + 64);
+       url = xmalloc(strlen(repo->base) + 64);
        sprintf(url, "%s/objects/pack/pack-%s.idx",
-               base, sha1_to_hex(sha1));
+               repo->base, sha1_to_hex(sha1));
        
        filename = sha1_pack_index_name(sha1);
        indexfile = fopen(filename, "w");
@@ -114,22 +122,92 @@ static int fetch_index(unsigned char *sha1)
        return 0;
 }
 
-static int setup_index(unsigned char *sha1)
+static int setup_index(struct alt_base *repo, unsigned char *sha1)
 {
        struct packed_git *new_pack;
        if (has_pack_file(sha1))
                return 0; // don't list this as something we can get
 
-       if (fetch_index(sha1))
+       if (fetch_index(repo, sha1))
                return -1;
 
        new_pack = parse_pack_index(sha1);
-       new_pack->next = packs;
-       packs = new_pack;
+       new_pack->next = repo->packs;
+       repo->packs = new_pack;
        return 0;
 }
 
-static int fetch_indices(void)
+static int fetch_alternates(char *base)
+{
+       int ret = 0;
+       struct buffer buffer;
+       char *url;
+       char *data;
+       int i = 0;
+       if (got_alternates)
+               return 0;
+       data = xmalloc(4096);
+       buffer.size = 4096;
+       buffer.posn = 0;
+       buffer.buffer = data;
+
+       if (get_verbosely)
+               fprintf(stderr, "Getting alternates list\n");
+       
+       url = xmalloc(strlen(base) + 31);
+       sprintf(url, "%s/objects/info/http-alternates", base);
+
+       curl_easy_setopt(curl, CURLOPT_FILE, &buffer);
+       curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+       curl_easy_setopt(curl, CURLOPT_URL, url);
+
+       if (curl_easy_perform(curl) || !buffer.posn) {
+               sprintf(url, "%s/objects/info/alternates", base);
+               
+               curl_easy_setopt(curl, CURLOPT_FILE, &buffer);
+               curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+               curl_easy_setopt(curl, CURLOPT_URL, url);
+               
+               if (curl_easy_perform(curl)) {
+                       return 0;
+               }
+       }
+
+       while (i < buffer.posn) {
+               int posn = i;
+               while (posn < buffer.posn && data[posn] != '\n')
+                       posn++;
+               if (data[posn] == '\n') {
+                       if (data[i] == '/') {
+                               int serverlen = strchr(base + 8, '/') - base;
+                               // skip 'objects' at end
+                               char *target = 
+                                       xmalloc(serverlen + posn - i - 6);
+                               struct alt_base *newalt;
+                               strncpy(target, base, serverlen);
+                               strncpy(target + serverlen, data + i,
+                                       posn - i - 7);
+                               target[serverlen + posn - i - 7] = '\0';
+                               if (get_verbosely)
+                                       fprintf(stderr, 
+                                               "Also look at %s\n", target);
+                               newalt = xmalloc(sizeof(*newalt));
+                               newalt->next = alt;
+                               newalt->base = target;
+                               newalt->got_indices = 0;
+                               newalt->packs = NULL;
+                               alt = newalt;
+                               ret++;
+                       }
+               }
+               i = posn + 1;
+       }
+       got_alternates = 1;
+       
+       return ret;
+}
+
+static int fetch_indices(struct alt_base *repo)
 {
        unsigned char sha1[20];
        char *url;
@@ -137,7 +215,7 @@ static int fetch_indices(void)
        char *data;
        int i = 0;
 
-       if (got_indices)
+       if (repo->got_indices)
                return 0;
 
        data = xmalloc(4096);
@@ -148,8 +226,8 @@ static int fetch_indices(void)
        if (get_verbosely)
                fprintf(stderr, "Getting pack list\n");
        
-       url = xmalloc(strlen(base) + 21);
-       sprintf(url, "%s/objects/info/packs", base);
+       url = xmalloc(strlen(repo->base) + 21);
+       sprintf(url, "%s/objects/info/packs", repo->base);
 
        curl_easy_setopt(curl, CURLOPT_FILE, &buffer);
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
@@ -160,7 +238,7 @@ static int fetch_indices(void)
                return error("Unable to get pack index %s", url);
        }
 
-       do {
+       while (i < buffer.posn) {
                switch (data[i]) {
                case 'P':
                        i++;
@@ -168,7 +246,7 @@ static int fetch_indices(void)
                            !strncmp(data + i, " pack-", 6) &&
                            !strncmp(data + i + 46, ".pack\n", 6)) {
                                get_sha1_hex(data + i + 6, sha1);
-                               setup_index(sha1);
+                               setup_index(repo, sha1);
                                i += 51;
                                break;
                        }
@@ -177,13 +255,13 @@ static int fetch_indices(void)
                                i++;
                }
                i++;
-       } while (i < buffer.posn);
+       }
 
-       got_indices = 1;
+       repo->got_indices = 1;
        return 0;
 }
 
-static int fetch_pack(unsigned char *sha1)
+static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
 {
        char *url;
        struct packed_git *target;
@@ -191,12 +269,11 @@ static int fetch_pack(unsigned char *sha1)
        FILE *packfile;
        char *filename;
 
-       if (fetch_indices())
+       if (fetch_indices(repo))
                return -1;
-       target = find_sha1_pack(sha1, packs);
+       target = find_sha1_pack(sha1, repo->packs);
        if (!target)
-               return error("Couldn't get %s: not separate or in any pack",
-                            sha1_to_hex(sha1));
+               return -1;
 
        if (get_verbosely) {
                fprintf(stderr, "Getting pack %s\n",
@@ -205,9 +282,9 @@ static int fetch_pack(unsigned char *sha1)
                        sha1_to_hex(sha1));
        }
 
-       url = xmalloc(strlen(base) + 65);
+       url = xmalloc(strlen(repo->base) + 65);
        sprintf(url, "%s/objects/pack/pack-%s.pack",
-               base, sha1_to_hex(target->sha1));
+               repo->base, sha1_to_hex(target->sha1));
 
        filename = sha1_pack_name(target->sha1);
        packfile = fopen(filename, "w");
@@ -227,7 +304,7 @@ static int fetch_pack(unsigned char *sha1)
 
        fclose(packfile);
 
-       lst = &packs;
+       lst = &repo->packs;
        while (*lst != target)
                lst = &((*lst)->next);
        *lst = (*lst)->next;
@@ -237,7 +314,7 @@ static int fetch_pack(unsigned char *sha1)
        return 0;
 }
 
-int fetch(unsigned char *sha1)
+int fetch_object(struct alt_base *repo, unsigned char *sha1)
 {
        char *hex = sha1_to_hex(sha1);
        char *filename = sha1_file_name(sha1);
@@ -261,9 +338,9 @@ int fetch(unsigned char *sha1)
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
        curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_pragma_header);
 
-       url = xmalloc(strlen(base) + 50);
-       strcpy(url, base);
-       posn = url + strlen(base);
+       url = xmalloc(strlen(repo->base) + 50);
+       strcpy(url, repo->base);
+       posn = url + strlen(repo->base);
        strcpy(posn, "objects/");
        posn += 8;
        memcpy(posn, hex, 2);
@@ -275,9 +352,7 @@ int fetch(unsigned char *sha1)
 
        if (curl_easy_perform(curl)) {
                unlink(filename);
-               if (fetch_pack(sha1))
-                       return error("Tried %s", url);
-               return 0;
+               return -1;
        }
 
        close(local);
@@ -296,11 +371,30 @@ int fetch(unsigned char *sha1)
        return 0;
 }
 
+int fetch(unsigned char *sha1)
+{
+       struct alt_base *altbase = alt;
+       while (altbase) {
+               if (!fetch_object(altbase, sha1))
+                       return 0;
+               if (!fetch_pack(altbase, sha1))
+                       return 0;
+               if (fetch_alternates(altbase->base) > 0) {
+                       altbase = alt;
+                       continue;
+               }
+               altbase = altbase->next;
+       }
+       return error("Unable to find %s under %s\n", sha1_to_hex(sha1), 
+                    initial_base);
+}
+
 int fetch_ref(char *ref, unsigned char *sha1)
 {
         char *url, *posn;
         char hex[42];
         struct buffer buffer;
+       char *base = initial_base;
         buffer.size = 41;
         buffer.posn = 0;
         buffer.buffer = hex;
@@ -368,7 +462,12 @@ int main(int argc, char **argv)
        curl_easy_setopt(curl, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
 #endif
 
-       base = url;
+       alt = xmalloc(sizeof(*alt));
+       alt->base = url;
+       alt->got_indices = 0;
+       alt->packs = NULL;
+       alt->next = NULL;
+       initial_base = url;
 
        if (pull(commit_id))
                return 1;