Add support for parallel HTTP transfers

Add support for parallel HTTP transfers.  Prefetch populates a queue of
objects to transfer and starts feeding requests to an active request
queue for processing; fetch_object keeps the active queue moving
while the specified object is being transferred.  The size of the active
queue can be restricted using -r and defaults to 5 concurrent transfers.
Requests for objects that are not prefetched are also processed via the
active queue.

Signed-off-by: Nick Hengeveld <nickh@reactrix.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

diff --git a/http-fetch.c b/http-fetch.c
index 71a8c60b56914ca579db3da1d2bef6795acc7bf9..0b01877b5c1b564b1fe65b7a960a73829a6479d6 100644 (file)
--- a/http-fetch.c
+++ b/http-fetch.c
@@ -6,6 +6,8 @@
 #include <curl/curl.h>
 #include <curl/easy.h>
 
+#define DEFAULT_MAX_REQUESTS 5
+
 #if LIBCURL_VERSION_NUM < 0x070704
 #define curl_global_cleanup() do { /* nothing */ } while(0)
 #endif
@@ -16,13 +18,16 @@
 #define PREV_BUF_SIZE 4096
 #define RANGE_HEADER_SIZE 30
 
-static CURL *curl;
+static int max_requests = DEFAULT_MAX_REQUESTS;
+static int active_requests = 0;
+static int data_received;
+
+static CURLM *curlm;
+static CURL *curl_default;
 static struct curl_slist *no_pragma_header;
 static struct curl_slist *no_range_header;
 static char curl_errorstr[CURL_ERROR_SIZE];
 
-static char *initial_base;
-
 struct alt_base
 {
        char *base;
@@ -33,11 +38,46 @@ struct alt_base
 
 static struct alt_base *alt = NULL;
 
-static SHA_CTX c;
-static z_stream stream;
+enum transfer_state {
+       WAITING,
+       ABORTED,
+       ACTIVE,
+       COMPLETE,
+};
 
-static int local;
-static int zret;
+struct transfer_request
+{
+       unsigned char sha1[20];
+       struct alt_base *repo;
+       char *url;
+       char filename[PATH_MAX];
+       char tmpfile[PATH_MAX];
+       int local;
+       enum transfer_state state;
+       CURLcode curl_result;
+       char errorstr[CURL_ERROR_SIZE];
+       long http_code;
+       unsigned char real_sha1[20];
+       SHA_CTX c;
+       z_stream stream;
+       int zret;
+       int rename;
+       struct active_request_slot *slot;
+       struct transfer_request *next;
+};
+
+struct active_request_slot
+{
+       CURL *curl;
+       FILE *local;
+       int in_use;
+       int done;
+       CURLcode curl_result;
+       struct active_request_slot *next;
+};
+
+static struct transfer_request *request_queue_head = NULL;
+static struct active_request_slot *active_queue_head = NULL;
 
 static int curl_ssl_verify;
 static char *ssl_cert;
@@ -60,6 +100,7 @@ static size_t fwrite_buffer(void *ptr, size_t eltsize, size_t nmemb,
                 size = buffer->size - buffer->posn;
         memcpy(buffer->buffer + buffer->posn, ptr, size);
         buffer->posn += size;
+       data_received++;
         return size;
 }
 
@@ -69,28 +110,28 @@ static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
        unsigned char expn[4096];
        size_t size = eltsize * nmemb;
        int posn = 0;
+       struct transfer_request *request = (struct transfer_request *)data;
        do {
-               ssize_t retval = write(local, ptr + posn, size - posn);
+               ssize_t retval = write(request->local,
+                                      ptr + posn, size - posn);
                if (retval < 0)
                        return posn;
                posn += retval;
        } while (posn < size);
 
-       stream.avail_in = size;
-       stream.next_in = ptr;
+       request->stream.avail_in = size;
+       request->stream.next_in = ptr;
        do {
-               stream.next_out = expn;
-               stream.avail_out = sizeof(expn);
-               zret = inflate(&stream, Z_SYNC_FLUSH);
-               SHA1_Update(&c, expn, sizeof(expn) - stream.avail_out);
-       } while (stream.avail_in && zret == Z_OK);
+               request->stream.next_out = expn;
+               request->stream.avail_out = sizeof(expn);
+               request->zret = inflate(&request->stream, Z_SYNC_FLUSH);
+               SHA1_Update(&request->c, expn,
+                           sizeof(expn) - request->stream.avail_out);
+       } while (request->stream.avail_in && request->zret == Z_OK);
+       data_received++;
        return size;
 }
 
-void prefetch(unsigned char *sha1)
-{
-}
-
 int relink_or_rename(char *old, char *new) {
        int ret;
 
@@ -110,10 +151,369 @@ int relink_or_rename(char *old, char *new) {
        return 0;
 }
 
+void process_curl_messages();
+void process_request_queue();
+
+struct active_request_slot *get_active_slot()
+{
+       struct active_request_slot *slot = active_queue_head;
+       struct active_request_slot *newslot;
+       int num_transfers;
+
+       /* Wait for a slot to open up if the queue is full */
+       while (active_requests >= max_requests) {
+               curl_multi_perform(curlm, &num_transfers);
+               if (num_transfers < active_requests) {
+                       process_curl_messages();
+               }
+       }
+
+       while (slot != NULL && slot->in_use) {
+               slot = slot->next;
+       }
+       if (slot == NULL) {
+               newslot = xmalloc(sizeof(*newslot));
+               newslot->curl = curl_easy_duphandle(curl_default);
+               newslot->in_use = 0;
+               newslot->next = NULL;
+
+               slot = active_queue_head;
+               if (slot == NULL) {
+                       active_queue_head = newslot;
+               } else {
+                       while (slot->next != NULL) {
+                               slot = slot->next;
+                       }
+                       slot->next = newslot;
+               }
+               slot = newslot;
+       }
+
+       active_requests++;
+       slot->in_use = 1;
+       slot->done = 0;
+       slot->local = NULL;
+       curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_pragma_header);
+       curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, no_range_header);
+       curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, curl_errorstr);
+
+       return slot;
+}
+
+int start_active_slot(struct active_request_slot *slot)
+{
+       CURLMcode curlm_result = curl_multi_add_handle(curlm, slot->curl);
+
+       if (curlm_result != CURLM_OK &&
+           curlm_result != CURLM_CALL_MULTI_PERFORM) {
+               active_requests--;
+               slot->in_use = 0;
+               return 0;
+       }
+
+       return 1;
+}
+
+void run_active_slot(struct active_request_slot *slot)
+{
+       int num_transfers;
+       long last_pos = 0;
+       long current_pos;
+       fd_set readfds;
+       fd_set writefds;
+       fd_set excfds;
+       int max_fd;
+       struct timeval select_timeout;
+       CURLMcode curlm_result;
+
+       while (!slot->done) {
+               data_received = 0;
+               do {
+                       curlm_result = curl_multi_perform(curlm,
+                                                         &num_transfers);
+               } while (curlm_result == CURLM_CALL_MULTI_PERFORM);
+               if (num_transfers < active_requests) {
+                       process_curl_messages();
+                       process_request_queue();
+               }
+
+               if (!data_received && slot->local != NULL) {
+                       current_pos = ftell(slot->local);
+                       if (current_pos > last_pos)
+                               data_received++;
+                       last_pos = current_pos;
+               }
+
+               if (!slot->done && !data_received) {
+                       max_fd = 0;
+                       FD_ZERO(&readfds);
+                       FD_ZERO(&writefds);
+                       FD_ZERO(&excfds);
+                       select_timeout.tv_sec = 0;
+                       select_timeout.tv_usec = 50000;
+                       select(max_fd, &readfds, &writefds,
+                              &excfds, &select_timeout);
+               }
+       }
+}
+
+void start_request(struct transfer_request *request)
+{
+       char *hex = sha1_to_hex(request->sha1);
+       char prevfile[PATH_MAX];
+       char *url;
+       char *posn;
+       int prevlocal;
+       unsigned char prev_buf[PREV_BUF_SIZE];
+       ssize_t prev_read = 0;
+       long prev_posn = 0;
+       char range[RANGE_HEADER_SIZE];
+       struct curl_slist *range_header = NULL;
+       struct active_request_slot *slot;
+
+       snprintf(prevfile, sizeof(prevfile), "%s.prev", request->filename);
+       unlink(prevfile);
+       rename(request->tmpfile, prevfile);
+       unlink(request->tmpfile);
+
+       request->local = open(request->tmpfile,
+                             O_WRONLY | O_CREAT | O_EXCL, 0666);
+       if (request->local < 0) {
+               request->state = ABORTED;
+               error("Couldn't create temporary file %s for %s: %s\n",
+                     request->tmpfile, request->filename, strerror(errno));
+               return;
+       }
+
+       memset(&request->stream, 0, sizeof(request->stream));
+
+       inflateInit(&request->stream);
+
+       SHA1_Init(&request->c);
+
+       url = xmalloc(strlen(request->repo->base) + 50);
+       request->url = xmalloc(strlen(request->repo->base) + 50);
+       strcpy(url, request->repo->base);
+       posn = url + strlen(request->repo->base);
+       strcpy(posn, "objects/");
+       posn += 8;
+       memcpy(posn, hex, 2);
+       posn += 2;
+       *(posn++) = '/';
+       strcpy(posn, hex + 2);
+       strcpy(request->url, url);
+
+       /* If a previous temp file is present, process what was already
+          fetched. */
+       prevlocal = open(prevfile, O_RDONLY);
+       if (prevlocal != -1) {
+               do {
+                       prev_read = read(prevlocal, prev_buf, PREV_BUF_SIZE);
+                       if (prev_read>0) {
+                               if (fwrite_sha1_file(prev_buf,
+                                                    1,
+                                                    prev_read,
+                                                    request) == prev_read) {
+                                       prev_posn += prev_read;
+                               } else {
+                                       prev_read = -1;
+                               }
+                       }
+               } while (prev_read > 0);
+               close(prevlocal);
+       }
+       unlink(prevfile);
+
+       /* Reset inflate/SHA1 if there was an error reading the previous temp
+          file; also rewind to the beginning of the local file. */
+       if (prev_read == -1) {
+               memset(&request->stream, 0, sizeof(request->stream));
+               inflateInit(&request->stream);
+               SHA1_Init(&request->c);
+               if (prev_posn>0) {
+                       prev_posn = 0;
+                       lseek(request->local, SEEK_SET, 0);
+                       ftruncate(request->local, 0);
+               }
+       }
+
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, request);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
+       curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, request->errorstr);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+
+       /* If we have successfully processed data from a previous fetch
+          attempt, only fetch the data we don't already have. */
+       if (prev_posn>0) {
+               if (get_verbosely)
+                       fprintf(stderr,
+                               "Resuming fetch of object %s at byte %ld\n",
+                               hex, prev_posn);
+               sprintf(range, "Range: bytes=%ld-", prev_posn);
+               range_header = curl_slist_append(range_header, range);
+               curl_easy_setopt(slot->curl,
+                                CURLOPT_HTTPHEADER, range_header);
+       }
+
+       /* Try to add to multi handle, abort the request on error */
+       if (!start_active_slot(slot)) {
+               request->state = ABORTED;
+               close(request->local);
+               free(request->url);
+               return;
+       }
+       
+       request->slot = slot;
+       request->state = ACTIVE;
+}
+
+void finish_request(struct transfer_request *request)
+{
+       fchmod(request->local, 0444);
+       close(request->local);
+
+       if (request->http_code == 416) {
+               fprintf(stderr, "Warning: requested range invalid; we may already have all the data.\n");
+       } else if (request->curl_result != CURLE_OK) {
+               return;
+       }
+
+       inflateEnd(&request->stream);
+       SHA1_Final(request->real_sha1, &request->c);
+       if (request->zret != Z_STREAM_END) {
+               unlink(request->tmpfile);
+               return;
+       }
+       if (memcmp(request->sha1, request->real_sha1, 20)) {
+               unlink(request->tmpfile);
+               return;
+       }
+       request->rename =
+               relink_or_rename(request->tmpfile, request->filename);
+
+       if (request->rename == 0)
+               pull_say("got %s\n", sha1_to_hex(request->sha1));
+}
+
+void release_request(struct transfer_request *request)
+{
+       struct transfer_request *entry = request_queue_head;
+
+       if (request == request_queue_head) {
+               request_queue_head = request->next;
+       } else {
+               while (entry->next != NULL && entry->next != request)
+                       entry = entry->next;
+               if (entry->next == request)
+                       entry->next = entry->next->next;
+       }
+
+       free(request->url);
+       free(request);
+}
+
+void process_curl_messages()
+{
+       int num_messages;
+       struct active_request_slot *slot;
+       struct transfer_request *request = NULL;
+       CURLMsg *curl_message = curl_multi_info_read(curlm, &num_messages);
+
+       while (curl_message != NULL) {
+               if (curl_message->msg == CURLMSG_DONE) {
+                       slot = active_queue_head;
+                       while (slot != NULL &&
+                              slot->curl != curl_message->easy_handle)
+                               slot = slot->next;
+                       if (slot != NULL) {
+                               curl_multi_remove_handle(curlm, slot->curl);
+                               active_requests--;
+                               slot->done = 1;
+                               slot->in_use = 0;
+                               slot->curl_result = curl_message->data.result;
+                               request = request_queue_head;
+                               while (request != NULL &&
+                                      request->slot != slot)
+                                       request = request->next;
+                       } else {
+                               fprintf(stderr, "Received DONE message for unknown request!\n");
+                       }
+                       if (request != NULL) {
+                               request->curl_result =
+                                       curl_message->data.result;
+                               curl_easy_getinfo(slot->curl,
+                                                 CURLINFO_HTTP_CODE,
+                                                 &request->http_code);
+                               request->slot = NULL;
+
+                               /* Use alternates if necessary */
+                               if (request->http_code == 404 &&
+                                   request->repo->next != NULL) {
+                                       request->repo = request->repo->next;
+                                       start_request(request);
+                               } else {
+                                       finish_request(request);
+                                       request->state = COMPLETE;
+                               }
+                       }
+               } else {
+                       fprintf(stderr, "Unknown CURL message received: %d\n",
+                               (int)curl_message->msg);
+               }
+               curl_message = curl_multi_info_read(curlm, &num_messages);
+       }
+}
+
+void process_request_queue()
+{
+       struct transfer_request *request = request_queue_head;
+       int num_transfers;
+
+       while (active_requests < max_requests && request != NULL) {
+               if (request->state == WAITING) {
+                       start_request(request);
+                       curl_multi_perform(curlm, &num_transfers);
+               }
+               request = request->next;
+       }
+}
+
+void prefetch(unsigned char *sha1)
+{
+       struct transfer_request *newreq;
+       struct transfer_request *tail;
+       char *filename = sha1_file_name(sha1);
+
+       newreq = xmalloc(sizeof(*newreq));
+       memcpy(newreq->sha1, sha1, 20);
+       newreq->repo = alt;
+       newreq->url = NULL;
+       newreq->local = -1;
+       newreq->state = WAITING;
+       snprintf(newreq->filename, sizeof(newreq->filename), "%s", filename);
+       snprintf(newreq->tmpfile, sizeof(newreq->tmpfile),
+                "%s.temp", filename);
+       newreq->next = NULL;
+
+       if (request_queue_head == NULL) {
+               request_queue_head = newreq;
+       } else {
+               tail = request_queue_head;
+               while (tail->next != NULL) {
+                       tail = tail->next;
+               }
+               tail->next = newreq;
+       }
+       process_request_queue();
+       process_curl_messages();
+}
+
 static int got_alternates = 0;
 
 static int fetch_index(struct alt_base *repo, unsigned char *sha1)
 {
+       char *hex = sha1_to_hex(sha1);
        char *filename;
        char *url;
        char tmpfile[PATH_MAX];
@@ -121,20 +521,18 @@ static int fetch_index(struct alt_base *repo, unsigned char *sha1)
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct curl_slist *range_header = NULL;
-       CURLcode curl_result;
 
        FILE *indexfile;
+       struct active_request_slot *slot;
 
        if (has_pack_index(sha1))
                return 0;
 
        if (get_verbosely)
-               fprintf(stderr, "Getting index for pack %s\n",
-                       sha1_to_hex(sha1));
+               fprintf(stderr, "Getting index for pack %s\n", hex);
        
        url = xmalloc(strlen(repo->base) + 64);
-       sprintf(url, "%s/objects/pack/pack-%s.idx",
-               repo->base, sha1_to_hex(sha1));
+       sprintf(url, "%s/objects/pack/pack-%s.idx", repo->base, hex);
        
        filename = sha1_pack_index_name(sha1);
        snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
@@ -143,12 +541,12 @@ static int fetch_index(struct alt_base *repo, unsigned char *sha1)
                return error("Unable to open local file %s for pack index",
                             filename);
 
-       curl_easy_setopt(curl, CURLOPT_FILE, indexfile);
-       curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite);
-       curl_easy_setopt(curl, CURLOPT_URL, url);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_pragma_header);
-       curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_errorstr);
-       
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+       slot->local = indexfile;
+
        /* If there is data present from a previous transfer attempt,
           resume where it left off */
        prev_posn = ftell(indexfile);
@@ -156,20 +554,21 @@ static int fetch_index(struct alt_base *repo, unsigned char *sha1)
                if (get_verbosely)
                        fprintf(stderr,
                                "Resuming fetch of index for pack %s at byte %ld\n",
-                               sha1_to_hex(sha1), prev_posn);
+                               hex, prev_posn);
                sprintf(range, "Range: bytes=%ld-", prev_posn);
                range_header = curl_slist_append(range_header, range);
-               curl_easy_setopt(curl, CURLOPT_HTTPHEADER, range_header);
+               curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
        }
 
-       /* Clear out the Range: header after performing the request, so
-          other curl requests don't inherit inappropriate header data */
-       curl_result = curl_easy_perform(curl);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_range_header);
-       if (curl_result != 0) {
-               fclose(indexfile);
-               return error("Unable to get pack index %s\n%s", url,
-                            curl_errorstr);
+       if (start_active_slot(slot)) {
+               run_active_slot(slot);
+               if (slot->curl_result != CURLE_OK) {
+                       fclose(indexfile);
+                       return error("Unable to get pack index %s\n%s", url,
+                                    curl_errorstr);
+               }
+       } else {
+               return error("Unable to start request");
        }
 
        fclose(indexfile);
@@ -205,6 +604,9 @@ static int fetch_alternates(char *base)
        char *data;
        int i = 0;
        int http_specific = 1;
+       struct alt_base *tail = alt;
+
+       struct active_request_slot *slot;
        if (got_alternates)
                return 0;
        data = xmalloc(4096);
@@ -218,22 +620,31 @@ static int fetch_alternates(char *base)
        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) {
-               http_specific = 0;
-
-               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;
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+       if (start_active_slot(slot)) {
+               run_active_slot(slot);
+               if (slot->curl_result != CURLE_OK || !buffer.posn) {
+                       http_specific = 0;
+
+                       sprintf(url, "%s/objects/info/alternates", base);
+
+                       slot = get_active_slot();
+                       curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
+                       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
+                                        fwrite_buffer);
+                       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+                       if (start_active_slot(slot)) {
+                               run_active_slot(slot);
+                               if (slot->curl_result != CURLE_OK) {
+                                       return 0;
+                               }
+                       }
                }
+       } else {
+               return 0;
        }
 
        data[buffer.posn] = '\0';
@@ -283,11 +694,13 @@ static int fetch_alternates(char *base)
                                        fprintf(stderr, 
                                                "Also look at %s\n", target);
                                newalt = xmalloc(sizeof(*newalt));
-                               newalt->next = alt;
+                               newalt->next = NULL;
                                newalt->base = target;
                                newalt->got_indices = 0;
                                newalt->packs = NULL;
-                               alt = newalt;
+                               while (tail->next != NULL)
+                                       tail = tail->next;
+                               tail->next = newalt;
                                ret++;
                        }
                }
@@ -306,6 +719,8 @@ static int fetch_indices(struct alt_base *repo)
        char *data;
        int i = 0;
 
+       struct active_request_slot *slot;
+
        if (repo->got_indices)
                return 0;
 
@@ -320,14 +735,18 @@ static int fetch_indices(struct alt_base *repo)
        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);
-       curl_easy_setopt(curl, CURLOPT_URL, url);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, NULL);
-       curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_errorstr);
-       
-       if (curl_easy_perform(curl))
-               return error("%s", curl_errorstr);
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+       curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
+       if (start_active_slot(slot)) {
+               run_active_slot(slot);
+               if (slot->curl_result != CURLE_OK)
+                       return error("%s", curl_errorstr);
+       } else {
+               return error("Unable to start request");
+       }
 
        while (i < buffer.posn) {
                switch (data[i]) {
@@ -364,7 +783,8 @@ static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct curl_slist *range_header = NULL;
-       CURLcode curl_result;
+
+       struct active_request_slot *slot;
 
        if (fetch_indices(repo))
                return -1;
@@ -390,11 +810,11 @@ static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
                return error("Unable to open local file %s for pack",
                             filename);
 
-       curl_easy_setopt(curl, CURLOPT_FILE, packfile);
-       curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite);
-       curl_easy_setopt(curl, CURLOPT_URL, url);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_pragma_header);
-       curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_errorstr);
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+       slot->local = packfile;
 
        /* If there is data present from a previous transfer attempt,
           resume where it left off */
@@ -406,17 +826,18 @@ static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
                                sha1_to_hex(target->sha1), prev_posn);
                sprintf(range, "Range: bytes=%ld-", prev_posn);
                range_header = curl_slist_append(range_header, range);
-               curl_easy_setopt(curl, CURLOPT_HTTPHEADER, range_header);
+               curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, range_header);
        }
 
-       /* Clear out the Range: header after performing the request, so
-          other curl requests don't inherit inappropriate header data */
-       curl_result = curl_easy_perform(curl);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_range_header);
-       if (curl_result != 0) {
-               fclose(packfile);
-               return error("Unable to get pack file %s\n%s", url,
-                            curl_errorstr);
+       if (start_active_slot(slot)) {
+               run_active_slot(slot);
+               if (slot->curl_result != CURLE_OK) {
+                       fclose(packfile);
+                       return error("Unable to get pack file %s\n%s", url,
+                                    curl_errorstr);
+               }
+       } else {
+               return error("Unable to start request");
        }
 
        fclose(packfile);
@@ -441,155 +862,73 @@ static int fetch_pack(struct alt_base *repo, unsigned char *sha1)
 static int fetch_object(struct alt_base *repo, unsigned char *sha1)
 {
        char *hex = sha1_to_hex(sha1);
-       char *filename = sha1_file_name(sha1);
-       unsigned char real_sha1[20];
-       char tmpfile[PATH_MAX];
-       char prevfile[PATH_MAX];
        int ret;
-       char *url;
-       char *posn;
-       int prevlocal;
-       unsigned char prev_buf[PREV_BUF_SIZE];
-       ssize_t prev_read = 0;
-       long prev_posn = 0;
-       char range[RANGE_HEADER_SIZE];
-       struct curl_slist *range_header = NULL;
-       CURLcode curl_result;
-
-       snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
-       snprintf(prevfile, sizeof(prevfile), "%s.prev", filename);
-
-       if (unlink(prevfile) && (errno != ENOENT))
-               return error("Failed to unlink %s (%s)",
-                            prevfile, strerror(errno));
-       if (rename(tmpfile, prevfile) && (errno != ENOENT))
-               return error("Failed to rename %s to %s (%s)",
-                            tmpfile, prevfile, strerror(errno));
-
-       local = open(tmpfile, O_WRONLY | O_CREAT | O_EXCL, 0666);
-
-       /* Note: if another instance starts now, it will turn our new
-          tmpfile into its prevfile. */
-
-       if (local < 0)
-               return error("Couldn't create temporary file %s for %s: %s\n",
-                            tmpfile, filename, strerror(errno));
-
-       memset(&stream, 0, sizeof(stream));
-
-       inflateInit(&stream);
-
-       SHA1_Init(&c);
-
-       curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
-       curl_easy_setopt(curl, CURLOPT_FILE, NULL);
-       curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_pragma_header);
-       curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_errorstr);
-
-       url = xmalloc(strlen(repo->base) + 50);
-       strcpy(url, repo->base);
-       posn = url + strlen(repo->base);
-       strcpy(posn, "objects/");
-       posn += 8;
-       memcpy(posn, hex, 2);
-       posn += 2;
-       *(posn++) = '/';
-       strcpy(posn, hex + 2);
+       struct transfer_request *request = request_queue_head;
+       int num_transfers;
+
+       while (request != NULL && memcmp(request->sha1, sha1, 20))
+               request = request->next;
+       if (request == NULL)
+               return error("Couldn't find request for %s in the queue", hex);
+
+       while (request->state == WAITING) {
+               curl_multi_perform(curlm, &num_transfers);
+               if (num_transfers < active_requests) {
+                       process_curl_messages();
+                       process_request_queue();
+               }
+       }
 
-       curl_easy_setopt(curl, CURLOPT_URL, url);
+       if (request->state == ACTIVE)
+               run_active_slot(request->slot);
 
-       /* If a previous temp file is present, process what was already
-          fetched. */
-       prevlocal = open(prevfile, O_RDONLY);
-       if (prevlocal != -1) {
-               do {
-                       prev_read = read(prevlocal, prev_buf, PREV_BUF_SIZE);
-                       if (prev_read>0) {
-                               if (fwrite_sha1_file(prev_buf,
-                                                    1,
-                                                    prev_read,
-                                                    NULL) == prev_read) {
-                                       prev_posn += prev_read;
-                               } else {
-                                       prev_read = -1;
-                               }
-                       }
-               } while (prev_read > 0);
-               close(prevlocal);
+       if (request->state == ABORTED) {
+               release_request(request);
+               return error("Request for %s aborted", hex);
        }
-       unlink(prevfile);
 
-       /* Reset inflate/SHA1 if there was an error reading the previous temp
-          file; also rewind to the beginning of the local file. */
-       if (prev_read == -1) {
-               memset(&stream, 0, sizeof(stream));
-               inflateInit(&stream);
-               SHA1_Init(&c);
-               if (prev_posn>0) {
-                       prev_posn = 0;
-                       lseek(local, SEEK_SET, 0);
-                       ftruncate(local, 0);
-               }
+       if (request->curl_result != CURLE_OK && request->http_code != 416) {
+               ret = error("%s", request->errorstr);
+               release_request(request);
+               return ret;
        }
 
-       /* If we have successfully processed data from a previous fetch
-          attempt, only fetch the data we don't already have. */
-       if (prev_posn>0) {
-               if (get_verbosely)
-                       fprintf(stderr,
-                               "Resuming fetch of object %s at byte %ld\n",
-                               hex, prev_posn);
-               sprintf(range, "Range: bytes=%ld-", prev_posn);
-               range_header = curl_slist_append(range_header, range);
-               curl_easy_setopt(curl, CURLOPT_HTTPHEADER, range_header);
+       if (request->zret != Z_STREAM_END) {
+               ret = error("File %s (%s) corrupt\n", hex, request->url);
+               release_request(request);
+               return ret;
        }
 
-       /* Clear out the Range: header after performing the request, so
-          other curl requests don't inherit inappropriate header data */
-       curl_result = curl_easy_perform(curl);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, no_range_header);
-       if (curl_result != 0) {
-               return error("%s", curl_errorstr);
+       if (memcmp(request->sha1, request->real_sha1, 20)) {
+               release_request(request);
+               return error("File %s has bad hash\n", hex);
        }
 
-       fchmod(local, 0444);
-       close(local);
-       inflateEnd(&stream);
-       SHA1_Final(real_sha1, &c);
-       if (zret != Z_STREAM_END) {
-               unlink(tmpfile);
-               return error("File %s (%s) corrupt\n", hex, url);
-       }
-       if (memcmp(sha1, real_sha1, 20)) {
-               unlink(tmpfile);
-               return error("File %s has bad hash\n", hex);
+       if (request->rename < 0) {
+               ret = error("unable to write sha1 filename %s: %s",
+                           request->filename,
+                           strerror(request->rename));
+               release_request(request);
+               return ret;
        }
-       ret = relink_or_rename(tmpfile, filename);
-       if (ret)
-               return error("unable to write sha1 filename %s: %s",
-                            filename, strerror(ret));
 
-       pull_say("got %s\n", hex);
+       release_request(request);
        return 0;
 }
 
 int fetch(unsigned char *sha1)
 {
        struct alt_base *altbase = alt;
+
+       if (!fetch_object(altbase, sha1))
+               return 0;
        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);
+                    alt->base);
 }
 
 int fetch_ref(char *ref, unsigned char *sha1)
@@ -597,17 +936,13 @@ int fetch_ref(char *ref, unsigned char *sha1)
         char *url, *posn;
         char hex[42];
         struct buffer buffer;
-       char *base = initial_base;
+       char *base = alt->base;
+       struct active_request_slot *slot;
         buffer.size = 41;
         buffer.posn = 0;
         buffer.buffer = hex;
         hex[41] = '\0';
         
-        curl_easy_setopt(curl, CURLOPT_FILE, &buffer);
-        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
-       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, NULL);
-       curl_easy_setopt(curl, CURLOPT_ERRORBUFFER, curl_errorstr);
-
         url = xmalloc(strlen(base) + 6 + strlen(ref));
         strcpy(url, base);
         posn = url + strlen(base);
@@ -615,11 +950,19 @@ int fetch_ref(char *ref, unsigned char *sha1)
         posn += 5;
         strcpy(posn, ref);
 
-        curl_easy_setopt(curl, CURLOPT_URL, url);
-
-        if (curl_easy_perform(curl))
-                return error("Couldn't get %s for %s\n%s",
-                            url, ref, curl_errorstr);
+       slot = get_active_slot();
+       curl_easy_setopt(slot->curl, CURLOPT_FILE, &buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_buffer);
+       curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, NULL);
+       curl_easy_setopt(slot->curl, CURLOPT_URL, url);
+       if (start_active_slot(slot)) {
+               run_active_slot(slot);
+               if (slot->curl_result != CURLE_OK)
+                       return error("Couldn't get %s for %s\n%s",
+                                    url, ref, curl_errorstr);
+       } else {
+               return error("Unable to start request");
+       }
 
         hex[40] = '\0';
         get_sha1_hex(hex, sha1);
@@ -631,6 +974,7 @@ int main(int argc, char **argv)
        char *commit_id;
        char *url;
        int arg = 1;
+       struct active_request_slot *slot;
 
        while (arg < argc && argv[arg][0] == '-') {
                if (argv[arg][1] == 't') {
@@ -648,6 +992,11 @@ int main(int argc, char **argv)
                        arg++;
                } else if (!strcmp(argv[arg], "--recover")) {
                        get_recover = 1;
+               } else if (argv[arg][1] == 'r') {
+                       max_requests = atoi(argv[arg + 1]);
+                       if (max_requests < 1)
+                               max_requests = DEFAULT_MAX_REQUESTS;
+                       arg++;
                }
                arg++;
        }
@@ -660,44 +1009,59 @@ int main(int argc, char **argv)
 
        curl_global_init(CURL_GLOBAL_ALL);
 
-       curl = curl_easy_init();
+       curlm = curl_multi_init();
+       if (curlm == NULL) {
+               fprintf(stderr, "Error creating curl multi handle.\n");
+               return 1;
+       }
        no_pragma_header = curl_slist_append(no_pragma_header, "Pragma:");
        no_range_header = curl_slist_append(no_range_header, "Range:");
 
+       curl_default = curl_easy_init();
+
        curl_ssl_verify = getenv("GIT_SSL_NO_VERIFY") ? 0 : 1;
-       curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, curl_ssl_verify);
+       curl_easy_setopt(curl_default, CURLOPT_SSL_VERIFYPEER, curl_ssl_verify);
 #if LIBCURL_VERSION_NUM >= 0x070907
-       curl_easy_setopt(curl, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
+       curl_easy_setopt(curl_default, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
 #endif
 
        if ((ssl_cert = getenv("GIT_SSL_CERT")) != NULL) {
-               curl_easy_setopt(curl, CURLOPT_SSLCERT, ssl_cert);
+               curl_easy_setopt(curl_default, CURLOPT_SSLCERT, ssl_cert);
        }
 #if LIBCURL_VERSION_NUM >= 0x070902
        if ((ssl_key = getenv("GIT_SSL_KEY")) != NULL) {
-               curl_easy_setopt(curl, CURLOPT_SSLKEY, ssl_key);
+               curl_easy_setopt(curl_default, CURLOPT_SSLKEY, ssl_key);
        }
 #endif
 #if LIBCURL_VERSION_NUM >= 0x070908
        if ((ssl_capath = getenv("GIT_SSL_CAPATH")) != NULL) {
-               curl_easy_setopt(curl, CURLOPT_CAPATH, ssl_capath);
+               curl_easy_setopt(curl_default, CURLOPT_CAPATH, ssl_capath);
        }
 #endif
        if ((ssl_cainfo = getenv("GIT_SSL_CAINFO")) != NULL) {
-               curl_easy_setopt(curl, CURLOPT_CAINFO, ssl_cainfo);
+               curl_easy_setopt(curl_default, CURLOPT_CAINFO, ssl_cainfo);
        }
+       curl_easy_setopt(curl_default, CURLOPT_FAILONERROR, 1);
 
        alt = xmalloc(sizeof(*alt));
        alt->base = url;
        alt->got_indices = 0;
        alt->packs = NULL;
        alt->next = NULL;
-       initial_base = url;
+       fetch_alternates(alt->base);
 
        if (pull(commit_id))
                return 1;
 
        curl_slist_free_all(no_pragma_header);
+       curl_slist_free_all(no_range_header);
+       curl_easy_cleanup(curl_default);
+       slot = active_queue_head;
+       while (slot != NULL) {
+               curl_easy_cleanup(slot->curl);
+               slot = slot->next;
+       }
+       curl_multi_cleanup(curlm);
        curl_global_cleanup();
        return 0;
 }