Staging
v0.8.1
Revision 68d06c5200775ffda91881254ca7a92f27db68ef authored by Jeff King on 19 February 2008, 16:25:22 UTC, committed by Junio C Hamano on 20 February 2008, 04:46:10 UTC
The previous text was correct, but it was easy to miss the
fact that we are talking about "matching" refs. That is, the
text can be parsed as "we push the union of the sets
of remote and local heads" and not "we push the intersection
of the sets of remote and local heads". (The former actually
doesn't make sense if you think about it, since we don't
even _have_ some of those heads). A careful reading would
reveal the correct meaning, but it makes sense to be as
explicit as possible in documentation.

We also explicitly use and introduce the term "matching";
this is a term discussed on the list, and it seems useful
to for users to be able to refer to this behavior by name.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
1 parent 2b8130c
Raw File
http-walker.c
#include "cache.h"
#include "commit.h"
#include "pack.h"
#include "walker.h"
#include "http.h"

#define PREV_BUF_SIZE 4096
#define RANGE_HEADER_SIZE 30

struct alt_base
{
	char *base;
	int got_indices;
	struct packed_git *packs;
	struct alt_base *next;
};

enum object_request_state {
	WAITING,
	ABORTED,
	ACTIVE,
	COMPLETE,
};

struct object_request
{
	struct walker *walker;
	unsigned char sha1[20];
	struct alt_base *repo;
	char *url;
	char filename[PATH_MAX];
	char tmpfile[PATH_MAX];
	int local;
	enum object_request_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 object_request *next;
};

struct alternates_request {
	struct walker *walker;
	const char *base;
	char *url;
	struct strbuf *buffer;
	struct active_request_slot *slot;
	int http_specific;
};

struct walker_data {
	const char *url;
	int got_alternates;
	struct alt_base *alt;
	struct curl_slist *no_pragma_header;
};

static struct object_request *object_queue_head;

static size_t fwrite_sha1_file(void *ptr, size_t eltsize, size_t nmemb,
			       void *data)
{
	unsigned char expn[4096];
	size_t size = eltsize * nmemb;
	int posn = 0;
	struct object_request *obj_req = (struct object_request *)data;
	do {
		ssize_t retval = xwrite(obj_req->local,
				       (char *) ptr + posn, size - posn);
		if (retval < 0)
			return posn;
		posn += retval;
	} while (posn < size);

	obj_req->stream.avail_in = size;
	obj_req->stream.next_in = ptr;
	do {
		obj_req->stream.next_out = expn;
		obj_req->stream.avail_out = sizeof(expn);
		obj_req->zret = inflate(&obj_req->stream, Z_SYNC_FLUSH);
		SHA1_Update(&obj_req->c, expn,
			    sizeof(expn) - obj_req->stream.avail_out);
	} while (obj_req->stream.avail_in && obj_req->zret == Z_OK);
	data_received++;
	return size;
}

static void fetch_alternates(struct walker *walker, const char *base);

static void process_object_response(void *callback_data);

static void start_object_request(struct walker *walker,
				 struct object_request *obj_req)
{
	char *hex = sha1_to_hex(obj_req->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;
	struct walker_data *data = walker->data;

	snprintf(prevfile, sizeof(prevfile), "%s.prev", obj_req->filename);
	unlink(prevfile);
	rename(obj_req->tmpfile, prevfile);
	unlink(obj_req->tmpfile);

	if (obj_req->local != -1)
		error("fd leakage in start: %d", obj_req->local);
	obj_req->local = open(obj_req->tmpfile,
			      O_WRONLY | O_CREAT | O_EXCL, 0666);
	/* This could have failed due to the "lazy directory creation";
	 * try to mkdir the last path component.
	 */
	if (obj_req->local < 0 && errno == ENOENT) {
		char *dir = strrchr(obj_req->tmpfile, '/');
		if (dir) {
			*dir = 0;
			mkdir(obj_req->tmpfile, 0777);
			*dir = '/';
		}
		obj_req->local = open(obj_req->tmpfile,
				      O_WRONLY | O_CREAT | O_EXCL, 0666);
	}

	if (obj_req->local < 0) {
		obj_req->state = ABORTED;
		error("Couldn't create temporary file %s for %s: %s",
		      obj_req->tmpfile, obj_req->filename, strerror(errno));
		return;
	}

	memset(&obj_req->stream, 0, sizeof(obj_req->stream));

	inflateInit(&obj_req->stream);

	SHA1_Init(&obj_req->c);

	url = xmalloc(strlen(obj_req->repo->base) + 51);
	obj_req->url = xmalloc(strlen(obj_req->repo->base) + 51);
	strcpy(url, obj_req->repo->base);
	posn = url + strlen(obj_req->repo->base);
	strcpy(posn, "/objects/");
	posn += 9;
	memcpy(posn, hex, 2);
	posn += 2;
	*(posn++) = '/';
	strcpy(posn, hex + 2);
	strcpy(obj_req->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 = xread(prevlocal, prev_buf, PREV_BUF_SIZE);
			if (prev_read>0) {
				if (fwrite_sha1_file(prev_buf,
						     1,
						     prev_read,
						     obj_req) == 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(&obj_req->stream, 0, sizeof(obj_req->stream));
		inflateInit(&obj_req->stream);
		SHA1_Init(&obj_req->c);
		if (prev_posn>0) {
			prev_posn = 0;
			lseek(obj_req->local, 0, SEEK_SET);
			ftruncate(obj_req->local, 0);
		}
	}

	slot = get_active_slot();
	slot->callback_func = process_object_response;
	slot->callback_data = obj_req;
	obj_req->slot = slot;

	curl_easy_setopt(slot->curl, CURLOPT_FILE, obj_req);
	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
	curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, obj_req->errorstr);
	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);

	/* 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 (walker->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 get the request started, abort the request on error */
	obj_req->state = ACTIVE;
	if (!start_active_slot(slot)) {
		obj_req->state = ABORTED;
		obj_req->slot = NULL;
		close(obj_req->local); obj_req->local = -1;
		free(obj_req->url);
		return;
	}
}

static void finish_object_request(struct object_request *obj_req)
{
	struct stat st;

	fchmod(obj_req->local, 0444);
	close(obj_req->local); obj_req->local = -1;

	if (obj_req->http_code == 416) {
		fprintf(stderr, "Warning: requested range invalid; we may already have all the data.\n");
	} else if (obj_req->curl_result != CURLE_OK) {
		if (stat(obj_req->tmpfile, &st) == 0)
			if (st.st_size == 0)
				unlink(obj_req->tmpfile);
		return;
	}

	inflateEnd(&obj_req->stream);
	SHA1_Final(obj_req->real_sha1, &obj_req->c);
	if (obj_req->zret != Z_STREAM_END) {
		unlink(obj_req->tmpfile);
		return;
	}
	if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
		unlink(obj_req->tmpfile);
		return;
	}
	obj_req->rename =
		move_temp_to_file(obj_req->tmpfile, obj_req->filename);

	if (obj_req->rename == 0)
		walker_say(obj_req->walker, "got %s\n", sha1_to_hex(obj_req->sha1));
}

static void process_object_response(void *callback_data)
{
	struct object_request *obj_req =
		(struct object_request *)callback_data;
	struct walker *walker = obj_req->walker;
	struct walker_data *data = walker->data;
	struct alt_base *alt = data->alt;

	obj_req->curl_result = obj_req->slot->curl_result;
	obj_req->http_code = obj_req->slot->http_code;
	obj_req->slot = NULL;
	obj_req->state = COMPLETE;

	/* Use alternates if necessary */
	if (missing_target(obj_req)) {
		fetch_alternates(walker, alt->base);
		if (obj_req->repo->next != NULL) {
			obj_req->repo =
				obj_req->repo->next;
			close(obj_req->local);
			obj_req->local = -1;
			start_object_request(walker, obj_req);
			return;
		}
	}

	finish_object_request(obj_req);
}

static void release_object_request(struct object_request *obj_req)
{
	struct object_request *entry = object_queue_head;

	if (obj_req->local != -1)
		error("fd leakage in release: %d", obj_req->local);
	if (obj_req == object_queue_head) {
		object_queue_head = obj_req->next;
	} else {
		while (entry->next != NULL && entry->next != obj_req)
			entry = entry->next;
		if (entry->next == obj_req)
			entry->next = entry->next->next;
	}

	free(obj_req->url);
	free(obj_req);
}

#ifdef USE_CURL_MULTI
static int fill_active_slot(struct walker *walker)
{
	struct object_request *obj_req;

	for (obj_req = object_queue_head; obj_req; obj_req = obj_req->next) {
		if (obj_req->state == WAITING) {
			if (has_sha1_file(obj_req->sha1))
				obj_req->state = COMPLETE;
			else {
				start_object_request(walker, obj_req);
				return 1;
			}
		}
	}
	return 0;
}
#endif

static void prefetch(struct walker *walker, unsigned char *sha1)
{
	struct object_request *newreq;
	struct object_request *tail;
	struct walker_data *data = walker->data;
	char *filename = sha1_file_name(sha1);

	newreq = xmalloc(sizeof(*newreq));
	newreq->walker = walker;
	hashcpy(newreq->sha1, sha1);
	newreq->repo = data->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->slot = NULL;
	newreq->next = NULL;

	if (object_queue_head == NULL) {
		object_queue_head = newreq;
	} else {
		tail = object_queue_head;
		while (tail->next != NULL) {
			tail = tail->next;
		}
		tail->next = newreq;
	}

#ifdef USE_CURL_MULTI
	fill_active_slots();
	step_active_slots();
#endif
}

static int fetch_index(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
{
	char *hex = sha1_to_hex(sha1);
	char *filename;
	char *url;
	char tmpfile[PATH_MAX];
	long prev_posn = 0;
	char range[RANGE_HEADER_SIZE];
	struct curl_slist *range_header = NULL;
	struct walker_data *data = walker->data;

	FILE *indexfile;
	struct active_request_slot *slot;
	struct slot_results results;

	if (has_pack_index(sha1))
		return 0;

	if (walker->get_verbosely)
		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, hex);

	filename = sha1_pack_index_name(sha1);
	snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
	indexfile = fopen(tmpfile, "a");
	if (!indexfile)
		return error("Unable to open local file %s for pack index",
			     tmpfile);

	slot = get_active_slot();
	slot->results = &results;
	curl_easy_setopt(slot->curl, CURLOPT_FILE, indexfile);
	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
	slot->local = indexfile;

	/* If there is data present from a previous transfer attempt,
	   resume where it left off */
	prev_posn = ftell(indexfile);
	if (prev_posn>0) {
		if (walker->get_verbosely)
			fprintf(stderr,
				"Resuming fetch of index for pack %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);
	}

	if (start_active_slot(slot)) {
		run_active_slot(slot);
		if (results.curl_result != CURLE_OK) {
			fclose(indexfile);
			return error("Unable to get pack index %s\n%s", url,
				     curl_errorstr);
		}
	} else {
		fclose(indexfile);
		return error("Unable to start request");
	}

	fclose(indexfile);

	return move_temp_to_file(tmpfile, filename);
}

static int setup_index(struct walker *walker, 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(walker, repo, sha1))
		return -1;

	new_pack = parse_pack_index(sha1);
	new_pack->next = repo->packs;
	repo->packs = new_pack;
	return 0;
}

static void process_alternates_response(void *callback_data)
{
	struct alternates_request *alt_req =
		(struct alternates_request *)callback_data;
	struct walker *walker = alt_req->walker;
	struct walker_data *cdata = walker->data;
	struct active_request_slot *slot = alt_req->slot;
	struct alt_base *tail = cdata->alt;
	const char *base = alt_req->base;
	static const char null_byte = '\0';
	char *data;
	int i = 0;

	if (alt_req->http_specific) {
		if (slot->curl_result != CURLE_OK ||
		    !alt_req->buffer->len) {

			/* Try reusing the slot to get non-http alternates */
			alt_req->http_specific = 0;
			sprintf(alt_req->url, "%s/objects/info/alternates",
				base);
			curl_easy_setopt(slot->curl, CURLOPT_URL,
					 alt_req->url);
			active_requests++;
			slot->in_use = 1;
			if (slot->finished != NULL)
				(*slot->finished) = 0;
			if (!start_active_slot(slot)) {
				cdata->got_alternates = -1;
				slot->in_use = 0;
				if (slot->finished != NULL)
					(*slot->finished) = 1;
			}
			return;
		}
	} else if (slot->curl_result != CURLE_OK) {
		if (!missing_target(slot)) {
			cdata->got_alternates = -1;
			return;
		}
	}

	fwrite_buffer(&null_byte, 1, 1, alt_req->buffer);
	alt_req->buffer->len--;
	data = alt_req->buffer->buf;

	while (i < alt_req->buffer->len) {
		int posn = i;
		while (posn < alt_req->buffer->len && data[posn] != '\n')
			posn++;
		if (data[posn] == '\n') {
			int okay = 0;
			int serverlen = 0;
			struct alt_base *newalt;
			char *target = NULL;
			if (data[i] == '/') {
				/* This counts
				 * http://git.host/pub/scm/linux.git/
				 * -----------here^
				 * so memcpy(dst, base, serverlen) will
				 * copy up to "...git.host".
				 */
				const char *colon_ss = strstr(base,"://");
				if (colon_ss) {
					serverlen = (strchr(colon_ss + 3, '/')
						     - base);
					okay = 1;
				}
			} else if (!memcmp(data + i, "../", 3)) {
				/* Relative URL; chop the corresponding
				 * number of subpath from base (and ../
				 * from data), and concatenate the result.
				 *
				 * The code first drops ../ from data, and
				 * then drops one ../ from data and one path
				 * from base.  IOW, one extra ../ is dropped
				 * from data than path is dropped from base.
				 *
				 * This is not wrong.  The alternate in
				 *     http://git.host/pub/scm/linux.git/
				 * to borrow from
				 *     http://git.host/pub/scm/linus.git/
				 * is ../../linus.git/objects/.  You need
				 * two ../../ to borrow from your direct
				 * neighbour.
				 */
				i += 3;
				serverlen = strlen(base);
				while (i + 2 < posn &&
				       !memcmp(data + i, "../", 3)) {
					do {
						serverlen--;
					} while (serverlen &&
						 base[serverlen - 1] != '/');
					i += 3;
				}
				/* If the server got removed, give up. */
				okay = strchr(base, ':') - base + 3 <
					serverlen;
			} else if (alt_req->http_specific) {
				char *colon = strchr(data + i, ':');
				char *slash = strchr(data + i, '/');
				if (colon && slash && colon < data + posn &&
				    slash < data + posn && colon < slash) {
					okay = 1;
				}
			}
			/* skip "objects\n" at end */
			if (okay) {
				target = xmalloc(serverlen + posn - i - 6);
				memcpy(target, base, serverlen);
				memcpy(target + serverlen, data + i,
				       posn - i - 7);
				target[serverlen + posn - i - 7] = 0;
				if (walker->get_verbosely)
					fprintf(stderr,
						"Also look at %s\n", target);
				newalt = xmalloc(sizeof(*newalt));
				newalt->next = NULL;
				newalt->base = target;
				newalt->got_indices = 0;
				newalt->packs = NULL;

				while (tail->next != NULL)
					tail = tail->next;
				tail->next = newalt;
			}
		}
		i = posn + 1;
	}

	cdata->got_alternates = 1;
}

static void fetch_alternates(struct walker *walker, const char *base)
{
	struct strbuf buffer = STRBUF_INIT;
	char *url;
	struct active_request_slot *slot;
	struct alternates_request alt_req;
	struct walker_data *cdata = walker->data;

	/* If another request has already started fetching alternates,
	   wait for them to arrive and return to processing this request's
	   curl message */
#ifdef USE_CURL_MULTI
	while (cdata->got_alternates == 0) {
		step_active_slots();
	}
#endif

	/* Nothing to do if they've already been fetched */
	if (cdata->got_alternates == 1)
		return;

	/* Start the fetch */
	cdata->got_alternates = 0;

	if (walker->get_verbosely)
		fprintf(stderr, "Getting alternates list for %s\n", base);

	url = xmalloc(strlen(base) + 31);
	sprintf(url, "%s/objects/info/http-alternates", base);

	/* Use a callback to process the result, since another request
	   may fail and need to have alternates loaded before continuing */
	slot = get_active_slot();
	slot->callback_func = process_alternates_response;
	alt_req.walker = walker;
	slot->callback_data = &alt_req;

	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);

	alt_req.base = base;
	alt_req.url = url;
	alt_req.buffer = &buffer;
	alt_req.http_specific = 1;
	alt_req.slot = slot;

	if (start_active_slot(slot))
		run_active_slot(slot);
	else
		cdata->got_alternates = -1;

	strbuf_release(&buffer);
	free(url);
}

static int fetch_indices(struct walker *walker, struct alt_base *repo)
{
	unsigned char sha1[20];
	char *url;
	struct strbuf buffer = STRBUF_INIT;
	char *data;
	int i = 0;
	int ret = 0;

	struct active_request_slot *slot;
	struct slot_results results;

	if (repo->got_indices)
		return 0;

	if (walker->get_verbosely)
		fprintf(stderr, "Getting pack list for %s\n", repo->base);

	url = xmalloc(strlen(repo->base) + 21);
	sprintf(url, "%s/objects/info/packs", repo->base);

	slot = get_active_slot();
	slot->results = &results;
	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 (results.curl_result != CURLE_OK) {
			if (missing_target(&results)) {
				repo->got_indices = 1;
				goto cleanup;
			} else {
				repo->got_indices = 0;
				ret = error("%s", curl_errorstr);
				goto cleanup;
			}
		}
	} else {
		repo->got_indices = 0;
		ret = error("Unable to start request");
		goto cleanup;
	}

	data = buffer.buf;
	while (i < buffer.len) {
		switch (data[i]) {
		case 'P':
			i++;
			if (i + 52 <= buffer.len &&
			    !prefixcmp(data + i, " pack-") &&
			    !prefixcmp(data + i + 46, ".pack\n")) {
				get_sha1_hex(data + i + 6, sha1);
				setup_index(walker, repo, sha1);
				i += 51;
				break;
			}
		default:
			while (i < buffer.len && data[i] != '\n')
				i++;
		}
		i++;
	}

	repo->got_indices = 1;
cleanup:
	strbuf_release(&buffer);
	free(url);
	return ret;
}

static int fetch_pack(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
{
	char *url;
	struct packed_git *target;
	struct packed_git **lst;
	FILE *packfile;
	char *filename;
	char tmpfile[PATH_MAX];
	int ret;
	long prev_posn = 0;
	char range[RANGE_HEADER_SIZE];
	struct curl_slist *range_header = NULL;
	struct walker_data *data = walker->data;

	struct active_request_slot *slot;
	struct slot_results results;

	if (fetch_indices(walker, repo))
		return -1;
	target = find_sha1_pack(sha1, repo->packs);
	if (!target)
		return -1;

	if (walker->get_verbosely) {
		fprintf(stderr, "Getting pack %s\n",
			sha1_to_hex(target->sha1));
		fprintf(stderr, " which contains %s\n",
			sha1_to_hex(sha1));
	}

	url = xmalloc(strlen(repo->base) + 65);
	sprintf(url, "%s/objects/pack/pack-%s.pack",
		repo->base, sha1_to_hex(target->sha1));

	filename = sha1_pack_name(target->sha1);
	snprintf(tmpfile, sizeof(tmpfile), "%s.temp", filename);
	packfile = fopen(tmpfile, "a");
	if (!packfile)
		return error("Unable to open local file %s for pack",
			     tmpfile);

	slot = get_active_slot();
	slot->results = &results;
	curl_easy_setopt(slot->curl, CURLOPT_FILE, packfile);
	curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
	curl_easy_setopt(slot->curl, CURLOPT_URL, url);
	curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, data->no_pragma_header);
	slot->local = packfile;

	/* If there is data present from a previous transfer attempt,
	   resume where it left off */
	prev_posn = ftell(packfile);
	if (prev_posn>0) {
		if (walker->get_verbosely)
			fprintf(stderr,
				"Resuming fetch of pack %s at byte %ld\n",
				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(slot->curl, CURLOPT_HTTPHEADER, range_header);
	}

	if (start_active_slot(slot)) {
		run_active_slot(slot);
		if (results.curl_result != CURLE_OK) {
			fclose(packfile);
			return error("Unable to get pack file %s\n%s", url,
				     curl_errorstr);
		}
	} else {
		fclose(packfile);
		return error("Unable to start request");
	}

	target->pack_size = ftell(packfile);
	fclose(packfile);

	ret = move_temp_to_file(tmpfile, filename);
	if (ret)
		return ret;

	lst = &repo->packs;
	while (*lst != target)
		lst = &((*lst)->next);
	*lst = (*lst)->next;

	if (verify_pack(target, 0))
		return -1;
	install_packed_git(target);

	return 0;
}

static void abort_object_request(struct object_request *obj_req)
{
	if (obj_req->local >= 0) {
		close(obj_req->local);
		obj_req->local = -1;
	}
	unlink(obj_req->tmpfile);
	if (obj_req->slot) {
		release_active_slot(obj_req->slot);
		obj_req->slot = NULL;
	}
	release_object_request(obj_req);
}

static int fetch_object(struct walker *walker, struct alt_base *repo, unsigned char *sha1)
{
	char *hex = sha1_to_hex(sha1);
	int ret = 0;
	struct object_request *obj_req = object_queue_head;

	while (obj_req != NULL && hashcmp(obj_req->sha1, sha1))
		obj_req = obj_req->next;
	if (obj_req == NULL)
		return error("Couldn't find request for %s in the queue", hex);

	if (has_sha1_file(obj_req->sha1)) {
		abort_object_request(obj_req);
		return 0;
	}

#ifdef USE_CURL_MULTI
	while (obj_req->state == WAITING) {
		step_active_slots();
	}
#else
	start_object_request(walker, obj_req);
#endif

	while (obj_req->state == ACTIVE) {
		run_active_slot(obj_req->slot);
	}
	if (obj_req->local != -1) {
		close(obj_req->local); obj_req->local = -1;
	}

	if (obj_req->state == ABORTED) {
		ret = error("Request for %s aborted", hex);
	} else if (obj_req->curl_result != CURLE_OK &&
		   obj_req->http_code != 416) {
		if (missing_target(obj_req))
			ret = -1; /* Be silent, it is probably in a pack. */
		else
			ret = error("%s (curl_result = %d, http_code = %ld, sha1 = %s)",
				    obj_req->errorstr, obj_req->curl_result,
				    obj_req->http_code, hex);
	} else if (obj_req->zret != Z_STREAM_END) {
		walker->corrupt_object_found++;
		ret = error("File %s (%s) corrupt", hex, obj_req->url);
	} else if (hashcmp(obj_req->sha1, obj_req->real_sha1)) {
		ret = error("File %s has bad hash", hex);
	} else if (obj_req->rename < 0) {
		ret = error("unable to write sha1 filename %s",
			    obj_req->filename);
	}

	release_object_request(obj_req);
	return ret;
}

static int fetch(struct walker *walker, unsigned char *sha1)
{
	struct walker_data *data = walker->data;
	struct alt_base *altbase = data->alt;

	if (!fetch_object(walker, altbase, sha1))
		return 0;
	while (altbase) {
		if (!fetch_pack(walker, altbase, sha1))
			return 0;
		fetch_alternates(walker, data->alt->base);
		altbase = altbase->next;
	}
	return error("Unable to find %s under %s", sha1_to_hex(sha1),
		     data->alt->base);
}

static int fetch_ref(struct walker *walker, char *ref, unsigned char *sha1)
{
	struct walker_data *data = walker->data;
	return http_fetch_ref(data->alt->base, ref, sha1);
}

static void cleanup(struct walker *walker)
{
	struct walker_data *data = walker->data;
	http_cleanup();

	curl_slist_free_all(data->no_pragma_header);
}

struct walker *get_http_walker(const char *url)
{
	char *s;
	struct walker_data *data = xmalloc(sizeof(struct walker_data));
	struct walker *walker = xmalloc(sizeof(struct walker));

	http_init();

	data->no_pragma_header = curl_slist_append(NULL, "Pragma:");

	data->alt = xmalloc(sizeof(*data->alt));
	data->alt->base = xmalloc(strlen(url) + 1);
	strcpy(data->alt->base, url);
	for (s = data->alt->base + strlen(data->alt->base) - 1; *s == '/'; --s)
		*s = 0;

	data->alt->got_indices = 0;
	data->alt->packs = NULL;
	data->alt->next = NULL;
	data->got_alternates = -1;

	walker->corrupt_object_found = 0;
	walker->fetch = fetch;
	walker->fetch_ref = fetch_ref;
	walker->prefetch = prefetch;
	walker->cleanup = cleanup;
	walker->data = data;

#ifdef USE_CURL_MULTI
	add_fill_function(walker, (int (*)(void *)) fill_active_slot);
#endif

	return walker;
}
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