#include "git-compat-util.h"
#include "http.h"
#include "pack.h"
#include "sideband.h"
#include "run-command.h"
#include "url.h"
#include "urlmatch.h"
#include "credential.h"
#include "version.h"
#include "pkt-line.h"
#include "gettext.h"
#include "transport.h"

int active_requests;
int http_is_verbose;
size_t http_post_buffer = 16 * LARGE_PACKET_MAX;

#if LIBCURL_VERSION_NUM >= 0x070a06
#define LIBCURL_CAN_HANDLE_AUTH_ANY
#endif

static int min_curl_sessions = 1;
static int curl_session_count;
#ifdef USE_CURL_MULTI
static int max_requests = -1;
static CURLM *curlm;
#endif
#ifndef NO_CURL_EASY_DUPHANDLE
static CURL *curl_default;
#endif

#define PREV_BUF_SIZE 4096
#define RANGE_HEADER_SIZE 30

char curl_errorstr[CURL_ERROR_SIZE];

static int curl_ssl_verify = -1;
static int curl_ssl_try;
static const char *ssl_cert;
#if LIBCURL_VERSION_NUM >= 0x070903
static const char *ssl_key;
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
static const char *ssl_capath;
#endif
static const char *ssl_cainfo;
static long curl_low_speed_limit = -1;
static long curl_low_speed_time = -1;
static int curl_ftp_no_epsv;
static const char *curl_http_proxy;
static const char *curl_cookie_file;
static int curl_save_cookies;
struct credential http_auth = CREDENTIAL_INIT;
static int http_proactive_auth;
static const char *user_agent;

#if LIBCURL_VERSION_NUM >= 0x071700
/* Use CURLOPT_KEYPASSWD as is */
#elif LIBCURL_VERSION_NUM >= 0x070903
#define CURLOPT_KEYPASSWD CURLOPT_SSLKEYPASSWD
#else
#define CURLOPT_KEYPASSWD CURLOPT_SSLCERTPASSWD
#endif

static struct credential cert_auth = CREDENTIAL_INIT;
static int ssl_cert_password_required;
#ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
static unsigned long http_auth_methods = CURLAUTH_ANY;
#endif

static struct curl_slist *pragma_header;
static struct curl_slist *no_pragma_header;

static struct active_request_slot *active_queue_head;

static char *cached_accept_language;

size_t fread_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
{
        size_t size = eltsize * nmemb;
        struct buffer *buffer = buffer_;

        if (size > buffer->buf.len - buffer->posn)
                size = buffer->buf.len - buffer->posn;
        memcpy(ptr, buffer->buf.buf + buffer->posn, size);
        buffer->posn += size;

        return size;
}

#ifndef NO_CURL_IOCTL
curlioerr ioctl_buffer(CURL *handle, int cmd, void *clientp)
{
        struct buffer *buffer = clientp;

        switch (cmd) {
        case CURLIOCMD_NOP:
                return CURLIOE_OK;

        case CURLIOCMD_RESTARTREAD:
                buffer->posn = 0;
                return CURLIOE_OK;

        default:
                return CURLIOE_UNKNOWNCMD;
        }
}
#endif

size_t fwrite_buffer(char *ptr, size_t eltsize, size_t nmemb, void *buffer_)
{
        size_t size = eltsize * nmemb;
        struct strbuf *buffer = buffer_;

        strbuf_add(buffer, ptr, size);
        return size;
}

size_t fwrite_null(char *ptr, size_t eltsize, size_t nmemb, void *strbuf)
{
        return eltsize * nmemb;
}

static void closedown_active_slot(struct active_request_slot *slot)
{
        active_requests--;
        slot->in_use = 0;
}

static void finish_active_slot(struct active_request_slot *slot)
{
        closedown_active_slot(slot);
        curl_easy_getinfo(slot->curl, CURLINFO_HTTP_CODE, &slot->http_code);

        if (slot->finished != NULL)
                (*slot->finished) = 1;

        /* Store slot results so they can be read after the slot is reused */
        if (slot->results != NULL) {
                slot->results->curl_result = slot->curl_result;
                slot->results->http_code = slot->http_code;
#if LIBCURL_VERSION_NUM >= 0x070a08
                curl_easy_getinfo(slot->curl, CURLINFO_HTTPAUTH_AVAIL,
                                  &slot->results->auth_avail);
#else
                slot->results->auth_avail = 0;
#endif
        }

        /* Run callback if appropriate */
        if (slot->callback_func != NULL)
                slot->callback_func(slot->callback_data);
}

#ifdef USE_CURL_MULTI
static void process_curl_messages(void)
{
        int num_messages;
        struct active_request_slot *slot;
        CURLMsg *curl_message = curl_multi_info_read(curlm, &num_messages);

        while (curl_message != NULL) {
                if (curl_message->msg == CURLMSG_DONE) {
                        int curl_result = curl_message->data.result;
                        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);
                                slot->curl_result = curl_result;
                                finish_active_slot(slot);
                        } else {
                                fprintf(stderr, "Received DONE message for unknown request!\n");
                        }
                } else {
                        fprintf(stderr, "Unknown CURL message received: %d\n",
                                (int)curl_message->msg);
                }
                curl_message = curl_multi_info_read(curlm, &num_messages);
        }
}
#endif

static int http_options(const char *var, const char *value, void *cb)
{
        if (!strcmp("http.sslverify", var)) {
                curl_ssl_verify = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.sslcert", var))
                return git_config_string(&ssl_cert, var, value);
#if LIBCURL_VERSION_NUM >= 0x070903
        if (!strcmp("http.sslkey", var))
                return git_config_string(&ssl_key, var, value);
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        if (!strcmp("http.sslcapath", var))
                return git_config_string(&ssl_capath, var, value);
#endif
        if (!strcmp("http.sslcainfo", var))
                return git_config_string(&ssl_cainfo, var, value);
        if (!strcmp("http.sslcertpasswordprotected", var)) {
                ssl_cert_password_required = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.ssltry", var)) {
                curl_ssl_try = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.minsessions", var)) {
                min_curl_sessions = git_config_int(var, value);
#ifndef USE_CURL_MULTI
                if (min_curl_sessions > 1)
                        min_curl_sessions = 1;
#endif
                return 0;
        }
#ifdef USE_CURL_MULTI
        if (!strcmp("http.maxrequests", var)) {
                max_requests = git_config_int(var, value);
                return 0;
        }
#endif
        if (!strcmp("http.lowspeedlimit", var)) {
                curl_low_speed_limit = (long)git_config_int(var, value);
                return 0;
        }
        if (!strcmp("http.lowspeedtime", var)) {
                curl_low_speed_time = (long)git_config_int(var, value);
                return 0;
        }

        if (!strcmp("http.noepsv", var)) {
                curl_ftp_no_epsv = git_config_bool(var, value);
                return 0;
        }
        if (!strcmp("http.proxy", var))
                return git_config_string(&curl_http_proxy, var, value);

        if (!strcmp("http.cookiefile", var))
                return git_config_string(&curl_cookie_file, var, value);
        if (!strcmp("http.savecookies", var)) {
                curl_save_cookies = git_config_bool(var, value);
                return 0;
        }

        if (!strcmp("http.postbuffer", var)) {
                http_post_buffer = git_config_int(var, value);
                if (http_post_buffer < LARGE_PACKET_MAX)
                        http_post_buffer = LARGE_PACKET_MAX;
                return 0;
        }

        if (!strcmp("http.useragent", var))
                return git_config_string(&user_agent, var, value);

        /* Fall back on the default ones */
        return git_default_config(var, value, cb);
}

static void init_curl_http_auth(CURL *result)
{
        if (!http_auth.username)
                return;

        credential_fill(&http_auth);

#if LIBCURL_VERSION_NUM >= 0x071301
        curl_easy_setopt(result, CURLOPT_USERNAME, http_auth.username);
        curl_easy_setopt(result, CURLOPT_PASSWORD, http_auth.password);
#else
        {
                static struct strbuf up = STRBUF_INIT;
                /*
                 * Note that we assume we only ever have a single set of
                 * credentials in a given program run, so we do not have
                 * to worry about updating this buffer, only setting its
                 * initial value.
                 */
                if (!up.len)
                        strbuf_addf(&up, "%s:%s",
                                http_auth.username, http_auth.password);
                curl_easy_setopt(result, CURLOPT_USERPWD, up.buf);
        }
#endif
}

static int has_cert_password(void)
{
        if (ssl_cert == NULL || ssl_cert_password_required != 1)
                return 0;
        if (!cert_auth.password) {
                cert_auth.protocol = xstrdup("cert");
                cert_auth.username = xstrdup("");
                cert_auth.path = xstrdup(ssl_cert);
                credential_fill(&cert_auth);
        }
        return 1;
}

#if LIBCURL_VERSION_NUM >= 0x071900
static void set_curl_keepalive(CURL *c)
{
        curl_easy_setopt(c, CURLOPT_TCP_KEEPALIVE, 1);
}

#elif LIBCURL_VERSION_NUM >= 0x071000
static int sockopt_callback(void *client, curl_socket_t fd, curlsocktype type)
{
        int ka = 1;
        int rc;
        socklen_t len = (socklen_t)sizeof(ka);

        if (type != CURLSOCKTYPE_IPCXN)
                return 0;

        rc = setsockopt(fd, SOL_SOCKET, SO_KEEPALIVE, (void *)&ka, len);
        if (rc < 0)
                warning("unable to set SO_KEEPALIVE on socket %s",
                        strerror(errno));

        return 0; /* CURL_SOCKOPT_OK only exists since curl 7.21.5 */
}

static void set_curl_keepalive(CURL *c)
{
        curl_easy_setopt(c, CURLOPT_SOCKOPTFUNCTION, sockopt_callback);
}

#else
static void set_curl_keepalive(CURL *c)
{
        /* not supported on older curl versions */
}
#endif

static CURL *get_curl_handle(void)
{
        CURL *result = curl_easy_init();
        long allowed_protocols = 0;

        if (!result)
                die("curl_easy_init failed");

        if (!curl_ssl_verify) {
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYPEER, 0);
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 0);
        } else {
                /* Verify authenticity of the peer's certificate */
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYPEER, 1);
                /* The name in the cert must match whom we tried to connect */
                curl_easy_setopt(result, CURLOPT_SSL_VERIFYHOST, 2);
        }

#if LIBCURL_VERSION_NUM >= 0x070907
        curl_easy_setopt(result, CURLOPT_NETRC, CURL_NETRC_OPTIONAL);
#endif
#ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
        curl_easy_setopt(result, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
#endif

        if (http_proactive_auth)
                init_curl_http_auth(result);

        if (ssl_cert != NULL)
                curl_easy_setopt(result, CURLOPT_SSLCERT, ssl_cert);
        if (has_cert_password())
                curl_easy_setopt(result, CURLOPT_KEYPASSWD, cert_auth.password);
#if LIBCURL_VERSION_NUM >= 0x070903
        if (ssl_key != NULL)
                curl_easy_setopt(result, CURLOPT_SSLKEY, ssl_key);
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        if (ssl_capath != NULL)
                curl_easy_setopt(result, CURLOPT_CAPATH, ssl_capath);
#endif
        if (ssl_cainfo != NULL)
                curl_easy_setopt(result, CURLOPT_CAINFO, ssl_cainfo);

        if (curl_low_speed_limit > 0 && curl_low_speed_time > 0) {
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_LIMIT,
                                 curl_low_speed_limit);
                curl_easy_setopt(result, CURLOPT_LOW_SPEED_TIME,
                                 curl_low_speed_time);
        }

        curl_easy_setopt(result, CURLOPT_FOLLOWLOCATION, 1);
        curl_easy_setopt(result, CURLOPT_MAXREDIRS, 20);
#if LIBCURL_VERSION_NUM >= 0x071301
        curl_easy_setopt(result, CURLOPT_POSTREDIR, CURL_REDIR_POST_ALL);
#elif LIBCURL_VERSION_NUM >= 0x071101
        curl_easy_setopt(result, CURLOPT_POST301, 1);
#endif
#if LIBCURL_VERSION_NUM >= 0x071304
        if (is_transport_allowed("http"))
                allowed_protocols |= CURLPROTO_HTTP;
        if (is_transport_allowed("https"))
                allowed_protocols |= CURLPROTO_HTTPS;
        if (is_transport_allowed("ftp"))
                allowed_protocols |= CURLPROTO_FTP;
        if (is_transport_allowed("ftps"))
                allowed_protocols |= CURLPROTO_FTPS;
        curl_easy_setopt(result, CURLOPT_REDIR_PROTOCOLS, allowed_protocols);
#else
        if (transport_restrict_protocols())
                warning("protocol restrictions not applied to curl redirects because\n"
                        "your curl version is too old (>= 7.19.4)");
#endif

        if (getenv("GIT_CURL_VERBOSE"))
                curl_easy_setopt(result, CURLOPT_VERBOSE, 1);

        curl_easy_setopt(result, CURLOPT_USERAGENT,
                user_agent ? user_agent : git_user_agent());

        if (curl_ftp_no_epsv)
                curl_easy_setopt(result, CURLOPT_FTP_USE_EPSV, 0);

#ifdef CURLOPT_USE_SSL
        if (curl_ssl_try)
                curl_easy_setopt(result, CURLOPT_USE_SSL, CURLUSESSL_TRY);
#endif

        if (curl_http_proxy) {
                curl_easy_setopt(result, CURLOPT_PROXY, curl_http_proxy);
#if LIBCURL_VERSION_NUM >= 0x071800
                if (starts_with(curl_http_proxy, "socks5"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS5);
                else if (starts_with(curl_http_proxy, "socks4a"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4A);
                else if (starts_with(curl_http_proxy, "socks"))
                        curl_easy_setopt(result,
                                CURLOPT_PROXYTYPE, CURLPROXY_SOCKS4);
#endif
        }
#if LIBCURL_VERSION_NUM >= 0x070a07
        curl_easy_setopt(result, CURLOPT_PROXYAUTH, CURLAUTH_ANY);
#endif

        set_curl_keepalive(result);

        return result;
}

static void set_from_env(const char **var, const char *envname)
{
        const char *val = getenv(envname);
        if (val)
                *var = val;
}

void http_init(struct remote *remote, const char *url, int proactive_auth)
{
        char *low_speed_limit;
        char *low_speed_time;
        char *normalized_url;
        struct urlmatch_config config = { STRING_LIST_INIT_DUP };

        config.section = "http";
        config.key = NULL;
        config.collect_fn = http_options;
        config.cascade_fn = git_default_config;
        config.cb = NULL;

        http_is_verbose = 0;
        normalized_url = url_normalize(url, &config.url);

        git_config(urlmatch_config_entry, &config);
        free(normalized_url);

        if (curl_global_init(CURL_GLOBAL_ALL) != CURLE_OK)
                die("curl_global_init failed");

        http_proactive_auth = proactive_auth;

        if (remote && remote->http_proxy)
                curl_http_proxy = xstrdup(remote->http_proxy);

        pragma_header = curl_slist_append(pragma_header, "Pragma: no-cache");
        no_pragma_header = curl_slist_append(no_pragma_header, "Pragma:");

#ifdef USE_CURL_MULTI
        {
                char *http_max_requests = getenv("GIT_HTTP_MAX_REQUESTS");
                if (http_max_requests != NULL)
                        max_requests = atoi(http_max_requests);
        }

        curlm = curl_multi_init();
        if (!curlm)
                die("curl_multi_init failed");
#endif

        if (getenv("GIT_SSL_NO_VERIFY"))
                curl_ssl_verify = 0;

        set_from_env(&ssl_cert, "GIT_SSL_CERT");
#if LIBCURL_VERSION_NUM >= 0x070903
        set_from_env(&ssl_key, "GIT_SSL_KEY");
#endif
#if LIBCURL_VERSION_NUM >= 0x070908
        set_from_env(&ssl_capath, "GIT_SSL_CAPATH");
#endif
        set_from_env(&ssl_cainfo, "GIT_SSL_CAINFO");

        set_from_env(&user_agent, "GIT_HTTP_USER_AGENT");

        low_speed_limit = getenv("GIT_HTTP_LOW_SPEED_LIMIT");
        if (low_speed_limit != NULL)
                curl_low_speed_limit = strtol(low_speed_limit, NULL, 10);
        low_speed_time = getenv("GIT_HTTP_LOW_SPEED_TIME");
        if (low_speed_time != NULL)
                curl_low_speed_time = strtol(low_speed_time, NULL, 10);

        if (curl_ssl_verify == -1)
                curl_ssl_verify = 1;

        curl_session_count = 0;
#ifdef USE_CURL_MULTI
        if (max_requests < 1)
                max_requests = DEFAULT_MAX_REQUESTS;
#endif

        if (getenv("GIT_CURL_FTP_NO_EPSV"))
                curl_ftp_no_epsv = 1;

        if (url) {
                credential_from_url(&http_auth, url);
                if (!ssl_cert_password_required &&
                    getenv("GIT_SSL_CERT_PASSWORD_PROTECTED") &&
                    starts_with(url, "https://"))
                        ssl_cert_password_required = 1;
        }

#ifndef NO_CURL_EASY_DUPHANDLE
        curl_default = get_curl_handle();
#endif
}

void http_cleanup(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (slot != NULL) {
                struct active_request_slot *next = slot->next;
                if (slot->curl != NULL) {
#ifdef USE_CURL_MULTI
                        curl_multi_remove_handle(curlm, slot->curl);
#endif
                        curl_easy_cleanup(slot->curl);
                }
                free(slot);
                slot = next;
        }
        active_queue_head = NULL;

#ifndef NO_CURL_EASY_DUPHANDLE
        curl_easy_cleanup(curl_default);
#endif

#ifdef USE_CURL_MULTI
        curl_multi_cleanup(curlm);
#endif
        curl_global_cleanup();

        curl_slist_free_all(pragma_header);
        pragma_header = NULL;

        curl_slist_free_all(no_pragma_header);
        no_pragma_header = NULL;

        if (curl_http_proxy) {
                free((void *)curl_http_proxy);
                curl_http_proxy = NULL;
        }

        if (cert_auth.password != NULL) {
                memset(cert_auth.password, 0, strlen(cert_auth.password));
                free(cert_auth.password);
                cert_auth.password = NULL;
        }
        ssl_cert_password_required = 0;

        free(cached_accept_language);
        cached_accept_language = NULL;
}

struct active_request_slot *get_active_slot(void)
{
        struct active_request_slot *slot = active_queue_head;
        struct active_request_slot *newslot;

#ifdef USE_CURL_MULTI
        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();
        }
#endif

        while (slot != NULL && slot->in_use)
                slot = slot->next;

        if (slot == NULL) {
                newslot = xmalloc(sizeof(*newslot));
                newslot->curl = NULL;
                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;
        }

        if (slot->curl == NULL) {
#ifdef NO_CURL_EASY_DUPHANDLE
                slot->curl = get_curl_handle();
#else
                slot->curl = curl_easy_duphandle(curl_default);
#endif
                curl_session_count++;
        }

        active_requests++;
        slot->in_use = 1;
        slot->results = NULL;
        slot->finished = NULL;
        slot->callback_data = NULL;
        slot->callback_func = NULL;
        curl_easy_setopt(slot->curl, CURLOPT_COOKIEFILE, curl_cookie_file);
        if (curl_save_cookies)
                curl_easy_setopt(slot->curl, CURLOPT_COOKIEJAR, curl_cookie_file);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, pragma_header);
        curl_easy_setopt(slot->curl, CURLOPT_ERRORBUFFER, curl_errorstr);
        curl_easy_setopt(slot->curl, CURLOPT_CUSTOMREQUEST, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_READFUNCTION, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_POSTFIELDS, NULL);
        curl_easy_setopt(slot->curl, CURLOPT_UPLOAD, 0);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);
        curl_easy_setopt(slot->curl, CURLOPT_FAILONERROR, 1);
#ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
        curl_easy_setopt(slot->curl, CURLOPT_HTTPAUTH, http_auth_methods);
#endif
        if (http_auth.password)
                init_curl_http_auth(slot->curl);

        return slot;
}

int start_active_slot(struct active_request_slot *slot)
{
#ifdef USE_CURL_MULTI
        CURLMcode curlm_result = curl_multi_add_handle(curlm, slot->curl);
        int num_transfers;

        if (curlm_result != CURLM_OK &&
            curlm_result != CURLM_CALL_MULTI_PERFORM) {
                active_requests--;
                slot->in_use = 0;
                return 0;
        }

        /*
         * We know there must be something to do, since we just added
         * something.
         */
        curl_multi_perform(curlm, &num_transfers);
#endif
        return 1;
}

#ifdef USE_CURL_MULTI
struct fill_chain {
        void *data;
        int (*fill)(void *);
        struct fill_chain *next;
};

static struct fill_chain *fill_cfg;

void add_fill_function(void *data, int (*fill)(void *))
{
        struct fill_chain *new = xmalloc(sizeof(*new));
        struct fill_chain **linkp = &fill_cfg;
        new->data = data;
        new->fill = fill;
        new->next = NULL;
        while (*linkp)
                linkp = &(*linkp)->next;
        *linkp = new;
}

void fill_active_slots(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (active_requests < max_requests) {
                struct fill_chain *fill;
                for (fill = fill_cfg; fill; fill = fill->next)
                        if (fill->fill(fill->data))
                                break;

                if (!fill)
                        break;
        }

        while (slot != NULL) {
                if (!slot->in_use && slot->curl != NULL
                        && curl_session_count > min_curl_sessions) {
                        curl_easy_cleanup(slot->curl);
                        slot->curl = NULL;
                        curl_session_count--;
                }
                slot = slot->next;
        }
}

void step_active_slots(void)
{
        int num_transfers;
        CURLMcode curlm_result;

        do {
                curlm_result = curl_multi_perform(curlm, &num_transfers);
        } while (curlm_result == CURLM_CALL_MULTI_PERFORM);
        if (num_transfers < active_requests) {
                process_curl_messages();
                fill_active_slots();
        }
}
#endif

void run_active_slot(struct active_request_slot *slot)
{
#ifdef USE_CURL_MULTI
        fd_set readfds;
        fd_set writefds;
        fd_set excfds;
        int max_fd;
        struct timeval select_timeout;
        int finished = 0;

        slot->finished = &finished;
        while (!finished) {
                step_active_slots();

                if (slot->in_use) {
#if LIBCURL_VERSION_NUM >= 0x070f04
                        long curl_timeout;
                        curl_multi_timeout(curlm, &curl_timeout);
                        if (curl_timeout == 0) {
                                continue;
                        } else if (curl_timeout == -1) {
                                select_timeout.tv_sec  = 0;
                                select_timeout.tv_usec = 50000;
                        } else {
                                select_timeout.tv_sec  =  curl_timeout / 1000;
                                select_timeout.tv_usec = (curl_timeout % 1000) * 1000;
                        }
#else
                        select_timeout.tv_sec  = 0;
                        select_timeout.tv_usec = 50000;
#endif

                        max_fd = -1;
                        FD_ZERO(&readfds);
                        FD_ZERO(&writefds);
                        FD_ZERO(&excfds);
                        curl_multi_fdset(curlm, &readfds, &writefds, &excfds, &max_fd);

                        /*
                         * It can happen that curl_multi_timeout returns a pathologically
                         * long timeout when curl_multi_fdset returns no file descriptors
                         * to read.  See commit message for more details.
                         */
                        if (max_fd < 0 &&
                            (select_timeout.tv_sec > 0 ||
                             select_timeout.tv_usec > 50000)) {
                                select_timeout.tv_sec  = 0;
                                select_timeout.tv_usec = 50000;
                        }

                        select(max_fd+1, &readfds, &writefds, &excfds, &select_timeout);
                }
        }
#else
        while (slot->in_use) {
                slot->curl_result = curl_easy_perform(slot->curl);
                finish_active_slot(slot);
        }
#endif
}

static void release_active_slot(struct active_request_slot *slot)
{
        closedown_active_slot(slot);
        if (slot->curl && curl_session_count > min_curl_sessions) {
#ifdef USE_CURL_MULTI
                curl_multi_remove_handle(curlm, slot->curl);
#endif
                curl_easy_cleanup(slot->curl);
                slot->curl = NULL;
                curl_session_count--;
        }
#ifdef USE_CURL_MULTI
        fill_active_slots();
#endif
}

void finish_all_active_slots(void)
{
        struct active_request_slot *slot = active_queue_head;

        while (slot != NULL)
                if (slot->in_use) {
                        run_active_slot(slot);
                        slot = active_queue_head;
                } else {
                        slot = slot->next;
                }
}

/* Helpers for modifying and creating URLs */
static inline int needs_quote(int ch)
{
        if (((ch >= 'A') && (ch <= 'Z'))
                        || ((ch >= 'a') && (ch <= 'z'))
                        || ((ch >= '0') && (ch <= '9'))
                        || (ch == '/')
                        || (ch == '-')
                        || (ch == '.'))
                return 0;
        return 1;
}

static char *quote_ref_url(const char *base, const char *ref)
{
        struct strbuf buf = STRBUF_INIT;
        const char *cp;
        int ch;

        end_url_with_slash(&buf, base);

        for (cp = ref; (ch = *cp) != 0; cp++)
                if (needs_quote(ch))
                        strbuf_addf(&buf, "%%%02x", ch);
                else
                        strbuf_addch(&buf, *cp);

        return strbuf_detach(&buf, NULL);
}

void append_remote_object_url(struct strbuf *buf, const char *url,
                              const char *hex,
                              int only_two_digit_prefix)
{
        end_url_with_slash(buf, url);

        strbuf_addf(buf, "objects/%.*s/", 2, hex);
        if (!only_two_digit_prefix)
                strbuf_addf(buf, "%s", hex+2);
}

char *get_remote_object_url(const char *url, const char *hex,
                            int only_two_digit_prefix)
{
        struct strbuf buf = STRBUF_INIT;
        append_remote_object_url(&buf, url, hex, only_two_digit_prefix);
        return strbuf_detach(&buf, NULL);
}

static int handle_curl_result(struct slot_results *results)
{
        /*
         * If we see a failing http code with CURLE_OK, we have turned off
         * FAILONERROR (to keep the server's custom error response), and should
         * translate the code into failure here.
         */
        if (results->curl_result == CURLE_OK &&
            results->http_code >= 400) {
                results->curl_result = CURLE_HTTP_RETURNED_ERROR;
                /*
                 * Normally curl will already have put the "reason phrase"
                 * from the server into curl_errorstr; unfortunately without
                 * FAILONERROR it is lost, so we can give only the numeric
                 * status code.
                 */
                snprintf(curl_errorstr, sizeof(curl_errorstr),
                         "The requested URL returned error: %ld",
                         results->http_code);
        }

        if (results->curl_result == CURLE_OK) {
                credential_approve(&http_auth);
                return HTTP_OK;
        } else if (missing_target(results))
                return HTTP_MISSING_TARGET;
        else if (results->http_code == 401) {
                if (http_auth.username && http_auth.password) {
                        credential_reject(&http_auth);
                        return HTTP_NOAUTH;
                } else {
#ifdef LIBCURL_CAN_HANDLE_AUTH_ANY
                        http_auth_methods &= ~CURLAUTH_GSSNEGOTIATE;
#endif
                        return HTTP_REAUTH;
                }
        } else {
#if LIBCURL_VERSION_NUM >= 0x070c00
                if (!curl_errorstr[0])
                        strlcpy(curl_errorstr,
                                curl_easy_strerror(results->curl_result),
                                sizeof(curl_errorstr));
#endif
                return HTTP_ERROR;
        }
}

int run_one_slot(struct active_request_slot *slot,
                 struct slot_results *results)
{
        slot->results = results;
        if (!start_active_slot(slot)) {
                snprintf(curl_errorstr, sizeof(curl_errorstr),
                         "failed to start HTTP request");
                return HTTP_START_FAILED;
        }

        run_active_slot(slot);
        return handle_curl_result(results);
}

static CURLcode curlinfo_strbuf(CURL *curl, CURLINFO info, struct strbuf *buf)
{
        char *ptr;
        CURLcode ret;

        strbuf_reset(buf);
        ret = curl_easy_getinfo(curl, info, &ptr);
        if (!ret && ptr)
                strbuf_addstr(buf, ptr);
        return ret;
}

/*
 * Check for and extract a content-type parameter. "raw"
 * should be positioned at the start of the potential
 * parameter, with any whitespace already removed.
 *
 * "name" is the name of the parameter. The value is appended
 * to "out".
 */
static int extract_param(const char *raw, const char *name,
                         struct strbuf *out)
{
        size_t len = strlen(name);

        if (strncasecmp(raw, name, len))
                return -1;
        raw += len;

        if (*raw != '=')
                return -1;
        raw++;

        while (*raw && !isspace(*raw) && *raw != ';')
                strbuf_addch(out, *raw++);
        return 0;
}

/*
 * Extract a normalized version of the content type, with any
 * spaces suppressed, all letters lowercased, and no trailing ";"
 * or parameters.
 *
 * Note that we will silently remove even invalid whitespace. For
 * example, "text / plain" is specifically forbidden by RFC 2616,
 * but "text/plain" is the only reasonable output, and this keeps
 * our code simple.
 *
 * If the "charset" argument is not NULL, store the value of any
 * charset parameter there.
 *
 * Example:
 *   "TEXT/PLAIN; charset=utf-8" -> "text/plain", "utf-8"
 *   "text / plain" -> "text/plain"
 */
static void extract_content_type(struct strbuf *raw, struct strbuf *type,
                                 struct strbuf *charset)
{
        const char *p;

        strbuf_reset(type);
        strbuf_grow(type, raw->len);
        for (p = raw->buf; *p; p++) {
                if (isspace(*p))
                        continue;
                if (*p == ';') {
                        p++;
                        break;
                }
                strbuf_addch(type, tolower(*p));
        }

        if (!charset)
                return;

        strbuf_reset(charset);
        while (*p) {
                while (isspace(*p) || *p == ';')
                        p++;
                if (!extract_param(p, "charset", charset))
                        return;
                while (*p && !isspace(*p))
                        p++;
        }

        if (!charset->len && starts_with(type->buf, "text/"))
                strbuf_addstr(charset, "ISO-8859-1");
}

static void write_accept_language(struct strbuf *buf)
{
        /*
         * MAX_DECIMAL_PLACES must not be larger than 3. If it is larger than
         * that, q-value will be smaller than 0.001, the minimum q-value the
         * HTTP specification allows. See
         * http://tools.ietf.org/html/rfc7231#section-5.3.1 for q-value.
         */
        const int MAX_DECIMAL_PLACES = 3;
        const int MAX_LANGUAGE_TAGS = 1000;
        const int MAX_ACCEPT_LANGUAGE_HEADER_SIZE = 4000;
        char **language_tags = NULL;
        int num_langs = 0;
        const char *s = get_preferred_languages();
        int i;
        struct strbuf tag = STRBUF_INIT;

        /* Don't add Accept-Language header if no language is preferred. */
        if (!s)
                return;

        /*
         * Split the colon-separated string of preferred languages into
         * language_tags array.
         */
        do {
                /* collect language tag */
                for (; *s && (isalnum(*s) || *s == '_'); s++)
                        strbuf_addch(&tag, *s == '_' ? '-' : *s);

                /* skip .codeset, @modifier and any other unnecessary parts */
                while (*s && *s != ':')
                        s++;

                if (tag.len) {
                        num_langs++;
                        REALLOC_ARRAY(language_tags, num_langs);
                        language_tags[num_langs - 1] = strbuf_detach(&tag, NULL);
                        if (num_langs >= MAX_LANGUAGE_TAGS - 1) /* -1 for '*' */
                                break;
                }
        } while (*s++);

        /* write Accept-Language header into buf */
        if (num_langs) {
                int last_buf_len = 0;
                int max_q;
                int decimal_places;
                char q_format[32];

                /* add '*' */
                REALLOC_ARRAY(language_tags, num_langs + 1);
                language_tags[num_langs++] = "*"; /* it's OK; this won't be freed */

                /* compute decimal_places */
                for (max_q = 1, decimal_places = 0;
                     max_q < num_langs && decimal_places <= MAX_DECIMAL_PLACES;
                     decimal_places++, max_q *= 10)
                        ;

                sprintf(q_format, ";q=0.%%0%dd", decimal_places);

                strbuf_addstr(buf, "Accept-Language: ");

                for (i = 0; i < num_langs; i++) {
                        if (i > 0)
                                strbuf_addstr(buf, ", ");

                        strbuf_addstr(buf, language_tags[i]);

                        if (i > 0)
                                strbuf_addf(buf, q_format, max_q - i);

                        if (buf->len > MAX_ACCEPT_LANGUAGE_HEADER_SIZE) {
                                strbuf_remove(buf, last_buf_len, buf->len - last_buf_len);
                                break;
                        }

                        last_buf_len = buf->len;
                }
        }

        /* free language tags -- last one is a static '*' */
        for (i = 0; i < num_langs - 1; i++)
                free(language_tags[i]);
        free(language_tags);
}

/*
 * Get an Accept-Language header which indicates user's preferred languages.
 *
 * Examples:
 *   LANGUAGE= -> ""
 *   LANGUAGE=ko:en -> "Accept-Language: ko, en; q=0.9, *; q=0.1"
 *   LANGUAGE=ko_KR.UTF-8:sr@latin -> "Accept-Language: ko-KR, sr; q=0.9, *; q=0.1"
 *   LANGUAGE=ko LANG=en_US.UTF-8 -> "Accept-Language: ko, *; q=0.1"
 *   LANGUAGE= LANG=en_US.UTF-8 -> "Accept-Language: en-US, *; q=0.1"
 *   LANGUAGE= LANG=C -> ""
 */
static const char *get_accept_language(void)
{
        if (!cached_accept_language) {
                struct strbuf buf = STRBUF_INIT;
                write_accept_language(&buf);
                if (buf.len > 0)
                        cached_accept_language = strbuf_detach(&buf, NULL);
        }

        return cached_accept_language;
}

/* http_request() targets */
#define HTTP_REQUEST_STRBUF     0
#define HTTP_REQUEST_FILE       1

static int http_request(const char *url,
                        void *result, int target,
                        const struct http_get_options *options)
{
        struct active_request_slot *slot;
        struct slot_results results;
        struct curl_slist *headers = NULL;
        struct strbuf buf = STRBUF_INIT;
        const char *accept_language;
        int ret;

        slot = get_active_slot();
        curl_easy_setopt(slot->curl, CURLOPT_HTTPGET, 1);

        if (result == NULL) {
                curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 1);
        } else {
                curl_easy_setopt(slot->curl, CURLOPT_NOBODY, 0);
                curl_easy_setopt(slot->curl, CURLOPT_FILE, result);

                if (target == HTTP_REQUEST_FILE) {
                        long posn = ftell(result);
                        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                                         fwrite);
                        if (posn > 0) {
                                strbuf_addf(&buf, "Range: bytes=%ld-", posn);
                                headers = curl_slist_append(headers, buf.buf);
                                strbuf_reset(&buf);
                        }
                } else
                        curl_easy_setopt(slot->curl, CURLOPT_WRITEFUNCTION,
                                         fwrite_buffer);
        }

        accept_language = get_accept_language();

        if (accept_language)
                headers = curl_slist_append(headers, accept_language);

        strbuf_addstr(&buf, "Pragma:");
        if (options && options->no_cache)
                strbuf_addstr(&buf, " no-cache");
        if (options && options->keep_error)
                curl_easy_setopt(slot->curl, CURLOPT_FAILONERROR, 0);

        headers = curl_slist_append(headers, buf.buf);

        curl_easy_setopt(slot->curl, CURLOPT_URL, url);
        curl_easy_setopt(slot->curl, CURLOPT_HTTPHEADER, headers);
        curl_easy_setopt(slot->curl, CURLOPT_ENCODING, "gzip");

        ret = run_one_slot(slot, &results);

        if (options && options->content_type) {
                struct strbuf raw = STRBUF_INIT;
                curlinfo_strbuf(slot->curl, CURLINFO_CONTENT_TYPE, &raw);
                extract_content_type(&raw, options->content_type,
                                     options->charset);
                strbuf_release(&raw);
        }

        if (options && options->effective_url)
                curlinfo_strbuf(slot->curl, CURLINFO_EFFECTIVE_URL,
                                options->effective_url);

        curl_slist_free_all(headers);
        strbuf_release(&buf);

        return ret;
}

/*
 * Update the "base" url to a more appropriate value, as deduced by
 * redirects seen when requesting a URL starting with "url".
 *
 * The "asked" parameter is a URL that we asked curl to access, and must begin
 * with "base".
 *
 * The "got" parameter is the URL that curl reported to us as where we ended
 * up.
 *
 * Returns 1 if we updated the base url, 0 otherwise.
 *
 * Our basic strategy is to compare "base" and "asked" to find the bits
 * specific to our request. We then strip those bits off of "got" to yield the
 * new base. So for example, if our base is "http://example.com/foo.git",
 * and we ask for "http://example.com/foo.git/info/refs", we might end up
 * with "https://other.example.com/foo.git/info/refs". We would want the
 * new URL to become "https://other.example.com/foo.git".
 *
 * Note that this assumes a sane redirect scheme. It's entirely possible
 * in the example above to end up at a URL that does not even end in
 * "info/refs".  In such a case we simply punt, as there is not much we can
 * do (and such a scheme is unlikely to represent a real git repository,
 * which means we are likely about to abort anyway).
 */
static int update_url_from_redirect(struct strbuf *base,
                                    const char *asked,
                                    const struct strbuf *got)
{
        const char *tail;
        size_t tail_len;

        if (!strcmp(asked, got->buf))
                return 0;

        if (!skip_prefix(asked, base->buf, &tail))
                die("BUG: update_url_from_redirect: %s is not a superset of %s",
                    asked, base->buf);

        tail_len = strlen(tail);

        if (got->len < tail_len ||
            strcmp(tail, got->buf + got->len - tail_len))
                return 0; /* insane redirect scheme */

        strbuf_reset(base);
        strbuf_add(base, got->buf, got->len - tail_len);
        return 1;
}

static int http_request_reauth(const char *url,
                               void *result, int target,
                               struct http_get_options *options)
{
        int ret = http_request(url, result, target, options);

        if (options && options->effective_url && options->base_url) {
                if (update_url_from_redirect(options->base_url,
                                             url, options->effective_url)) {
                        credential_from_url(&http_auth, options->base_url->buf);
                        url = options->effective_url->buf;
                }
        }

        if (ret != HTTP_REAUTH)
                return ret;

        /*
         * If we are using KEEP_ERROR, the previous request may have
         * put cruft into our output stream; we should clear it out before
         * making our next request. We only know how to do this for
         * the strbuf case, but that is enough to satisfy current callers.
         */
        if (options && options->keep_error) {
                switch (target) {
                case HTTP_REQUEST_STRBUF:
                        strbuf_reset(result);
                        break;
                default:
                        die("BUG: HTTP_KEEP_ERROR is only supported with strbufs");
                }
        }

        credential_fill(&http_auth);

        return http_request(url, result, target, options);
}

int http_get_strbuf(const char *url,
                    struct strbuf *result,
                    struct http_get_options *options)
{
        return http_request_reauth(url, result, HTTP_REQUEST_STRBUF, options);
}

/*
 * Downloads a URL and stores the result in the given file.
 *
 * If a previous interrupted download is detected (i.e. a previous temporary
 * file is still around) the download is resumed.
 */
static int http_get_file(const char *url, const char *filename,
                         struct http_get_options *options)
{
        int ret;
        struct strbuf tmpfile = STRBUF_INIT;
        FILE *result;

        strbuf_addf(&tmpfile, "%s.temp", filename);
        result = fopen(tmpfile.buf, "a");
        if (!result) {
                error("Unable to open local file %s", tmpfile.buf);
                ret = HTTP_ERROR;
                goto cleanup;
        }

        ret = http_request_reauth(url, result, HTTP_REQUEST_FILE, options);
        fclose(result);

        if (ret == HTTP_OK && move_temp_to_file(tmpfile.buf, filename))
                ret = HTTP_ERROR;
cleanup:
        strbuf_release(&tmpfile);
        return ret;
}

int http_fetch_ref(const char *base, struct ref *ref)
{
        struct http_get_options options = {0};
        char *url;
        struct strbuf buffer = STRBUF_INIT;
        int ret = -1;

        options.no_cache = 1;

        url = quote_ref_url(base, ref->name);
        if (http_get_strbuf(url, &buffer, &options) == HTTP_OK) {
                strbuf_rtrim(&buffer);
                if (buffer.len == 40)
                        ret = get_sha1_hex(buffer.buf, ref->old_sha1);
                else if (starts_with(buffer.buf, "ref: ")) {
                        ref->symref = xstrdup(buffer.buf + 5);
                        ret = 0;
                }
        }

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

/* Helpers for fetching packs */
static char *fetch_pack_index(unsigned char *sha1, const char *base_url)
{
        char *url, *tmp;
        struct strbuf buf = STRBUF_INIT;

        if (http_is_verbose)
                fprintf(stderr, "Getting index for pack %s\n", sha1_to_hex(sha1));

        end_url_with_slash(&buf, base_url);
        strbuf_addf(&buf, "objects/pack/pack-%s.idx", sha1_to_hex(sha1));
        url = strbuf_detach(&buf, NULL);

        strbuf_addf(&buf, "%s.temp", sha1_pack_index_name(sha1));
        tmp = strbuf_detach(&buf, NULL);

        if (http_get_file(url, tmp, NULL) != HTTP_OK) {
                error("Unable to get pack index %s", url);
                free(tmp);
                tmp = NULL;
        }

        free(url);
        return tmp;
}

static int fetch_and_setup_pack_index(struct packed_git **packs_head,
        unsigned char *sha1, const char *base_url)
{
        struct packed_git *new_pack;
        char *tmp_idx = NULL;
        int ret;

        if (has_pack_index(sha1)) {
                new_pack = parse_pack_index(sha1, sha1_pack_index_name(sha1));
                if (!new_pack)
                        return -1; /* parse_pack_index() already issued error message */
                goto add_pack;
        }

        tmp_idx = fetch_pack_index(sha1, base_url);
        if (!tmp_idx)
                return -1;

        new_pack = parse_pack_index(sha1, tmp_idx);
        if (!new_pack) {
                unlink(tmp_idx);
                free(tmp_idx);

                return -1; /* parse_pack_index() already issued error message */
        }

        ret = verify_pack_index(new_pack);
        if (!ret) {
                close_pack_index(new_pack);
                ret = move_temp_to_file(tmp_idx, sha1_pack_index_name(sha1));
        }
        free(tmp_idx);
        if (ret)
                return -1;

add_pack:
        new_pack->next = *packs_head;
        *packs_head = new_pack;
        return 0;
}

int http_get_info_packs(const char *base_url, struct packed_git **packs_head)
{
        struct http_get_options options = {0};
        int ret = 0, i = 0;
        char *url, *data;
        struct strbuf buf = STRBUF_INIT;
        unsigned char sha1[20];

        end_url_with_slash(&buf, base_url);
        strbuf_addstr(&buf, "objects/info/packs");
        url = strbuf_detach(&buf, NULL);

        options.no_cache = 1;
        ret = http_get_strbuf(url, &buf, &options);
        if (ret != HTTP_OK)
                goto cleanup;

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

cleanup:
        free(url);
        return ret;
}

void release_http_pack_request(struct http_pack_request *preq)
{
        if (preq->packfile != NULL) {
                fclose(preq->packfile);
                preq->packfile = NULL;
        }
        if (preq->range_header != NULL) {
                curl_slist_free_all(preq->range_header);
                preq->range_header = NULL;
        }
        preq->slot = NULL;
        free(preq->url);
        free(preq);
}

int finish_http_pack_request(struct http_pack_request *preq)
{
        struct packed_git **lst;
        struct packed_git *p = preq->target;
        char *tmp_idx;
        struct child_process ip = CHILD_PROCESS_INIT;
        const char *ip_argv[8];

        close_pack_index(p);

        fclose(preq->packfile);
        preq->packfile = NULL;

        lst = preq->lst;
        while (*lst != p)
                lst = &((*lst)->next);
        *lst = (*lst)->next;

        tmp_idx = xstrdup(preq->tmpfile);
        strcpy(tmp_idx + strlen(tmp_idx) - strlen(".pack.temp"),
               ".idx.temp");

        ip_argv[0] = "index-pack";
        ip_argv[1] = "-o";
        ip_argv[2] = tmp_idx;
        ip_argv[3] = preq->tmpfile;
        ip_argv[4] = NULL;

        ip.argv = ip_argv;
        ip.git_cmd = 1;
        ip.no_stdin = 1;
        ip.no_stdout = 1;

        if (run_command(&ip)) {
                unlink(preq->tmpfile);
                unlink(tmp_idx);
                free(tmp_idx);
                return -1;
        }

        unlink(sha1_pack_index_name(p->sha1));

        if (move_temp_to_file(preq->tmpfile, sha1_pack_name(p->sha1))
         || move_temp_to_file(tmp_idx, sha1_pack_index_name(p->sha1))) {
                free(tmp_idx);
                return -1;
        }

        install_packed_git(p);
        free(tmp_idx);
        return 0;
}

struct http_pack_request *new_http_pack_request(
        struct packed_git *target, const char *base_url)
{
        long prev_posn = 0;
        char range[RANGE_HEADER_SIZE];
        struct strbuf buf = STRBUF_INIT;
        struct http_pack_request *preq;

        preq = xcalloc(1, sizeof(*preq));
        preq->target = target;

        end_url_with_slash(&buf, base_url);
        strbuf_addf(&buf, "objects/pack/pack-%s.pack",
                sha1_to_hex(target->sha1));
        preq->url = strbuf_detach(&buf, NULL);

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

        preq->slot = get_active_slot();
        curl_easy_setopt(preq->slot->curl, CURLOPT_FILE, preq->packfile);
        curl_easy_setopt(preq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite);
        curl_easy_setopt(preq->slot->curl, CURLOPT_URL, preq->url);
        curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER,
                no_pragma_header);

        /*
         * If there is data present from a previous transfer attempt,
         * resume where it left off
         */
        prev_posn = ftell(preq->packfile);
        if (prev_posn>0) {
                if (http_is_verbose)
                        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);
                preq->range_header = curl_slist_append(NULL, range);
                curl_easy_setopt(preq->slot->curl, CURLOPT_HTTPHEADER,
                        preq->range_header);
        }

        return preq;

abort:
        free(preq->url);
        free(preq);
        return NULL;
}

/* Helpers for fetching objects (loose) */
static size_t fwrite_sha1_file(char *ptr, size_t eltsize, size_t nmemb,
                               void *data)
{
        unsigned char expn[4096];
        size_t size = eltsize * nmemb;
        int posn = 0;
        struct http_object_request *freq =
                (struct http_object_request *)data;
        do {
                ssize_t retval = xwrite(freq->localfile,
                                        (char *) ptr + posn, size - posn);
                if (retval < 0)
                        return posn;
                posn += retval;
        } while (posn < size);

        freq->stream.avail_in = size;
        freq->stream.next_in = (void *)ptr;
        do {
                freq->stream.next_out = expn;
                freq->stream.avail_out = sizeof(expn);
                freq->zret = git_inflate(&freq->stream, Z_SYNC_FLUSH);
                git_SHA1_Update(&freq->c, expn,
                                sizeof(expn) - freq->stream.avail_out);
        } while (freq->stream.avail_in && freq->zret == Z_OK);
        return size;
}

struct http_object_request *new_http_object_request(const char *base_url,
        unsigned char *sha1)
{
        char *hex = sha1_to_hex(sha1);
        const char *filename;
        char prevfile[PATH_MAX];
        int prevlocal;
        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 http_object_request *freq;

        freq = xcalloc(1, sizeof(*freq));
        hashcpy(freq->sha1, sha1);
        freq->localfile = -1;

        filename = sha1_file_name(sha1);
        snprintf(freq->tmpfile, sizeof(freq->tmpfile),
                 "%s.temp", filename);

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

        if (freq->localfile != -1)
                error("fd leakage in start: %d", freq->localfile);
        freq->localfile = open(freq->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 (freq->localfile < 0 && errno == ENOENT) {
                char *dir = strrchr(freq->tmpfile, '/');
                if (dir) {
                        *dir = 0;
                        mkdir(freq->tmpfile, 0777);
                        *dir = '/';
                }
                freq->localfile = open(freq->tmpfile,
                                       O_WRONLY | O_CREAT | O_EXCL, 0666);
        }

        if (freq->localfile < 0) {
                error("Couldn't create temporary file %s: %s",
                      freq->tmpfile, strerror(errno));
                goto abort;
        }

        git_inflate_init(&freq->stream);

        git_SHA1_Init(&freq->c);

        freq->url = get_remote_object_url(base_url, hex, 0);

        /*
         * 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,
                                                     freq) == prev_read) {
                                        prev_posn += prev_read;
                                } else {
                                        prev_read = -1;
                                }
                        }
                } while (prev_read > 0);
                close(prevlocal);
        }
        unlink_or_warn(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(&freq->stream, 0, sizeof(freq->stream));
                git_inflate_init(&freq->stream);
                git_SHA1_Init(&freq->c);
                if (prev_posn>0) {
                        prev_posn = 0;
                        lseek(freq->localfile, 0, SEEK_SET);
                        if (ftruncate(freq->localfile, 0) < 0) {
                                error("Couldn't truncate temporary file %s: %s",
                                          freq->tmpfile, strerror(errno));
                                goto abort;
                        }
                }
        }

        freq->slot = get_active_slot();

        curl_easy_setopt(freq->slot->curl, CURLOPT_FILE, freq);
        curl_easy_setopt(freq->slot->curl, CURLOPT_WRITEFUNCTION, fwrite_sha1_file);
        curl_easy_setopt(freq->slot->curl, CURLOPT_ERRORBUFFER, freq->errorstr);
        curl_easy_setopt(freq->slot->curl, CURLOPT_URL, freq->url);
        curl_easy_setopt(freq->slot->curl, CURLOPT_HTTPHEADER, 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 (http_is_verbose)
                        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(freq->slot->curl,
                                 CURLOPT_HTTPHEADER, range_header);
        }

        return freq;

abort:
        free(freq->url);
        free(freq);
        return NULL;
}

void process_http_object_request(struct http_object_request *freq)
{
        if (freq->slot == NULL)
                return;
        freq->curl_result = freq->slot->curl_result;
        freq->http_code = freq->slot->http_code;
        freq->slot = NULL;
}

int finish_http_object_request(struct http_object_request *freq)
{
        struct stat st;

        close(freq->localfile);
        freq->localfile = -1;

        process_http_object_request(freq);

        if (freq->http_code == 416) {
                warning("requested range invalid; we may already have all the data.");
        } else if (freq->curl_result != CURLE_OK) {
                if (stat(freq->tmpfile, &st) == 0)
                        if (st.st_size == 0)
                                unlink_or_warn(freq->tmpfile);
                return -1;
        }

        git_inflate_end(&freq->stream);
        git_SHA1_Final(freq->real_sha1, &freq->c);
        if (freq->zret != Z_STREAM_END) {
                unlink_or_warn(freq->tmpfile);
                return -1;
        }
        if (hashcmp(freq->sha1, freq->real_sha1)) {
                unlink_or_warn(freq->tmpfile);
                return -1;
        }
        freq->rename =
                move_temp_to_file(freq->tmpfile, sha1_file_name(freq->sha1));

        return freq->rename;
}

void abort_http_object_request(struct http_object_request *freq)
{
        unlink_or_warn(freq->tmpfile);

        release_http_object_request(freq);
}

void release_http_object_request(struct http_object_request *freq)
{
        if (freq->localfile != -1) {
                close(freq->localfile);
                freq->localfile = -1;
        }
        if (freq->url != NULL) {
                free(freq->url);
                freq->url = NULL;
        }
        if (freq->slot != NULL) {
                freq->slot->callback_func = NULL;
                freq->slot->callback_data = NULL;
                release_active_slot(freq->slot);
                freq->slot = NULL;
        }
}