advice: revamp advise API

[git] / sub-process.c

/*
 * Generic implementation of background process infrastructure.
 */
#include "sub-process.h"
#include "sigchain.h"
#include "pkt-line.h"

int cmd2process_cmp(const void *unused_cmp_data,
                    const struct hashmap_entry *eptr,
                    const struct hashmap_entry *entry_or_key,
                    const void *unused_keydata)
{
        const struct subprocess_entry *e1, *e2;

        e1 = container_of(eptr, const struct subprocess_entry, ent);
        e2 = container_of(entry_or_key, const struct subprocess_entry, ent);

        return strcmp(e1->cmd, e2->cmd);
}

struct subprocess_entry *subprocess_find_entry(struct hashmap *hashmap, const char *cmd)
{
        struct subprocess_entry key;

        hashmap_entry_init(&key.ent, strhash(cmd));
        key.cmd = cmd;
        return hashmap_get_entry(hashmap, &key, ent, NULL);
}

int subprocess_read_status(int fd, struct strbuf *status)
{
        struct strbuf **pair;
        char *line;
        int len;

        for (;;) {
                len = packet_read_line_gently(fd, NULL, &line);
                if ((len < 0) || !line)
                        break;
                pair = strbuf_split_str(line, '=', 2);
                if (pair[0] && pair[0]->len && pair[1]) {
                        /* the last "status=<foo>" line wins */
                        if (!strcmp(pair[0]->buf, "status=")) {
                                strbuf_reset(status);
                                strbuf_addbuf(status, pair[1]);
                        }
                }
                strbuf_list_free(pair);
        }

        return (len < 0) ? len : 0;
}

void subprocess_stop(struct hashmap *hashmap, struct subprocess_entry *entry)
{
        if (!entry)
                return;

        entry->process.clean_on_exit = 0;
        kill(entry->process.pid, SIGTERM);
        finish_command(&entry->process);

        hashmap_remove(hashmap, &entry->ent, NULL);
}

static void subprocess_exit_handler(struct child_process *process)
{
        sigchain_push(SIGPIPE, SIG_IGN);
        /* Closing the pipe signals the subprocess to initiate a shutdown. */
        close(process->in);
        close(process->out);
        sigchain_pop(SIGPIPE);
        /* Finish command will wait until the shutdown is complete. */
        finish_command(process);
}

int subprocess_start(struct hashmap *hashmap, struct subprocess_entry *entry, const char *cmd,
        subprocess_start_fn startfn)
{
        int err;
        struct child_process *process;

        entry->cmd = cmd;
        process = &entry->process;

        child_process_init(process);
        argv_array_push(&process->args, cmd);
        process->use_shell = 1;
        process->in = -1;
        process->out = -1;
        process->clean_on_exit = 1;
        process->clean_on_exit_handler = subprocess_exit_handler;
        process->trace2_child_class = "subprocess";

        err = start_command(process);
        if (err) {
                error("cannot fork to run subprocess '%s'", cmd);
                return err;
        }

        hashmap_entry_init(&entry->ent, strhash(cmd));

        err = startfn(entry);
        if (err) {
                error("initialization for subprocess '%s' failed", cmd);
                subprocess_stop(hashmap, entry);
                return err;
        }

        hashmap_add(hashmap, &entry->ent);
        return 0;
}

static int handshake_version(struct child_process *process,
                             const char *welcome_prefix, int *versions,
                             int *chosen_version)
{
        int version_scratch;
        int i;
        char *line;
        const char *p;

        if (!chosen_version)
                chosen_version = &version_scratch;

        if (packet_write_fmt_gently(process->in, "%s-client\n",
                                    welcome_prefix))
                return error("Could not write client identification");
        for (i = 0; versions[i]; i++) {
                if (packet_write_fmt_gently(process->in, "version=%d\n",
                                            versions[i]))
                        return error("Could not write requested version");
        }
        if (packet_flush_gently(process->in))
                return error("Could not write flush packet");

        if (!(line = packet_read_line(process->out, NULL)) ||
            !skip_prefix(line, welcome_prefix, &p) ||
            strcmp(p, "-server"))
                return error("Unexpected line '%s', expected %s-server",
                             line ? line : "<flush packet>", welcome_prefix);
        if (!(line = packet_read_line(process->out, NULL)) ||
            !skip_prefix(line, "version=", &p) ||
            strtol_i(p, 10, chosen_version))
                return error("Unexpected line '%s', expected version",
                             line ? line : "<flush packet>");
        if ((line = packet_read_line(process->out, NULL)))
                return error("Unexpected line '%s', expected flush", line);

        /* Check to make sure that the version received is supported */
        for (i = 0; versions[i]; i++) {
                if (versions[i] == *chosen_version)
                        break;
        }
        if (!versions[i])
                return error("Version %d not supported", *chosen_version);

        return 0;
}

static int handshake_capabilities(struct child_process *process,
                                  struct subprocess_capability *capabilities,
                                  unsigned int *supported_capabilities)
{
        int i;
        char *line;

        for (i = 0; capabilities[i].name; i++) {
                if (packet_write_fmt_gently(process->in, "capability=%s\n",
                                            capabilities[i].name))
                        return error("Could not write requested capability");
        }
        if (packet_flush_gently(process->in))
                return error("Could not write flush packet");

        while ((line = packet_read_line(process->out, NULL))) {
                const char *p;
                if (!skip_prefix(line, "capability=", &p))
                        continue;

                for (i = 0;
                     capabilities[i].name && strcmp(p, capabilities[i].name);
                     i++)
                        ;
                if (capabilities[i].name) {
                        if (supported_capabilities)
                                *supported_capabilities |= capabilities[i].flag;
                } else {
                        die("subprocess '%s' requested unsupported capability '%s'",
                            process->argv[0], p);
                }
        }

        return 0;
}

int subprocess_handshake(struct subprocess_entry *entry,
                         const char *welcome_prefix,
                         int *versions,
                         int *chosen_version,
                         struct subprocess_capability *capabilities,
                         unsigned int *supported_capabilities)
{
        int retval;
        struct child_process *process = &entry->process;

        sigchain_push(SIGPIPE, SIG_IGN);

        retval = handshake_version(process, welcome_prefix, versions,
                                   chosen_version) ||
                 handshake_capabilities(process, capabilities,
                                        supported_capabilities);

        sigchain_pop(SIGPIPE);
        return retval;
}