source: mainline/uspace/lib/c/generic/vfs/inbox.c@ c23275a

#include <vfs/inbox.h>
#include <vfs/vfs.h>

#include <adt/list.h>
#include <str.h>
#include <stdlib.h>
#include <loader/pcb.h>
#include "../private/io.h"
#include <errno.h>

/* This is an attempt at generalization of the "standard files" concept to arbitrary names.
 * When loading a task, the parent can put arbitrary files to an "inbox" through IPC calls,
 * every file in an inbox has a name assigned (e.g. "stdin", "stdout", "stderr", "data", "logfile",
 * etc.). The client then retrieves those files from inbox by name. "stdin", "stdout" and "stderr"
 * are handled automatically by libc to initialize standard <stdio.h> streams and legacy file
 * descriptors 0, 1, 2. Other names are subject to conventions and application-specific rules.
 */

typedef struct {
        link_t link;
        char *name;
        int file;
} inbox_entry;

static LIST_INITIALIZE(inb_list);

/* Inserts a named file into the inbox.
 * If a file with the same name is already present, it overwrites it and returns the original
 * value. Otherwise, it returns -1.
 * If the argument 'file' is -1, nothing is inserted and the file with specified name is
 * removed and returned if present.
 *
 * @param name Name of the inbox entry.
 * @param file File to insert or -1.
 * @return Original value of the entry or -1 if not originally present.
 */
int inbox_set(const char *name, int file)
{
        inbox_entry *next = NULL;
        
        list_foreach(inb_list, link, inbox_entry, e) {
                int cmp = str_cmp(e->name, name);
                switch (cmp) {
                case -1:
                        continue;
                case 0:;
                        int result = e->file;
                        if (file == -1) {
                                free(e->name);
                                /* Safe because we exit immediately. */
                                list_remove(&e->link);
                        } else {
                                e->file = file;
                        }
                        return result;
                case 1:
                        next = e;
                        goto out;
                }
        }

out:
        if (file == -1) {
                return -1;
        }

        inbox_entry *entry = calloc(sizeof(inbox_entry), 1);
        entry->name = str_dup(name);
        entry->file = file;

        if (next == NULL) {
                list_append((link_t *)entry, &inb_list);
        } else {
                list_insert_before((link_t *)entry, (link_t *)next);
        }
        return -1;
}

/* Retrieve a file with this name.
 *
 * @param name Name of the entry.
 * @return Requested file or ENOENT if not set.
 */
int inbox_get(const char *name)
{
        list_foreach(inb_list, link, inbox_entry, e) {
                int cmp = str_cmp(e->name, name);
                switch (cmp) {
                case 0:
                        return e->file;
                case 1:
                        return ENOENT;
                } 
        }

        return ENOENT;
}

/* Writes names of entries that are currently set into and array provided by the user.
 *
 * @param names Array in which names are stored.
 * @param capacity Capacity of the array.
 * @return Number of entries written. If capacity == 0, return the total number of entries.
 */
int inbox_list(const char **names, int capacity)
{
        if (capacity == 0) {
                return list_count(&inb_list);
        }

        int used = 0;

        list_foreach(inb_list, link, inbox_entry, e) {
                if (used == capacity) {
                        return used;
                }
                names[used] = e->name;
                used++;
        }

        return used;
}

void __inbox_init(struct pcb_inbox_entry *entries, int count) {
        for (int i = 0; i < count; i++) {
                int original = inbox_set(entries[i].name, entries[i].file);
                if (original >= 0) {
                        vfs_put(original);
                }
        }
}