file.c

/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Copyright (C) 1999 - 2006, Digium, Inc.
 *
 * Mark Spencer <markster@digium.com>
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 */

/*! \file
 *
 * \brief Generic File Format Support.
 *
 * \author Mark Spencer <markster@digium.com>
 */

/*** MODULEINFO
	<support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <dirent.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <math.h>

#include "asterisk/_private.h"	/* declare ast_file_init() */
#include "asterisk/paths.h"	/* use ast_config_AST_DATA_DIR */
#include "asterisk/mod_format.h"
#include "asterisk/cli.h"
#include "asterisk/channel.h"
#include "asterisk/sched.h"
#include "asterisk/translate.h"
#include "asterisk/utils.h"
#include "asterisk/lock.h"
#include "asterisk/app.h"
#include "asterisk/pbx.h"
#include "asterisk/linkedlists.h"
#include "asterisk/module.h"
#include "asterisk/astobj2.h"
#include "asterisk/test.h"
#include "asterisk/stasis.h"
#include "asterisk/json.h"
#include "asterisk/stasis_system.h"
#include "asterisk/media_cache.h"

/*! \brief
 * The following variable controls the layout of localized sound files.
 * If 0, use the historical layout with prefix just before the filename
 * (i.e. digits/en/1.gsm , digits/it/1.gsm or default to digits/1.gsm),
 * if 1 put the prefix at the beginning of the filename
 * (i.e. en/digits/1.gsm, it/digits/1.gsm or default to digits/1.gsm).
 * The latter permits a language to be entirely in one directory.
 *
 * This is settable in asterisk.conf.
 */
int ast_language_is_prefix = 1;

static AST_RWLIST_HEAD_STATIC(formats, ast_format_def);

STASIS_MESSAGE_TYPE_DEFN(ast_format_register_type);
STASIS_MESSAGE_TYPE_DEFN(ast_format_unregister_type);

static struct ast_json *json_array_from_list(const char *list, const char *sep)
{
	RAII_VAR(struct ast_json *, array, ast_json_array_create(), ast_json_unref);
	char *stringp, *ext;

	stringp = ast_strdupa(list);	/* this is in the stack so does not need to be freed */
	if (!array || !stringp) {
		return NULL;
	}

	while ((ext = strsep(&stringp, sep))) {
		if (ast_json_array_append(array, ast_json_string_create(ext))) {
			return NULL;
		}
	}

	return ast_json_ref(array);
}

static int publish_format_update(const struct ast_format_def *f, struct stasis_message_type *type)
{
	RAII_VAR(struct stasis_message *, msg, NULL, ao2_cleanup);
	RAII_VAR(struct ast_json_payload *, json_payload, NULL, ao2_cleanup);
	RAII_VAR(struct ast_json *, json_object, NULL, ast_json_unref);

	if (!type) {
		return -1;
	}

	json_object = ast_json_pack("{s: s, s: o}",
		"format", f->name,
		"extensions", json_array_from_list(f->exts, "|"));
	if (!json_object) {
		return -1;
	}

	json_payload = ast_json_payload_create(json_object);
	if (!json_payload) {
		return -1;
	}

	msg = stasis_message_create(type, json_payload);
	if (!msg) {
		return -1;
	}

	stasis_publish(ast_system_topic(), msg);
	return 0;
}

int __ast_format_def_register(const struct ast_format_def *f, struct ast_module *mod)
{
	struct ast_format_def *tmp;

	AST_RWLIST_WRLOCK(&formats);
	AST_RWLIST_TRAVERSE(&formats, tmp, list) {
		if (!strcasecmp(f->name, tmp->name)) {
			AST_RWLIST_UNLOCK(&formats);
			ast_log(LOG_WARNING, "Tried to register '%s' format, already registered\n", f->name);
			return -1;
		}
	}
	if (!(tmp = ast_calloc(1, sizeof(*tmp)))) {
		AST_RWLIST_UNLOCK(&formats);
		return -1;
	}
	*tmp = *f;
	tmp->module = mod;
	if (tmp->buf_size) {
		/*
		 * Align buf_size properly, rounding up to the machine-specific
		 * alignment for pointers.
		 */
		struct _test_align { void *a, *b; } p;
		int align = (char *)&p.b - (char *)&p.a;
		tmp->buf_size = ((f->buf_size + align - 1) / align) * align;
	}

	memset(&tmp->list, 0, sizeof(tmp->list));

	AST_RWLIST_INSERT_HEAD(&formats, tmp, list);
	AST_RWLIST_UNLOCK(&formats);
	ast_verb(2, "Registered file format %s, extension(s) %s\n", f->name, f->exts);
	publish_format_update(f, ast_format_register_type());

	return 0;
}

int ast_format_def_unregister(const char *name)
{
	struct ast_format_def *tmp;
	int res = -1;

	AST_RWLIST_WRLOCK(&formats);
	AST_RWLIST_TRAVERSE_SAFE_BEGIN(&formats, tmp, list) {
		if (!strcasecmp(name, tmp->name)) {
			AST_RWLIST_REMOVE_CURRENT(list);
			publish_format_update(tmp, ast_format_unregister_type());
			ast_free(tmp);
			res = 0;
		}
	}
	AST_RWLIST_TRAVERSE_SAFE_END;
	AST_RWLIST_UNLOCK(&formats);

	if (!res)
		ast_verb(2, "Unregistered format %s\n", name);
	else
		ast_log(LOG_WARNING, "Tried to unregister format %s, already unregistered\n", name);

	return res;
}

int ast_stopstream(struct ast_channel *tmp)
{
	ast_channel_lock(tmp);

	/* Stop a running stream if there is one */
	if (ast_channel_stream(tmp)) {
		ast_closestream(ast_channel_stream(tmp));
		ast_channel_stream_set(tmp, NULL);
		if (ast_channel_oldwriteformat(tmp) && ast_set_write_format(tmp, ast_channel_oldwriteformat(tmp)))
			ast_log(LOG_WARNING, "Unable to restore format back to %s\n", ast_format_get_name(ast_channel_oldwriteformat(tmp)));
	}
	/* Stop the video stream too */
	if (ast_channel_vstream(tmp) != NULL) {
		ast_closestream(ast_channel_vstream(tmp));
		ast_channel_vstream_set(tmp, NULL);
	}

	ast_channel_unlock(tmp);

	return 0;
}

int ast_writestream(struct ast_filestream *fs, struct ast_frame *f)
{
	int res = -1;
	if (f->frametype == AST_FRAME_VIDEO) {
		if (ast_format_get_type(fs->fmt->format) == AST_MEDIA_TYPE_AUDIO) {
			/* This is the audio portion.  Call the video one... */
			if (!fs->vfs && fs->filename) {
				const char *type = ast_format_get_name(f->subclass.format);
				fs->vfs = ast_writefile(fs->filename, type, NULL, fs->flags, 0, fs->mode);
				ast_debug(1, "Opened video output file\n");
			}
			if (fs->vfs)
				return ast_writestream(fs->vfs, f);
			/* else ignore */
			return 0;
		}
	} else if (f->frametype != AST_FRAME_VOICE) {
		ast_log(LOG_WARNING, "Tried to write non-voice frame\n");
		return -1;
	}
	if (ast_format_cmp(f->subclass.format, fs->fmt->format) != AST_FORMAT_CMP_NOT_EQUAL) {
		res =  fs->fmt->write(fs, f);
		if (res < 0)
			ast_log(LOG_WARNING, "Natural write failed\n");
		else if (res > 0)
			ast_log(LOG_WARNING, "Huh??\n");
	} else {
		/* XXX If they try to send us a type of frame that isn't the normal frame, and isn't
		       the one we've setup a translator for, we do the "wrong thing" XXX */
		if (fs->trans && (ast_format_cmp(f->subclass.format, fs->lastwriteformat) != AST_FORMAT_CMP_EQUAL)) {
			ast_translator_free_path(fs->trans);
			fs->trans = NULL;
		}
		if (!fs->trans) {
			fs->trans = ast_translator_build_path(fs->fmt->format, f->subclass.format);
		}
		if (!fs->trans) {
			ast_log(LOG_WARNING, "Unable to translate to format %s, source format %s\n",
				fs->fmt->name, ast_format_get_name(f->subclass.format));
		} else {
			struct ast_frame *trf;
			ao2_replace(fs->lastwriteformat, f->subclass.format);
			/* Get the translated frame but don't consume the original in case they're using it on another stream */
			if ((trf = ast_translate(fs->trans, f, 0))) {
				struct ast_frame *cur;

				/* the translator may have returned multiple frames, so process them */
				for (cur = trf; cur; cur = AST_LIST_NEXT(cur, frame_list)) {
					if ((res = fs->fmt->write(fs, trf))) {
						ast_log(LOG_WARNING, "Translated frame write failed\n");
						break;
					}
				}
				ast_frfree(trf);
			} else {
				res = 0;
			}
		}
	}
	return res;
}

static int copy(const char *infile, const char *outfile)
{
	int ifd, ofd, len;
	char buf[4096];	/* XXX make it lerger. */

	if ((ifd = open(infile, O_RDONLY)) < 0) {
		ast_log(LOG_WARNING, "Unable to open %s in read-only mode\n", infile);
		return -1;
	}
	if ((ofd = open(outfile, O_WRONLY | O_TRUNC | O_CREAT, AST_FILE_MODE)) < 0) {
		ast_log(LOG_WARNING, "Unable to open %s in write-only mode\n", outfile);
		close(ifd);
		return -1;
	}
	while ( (len = read(ifd, buf, sizeof(buf)) ) ) {
		int res;
		if (len < 0) {
			ast_log(LOG_WARNING, "Read failed on %s: %s\n", infile, strerror(errno));
			break;
		}
		/* XXX handle partial writes */
		res = write(ofd, buf, len);
		if (res != len) {
			ast_log(LOG_WARNING, "Write failed on %s (%d of %d): %s\n", outfile, res, len, strerror(errno));
			len = -1; /* error marker */
			break;
		}
	}
	close(ifd);
	close(ofd);
	if (len < 0) {
		unlink(outfile);
		return -1; /* error */
	}
	return 0;	/* success */
}

/*!
 * \brief construct a filename. Absolute pathnames are preserved,
 * relative names are prefixed by the sounds/ directory.
 * The wav49 suffix is replaced by 'WAV'.
 * Returns a malloc'ed string to be freed by the caller.
 */
static char *build_filename(const char *filename, const char *ext)
{
	char *fn = NULL;

	if (!strcmp(ext, "wav49"))
		ext = "WAV";

	if (filename[0] == '/') {
		if (ast_asprintf(&fn, "%s.%s", filename, ext) < 0) {
			fn = NULL;
		}
	} else {
		if (ast_asprintf(&fn, "%s/sounds/%s.%s",
			     ast_config_AST_DATA_DIR, filename, ext) < 0) {
			fn = NULL;
		}
	}
	return fn;
}

/* compare type against the list 'exts' */
/* XXX need a better algorithm */
static int type_in_list(const char *list, const char *type, int (*cmp)(const char *s1, const char *s2))
{
	char *stringp = ast_strdupa(list), *item;

	while ((item = strsep(&stringp, "|"))) {
		if (!cmp(item, type)) {
			return 1;
		}
	}

	return 0;
}

#define exts_compare(list, type) (type_in_list((list), (type), strcmp))

/*!
 * \internal
 * \brief Close the file stream by canceling any pending read / write callbacks
 */
static void filestream_close(struct ast_filestream *f)
{
	enum ast_media_type format_type = ast_format_get_type(f->fmt->format);

	if (!f->owner) {
		return;
	}

	/* Stop a running stream if there is one */
	switch (format_type)
	{
	case AST_MEDIA_TYPE_AUDIO:
		ast_channel_stream_set(f->owner, NULL);
		AST_SCHED_DEL_ACCESSOR(ast_channel_sched(f->owner), f->owner, ast_channel_streamid, ast_channel_streamid_set);
		ast_settimeout(f->owner, 0, NULL, NULL);
		break;
	case AST_MEDIA_TYPE_VIDEO:
		ast_channel_vstream_set(f->owner, NULL);
		AST_SCHED_DEL_ACCESSOR(ast_channel_sched(f->owner), f->owner, ast_channel_vstreamid, ast_channel_vstreamid_set);
		break;
	default:
		ast_log(AST_LOG_WARNING, "Unable to schedule deletion of filestream with unsupported type %s\n", f->fmt->name);
		break;
	}
}

static void filestream_destructor(void *arg)
{
	struct ast_filestream *f = arg;
	int status;
	int pid = -1;

	/* Stop a running stream if there is one */
	filestream_close(f);

	/* destroy the translator on exit */
	if (f->trans)
		ast_translator_free_path(f->trans);

	if (f->fmt->close) {
		void (*closefn)(struct ast_filestream *) = f->fmt->close;
		closefn(f);
	}

	if (f->f) {
		fclose(f->f);
	}

	if (f->realfilename && f->filename) {
		pid = ast_safe_fork(0);
		if (!pid) {
			execl("/bin/mv", "mv", "-f", f->filename, f->realfilename, SENTINEL);
			_exit(1);
		}
		else if (pid > 0) {
			/* Block the parent until the move is complete.*/
			waitpid(pid, &status, 0);
		}
	}

	ast_free(f->filename);
	ast_free(f->realfilename);
	if (f->vfs)
		ast_closestream(f->vfs);
	ast_free(f->write_buffer);
	ast_free((void *)f->orig_chan_name);
	ao2_cleanup(f->lastwriteformat);
	ao2_cleanup(f->fr.subclass.format);
	ast_module_unref(f->fmt->module);
}

static struct ast_filestream *get_filestream(struct ast_format_def *fmt, FILE *bfile)
{
	struct ast_filestream *s;
	int l = sizeof(*s) + fmt->buf_size + fmt->desc_size;	/* total allocation size */

	if (!ast_module_running_ref(fmt->module)) {
		return NULL;
	}

	s = ao2_alloc(l, filestream_destructor);
	if (!s) {
		ast_module_unref(fmt->module);
		return NULL;
	}
	s->fmt = fmt;
	s->f = bfile;

	if (fmt->desc_size)
		s->_private = ((char *)(s + 1)) + fmt->buf_size;
	if (fmt->buf_size)
		s->buf = (char *)(s + 1);
	s->fr.src = fmt->name;

	if (ast_format_get_type(fmt->format) == AST_MEDIA_TYPE_AUDIO) {
		s->fr.frametype = AST_FRAME_VOICE;
	} else if (ast_format_get_type(fmt->format) == AST_MEDIA_TYPE_VIDEO) {
		s->fr.frametype = AST_FRAME_VIDEO;
	}
	s->fr.mallocd = 0;
	s->fr.subclass.format = ao2_bump(fmt->format);

	return s;
}

/*
 * Default implementations of open and rewrite.
 * Only use them if you don't have expensive stuff to do.
 */
enum wrap_fn { WRAP_OPEN, WRAP_REWRITE };

static int fn_wrapper(struct ast_filestream *s, const char *comment, enum wrap_fn mode)
{
	struct ast_format_def *f = s->fmt;
	int ret = -1;
	int (*openfn)(struct ast_filestream *s);

	if (mode == WRAP_OPEN && (openfn = f->open) && openfn(s))
		ast_log(LOG_WARNING, "Unable to open format %s\n", f->name);
	else if (mode == WRAP_REWRITE && f->rewrite && f->rewrite(s, comment))
		ast_log(LOG_WARNING, "Unable to rewrite format %s\n", f->name);
	else {
		/* preliminary checks succeed. */
		ret = 0;
	}
	return ret;
}

static int rewrite_wrapper(struct ast_filestream *s, const char *comment)
{
	return fn_wrapper(s, comment, WRAP_REWRITE);
}

static int open_wrapper(struct ast_filestream *s)
{
	return fn_wrapper(s, NULL, WRAP_OPEN);
}

enum file_action {
	ACTION_EXISTS = 1, /* return matching format if file exists, 0 otherwise */
	ACTION_DELETE,	/* delete file, return 0 on success, -1 on error */
	ACTION_RENAME,	/* rename file. return 0 on success, -1 on error */
	ACTION_OPEN,
	ACTION_COPY	/* copy file. return 0 on success, -1 on error */
};

/*!
 * \internal
 * \brief perform various actions on a file. Second argument
 * \note arg2 depends on the command:
 *	unused for DELETE
 *  optional ast_format_cap holding all the formats found for a file, for EXISTS.
 *	destination file name (const char *) for COPY and RENAME
 *	struct ast_channel * for OPEN
 * if fmt is NULL, OPEN will return the first matching entry,
 * whereas other functions will run on all matching entries.
 */
static int filehelper(const char *filename, const void *arg2, const char *fmt, const enum file_action action)
{
	struct ast_format_def *f;
	int res = (action == ACTION_EXISTS) ? 0 : -1;

	AST_RWLIST_RDLOCK(&formats);
	/* Check for a specific format */
	AST_RWLIST_TRAVERSE(&formats, f, list) {
		char *stringp, *ext = NULL;

		if (fmt && !exts_compare(f->exts, fmt))
			continue;

		/* Look for a file matching the supported extensions.
		 * The file must exist, and for OPEN, must match
		 * one of the formats supported by the channel.
		 */
		stringp = ast_strdupa(f->exts);	/* this is in the stack so does not need to be freed */
		while ( (ext = strsep(&stringp, "|")) ) {
			struct stat st;
			char *fn = build_filename(filename, ext);

			if (fn == NULL)
				continue;

			if ( stat(fn, &st) ) { /* file not existent */
				ast_free(fn);
				continue;
			}
			/* for 'OPEN' we need to be sure that the format matches
			 * what the channel can process
			 */
			if (action == ACTION_OPEN) {
				struct ast_channel *chan = (struct ast_channel *)arg2;
				FILE *bfile;
				struct ast_filestream *s;

				if ((ast_format_cmp(ast_channel_writeformat(chan), f->format) == AST_FORMAT_CMP_NOT_EQUAL) &&
				     !(((ast_format_get_type(f->format) == AST_MEDIA_TYPE_AUDIO) && fmt) ||
					  ((ast_format_get_type(f->format) == AST_MEDIA_TYPE_VIDEO) && fmt))) {
					ast_free(fn);
					continue;	/* not a supported format */
				}
				if ( (bfile = fopen(fn, "r")) == NULL) {
					ast_free(fn);
					continue;	/* cannot open file */
				}
				s = get_filestream(f, bfile);
				if (!s) {
					fclose(bfile);
					ast_free(fn);	/* cannot allocate descriptor */
					continue;
				}
				if (open_wrapper(s)) {
					ast_free(fn);
					ast_closestream(s);
					continue;	/* cannot run open on file */
				}
				if (st.st_size == 0) {
					ast_log(LOG_WARNING, "File %s detected to have zero size.\n", fn);
				}
				/* ok this is good for OPEN */
				res = 1;	/* found */
				s->lasttimeout = -1;
				s->fmt = f;
				s->trans = NULL;
				s->filename = NULL;
				if (ast_format_get_type(s->fmt->format) == AST_MEDIA_TYPE_AUDIO) {
					if (ast_channel_stream(chan))
						ast_closestream(ast_channel_stream(chan));
					ast_channel_stream_set(chan, s);
				} else {
					if (ast_channel_vstream(chan))
						ast_closestream(ast_channel_vstream(chan));
					ast_channel_vstream_set(chan, s);
				}
				ast_free(fn);
				break;
			}
			switch (action) {
			case ACTION_OPEN:
				break;	/* will never get here */

			case ACTION_EXISTS:	/* return the matching format */
				/* if arg2 is present, it is a format capabilities structure.
				 * Add this format to the set of formats this file can be played in */
				if (arg2) {
					ast_format_cap_append((struct ast_format_cap *) arg2, f->format, 0);
				}
				res = 1; /* file does exist and format it exists in is returned in arg2 */
				break;

			case ACTION_DELETE:
				if ( (res = unlink(fn)) )
					ast_log(LOG_WARNING, "unlink(%s) failed: %s\n", fn, strerror(errno));
				break;

			case ACTION_RENAME:
			case ACTION_COPY: {
				char *nfn = build_filename((const char *)arg2, ext);
				if (!nfn)
					ast_log(LOG_WARNING, "Out of memory\n");
				else {
					res = action == ACTION_COPY ? copy(fn, nfn) : rename(fn, nfn);
					if (res)
						ast_log(LOG_WARNING, "%s(%s,%s) failed: %s\n",
							action == ACTION_COPY ? "copy" : "rename",
							 fn, nfn, strerror(errno));
					ast_free(nfn);
				}
			    }
				break;

			default:
				ast_log(LOG_WARNING, "Unknown helper %u\n", action);
			}
			ast_free(fn);
		}
	}
	AST_RWLIST_UNLOCK(&formats);
	return res;
}

static int is_absolute_path(const char *filename)
{
	return filename[0] == '/';
}

/*!
 * \brief test if a file exists for a given format.
 * \note result_cap is OPTIONAL
 * \retval 1, true and result_cap represents format capabilities file exists in.
 * \retval 0, false
 */
static int fileexists_test(const char *filename, const char *fmt, const char *lang,
			   char *buf, int buflen, struct ast_format_cap *result_cap)
{
	if (buf == NULL) {
		return 0;
	}

	if (!ast_media_cache_retrieve(filename, NULL, buf, buflen)) {
		return filehelper(buf, result_cap, NULL, ACTION_EXISTS);
	}

	if (ast_language_is_prefix && !is_absolute_path(filename)) { /* new layout */
		if (lang) {
			snprintf(buf, buflen, "%s/%s", lang, filename);
		} else {
			snprintf(buf, buflen, "%s", filename);
		}
	} else { /* old layout */
		strcpy(buf, filename);	/* first copy the full string */
		if (lang) {
			/* insert the language and suffix if needed */
			const char *c = strrchr(filename, '/');
			int offset = c ? c - filename + 1 : 0;	/* points right after the last '/' */
			snprintf(buf + offset, buflen - offset, "%s/%s", lang, filename + offset);
		}
	}

	return filehelper(buf, result_cap, fmt, ACTION_EXISTS);
}

/*!
 * \brief helper routine to locate a file with a given format
 * and language preference.
 *
 * \note Try preflang, preflang with stripped '_' suffices, or NULL.
 *
 * \note The last parameter(s) point to a buffer of sufficient size,
 * which on success is filled with the matching filename.
 *
 * \param filename Name of the file.
 * \param fmt Format to look for the file in. OPTIONAL
 * \param preflang The perfered language
 * \param buf Returns the matching filename
 * \param buflen Size of the buf
 * \param result_cap OPTIONAL format capabilities result structure
 *        returns what formats the file was found in.
 *
 * \retval 1, true. file exists and result format is set
 * \retval 0, false. file does not exist.
 */
static int fileexists_core(const char *filename, const char *fmt, const char *preflang,
			   char *buf, int buflen, struct ast_format_cap *result_cap)
{
	char *lang;

	if (buf == NULL) {
		return 0;
	}

	/* We try languages in the following order:
	 *    preflang (may include dialect and style codes)
	 *    lang (preflang without dialect - if any)
	 *    <none>
	 *    default (unless the same as preflang or lang without dialect)
	 */

	lang = ast_strdupa(preflang);

	/* Try preferred language, including removing any style or dialect codes */
	while (!ast_strlen_zero(lang)) {
		char *end;

		if (fileexists_test(filename, fmt, lang, buf, buflen, result_cap)) {
			return 1;
		}

		if ((end = strrchr(lang, '_')) != NULL) {
			*end = '\0';
			continue;
		}

		break;
	}

	/* Try without any language */
	if (fileexists_test(filename, fmt, NULL, buf, buflen, result_cap)) {
		return 1;
	}

	/* Finally try the default language unless it was already tried before */
	if ((ast_strlen_zero(preflang) || strcmp(preflang, DEFAULT_LANGUAGE)) && (ast_strlen_zero(lang) || strcmp(lang, DEFAULT_LANGUAGE))) {
		if ((fileexists_test(filename, fmt, DEFAULT_LANGUAGE, buf, buflen, result_cap)) > 0) {
			return 1;
		}
	}

	return 0;
}

struct ast_filestream *ast_openstream(struct ast_channel *chan, const char *filename, const char *preflang)
{
	return ast_openstream_full(chan, filename, preflang, 0);
}

struct ast_filestream *ast_openstream_full(struct ast_channel *chan, const char *filename, const char *preflang, int asis)
{
	/*
	 * Use fileexists_core() to find a file in a compatible
	 * language and format, set up a suitable translator,
	 * and open the stream.
	 */
	struct ast_format_cap *file_fmt_cap;
	int res;
	int buflen;
	char *buf;

	if (!asis) {
		/* do this first, otherwise we detect the wrong writeformat */
		ast_stopstream(chan);
		if (ast_channel_generator(chan))
			ast_deactivate_generator(chan);
	}
	if (preflang == NULL)
		preflang = "";
	buflen = strlen(preflang) + strlen(filename) + 4;
	buf = ast_alloca(buflen);

	if (!(file_fmt_cap = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
		return NULL;
	}
	if (!fileexists_core(filename, NULL, preflang, buf, buflen, file_fmt_cap) ||
		!ast_format_cap_has_type(file_fmt_cap, AST_MEDIA_TYPE_AUDIO)) {

		ast_log(LOG_WARNING, "File %s does not exist in any format\n", filename);
		ao2_ref(file_fmt_cap, -1);
		return NULL;
	}

	/* Set the channel to a format we can work with and save off the previous format. */
	ast_channel_lock(chan);
	ast_channel_set_oldwriteformat(chan, ast_channel_writeformat(chan));
	/* Set the channel to the best format that exists for the file. */
	res = ast_set_write_format_from_cap(chan, file_fmt_cap);
	ast_channel_unlock(chan);
	/* don't need this anymore now that the channel's write format is set. */
	ao2_ref(file_fmt_cap, -1);

	if (res == -1) {	/* No format available that works with this channel */
		return NULL;
	}
	res = filehelper(buf, chan, NULL, ACTION_OPEN);
	if (res >= 0)
		return ast_channel_stream(chan);
	return NULL;
}

struct ast_filestream *ast_openvstream(struct ast_channel *chan, const char *filename, const char *preflang)
{
	/* As above, but for video. But here we don't have translators
	 * so we must enforce a format.
	 */
	struct ast_format_cap *nativeformats, *tmp_cap;
	char *buf;
	int buflen;
	int i, fd;

	if (preflang == NULL) {
		preflang = "";
	}
	buflen = strlen(preflang) + strlen(filename) + 4;
	buf = ast_alloca(buflen);

	ast_channel_lock(chan);
	nativeformats = ao2_bump(ast_channel_nativeformats(chan));
	ast_channel_unlock(chan);

	/* is the channel capable of video without translation ?*/
	if (!ast_format_cap_has_type(nativeformats, AST_MEDIA_TYPE_VIDEO)) {
		ao2_cleanup(nativeformats);
		return NULL;
	}
	if (!(tmp_cap = ast_format_cap_alloc(AST_FORMAT_CAP_FLAG_DEFAULT))) {
		ao2_cleanup(nativeformats);
		return NULL;
	}
	/* Video is supported, so see what video formats exist for this file */
	if (!fileexists_core(filename, NULL, preflang, buf, buflen, tmp_cap)) {
		ao2_ref(tmp_cap, -1);
		ao2_cleanup(nativeformats);
		return NULL;
	}

	/* iterate over file formats and pick the first one compatible with the channel's native formats */
	for (i = 0; i < ast_format_cap_count(tmp_cap); ++i) {
		struct ast_format *format = ast_format_cap_get_format(tmp_cap, i);

		if ((ast_format_get_type(format) != AST_MEDIA_TYPE_VIDEO) ||
			!ast_format_cap_iscompatible(nativeformats, tmp_cap)) {
			ao2_ref(format, -1);
			continue;
		}

		fd = filehelper(buf, chan, ast_format_get_name(format), ACTION_OPEN);
		if (fd >= 0) {
			ao2_ref(format, -1);
			ao2_ref(tmp_cap, -1);
			ao2_cleanup(nativeformats);
			return ast_channel_vstream(chan);
		}
		ast_log(LOG_WARNING, "File %s has video but couldn't be opened\n", filename);
		ao2_ref(format, -1);
	}
	ao2_ref(tmp_cap, -1);
	ao2_cleanup(nativeformats);

	return NULL;
}

static struct ast_frame *read_frame(struct ast_filestream *s, int *whennext)
{
	struct ast_frame *fr, *new_fr;

	if (!s || !s->fmt) {
		return NULL;
	}

	if (!(fr = s->fmt->read(s, whennext))) {
		return NULL;
	}

	if (!(new_fr = ast_frisolate(fr))) {
		ast_frfree(fr);
		return NULL;
	}

	if (new_fr != fr) {
		ast_frfree(fr);
		fr = new_fr;
	}

	return fr;
}

struct ast_frame *ast_readframe(struct ast_filestream *s)
{
	int whennext = 0;

	return read_frame(s, &whennext);
}

enum fsread_res {
	FSREAD_FAILURE,
	FSREAD_SUCCESS_SCHED,
	FSREAD_SUCCESS_NOSCHED,
};

static int ast_fsread_audio(const void *data);

static enum fsread_res ast_readaudio_callback(struct ast_filestream *s)
{
	int whennext = 0;

	while (!whennext) {
		struct ast_frame *fr;

		if (s->orig_chan_name && strcasecmp(ast_channel_name(s->owner), s->orig_chan_name)) {
			goto return_failure;
		}

		fr = read_frame(s, &whennext);

		if (!fr /* stream complete */ || ast_write(s->owner, fr) /* error writing */) {
			if (fr) {
				ast_debug(2, "Failed to write frame\n");
				ast_frfree(fr);
			}
			goto return_failure;
		}

		if (fr) {
			ast_frfree(fr);
		}
	}

	if (whennext != s->lasttimeout) {
		if (ast_channel_timingfd(s->owner) > -1) {
			float samp_rate = (float) ast_format_get_sample_rate(s->fmt->format);
			unsigned int rate;

			rate = (unsigned int) roundf(samp_rate / ((float) whennext));

			ast_settimeout_full(s->owner, rate, ast_fsread_audio, s, 1);
		} else {
			ast_channel_streamid_set(s->owner, ast_sched_add(ast_channel_sched(s->owner), whennext / (ast_format_get_sample_rate(s->fmt->format) / 1000), ast_fsread_audio, s));
		}
		s->lasttimeout = whennext;
		return FSREAD_SUCCESS_NOSCHED;
	}
	return FSREAD_SUCCESS_SCHED;

return_failure:
	ast_channel_streamid_set(s->owner, -1);
	ast_settimeout(s->owner, 0, NULL, NULL);
	return FSREAD_FAILURE;
}

static int ast_fsread_audio(const void *data)
{
	struct ast_filestream *fs = (struct ast_filestream *)data;
	enum fsread_res res;

	res = ast_readaudio_callback(fs);

	if (res == FSREAD_SUCCESS_SCHED)
		return 1;

	return 0;
}

static int ast_fsread_video(const void *data);

static enum fsread_res ast_readvideo_callback(struct ast_filestream *s)
{
	int whennext = 0;

	while (!whennext) {
		struct ast_frame *fr = read_frame(s, &whennext);

		if (!fr /* stream complete */ || ast_write(s->owner, fr) /* error writing */) {
			if (fr) {
				ast_debug(2, "Failed to write frame\n");
				ast_frfree(fr);
			}
			ast_channel_vstreamid_set(s->owner, -1);
			return FSREAD_FAILURE;
		}

		if (fr) {
			ast_frfree(fr);
		}
	}

	if (whennext != s->lasttimeout) {
		ast_channel_vstreamid_set(s->owner, ast_sched_add(ast_channel_sched(s->owner), whennext / (ast_format_get_sample_rate(s->fmt->format) / 1000), ast_fsread_video, s));
		s->lasttimeout = whennext;
		return FSREAD_SUCCESS_NOSCHED;
	}

	return FSREAD_SUCCESS_SCHED;
}

static int ast_fsread_video(const void *data)
{
	struct ast_filestream *fs = (struct ast_filestream *)data;
	enum fsread_res res;