Addition of "infile" parameter (virtual mic) to the file plugin

When this new parameter is specified, the behavior of opening a file PCM
for input is changed to the following: reads from the device, instead of
being passed down to the slave PCM, will read the raw data from the
specified file. No file writes will take place in this case. In the
absence of this parameter, previous behavior is unchanged.

The input file name and descriptor are kept in the snd_pcm_file_t struct
in a manner analogous to the already existing output file parameter.

TODO:

(1) Only interleaved reads (snd_pcm_file_readi) have been implemented
for now.

(2) File read()'s that return a number of bytes that's not a multiple of
the frame size will result in data loss (choppiness). The rbuf,
rbuf_size_bytes, and rbuf_used_bytes members of the snd_pcm_file_t
struct will be used to address this problem in the future.

(3) Mind whether the PCM was opened in blocking mode. If so, we'll have
to loop until the buffer has been filled with read()'s.

Signed-off-by: Juan Carlos Castro y Castro <jcastro@vialink.com.br>

src/pcm/pcm_file.c

@@ -46,6 +46,8 @@ typedef struct {
 	snd_pcm_generic_t gen;
 	char *fname;
 	int fd;
+	char *ifname;
+	int ifd;
 	int format;
 	snd_pcm_uframes_t appl_ptr;
 	snd_pcm_uframes_t file_ptr_bytes;
@@ -53,6 +55,9 @@ typedef struct {
 	size_t wbuf_size_bytes;
 	size_t wbuf_used_bytes;
 	char *wbuf;
+	size_t rbuf_size_bytes;
+	size_t rbuf_used_bytes;
+	char *rbuf;
 	snd_pcm_channel_area_t *wbuf_areas;
 	size_t buffer_bytes;
 } snd_pcm_file_t;
@@ -120,6 +125,10 @@ static int snd_pcm_file_close(snd_pcm_t *pcm)
 		free((void *)file->fname);
 		close(file->fd);
 	}
+	if (file->ifname) {
+		free((void *)file->ifname);
+		close(file->ifd);
+	}
 	return snd_pcm_generic_close(pcm);
 }
 
@@ -222,10 +231,20 @@ static snd_pcm_sframes_t snd_pcm_file_readi(snd_pcm_t *pcm, void *buffer, snd_pc
 {
 	snd_pcm_file_t *file = pcm->private_data;
 	snd_pcm_channel_area_t areas[pcm->channels];
-	snd_pcm_sframes_t n = snd_pcm_readi(file->gen.slave, buffer, size);
+	snd_pcm_sframes_t n /* , bytesn */;
-	if (n > 0) {
+
-		snd_pcm_areas_from_buf(pcm, areas, buffer);
+	if (file->ifd >= 0) {
-		snd_pcm_file_add_frames(pcm, areas, 0, n);
+		n = /* bytesn = */ read(file->ifd, buffer, size * pcm->frame_bits / 8);
+		if (n > 0)
+			n = n * 8 / pcm->frame_bits;
+		/* SNDERR("DEBUG: channels = %d, sample_bits = %d, frame_bits = %d, bytes = %d, frames = %d",
+		        pcm->channels, pcm->sample_bits, pcm->frame_bits, bytesn, n); */
+	} else {
+		n = snd_pcm_readi(file->gen.slave, buffer, size);
+		if (n > 0) {
+			snd_pcm_areas_from_buf(pcm, areas, buffer);
+			snd_pcm_file_add_frames(pcm, areas, 0, n);
+		}
 	}
 	return n;
 }
@@ -234,7 +253,14 @@ static snd_pcm_sframes_t snd_pcm_file_readn(snd_pcm_t *pcm, void **bufs, snd_pcm
 {
 	snd_pcm_file_t *file = pcm->private_data;
 	snd_pcm_channel_area_t areas[pcm->channels];
-	snd_pcm_sframes_t n = snd_pcm_readn(file->gen.slave, bufs, size);
+	snd_pcm_sframes_t n;
+
+	if (file->ifd >= 0) {
+		SNDERR("DEBUG: Noninterleaved read not yet implemented.\n");
+		return 0;	/* TODO: Noninterleaved read */
+	}
+
+	n = snd_pcm_readn(file->gen.slave, bufs, size);
 	if (n > 0) {
 		snd_pcm_areas_from_bufs(pcm, areas, bufs);
 		snd_pcm_file_add_frames(pcm, areas, 0, n);
@@ -365,8 +391,11 @@ static snd_pcm_fast_ops_t snd_pcm_file_fast_ops = {
  * \brief Creates a new File PCM
  * \param pcmp Returns created PCM handle
  * \param name Name of PCM
- * \param fname Filename (or NULL if file descriptor is available)
+ * \param fname Output filename (or NULL if file descriptor fd is available)
- * \param fd File descriptor
+ * \param fd Output file descriptor
+ * \param ifname Input filename (or NULL if file descriptor ifd is available)
+ * \param ifd Input file descriptor (if (ifd < 0) && (ifname == NULL), no input
+ *            redirection will be performed)
  * \param fmt File format ("raw" is supported only)
  * \param perm File permission
  * \param slave Slave PCM handle
@@ -377,8 +406,8 @@ static snd_pcm_fast_ops_t snd_pcm_file_fast_ops = {
  *          changed in future.
  */
 int snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
-		      const char *fname, int fd, const char *fmt, int perm,
+		      const char *fname, int fd, const char *ifname, int ifd, 
-		      snd_pcm_t *slave, int close_slave)
+		      const char *fmt, int perm, snd_pcm_t *slave, int close_slave)
 {
 	snd_pcm_t *pcm;
 	snd_pcm_file_t *file;
@@ -395,7 +424,7 @@ int snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 	if (fname) {
 		fd = open(fname, O_WRONLY|O_CREAT, perm);
 		if (fd < 0) {
-			SYSERR("open %s failed", fname);
+			SYSERR("open %s for writing failed", fname);
 			return -errno;
 		}
 	}
@@ -406,9 +435,22 @@ int snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 		return -ENOMEM;
 	}
 
+	if (ifname) {
+		ifd = open(ifname, O_RDONLY);	/* TODO: mind blocking mode */
+		if (ifd < 0) {
+			SYSERR("open %s for reading failed", ifname);
+			if (fname)
+				close(fd);
+			return -errno;
+		}
+	}
+
 	if (fname)
 		file->fname = strdup(fname);
+	if (ifname)
+		file->ifname = strdup(ifname);
 	file->fd = fd;
+	file->ifd = ifd;
 	file->format = format;
 	file->gen.slave = slave;
 	file->gen.close_slave = close_slave;
@@ -436,7 +478,8 @@ int snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 
 \section pcm_plugins_file Plugin: File
 
-This plugin stores contents of a PCM stream to file.
+This plugin stores contents of a PCM stream to file, and optionally
+uses an existing file as an input data source (i.e., "virtual mic")
 
 \code
 pcm.name {
@@ -448,11 +491,14 @@ pcm.name {
                 # or
                 pcm { }         # Slave PCM definition
         }
-	file STR		# Filename
+	file STR		# Output filename
 	or
-	file INT		# File descriptor number
+	file INT		# Output file descriptor number
+	infile STR		# Input filename
+	or
+	infile INT		# Input file descriptor number
 	[format STR]		# File format (only "raw" at the moment)
-	[perm INT]		# File permission (octal, default 0600)
+	[perm INT]		# Output file permission (octal, def. 0600)
 }
 \endcode
 
@@ -486,9 +532,9 @@ int _snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 	int err;
 	snd_pcm_t *spcm;
 	snd_config_t *slave = NULL, *sconf;
-	const char *fname = NULL;
+	const char *fname = NULL, *ifname = NULL;
 	const char *format = NULL;
-	long fd = -1;
+	long fd = -1, ifd = -1;
 	int perm = 0600;
 	snd_config_for_each(i, next, conf) {
 		snd_config_t *n = snd_config_iterator_entry(i);
@@ -520,6 +566,17 @@ int _snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 			}
 			continue;
 		}
+		if (strcmp(id, "infile") == 0) {
+			err = snd_config_get_string(n, &ifname);
+			if (err < 0) {
+				err = snd_config_get_integer(n, &ifd);
+				if (err < 0) {
+					SNDERR("Invalid type for %s", id);
+					return -EINVAL;
+				}
+			}
+			continue;
+		}
 		if (strcmp(id, "perm") == 0) {
 			char *str;
 			char *endp;
@@ -556,7 +613,7 @@ int _snd_pcm_file_open(snd_pcm_t **pcmp, const char *name,
 	snd_config_delete(sconf);
 	if (err < 0)
 		return err;
-	err = snd_pcm_file_open(pcmp, name, fname, fd, format, perm, spcm, 1);
+	err = snd_pcm_file_open(pcmp, name, fname, fd, ifname, ifd, format, perm, spcm, 1);
 	if (err < 0)
 		snd_pcm_close(spcm);
 	return err;