From: Ralph Ronnquist <ralph.ronnquist@gmail.com>
Date: Sat, 29 Apr 2023 02:54:09 +0000 (+1000)
Subject: some cleanup
X-Git-Url: https://git.rrq.au/?a=commitdiff_plain;h=98563e2eb6f57ac720234fffa6b14a84a31004c5;p=rrq%2Fnewlisp%2Falsa-dispatcher.git

some cleanup
---

diff --git a/alsa-dispatcher.lsp b/alsa-dispatcher.lsp
index deb557c..df8863b 100755
--- a/alsa-dispatcher.lsp
+++ b/alsa-dispatcher.lsp
@@ -9,35 +9,35 @@
 (signal 2 (fn (x) (exit 0)))
 (signal 15 (fn (x) (exit 0)))
 
+; Optionally print output to stderr and optionally exit with code
 (define (die N)
   (when (args) (write-line 2 (join (map string (args)) " ")))
   (when (number? N) (exit N)))
 
-(define (enlist X) (if (list? X) X (list X)))
+; Return non-nil for comment line (starts with # or is blank)
+(define (comment? LINE) (regex "^\\s*(#|$)" LINE 0))
 
-(define (comment? LINE) (and (regex "^\\s*(#|$)" LINE 0) true))
+; Return list of space-separated words on a line
+(define (words LINE)
+  (parse (trim LINE) "\\s+" 0))
 
-(define (first-word LINE) (and (regex "^\\s*(\\S+)" LINE 0) $1))
-
-(define (prog1 X) X)
-
-(define (read-config-line LINE)
-  (map (fn (x) (if (regex "^([^=]+)=(.*)" x) (list $1 $2) x))
-       (map trim (find-all "([^, ]+)" LINE $1 0))))
+; Read the configuration file and return it as list of plugs or the default
+(define (read-config FILE)
+  (or
+   (if (read-file FILE) (map words (clean comment? (parse $it "\n"))))
+   '(("plughw")) ; the default priority list
+   ))
 
 ;; ############################################################
 ;; Load Configuration (~/.alsa-dispatcher)
 ; Format: one-liners for each option, ignoring comment lines starting
 ; with # and blank lines.
 (constant
- 'HOME (env "HOME")
- 'CONFIG (format "%s/.alsa-dispatcher" HOME)
- 'CFGLINES (if (read-file CONFIG) (clean comment? (parse $it "\n" ))
-             '("bt,latency=1000" "plughw"))
- 'CFGMAP (map read-config-line CFGLINES)
- 'PCM-LIST (map first-word CFGLINES)
+ 'CFGMAP (read-config (format "%s/.alsa-dispatcher" (env "HOME")))
+ 'PCM-LIST (map first CFGMAP)
  )
 
+; Return value of configuration setting KEY for plug PCM, or DEFAULT.
 (define (cfg-lookup PCM KEY DEFAULT)
   (if (if (assoc PCM CFGMAP) (lookup KEY $it)) (read-expr $it) DEFAULT))
 
@@ -117,25 +117,22 @@
         "long"   ; snd_pcm_uframes_t size
         )
 
-;; Open a PCM by name
+;; Open a PCM by name. Returns list of (NAME PCM) or nil.
 (define (open-pcm NAME)
-  (snd_pcm_open NAME SND_PCM_STREAM_PLAYBACK SND_PCM_MODE_BLOCK))
+  (if (snd_pcm_open NAME SND_PCM_STREAM_PLAYBACK SND_PCM_MODE_BLOCK)
+      (list NAME $it)))
 
-;; Setup PCM 
+;; Setup PCM. Preset format. access, channels, rate and soft resample.
+;; Configurable latency.
 (define (setup-pcm PCM NAME)
-  (snd_pcm_set_params PCM
-                      (cfg-lookup NAME "format" SND_PCM_FORMAT_S16_LE)
-                      SND_PCM_ACCESS_RW_INTERLEAVED
-                      2 ; channels
-                      48000 ; rate
-                      1 ; soft resample (0/1)
-                      (cfg-lookup NAME "latency" 100000) ; (microseconds)
-                      ))
+  (let ((LATENCY (cfg-lookup NAME "latency" 100000)))
+    (snd_pcm_set_params PCM SND_PCM_FORMAT_S16_LE SND_PCM_ACCESS_RW_INTERLEAVED
+                        2 48000 1 LATENCY )))
 
 ;; ############################################################
 ; The main program
 
-;; redirect stdout/err to /dev/null
+; redirect stdout/err to /dev/null (flagged for debugging purposes)
 (when true
   (let ((REDIR (open "/dev/null" "append")))
     (when (< REDIR) (exit 1))
@@ -145,27 +142,29 @@
   ))
 
 ; find the first usable PCM
-(setf PCM (unless (dolist (N PCM-LIST (open-pcm (setf NAME N))))
-            (die 1 "No PCM available")))
+(map set '(NAME PCM) (unless (dolist (N PCM-LIST (open-pcm N)))
+                       (die 1 "No PCM available")))
 
 ; configure the PCM
 (when (!= (setf E (setup-pcm PCM NAME)))
   (snd_pcm_close PCM)
   (die 1 "setup pcm" E))
 
-(setf N 0 x 0 E 0 i 0)
-
-(while (> (or (setf N (read 0 BUFFER 1000000)) 0))
-  (while (> N) 
+; channel stdin audio onto selected pcm
+(while (> (or (setf N (read 0 BUFFER 2000000)) 0))
+  (while (> N)
+    ; N  is in bytes while snd_pcm_writei counts "frames" of 4 bytes
     (when (< (setf E (snd_pcm_writei PCM BUFFER (/ N 4))))
       (snd_pcm_close PCM)
-      (die 1 "writing" E N))
+      (die 1 "writing failed"))
     (setf E (* E 4))
     (setf BUFFER (E BUFFER))
     (dec N E)
     )
   )
 
+; let the pcm complete its output
 (snd_pcm_drain PCM)
+
 (snd_pcm_close PCM)
 (exit 0)