MP3File: Add a settable ".file" property

This enables jeplayer to allocate just one MP3File at startup, rather
than have to make repeated large allocations while the application is
running.

The buffers have to be allocated their theoretical maximum, but that
doesn't matter much as all the real-life MP3 files I checked needed
that much allocation anyway.

1 files changed, 28 insertions, 18 deletions

diff --git a/shared-module/audiomp3/MP3File.c b/shared-module/audiomp3/MP3File.c
index 0aa4f24a6..5896a2561 100644
--- a/shared-module/audiomp3/MP3File.c
+++ b/shared-module/audiomp3/MP3File.c
@@ -37,6 +37,8 @@
 #include "supervisor/shared/translate.h"
 #include "lib/mp3/src/mp3common.h"
 
+#define MAX_BUFFER_LEN (MAX_NSAMP * MAX_NGRAN * MAX_NCHAN * sizeof(int16_t))
+
 /** Fill the input buffer if it is less than half full.
  *
  * Returns true if the input buffer contains any useful data,
@@ -165,7 +167,6 @@ void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t* self,
     // than the two 4kB output buffers, except that the alignment allows to
     // never allocate that extra frame buffer.
 
-    self->file = file;
     self->inbuf_length = 2048;
     self->inbuf_offset = self->inbuf_length;
     self->inbuf = m_malloc(self->inbuf_length, false);
@@ -181,40 +182,49 @@ void common_hal_audiomp3_mp3file_construct(audiomp3_mp3file_obj_t* self,
                      translate("Couldn't allocate decoder"));
     }
 
-    mp3file_find_sync_word(self);
-    MP3FrameInfo fi;
-    if(!mp3file_get_next_frame_info(self, &fi)) {
-        mp_raise_msg(&mp_type_RuntimeError,
-                     translate("Failed to parse MP3 file"));
-    }
-
-    self->sample_rate = fi.samprate;
-    self->channel_count = fi.nChans;
-    self->frame_buffer_size = fi.outputSamps*sizeof(int16_t);
-
     if ((intptr_t)buffer & 1) {
         buffer += 1; buffer_size -= 1;
     }
-    if (buffer_size >= 2 * self->frame_buffer_size) {
-        self->len = buffer_size / 2 / self->frame_buffer_size * self->frame_buffer_size;
+    if (buffer_size >= 2 * MAX_BUFFER_LEN) {
         self->buffers[0] = (int16_t*)(void*)buffer;
-        self->buffers[1] = (int16_t*)(void*)buffer + self->len;
+        self->buffers[1] = (int16_t*)(void*)(buffer + MAX_BUFFER_LEN);
     } else {
-        self->len = 2 * self->frame_buffer_size;
-        self->buffers[0] = m_malloc(self->len, false);
+        self->buffers[0] = m_malloc(MAX_BUFFER_LEN, false);
         if (self->buffers[0] == NULL) {
             common_hal_audiomp3_mp3file_deinit(self);
             mp_raise_msg(&mp_type_MemoryError,
                          translate("Couldn't allocate first buffer"));
         }
 
-        self->buffers[1] = m_malloc(self->len, false);
+        self->buffers[1] = m_malloc(MAX_BUFFER_LEN, false);
         if (self->buffers[1] == NULL) {
             common_hal_audiomp3_mp3file_deinit(self);
             mp_raise_msg(&mp_type_MemoryError,
                          translate("Couldn't allocate second buffer"));
         }
     }
+
+    common_hal_audiomp3_mp3file_set_file(self, file);
+}
+
+void common_hal_audiomp3_mp3file_set_file(audiomp3_mp3file_obj_t* self, pyb_file_obj_t* file) {
+    self->file = file;
+    f_lseek(&self->file->fp, 0);
+    self->inbuf_offset = self->inbuf_length;
+    self->eof = 0;
+    self->other_channel = -1;
+    mp3file_update_inbuf(self);
+    mp3file_find_sync_word(self);
+    MP3FrameInfo fi;
+    if(!mp3file_get_next_frame_info(self, &fi)) {
+        mp_raise_msg(&mp_type_RuntimeError,
+                     translate("Failed to parse MP3 file"));
+    }
+
+    self->sample_rate = fi.samprate;
+    self->channel_count = fi.nChans;
+    self->frame_buffer_size = fi.outputSamps*sizeof(int16_t);
+    self->len = 2 * self->frame_buffer_size;
 }
 
 void common_hal_audiomp3_mp3file_deinit(audiomp3_mp3file_obj_t* self) {