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minimp3_ex: add mp3dec_ex_read_frame() function

--- a/minimp3_ex.h

+++ b/minimp3_ex.h

@@ -101,6 +101,7 @@

 int mp3dec_ex_open_cb(mp3dec_ex_t *dec, mp3dec_io_t *io, int flags);

 void mp3dec_ex_close(mp3dec_ex_t *dec);

 int mp3dec_ex_seek(mp3dec_ex_t *dec, uint64_t position);

+size_t mp3dec_ex_read_frame(mp3dec_ex_t *dec, mp3d_sample_t **buf, size_t max_samples);

 size_t mp3dec_ex_read(mp3dec_ex_t *dec, mp3d_sample_t *buf, size_t samples);

 #ifndef MINIMP3_NO_STDIO

 /* stdio versions of file detect, load, iterate and stream */

@@ -843,7 +844,7 @@

     return 0;

 }

-size_t mp3dec_ex_read(mp3dec_ex_t *dec, mp3d_sample_t *buf, size_t samples)

+size_t mp3dec_ex_read_frame(mp3dec_ex_t *dec, mp3d_sample_t **buf, size_t max_samples)

 {

     if (!dec || !buf)

     {

@@ -851,8 +852,8 @@

             dec->last_error = MP3D_E_PARAM;

         return 0;

     }

+    *buf = NULL;

     uint64_t end_offset = dec->end_offset ? dec->end_offset : dec->file.size;

-    size_t samples_requested = samples;

     int eof = 0;

     mp3dec_frame_info_t frame_info;

     memset(&frame_info, 0, sizeof(frame_info));

@@ -860,24 +861,8 @@

         return 0; /* at end of stream */

     if (dec->last_error)

         return 0; /* error eof state, seek can reset it */

-    if (dec->buffer_consumed < dec->buffer_samples)

+    while (dec->buffer_consumed == dec->buffer_samples)

     {

-        size_t to_copy = MINIMP3_MIN((size_t)(dec->buffer_samples - dec->buffer_consumed), samples);

-        if (dec->detected_samples)

-        {   /* count decoded samples to properly cut padding */

-            if (dec->cur_sample + to_copy >= dec->detected_samples)

-                to_copy = dec->detected_samples - dec->cur_sample;

-        }

-        dec->cur_sample += to_copy;

-        memcpy(buf, dec->buffer + dec->buffer_consumed, to_copy*sizeof(mp3d_sample_t));

-        buf += to_copy;

-        dec->buffer_consumed += to_copy;

-        samples -= to_copy;

-    }

-    while (samples)

-    {

-        if (dec->detected_samples && dec->cur_sample >= dec->detected_samples)

-            break;

         const uint8_t *dec_buf;

         if (dec->io)

         {

@@ -900,7 +885,7 @@

             }

             dec_buf = dec->file.buffer + dec->input_consumed;

             if (!(dec->input_filled - dec->input_consumed))

-                break;

+                return 0;

             dec->buffer_samples = mp3dec_decode_frame(&dec->mp3d, dec_buf, dec->input_filled - dec->input_consumed, dec->buffer, &frame_info);

             dec->input_consumed += frame_info.frame_bytes;

         } else

@@ -908,7 +893,7 @@

             dec_buf = dec->file.buffer + dec->offset;

             uint64_t buf_size = end_offset - dec->offset;

             if (!buf_size)

-                break;

+                return 0;

             dec->buffer_samples = mp3dec_decode_frame(&dec->mp3d, dec_buf, MINIMP3_MIN(buf_size, (uint64_t)INT_MAX), dec->buffer, &frame_info);

         }

         dec->buffer_consumed = 0;

@@ -919,7 +904,7 @@

             )

         {

             dec->last_error = MP3D_E_DECODE;

-            break;

+            return 0;

         }

         if (dec->buffer_samples)

         {

@@ -930,17 +915,6 @@

                 dec->buffer_consumed += skip;

                 dec->to_skip -= skip;

             }

-            size_t to_copy = MINIMP3_MIN((size_t)(dec->buffer_samples - dec->buffer_consumed), samples);

-            if (dec->detected_samples)

-            {   /* ^ handle padding */

-                if (dec->cur_sample + to_copy >= dec->detected_samples)

-                    to_copy = dec->detected_samples - dec->cur_sample;

-            }

-            dec->cur_sample += to_copy;

-            memcpy(buf, dec->buffer + dec->buffer_consumed, to_copy*sizeof(mp3d_sample_t));

-            buf += to_copy;

-            dec->buffer_consumed += to_copy;

-            samples -= to_copy;

         } else if (dec->to_skip)

         {   /* In mp3 decoding not always can start decode from any frame because of bit reservoir,

                count skip samples for such frames */

@@ -948,6 +922,39 @@

             dec->to_skip -= MINIMP3_MIN(frame_samples, dec->to_skip);

         }

         dec->offset += frame_info.frame_bytes;

+    }

+    size_t out_samples = MINIMP3_MIN((size_t)(dec->buffer_samples - dec->buffer_consumed), max_samples);

+    if (dec->detected_samples)

+    {   /* count decoded samples to properly cut padding */

+        if (dec->cur_sample + out_samples >= dec->detected_samples)

+            out_samples = dec->detected_samples - dec->cur_sample;

+    }

+    dec->cur_sample += out_samples;

+    *buf = dec->buffer + dec->buffer_consumed;

+    dec->buffer_consumed += out_samples;

+    return out_samples;

+}

+

+size_t mp3dec_ex_read(mp3dec_ex_t *dec, mp3d_sample_t *buf, size_t samples)

+{

+    if (!dec || !buf)

+    {

+        if (dec)

+            dec->last_error = MP3D_E_PARAM;

+        return 0;

+    }

+    size_t samples_requested = samples;

+    while (samples)

+    {

+        mp3d_sample_t *buf_frame = NULL;

+        size_t read_samples = mp3dec_ex_read_frame(dec, &buf_frame, samples);

+        if (!read_samples)

+        {

+            break;

+        }

+        memcpy(buf, buf_frame, read_samples * sizeof(mp3d_sample_t));

+        buf += read_samples;

+        samples -= read_samples;

     }

     return samples_requested - samples;

 }