--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/decoders/mpglib.c	Thu Feb 21 19:46:09 2002 +0000
@@ -0,0 +1,258 @@
+/*
+ * SDL_sound -- An abstract sound format decoding API.
+ * Copyright (C) 2001  Ryan C. Gordon.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ */
+
+/*
+ * MPGLIB decoder for SDL_sound. This is a very lightweight MP3 decoder,
+ *  which is included with the SDL_sound source, so that it doesn't rely on
+ *  unnecessary external libraries.
+ *
+ * The SMPEG decoder plays back more forms of MPEGs, and may behave better or
+ *  worse under various conditions. mpglib is (apparently) more efficient than
+ *  SMPEG, and, again, doesn't need an external library. You should test both
+ *  decoders and use what you find works best for you.
+ *
+ * mpglib is part of mpg123, which can be found in its original form at:
+ *   http://www.mpg123.de/
+ *
+ * Please see the file COPYING in the source's root directory. The included
+ *  source code for mpglib falls under the LGPL, which is the same license as
+ *  SDL_sound (so you can consider it a single work).
+ *
+ *  This file written by Ryan C. Gordon. (icculus@clutteredmind.org)
+ */
+
+#if HAVE_CONFIG_H
+#  include <config.h>
+#endif
+
+#ifdef SOUND_SUPPORTS_MPGLIB
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include "mpglib/mpg123_sdlsound.h"
+#include "mpglib/mpglib_sdlsound.h"
+
+#include "SDL_sound.h"
+
+#define __SDL_SOUND_INTERNAL__
+#include "SDL_sound_internal.h"
+
+static int MPGLIB_init(void);
+static void MPGLIB_quit(void);
+static int MPGLIB_open(Sound_Sample *sample, const char *ext);
+static void MPGLIB_close(Sound_Sample *sample);
+static Uint32 MPGLIB_read(Sound_Sample *sample);
+static int MPGLIB_rewind(Sound_Sample *sample);
+
+static const char *extensions_mpglib[] = { "MP3", NULL };
+const Sound_DecoderFunctions __Sound_DecoderFunctions_MPGLIB =
+{
+    {
+        extensions_mpglib,
+        "MP3 decoding via internal mpglib",
+        "Ryan C. Gordon <icculus@clutteredmind.org>",
+        "http://www.icculus.org/SDL_sound/"
+    },
+
+    MPGLIB_init,       /*   init() method */
+    MPGLIB_quit,       /*   quit() method */
+    MPGLIB_open,       /*   open() method */
+    MPGLIB_close,      /*  close() method */
+    MPGLIB_read,       /*   read() method */
+    MPGLIB_rewind      /* rewind() method */
+};
+
+
+/* this is what we store in our internal->decoder_private field... */
+typedef struct
+{
+    struct mpstr mp;
+    Uint8 inbuf[16384];
+    Uint8 outbuf[8192];
+    int outleft;
+    int outpos;
+} mpglib_t;
+
+
+
+static int MPGLIB_init(void)
+{
+    return(1);  /* always succeeds. */
+} /* MPGLIB_init */
+
+
+static void MPGLIB_quit(void)
+{
+    /* it's a no-op. */
+} /* MPGLIB_quit */
+
+
+static int MPGLIB_open(Sound_Sample *sample, const char *ext)
+{
+    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
+    mpglib_t *mpg = NULL;
+
+       /*
+        * If I understand things correctly, MP3 files don't really have any
+        * magic header we can check for. The MP3 player is expected to just
+        * pick the first thing that looks like a valid frame and start
+        * playing from there.
+        *
+        * So here's what we do: If the caller insists that this is really
+        * MP3 we'll take his word for it. Otherwise, use the same test as
+        * SDL_mixer does and check if the stream starts with something that
+        * looks like a frame.
+        *
+        * A frame begins with 11 bits of frame sync (all bits must be set),
+        * followed by a two-bit MPEG Audio version ID:
+        *
+        *   00 - MPEG Version 2.5 (later extension of MPEG 2)
+        *   01 - reserved
+        *   10 - MPEG Version 2 (ISO/IEC 13818-3)
+        *   11 - MPEG Version 1 (ISO/IEC 11172-3)
+        *
+        * Apparently we don't handle MPEG Version 2.5.
+        */
+    if (__Sound_strcasecmp(ext, "MP3") != 0)
+    {
+        Uint8 mp3_magic[2];
+
+        if (SDL_RWread(internal->rw, mp3_magic, sizeof (mp3_magic), 1) != 1)
+        {
+            Sound_SetError("MP3: Could not read MP3 magic.");
+            return(0);
+        } /*if */
+
+        if (mp3_magic[0] != 0xFF || (mp3_magic[1] & 0xF0) != 0xF0)
+        {
+            Sound_SetError("MP3: Not an MP3 stream.");
+            return(0);
+        } /* if */
+
+            /* !!! FIXME: If the seek fails, we'll probably miss a frame */
+        SDL_RWseek(internal->rw, -sizeof (mp3_magic), SEEK_CUR);
+    } /* if */
+
+    mpg = (mpglib_t *) malloc(sizeof (mpglib_t));
+    BAIL_IF_MACRO(mpg == NULL, ERR_OUT_OF_MEMORY, 0);
+    mpg->outpos = mpg->outleft = 0;
+    InitMP3(&mpg->mp);
+
+    SNDDBG(("MPGLIB: Accepting data stream.\n"));
+
+    internal->decoder_private = mpg;
+    sample->actual.rate = 44100;
+    sample->actual.channels = 2;
+    sample->actual.format = AUDIO_S16LSB;
+    sample->flags = SOUND_SAMPLEFLAG_NONE;
+
+    return(1); /* we'll handle this data. */
+} /* MPGLIB_open */
+
+
+static void MPGLIB_close(Sound_Sample *sample)
+{
+    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
+    mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
+    ExitMP3(&mpg->mp);
+    free(mpg);
+} /* MPGLIB_close */
+
+
+static Uint32 MPGLIB_read(Sound_Sample *sample)
+{
+    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
+    mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
+    Uint32 bw = 0;
+    int rc;
+
+    while (bw < internal->buffer_size)
+    {
+        if (mpg->outleft > 0)
+        {
+            Uint16 cpysize = internal->buffer_size - bw;
+            if (cpysize > mpg->outleft)
+                cpysize = mpg->outleft;
+            memcpy(((Uint8 *) internal->buffer) + bw,
+                    mpg->outbuf + mpg->outpos, cpysize);
+            bw += cpysize;
+            mpg->outpos += cpysize;
+            mpg->outleft -= cpysize;
+            continue;
+        } /* if */
+
+        /* need to decode more from the MP3 stream... */
+        mpg->outpos = 0;
+        rc = decodeMP3(&mpg->mp, NULL, 0, mpg->outbuf,
+                       sizeof (mpg->outbuf), &mpg->outleft);
+        if (rc == MP3_ERR)
+        {
+            sample->flags |= SOUND_SAMPLEFLAG_ERROR;
+            return(bw);
+        } /* if */
+
+        else if (rc == MP3_NEED_MORE)
+        {
+            rc = SDL_RWread(internal->rw, mpg->inbuf, 1, sizeof (mpg->inbuf));
+            if (rc == -1)
+            {
+                sample->flags |= SOUND_SAMPLEFLAG_ERROR;
+                return(bw);
+            } /* if */
+            else if (rc == 0)
+            {
+                sample->flags |= SOUND_SAMPLEFLAG_EOF;
+                return(bw);
+            } /* else if */
+
+            rc = decodeMP3(&mpg->mp, mpg->inbuf, sizeof (mpg->inbuf),
+                           mpg->outbuf, sizeof (mpg->outbuf), &mpg->outleft);
+            if (rc == MP3_ERR)
+            {
+                sample->flags |= SOUND_SAMPLEFLAG_ERROR;
+                return(bw);
+            } /* if */
+        } /* else if */
+    } /* while */
+
+    return(bw);
+} /* MPGLIB_read */
+
+
+static int MPGLIB_rewind(Sound_Sample *sample)
+{
+    Sound_SampleInternal *internal = (Sound_SampleInternal *) sample->opaque;
+    mpglib_t *mpg = ((mpglib_t *) internal->decoder_private);
+    BAIL_IF_MACRO(SDL_RWseek(internal->rw, 0, SEEK_SET) != 0, ERR_IO_ERROR, 0);
+
+    /* this is just resetting some fields in a structure; it's very fast. */
+    ExitMP3(&mpg->mp);
+    InitMP3(&mpg->mp);
+    mpg->outpos = mpg->outleft = 0;
+    return(1);
+} /* MPGLIB_rewind */
+
+
+#endif /* SOUND_SUPPORTS_MPGLIB */
+
+
+/* end of mpglib.c ... */
+