readers.c

mips上编译过的mpg 运行正常 环境：AU12

	free(bc->last);
	cur->next = NULL;
	bc->last  = cur;
}
#endif

/* Append a new buffer and copy content to it. */
static int bc_add(struct bufferchain *bc, unsigned char *data, ssize_t size)
{
	int ret = 0;
	if((ret = bc_append(bc, size)) == 0)
	memcpy(bc->last->data, data, size);

	return ret;
}

/* Give some data, advancing position but not forgetting yet. */
static ssize_t bc_give(struct bufferchain *bc, unsigned char *out, size_t size)
{
	struct buffy *b = bc->first;
	ssize_t gotcount = 0;
	ssize_t offset = 0;
	if(bc->size - bc->pos < size)
	{
		debug3("hit end, back to beginning (%li - %li < %li)", (long)bc->size, (long)bc->pos, (long)size);
		/* go back to firstpos, undo the previous reads */
		bc->pos = bc->firstpos;
		return READER_MORE;
	}
	/* find the current buffer */
	while(b != NULL && (offset + b->size) <= bc->pos)
	{
		offset += b->size;
		b = b->next;
	}
	/* now start copying from there */
	while(gotcount < size && (b != NULL))
	{
		ssize_t loff = bc->pos - offset;
		ssize_t chunk = size - gotcount; /* amount of bytes to get from here... */
		if(chunk > b->size - loff) chunk = b->size - loff;
		debug3("copying %liB from %p+%li",(long)chunk, b->data, (long)loff);
		memcpy(out+gotcount, b->data+loff, chunk);
		gotcount += chunk;
		bc->pos  += chunk;
		offset += b->size;
		b = b->next;
	}
	debug2("got %li bytes, pos advanced to %li", (long)gotcount, (long)bc->pos);

	return gotcount;
}

/* Skip some bytes and return the new position.
   The buffers are still there, just the read pointer is moved! */
static ssize_t bc_skip(struct bufferchain *bc, ssize_t count)
{
	if(count >= 0)
	{
		if(bc->size - bc->pos < count) return READER_MORE;
		else return bc->pos += count;
	}
	else return READER_ERROR;
}

static ssize_t bc_seekback(struct bufferchain *bc, ssize_t count)
{
	if(count >= 0 && count <= bc->pos) return bc->pos -= count;
	else return READER_ERROR;
}

/* Throw away buffies that we passed. */
static void bc_forget(struct bufferchain *bc)
{
	struct buffy *b = bc->first;
	/* free all buffers that are def'n'tly outdated */
	/* we have buffers until filepos... delete all buffers fully below it */
	if(b) debug2("bc_forget: block %lu pos %lu", (unsigned long)b->size, (unsigned long)bc->pos);
	else debug("forget with nothing there!");
	while(b != NULL && bc->pos >= b->size)
	{
		struct buffy *n = b->next; /* != NULL or this is indeed the end and the last cycle anyway */
		if(n == NULL) bc->last = NULL; /* Going to delete the last buffy... */
		bc->fileoff += b->size;
		bc->pos  -= b->size;
		bc->size -= b->size;
		debug5("bc_forget: forgot %p with %lu, pos=%li, size=%li, fileoff=%li", (void*)b->data, (long)b->size, (long)bc->pos,  (long)bc->size, (long)bc->fileoff);
		free(b->data);
		free(b);
		b = n;
	}
	bc->first = b;
	bc->firstpos = bc->pos;
}

/* reader for input via manually provided buffers */

static int feed_init(mpg123_handle *fr)
{
	bc_init(&fr->rdat.buffer);
	fr->rdat.filelen = 0;
	fr->rdat.filepos = 0;
	fr->rdat.flags |= READER_BUFFERED;
	return 0;
}

/* externally called function, returns 0 on success, -1 on error */
int feed_more(mpg123_handle *fr, unsigned char *in, long count)
{
	int ret = 0;
	debug("feed_more");
	if((ret = bc_add(&fr->rdat.buffer, in, count)) != 0)
	{
		ret = READER_ERROR;
		if(NOQUIET) error1("Failed to add buffer, return: %i", ret);
	}
	else /* Not talking about filelen... that stays at 0. */
	debug3("feed_more: %p %luB bufsize=%lu", fr->rdat.buffer.last->data,
		(unsigned long)fr->rdat.buffer.last->size, (unsigned long)fr->rdat.buffer.size);
	return ret;
}

static ssize_t feed_read(mpg123_handle *fr, unsigned char *out, ssize_t count)
{
	ssize_t gotcount = bc_give(&fr->rdat.buffer, out, count);
	if(gotcount >= 0 && gotcount != count) return READER_ERROR;
	else return gotcount;
}

/* returns reached position... negative ones are bad... */
static off_t feed_skip_bytes(mpg123_handle *fr,off_t len)
{
	return fr->rdat.buffer.fileoff+bc_skip(&fr->rdat.buffer, (ssize_t)len);
}

static int feed_back_bytes(mpg123_handle *fr, off_t bytes)
{
	if(bytes >=0)
	return bc_seekback(&fr->rdat.buffer, (ssize_t)bytes) >= 0 ? 0 : READER_ERROR;
	else
	return feed_skip_bytes(fr, -bytes) >= 0 ? 0 : READER_ERROR;
}

static int buffered_seek_frame(mpg123_handle *fr, off_t num){ return READER_ERROR; }

/* Not just for feed reader, also for self-feeding buffered reader. */
static void buffered_forget(mpg123_handle *fr)
{
	bc_forget(&fr->rdat.buffer);
	fr->rdat.filepos = fr->rdat.buffer.fileoff + fr->rdat.buffer.pos;
}

off_t feed_set_pos(mpg123_handle *fr, off_t pos)
{
	struct bufferchain *bc = &fr->rdat.buffer;
	if(pos >= bc->fileoff && pos-bc->fileoff < bc->size)
	{ /* We have the position! */
		bc->pos = (ssize_t)(pos - bc->fileoff);
		return pos+bc->size; /* Next input after end of buffer... */
	}
	else
	{ /* I expect to get the specific position on next feed. Forget what I have now. */
		bc_reset(bc);
		bc->fileoff = pos;
		return pos; /* Next input from exactly that position. */
	}
}

/* The specific stuff for buffered stream reader. */

/* Let's work in nice 4K blocks, that may be nicely reusable (by malloc(), even). */
#define BUFFBLOCK 4096
static ssize_t buffered_fullread(mpg123_handle *fr, unsigned char *out, ssize_t count)
{
	struct bufferchain *bc = &fr->rdat.buffer;
	ssize_t gotcount;
	if(bc->size - bc->pos < count)
	{ /* Add more stuff to buffer. If hitting end of file, adjust count. */
		unsigned char readbuf[BUFFBLOCK];
		ssize_t need = count - (bc->size-bc->pos);
		while(need>0)
		{
			int ret;
			ssize_t got = fr->rdat.fullread(fr, readbuf, BUFFBLOCK);
			if(got < 0)
			{
				if(NOQUIET) error("buffer reading");
				return READER_ERROR;
			}

			debug1("buffered_fullread: buffering %li bytes from stream (if > 0)", (long)got);
			if(got > 0 && (ret=bc_add(bc, readbuf, got)) != 0)
			{
				if(NOQUIET) error1("unable to add to chain, return: %i", ret);
				return READER_ERROR;
			}

			need -= got; /* May underflow here... */
			if(got < BUFFBLOCK) /* That naturally catches got == 0, too. */
			{
				if(VERBOSE3) fprintf(stderr, "Note: Input data end.\n");
				break; /* End. */
			}
		}
		if(bc->size - bc->pos < count)
		count = bc->size - bc->pos; /* We want only what we got. */
	}
	gotcount = bc_give(bc, out, count);
	debug2("wanted %li, got %li", (long)count, (long)gotcount);
	if(gotcount != count){ if(NOQUIET) error("gotcount != count"); return READER_ERROR; }
	else return gotcount;
}



/*****************************************************************
 * read frame helper
 */

#define bugger_off { mh->err = MPG123_NO_READER; return MPG123_ERR; }
int bad_init(mpg123_handle *mh) bugger_off
void bad_close(mpg123_handle *mh){}
ssize_t bad_fullread(mpg123_handle *mh, unsigned char *data, ssize_t count) bugger_off
int bad_head_read(mpg123_handle *mh, unsigned long *newhead) bugger_off
int bad_head_shift(mpg123_handle *mh, unsigned long *head) bugger_off
off_t bad_skip_bytes(mpg123_handle *mh, off_t len) bugger_off
int bad_read_frame_body(mpg123_handle *mh, unsigned char *data, int size) bugger_off
int bad_back_bytes(mpg123_handle *mh, off_t bytes) bugger_off
int bad_seek_frame(mpg123_handle *mh, off_t num) bugger_off
off_t bad_tell(mpg123_handle *mh) bugger_off
void bad_rewind(mpg123_handle *mh){}
#undef bugger_off

#define READER_STREAM 0
#define READER_ICY_STREAM 1
#define READER_FEED       2
#define READER_BUF_STREAM 3
#define READER_BUF_ICY_STREAM 4
struct reader readers[] =
{
	{ /* READER_STREAM */
		default_init,
		stream_close,
		plain_fullread,
		generic_head_read,
		generic_head_shift,
		stream_skip_bytes,
		generic_read_frame_body,
		stream_back_bytes,
		stream_seek_frame,
		generic_tell,
		stream_rewind,
		NULL
	} ,
	{ /* READER_ICY_STREAM */
		default_init,
		stream_close,
		icy_fullread,
		generic_head_read,
		generic_head_shift,
		stream_skip_bytes,
		generic_read_frame_body,
		stream_back_bytes,
		stream_seek_frame,
		generic_tell,
		stream_rewind,
		NULL
	},
	{ /* READER_FEED */
		feed_init,
		stream_close,
		feed_read,
		generic_head_read,
		generic_head_shift,
		feed_skip_bytes,
		generic_read_frame_body,
		feed_back_bytes,
		buffered_seek_frame,
		generic_tell,
		stream_rewind,
		buffered_forget
	},
	{ /* READER_BUF_STREAM */
		default_init,
		stream_close,
		buffered_fullread,
		generic_head_read,
		generic_head_shift,
		stream_skip_bytes,
		generic_read_frame_body,
		stream_back_bytes,
		buffered_seek_frame,
		generic_tell,
		stream_rewind,
		buffered_forget
	} ,
	{ /* READER_BUF_ICY_STREAM */
		default_init,
		stream_close,
		buffered_fullread,
		generic_head_read,
		generic_head_shift,
		stream_skip_bytes,
		generic_read_frame_body,
		stream_back_bytes,
		buffered_seek_frame,
		generic_tell,
		stream_rewind,
		buffered_forget
	},
#ifdef READ_SYSTEM
	,{
		system_init,
		NULL,	/* filled in by system_init() */
		fullread,
		NULL,
		NULL,
		NULL,
		NULL,
		NULL,
		NULL,
		NULL,
		NULL,
		NULL,
	}
#endif
};

struct reader bad_reader =
{
	bad_init,
	bad_close,
	bad_fullread,
	bad_head_read,
	bad_head_shift,
	bad_skip_bytes,
	bad_read_frame_body,
	bad_back_bytes,
	bad_seek_frame,
	bad_tell,
	bad_rewind,
	NULL
};

static int default_init(mpg123_handle *fr)
{
#ifndef WIN32
	if(fr->p.timeout > 0)
	{
		fcntl(fr->rdat.filept, F_SETFL, O_NONBLOCK);
		fr->rdat.fdread = timeout_read;
		fr->rdat.timeout_sec = fr->p.timeout;
		fr->rdat.flags |= READER_NONBLOCK;
	}
	else
#endif
	fr->rdat.fdread = plain_read;

	fr->rdat.read  = fr->rdat.r_read  != NULL ? fr->rdat.r_read  : posix_read;
	fr->rdat.lseek = fr->rdat.r_lseek != NULL ? fr->rdat.r_lseek : posix_lseek;
	fr->rdat.filelen = get_fileinfo(fr);
	fr->rdat.filepos = 0;
	if(fr->rdat.filelen >= 0)
	{
		fr->rdat.flags |= READER_SEEKABLE;
		if(!strncmp((char*)fr->id3buf,"TAG",3))
		{
			fr->rdat.flags |= READER_ID3TAG;
			fr->metaflags  |= MPG123_NEW_ID3;
		}
	}
	/* Switch reader to a buffered one, if allowed. */
	else if(fr->p.flags & MPG123_SEEKBUFFER)
	{
		if     (fr->rd == &readers[READER_STREAM])
		{
			fr->rd = &readers[READER_BUF_STREAM];
			fr->rdat.fullread = plain_fullread;
		}
		else if(fr->rd == &readers[READER_ICY_STREAM])
		{
			fr->rd = &readers[READER_BUF_ICY_STREAM];
			fr->rdat.fullread = icy_fullread;
		}
		else
		{
			if(NOQUIET) error("mpg123 Programmer's fault: invalid reader");
			return -1;
		}
		bc_init(&fr->rdat.buffer);
		fr->rdat.filelen = 0; /* We carry the offset, but never know how big the stream is. */
		fr->rdat.flags |= READER_BUFFERED;
	}
	return 0;
}


void open_bad(mpg123_handle *mh)
{
	clear_icy(&mh->icy);
	mh->rd = &bad_reader;
	mh->rdat.flags = 0;
	bc_init(&mh->rdat.buffer);
}

int open_feed(mpg123_handle *fr)
{
	debug("feed reader");
	clear_icy(&fr->icy);
	fr->rd = &readers[READER_FEED];
	fr->rdat.flags = 0;
	if(fr->rd->init(fr) < 0) return -1;
	return 0;
}

int open_stream(mpg123_handle *fr, char *bs_filenam, int fd)
{
	int filept_opened = 1;
	int filept; /* descriptor of opened file/stream */

	clear_icy(&fr->icy); /* can be done inside frame_clear ...? */
	if(!bs_filenam) /* no file to open, got a descriptor (stdin) */
	{
		filept = fd;
		filept_opened = 0; /* and don't try to close it... */
	}
	#ifndef O_BINARY
	#define O_BINARY (0)
	#endif
	else if((filept = open(bs_filenam, O_RDONLY|O_BINARY)) < 0) /* a plain old file to open... */
	{
		if(NOQUIET) error2("Cannot file %s: %s", bs_filenam, strerror(errno));
		fr->err = MPG123_BAD_FILE;
		return filept; /* error... */
	}

	/* now we have something behind filept and can init the reader */
	fr->rdat.filelen = -1;
	fr->rdat.filept  = filept;
	fr->rdat.flags = 0;
	if(filept_opened)	fr->rdat.flags |= READER_FD_OPENED;

	if(fr->p.icy_interval > 0)
	{
		debug("ICY reader");
		fr->icy.interval = fr->p.icy_interval;
		fr->icy.next = fr->icy.interval;
		fr->rd = &readers[READER_ICY_STREAM];
	}
	else
	{
		fr->rd = &readers[READER_STREAM];
		debug("stream reader");
	}

	if(fr->rd->init(fr) < 0) return -1;

	return MPG123_OK;
}