From d868c56eb7c65b2c5a287998b08201986e361c5f Mon Sep 17 00:00:00 2001
Message-Id: <d868c56eb7c65b2c5a287998b08201986e361c5f.1715081652.git.mdw@distorted.org.uk>
From: Mark Wooding <mdw@chiark.greenend.org.uk>
Date: Mon, 7 Jun 2010 22:15:04 +0100
Subject: [PATCH] Hands-off reading for FLAC.
Organization: Straylight/Edgeware

From: Richard Kettlewell <richard@kakajou.wlan.anjou.terraraq.org.uk>

---
 lib/hreader.h   | 20 ++++++++++++++
 server/decode.c | 70 ++++++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 86 insertions(+), 4 deletions(-)

diff --git a/lib/hreader.h b/lib/hreader.h
index 46f8bd9..9e9a91c 100644
--- a/lib/hreader.h
+++ b/lib/hreader.h
@@ -69,6 +69,26 @@ int hreader_pread(struct hreader *h, void *buffer, size_t n, off_t offset);
  */
 off_t hreader_seek(struct hreader *h, off_t offset, int whence);
 
+/** @brief Return file size
+ * @param h Reader to find size of
+ * @return Size in bytes
+ */
+static inline off_t hreader_size(const struct hreader *h) {
+  return h->size;
+}
+
+/** @brief Test for end of file
+ * @param h Reader to test
+ * @return 1 at eof, 0 otherwise
+ *
+ * This tells you whether the next read will return 0 bytes, rather than
+ * whether the last read reached end of file.  So it is slightly different to
+ * feof().
+ */
+static inline int hreader_eof(const struct hreader *h) {
+  return h->read_offset == h->size;
+}
+
 #endif /* HREADER_H */
 
 /*
diff --git a/server/decode.c b/server/decode.c
index 19f7f3a..303fef0 100644
--- a/server/decode.c
+++ b/server/decode.c
@@ -397,18 +397,80 @@ static FLAC__StreamDecoderWriteStatus flac_write
   return FLAC__STREAM_DECODER_WRITE_STATUS_CONTINUE;
 }
 
+static FLAC__StreamDecoderReadStatus flac_read(const FLAC__StreamDecoder attribute((unused)) *decoder,
+                                               FLAC__byte buffer[],
+                                               size_t *bytes,
+                                               void *client_data) {
+  struct hreader *flacinput = client_data;
+  int n = hreader_read(flacinput, buffer, *bytes);
+  if(n == 0) {
+    *bytes = 0;
+    return FLAC__STREAM_DECODER_READ_STATUS_END_OF_STREAM;
+  }
+  if(n < 0) {
+    *bytes = 0;
+    return FLAC__STREAM_DECODER_READ_STATUS_ABORT;
+  }
+  *bytes = n;
+  return FLAC__STREAM_DECODER_READ_STATUS_CONTINUE;
+}
+
+static FLAC__StreamDecoderSeekStatus flac_seek(const FLAC__StreamDecoder attribute((unused)) *decoder,
+                                               FLAC__uint64 absolute_byte_offset, 
+                                               void *client_data) {
+  struct hreader *flacinput = client_data;
+  if(hreader_seek(flacinput, absolute_byte_offset, SEEK_SET) < 0)
+    return FLAC__STREAM_DECODER_SEEK_STATUS_ERROR;
+  else
+    return FLAC__STREAM_DECODER_SEEK_STATUS_OK;
+}
+
+static FLAC__StreamDecoderTellStatus flac_tell(const FLAC__StreamDecoder attribute((unused)) *decoder, 
+                                               FLAC__uint64 *absolute_byte_offset,
+                                               void *client_data) {
+  struct hreader *flacinput = client_data;
+  off_t offset = hreader_seek(flacinput, 0, SEEK_CUR);
+  if(offset < 0)
+    return FLAC__STREAM_DECODER_TELL_STATUS_ERROR;
+  *absolute_byte_offset = offset;
+  return FLAC__STREAM_DECODER_TELL_STATUS_OK;
+}
+
+static FLAC__StreamDecoderLengthStatus flac_length(const FLAC__StreamDecoder attribute((unused)) *decoder, 
+                                                   FLAC__uint64 *stream_length, 
+                                                   void *client_data) {
+  struct hreader *flacinput = client_data;
+  *stream_length = hreader_size(flacinput);
+  return FLAC__STREAM_DECODER_LENGTH_STATUS_OK;
+}
+
+static FLAC__bool flac_eof(const FLAC__StreamDecoder attribute((unused)) *decoder, 
+                           void *client_data) {
+  struct hreader *flacinput = client_data;
+  return hreader_eof(flacinput);
+}
 
 /** @brief FLAC file decoder */
 static void decode_flac(void) {
   FLAC__StreamDecoder *sd = FLAC__stream_decoder_new();
   FLAC__StreamDecoderInitStatus is;
+  struct hreader flacinput[1];
 
   if (!sd)
     disorder_fatal(0, "FLAC__stream_decoder_new failed");
-
-  if((is = FLAC__stream_decoder_init_file(sd, path, flac_write, flac_metadata,
-                                          flac_error, 0)))
-    disorder_fatal(0, "FLAC__stream_decoder_init_file %s: %s",
+  if(hreader_init(path, flacinput))
+    disorder_fatal(errno, "error opening %s", path);
+
+  if((is = FLAC__stream_decoder_init_stream(sd,
+                                            flac_read,
+                                            flac_seek,
+                                            flac_tell,
+                                            flac_length,
+                                            flac_eof,
+                                            flac_write, flac_metadata,
+                                            flac_error, 
+                                            flacinput)))
+    disorder_fatal(0, "FLAC__stream_decoder_init_stream %s: %s",
                    path, FLAC__StreamDecoderInitStatusString[is]);
 
   FLAC__stream_decoder_process_until_end_of_stream(sd);
-- 
[mdw]