From: Andre Noll <maan@systemlinux.org>
Date: Sat, 7 Aug 2010 15:46:44 +0000 (+0200)
Subject: Compute the maximal chunk size only once.
X-Git-Tag: v0.4.5~17
X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=commitdiff_plain;h=12379df1a1f89645e04c393d614937c0e6439ae0;ds=sidebyside

Compute the maximal chunk size only once.

This patch adds the new field max_chunk_size to struct audio_file_data.
It is initialized in the afs process when the chunk table is saved,
just before the audio_file_data struct is passed to the server process.

The vss code benefits from this change since it can just use the
new information rather than calling afh_get_largest_chunk_size()
to recompute the maximal chunk size from scratch whenever a new
client connects.

Since vss.c was the only user of afh_get_largest_chunk_size(), we
may kill this function.
---

diff --git a/afh.h b/afh.h
index 6dfd03ed..ccfed2fb 100644
--- a/afh.h
+++ b/afh.h
@@ -104,5 +104,4 @@ int compute_afhi(const char *path, char *data, size_t size,
 const char *audio_format_name(int);
 void afh_get_chunk(long unsigned chunk_num, struct afh_info *afhi,
 		void *map, const char **buf, size_t *len);
-uint32_t afh_get_largest_chunk_size(struct afh_info *afhi);
 void afh_get_header(struct afh_info *afhi, void *map, const char **buf, size_t *len);
diff --git a/afh_common.c b/afh_common.c
index 4464987a..952ef7ca 100644
--- a/afh_common.c
+++ b/afh_common.c
@@ -245,22 +245,6 @@ void afh_get_chunk(long unsigned chunk_num, struct afh_info *afhi,
 	*len = afhi->chunk_table[chunk_num + 1] - pos;
 }
 
-/**
- * Compute the size of the largest chunk of an audio file.
- *
- * \param afhi The audio format handler struct containing the chunk table.
- *
- * \return The number of bytes of the largest chunk.
- */
-uint32_t afh_get_largest_chunk_size(struct afh_info *afhi)
-{
-	uint32_t n, largest = 0, *ct = afhi->chunk_table;
-
-	for (n = 1; n <= afhi->chunks_total; n++)
-		largest = PARA_MAX(largest, ct[n] - ct[n - 1]);
-	return largest;
-}
-
 /**
  * Get the header of an audio file.
  *
diff --git a/afs.h b/afs.h
index 76b81905..ba5e134c 100644
--- a/afs.h
+++ b/afs.h
@@ -129,6 +129,8 @@ struct audio_file_data {
 	int fd;
 	/** Vss needs this for streaming. */
 	struct afh_info afhi;
+	/** Size of the largest chunk. */
+	uint32_t max_chunk_size;
 };
 
 /**
diff --git a/aft.c b/aft.c
index eb0f7b57..aa6ef08f 100644
--- a/aft.c
+++ b/aft.c
@@ -434,12 +434,26 @@ static unsigned sizeof_chunk_table(struct afh_info *afhi)
 	return 4 * (afhi->chunks_total + 1);
 }
 
-static void save_chunk_table(struct afh_info *afhi, char *buf)
+static uint32_t save_chunk_table(struct afh_info *afhi, char *buf)
 {
 	int i;
-
-	for (i = 0; i <= afhi->chunks_total; i++)
-		write_u32(buf + 4 * i, afhi->chunk_table[i]);
+	uint32_t max = 0, old = 0;
+
+	for (i = 0; i <= afhi->chunks_total; i++) {
+		uint32_t val = afhi->chunk_table[i];
+		write_u32(buf + 4 * i, val);
+		/*
+		 * If the first chunk is the header, do not consider it for the
+		 * calculation of the largest chunk size.
+		 */
+		if (i == 0 || (i == 1 && afhi->header_len > 0)) {
+			old = val;
+			continue;
+		}
+		max = PARA_MAX(max, val - old);
+		old = val;
+	}
+	return max;
 }
 
 static void load_chunk_table(struct afh_info *afhi, char *buf)
@@ -640,10 +654,10 @@ static int save_afd(struct audio_file_data *afd)
 	ret = shm_attach(shmid, ATTACH_RW, &shm_afd);
 	if (ret < 0)
 		goto err;
-	*(struct audio_file_data *)shm_afd = *afd;
 	buf = shm_afd;
 	buf += sizeof(*afd);
-	save_chunk_table(&afd->afhi, buf);
+	afd->max_chunk_size = save_chunk_table(&afd->afhi, buf);
+	*(struct audio_file_data *)shm_afd = *afd;
 	shm_detach(shm_afd);
 	return shmid;
 err:
diff --git a/vss.c b/vss.c
index 25082834..383a8fda 100644
--- a/vss.c
+++ b/vss.c
@@ -283,8 +283,7 @@ static int initialize_fec_client(struct fec_client *fc, struct vss_task *vsst)
 	if (ret < 0)
 		goto err;
 	hs = ret;
-	ret = num_slices(afh_get_largest_chunk_size(&mmd->afd.afhi),
-		mps, rs);
+	ret = num_slices(mmd->afd.max_chunk_size, mps, rs);
 	if (ret < 0)
 		goto err;
 	ds = ret;