From 83b222427d80c325b6f30e6693fbc5c05d8fa11f Mon Sep 17 00:00:00 2001
From: Andre Noll <maan@systemlinux.org>
Date: Mon, 4 Jan 2010 18:37:35 +0100
Subject: [PATCH 1/1] amp filter improvements.

If amp == 0, this filter now splices itself out of the buffer tree.
---
 amp_filter.c | 50 ++++++++++++++++++++++++++++----------------------
 error.h      |  1 +
 2 files changed, 29 insertions(+), 22 deletions(-)

diff --git a/amp_filter.c b/amp_filter.c
index 0ed2d8e0..c0835f80 100644
--- a/amp_filter.c
+++ b/amp_filter.c
@@ -90,6 +90,7 @@ static void amp_open(struct filter_node *fn)
 
 	pad->conf = fn->conf;
 	fn->private_data = pad;
+	fn->min_iqs = 2;
 	if (!pad->conf->amp_given && stat_item_values[SI_AMPLIFICATION])
 		sscanf(stat_item_values[SI_AMPLIFICATION], "%u", &pad->amp);
 	else
@@ -104,47 +105,52 @@ static void amp_post_select(__a_unused struct sched *s, struct task *t)
 	struct private_amp_data *pad = fn->private_data;
 	struct btr_node *btrn = fn->btrn;
 	int ret, factor = 64 + pad->amp;
-	char *in;
-	size_t in_len = btr_next_buffer(btrn, &in);
-	size_t i, length = in_len / 2;
-	int16_t *ip = (int16_t *)in, *op;
+	size_t i, in_bytes, len;
+	int16_t *in, *out;
 	bool inplace = btr_inplace_ok(btrn);
 
+	if (pad->amp == 0) { /* no amplification */
+		t->error = -E_AMP_ZERO_AMP;
+		btr_splice_out_node(btrn);
+		amp_close(fn);
+		return;
+	}
+next_buffer:
 	ret = prepare_filter_node(fn);
+	in_bytes = btr_next_buffer(btrn, (char **)&in);
 	if (ret < 0)
 		goto err;
-	if (ret == 0)
+	len = in_bytes / 2;
+	/* len == 0 happens if eof and in_bytes == 1. */
+	if (ret == 0 || len == 0)
 		return;
 
 	if (inplace)
-		op = ip;
+		out = in;
 	else
-		op = para_malloc(length * 2);
-	if (pad->amp == 0) {
-		memcpy(op, ip, length * 2);
-		goto success;
-	}
-	for (i = 0; i < length; i++) {
-		int x = (ip[i] * factor) >> 6;
+		out = para_malloc(len * 2);
 
-		op[i] = x;
-		if (op[i] != x)
-			op[i] = (x >= 32768)? 32767 : -32768;
+	for (i = 0; i < len; i++) {
+		int x = (in[i] * factor) >> 6;
+
+		out[i] = x;
+		if (out[i] != x) /* overflow, clip */
+			out[i] = (x >= 0)? 32767 : -32768;
 	}
-success:
-	t->error = 0;
+
 	if (inplace)
 		btr_pushdown_one(btrn);
 	else {
-		btr_consume(btrn, length * 2);
-		btr_add_output((char *)op, length * 2, btrn);
+		btr_consume(btrn, len * 2);
+		btr_add_output((char *)out, len * 2, btrn);
 	}
-	return;
+	t->error = 0;
+	goto next_buffer;
 err:
 	assert(ret < 0);
-	amp_close(fn);
 	t->error = ret;
 	btr_del_node(btrn);
+	amp_close(fn);
 }
 
 /**
diff --git a/error.h b/error.h
index fd0213b2..1a2b3a4c 100644
--- a/error.h
+++ b/error.h
@@ -106,6 +106,7 @@ extern const char **para_errlist[];
 
 #define AMP_FILTER_ERRORS \
 	PARA_ERROR(AMP_SYNTAX, "syntax error in amp filter config"), \
+	PARA_ERROR(AMP_ZERO_AMP, "no amplification necessary"), \
 
 
 #define SEND_COMMON_ERRORS \
-- 
2.39.2