From e565dcf18c3a2f64d439dcbcd6c324ef84a25441 Mon Sep 17 00:00:00 2001
From: Max Kellermann <max@musicpd.org>
Date: Tue, 14 Jan 2020 17:41:07 +0100
Subject: [PATCH] pcm/dsd2pcm: convert to C++

---
 src/pcm/{dsd2pcm/dsd2pcm.c => Dsd2Pcm.cxx} | 29 +++++++++++++---------
 src/pcm/{dsd2pcm/dsd2pcm.h => Dsd2Pcm.hxx} | 10 +-------
 src/pcm/PcmDsd.cxx                         |  2 +-
 src/pcm/meson.build                        |  2 +-
 4 files changed, 20 insertions(+), 23 deletions(-)
 rename src/pcm/{dsd2pcm/dsd2pcm.c => Dsd2Pcm.cxx} (90%)
 rename src/pcm/{dsd2pcm/dsd2pcm.h => Dsd2Pcm.hxx} (95%)

diff --git a/src/pcm/dsd2pcm/dsd2pcm.c b/src/pcm/Dsd2Pcm.cxx
similarity index 90%
rename from src/pcm/dsd2pcm/dsd2pcm.c
rename to src/pcm/Dsd2Pcm.cxx
index f089102ef..feb7f25e3 100644
--- a/src/pcm/dsd2pcm/dsd2pcm.c
+++ b/src/pcm/Dsd2Pcm.cxx
@@ -2,6 +2,8 @@
 
 Copyright 2009, 2011 Sebastian Gesemann. All rights reserved.
 
+Copyright 2020 Max Kellermann <max.kellermann@gmail.com>
+
 Redistribution and use in source and binary forms, with or without modification, are
 permitted provided that the following conditions are met:
 
@@ -28,21 +30,25 @@ or implied, of Sebastian Gesemann.
 
  */
 
+#include "Dsd2Pcm.hxx"
 #include "util/bit_reverse.h"
 
 #include <stdlib.h>
 #include <string.h>
 
-#include "dsd2pcm.h"
+/** number of FIR constants */
+static constexpr size_t HTAPS = 48;
 
-#define HTAPS    48             /* number of FIR constants */
-#define FIFOSIZE 16             /* must be a power of two */
-#define FIFOMASK (FIFOSIZE-1)   /* bit mask for FIFO offsets */
-#define CTABLES ((HTAPS+7)/8)   /* number of "8 MACs" lookup tables */
+/** number of "8 MACs" lookup tables */
+static constexpr int CTABLES = (HTAPS + 7) / 8;
 
-#if FIFOSIZE*8 < HTAPS*2
-#error "FIFOSIZE too small"
-#endif
+/* must be a power of two */
+static constexpr int FIFOSIZE = 16;
+
+/** bit mask for FIFO offsets */
+static constexpr size_t FIFOMASK = FIFOSIZE - 1;
+
+static_assert(FIFOSIZE*8 >= HTAPS*2, "FIFOSIZE too small");
 
 /*
  * Properties of this 96-tap lowpass filter when applied on a signal
@@ -64,7 +70,7 @@ or implied, of Sebastian Gesemann.
 /*
  * The 2nd half (48 coeffs) of a 96-tap symmetric lowpass filter
  */
-static const double htaps[HTAPS] = {
+static constexpr double htaps[HTAPS] = {
   0.09950731974056658,
   0.09562845727714668,
   0.08819647126516944,
@@ -118,7 +124,7 @@ static const double htaps[HTAPS] = {
 static float ctables[CTABLES][256];
 static int precalculated = 0;
 
-static void precalc(void)
+static void precalc()
 {
 	int t, e, m, k;
 	double acc;
@@ -143,7 +149,7 @@ struct dsd2pcm_ctx_s
 	unsigned fifopos;
 };
 
-extern dsd2pcm_ctx* dsd2pcm_init(void)
+extern dsd2pcm_ctx* dsd2pcm_init()
 {
 	dsd2pcm_ctx* ptr;
 	if (!precalculated) precalc();
@@ -211,4 +217,3 @@ extern void dsd2pcm_translate(
 	}
 	ptr->fifopos = ffp;
 }
-
diff --git a/src/pcm/dsd2pcm/dsd2pcm.h b/src/pcm/Dsd2Pcm.hxx
similarity index 95%
rename from src/pcm/dsd2pcm/dsd2pcm.h
rename to src/pcm/Dsd2Pcm.hxx
index 4267b42c3..a56ff92cc 100644
--- a/src/pcm/dsd2pcm/dsd2pcm.h
+++ b/src/pcm/Dsd2Pcm.hxx
@@ -33,10 +33,6 @@ or implied, of Sebastian Gesemann.
 
 #include <stddef.h>
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 struct dsd2pcm_ctx_s;
 
 typedef struct dsd2pcm_ctx_s dsd2pcm_ctx;
@@ -49,7 +45,7 @@ typedef struct dsd2pcm_ctx_s dsd2pcm_ctx;
  * POSIX thread-safety definition because it modifies global state
  * (lookup tables are computed during the first call)
  */
-extern dsd2pcm_ctx* dsd2pcm_init(void);
+extern dsd2pcm_ctx* dsd2pcm_init();
 
 /**
  * deinitializes a "dsd2pcm engine"
@@ -85,9 +81,5 @@ extern void dsd2pcm_translate(dsd2pcm_ctx *ctx,
 	int lsbitfirst,
 	float *dst, ptrdiff_t dst_stride);
 
-#ifdef __cplusplus
-} /* extern "C" */
-#endif
-
 #endif /* include guard DSD2PCM_H_INCLUDED */
 
diff --git a/src/pcm/PcmDsd.cxx b/src/pcm/PcmDsd.cxx
index b608bc9dd..0d8a65232 100644
--- a/src/pcm/PcmDsd.cxx
+++ b/src/pcm/PcmDsd.cxx
@@ -18,7 +18,7 @@
  */
 
 #include "PcmDsd.hxx"
-#include "dsd2pcm/dsd2pcm.h"
+#include "Dsd2Pcm.hxx"
 #include "util/ConstBuffer.hxx"
 
 #include <assert.h>
diff --git a/src/pcm/meson.build b/src/pcm/meson.build
index 1f8bf6c38..0ee8b6766 100644
--- a/src/pcm/meson.build
+++ b/src/pcm/meson.build
@@ -28,7 +28,7 @@ if get_option('dsd')
     'Dsd16.cxx',
     'Dsd32.cxx',
     'PcmDsd.cxx',
-    'dsd2pcm/dsd2pcm.c',
+    'Dsd2Pcm.cxx',
   ]
 endif