*: add "noexcept" to many, many function prototypes

This eliminates some overhead, because the compiler doesn't need to
consider these functions throwing.

src/mixer/MixerAll.cxx

@@ -30,8 +30,9 @@
 
 #include <assert.h>
 
+gcc_pure
 static int
-output_mixer_get_volume(const AudioOutput &ao)
+output_mixer_get_volume(const AudioOutput &ao) noexcept
 {
 	if (!ao.enabled)
 		return -1;
@@ -51,7 +52,7 @@ output_mixer_get_volume(const AudioOutput &ao)
 }
 
 int
-MultipleOutputs::GetVolume() const
+MultipleOutputs::GetVolume() const noexcept
 {
 	unsigned ok = 0;
 	int total = 0;
@@ -71,7 +72,7 @@ MultipleOutputs::GetVolume() const
 }
 
 static bool
-output_mixer_set_volume(AudioOutput &ao, unsigned volume)
+output_mixer_set_volume(AudioOutput &ao, unsigned volume) noexcept
 {
 	assert(volume <= 100);
 
@@ -94,7 +95,7 @@ output_mixer_set_volume(AudioOutput &ao, unsigned volume)
 }
 
 bool
-MultipleOutputs::SetVolume(unsigned volume)
+MultipleOutputs::SetVolume(unsigned volume) noexcept
 {
 	assert(volume <= 100);
 
@@ -107,7 +108,7 @@ MultipleOutputs::SetVolume(unsigned volume)
 }
 
 static int
-output_mixer_get_software_volume(const AudioOutput &ao)
+output_mixer_get_software_volume(const AudioOutput &ao) noexcept
 {
 	if (!ao.enabled)
 		return -1;
@@ -120,7 +121,7 @@ output_mixer_get_software_volume(const AudioOutput &ao)
 }
 
 int
-MultipleOutputs::GetSoftwareVolume() const
+MultipleOutputs::GetSoftwareVolume() const noexcept
 {
 	unsigned ok = 0;
 	int total = 0;
@@ -140,7 +141,7 @@ MultipleOutputs::GetSoftwareVolume() const
 }
 
 void
-MultipleOutputs::SetSoftwareVolume(unsigned volume)
+MultipleOutputs::SetSoftwareVolume(unsigned volume) noexcept
 {
 	assert(volume <= PCM_VOLUME_1);
 

src/mixer/MixerType.cxx

@@ -24,7 +24,7 @@
 #include <string.h>
 
 MixerType
-mixer_type_parse(const char *input)
+mixer_type_parse(const char *input) noexcept
 {
 	assert(input != NULL);
 

src/mixer/MixerType.hxx

@@ -20,6 +20,8 @@
 #ifndef MPD_MIXER_TYPE_HXX
 #define MPD_MIXER_TYPE_HXX
 
+#include "Compiler.h"
+
 enum class MixerType {
 	/** parser error */
 	UNKNOWN,
@@ -44,7 +46,8 @@ enum class MixerType {
  * a #MixerType value; #MixerType::UNKNOWN means #input could not be
  * parsed
  */
+gcc_pure
 MixerType
-mixer_type_parse(const char *input);
+mixer_type_parse(const char *input) noexcept;
 
 #endif

src/mixer/Volume.cxx

@@ -42,14 +42,14 @@ static int last_hardware_volume = -1;
 static PeriodClock hardware_volume_clock;
 
 void
-InvalidateHardwareVolume()
+InvalidateHardwareVolume() noexcept
 {
 	/* flush the hardware volume cache */
 	last_hardware_volume = -1;
 }
 
 int
-volume_level_get(const MultipleOutputs &outputs)
+volume_level_get(const MultipleOutputs &outputs) noexcept
 {
 	if (last_hardware_volume >= 0 &&
 	    !hardware_volume_clock.CheckUpdate(std::chrono::seconds(1)))
@@ -118,7 +118,7 @@ save_sw_volume_state(BufferedOutputStream &os)
 }
 
 unsigned
-sw_volume_state_get_hash(void)
+sw_volume_state_get_hash() noexcept
 {
 	return volume_software_set;
 }

src/mixer/Volume.hxx

@@ -26,11 +26,11 @@ class MultipleOutputs;
 class BufferedOutputStream;
 
 void
-InvalidateHardwareVolume();
+InvalidateHardwareVolume() noexcept;
 
 gcc_pure
 int
-volume_level_get(const MultipleOutputs &outputs);
+volume_level_get(const MultipleOutputs &outputs) noexcept;
 
 bool
 volume_level_change(MultipleOutputs &outputs, unsigned volume);
@@ -49,6 +49,6 @@ save_sw_volume_state(BufferedOutputStream &os);
  */
 gcc_pure
 unsigned
-sw_volume_state_get_hash();
+sw_volume_state_get_hash() noexcept;
 
 #endif

src/mixer/plugins/AlsaMixerPlugin.cxx

@@ -201,7 +201,8 @@ AlsaMixer::~AlsaMixer()
 
 gcc_pure
 static snd_mixer_elem_t *
-alsa_mixer_lookup_elem(snd_mixer_t *handle, const char *name, unsigned idx)
+alsa_mixer_lookup_elem(snd_mixer_t *handle,
+		       const char *name, unsigned idx) noexcept
 {
 	for (snd_mixer_elem_t *elem = snd_mixer_first_elem(handle);
 	     elem != nullptr; elem = snd_mixer_elem_next(elem)) {

src/mixer/plugins/SoftwareMixerPlugin.cxx

@@ -71,7 +71,7 @@ software_mixer_init(gcc_unused EventLoop &event_loop,
 
 gcc_const
 static unsigned
-PercentVolumeToSoftwareVolume(unsigned volume)
+PercentVolumeToSoftwareVolume(unsigned volume) noexcept
 {
 	assert(volume <= 100);