Golang C.sf_command类(方法)实例源码

// Retrieve the log buffer generated when opening a file as a string. This log buffer can often contain a good reason for why libsndfile failed to open a particular file.
func (f *File) GetLogInfo() (s string, err error) {
	l := C.sf_command(f.s, C.SFC_GET_LOG_INFO, nil, 0)
	c := make([]byte, l)
	m := C.sf_command(f.s, C.SFC_GET_LOG_INFO, unsafe.Pointer(&c[0]), l)

	if m != l {
		c = c[0:m]
	}
	s = string(c)
	return
}

// GetLibVersion retrieves the version of the library as a string
func GetLibVersion() (s string, err error) {
	l := C.sf_command(nil, C.SFC_GET_LIB_VERSION, nil, 0)
	c := make([]byte, l)
	m := C.sf_command(nil, C.SFC_GET_LIB_VERSION, unsafe.Pointer(&c[0]), l)

	if m != l {
		err = errors.New(fmt.Sprintf("GetLibVersion: expected %d bytes in string, recv'd %d", l, m))
	}
	s = string(c)
	return
}

//Retrieve the peak value for the file as stored in the file header.
func (f *File) GetSignalMax() (ret float64, ok bool) {
	r := C.sf_command(f.s, C.SFC_GET_SIGNAL_MAX, unsafe.Pointer(&ret), 8)
	if r == C.SF_TRUE {
		ok = true
	}
	return
}

// Retrieve the measured normalised maximum signal value. This involves reading through the whole file which can be slow on large files.
func (f *File) CalcNormSignalMax() (ret float64, err error) {
	e := C.sf_command(f.s, C.SFC_CALC_NORM_SIGNAL_MAX, unsafe.Pointer(&ret), 8)
	if e != 0 {
		err = sErrorType(e)
	}
	return
}

// Return true if the file header contains instrument information for the file. false otherwise.
func (f *File) SetInstrument(i *Instrument) bool {
	c := new(C.SF_INSTRUMENT)
	c.gain = C.int(i.Gain)
	c.basenote = C.char(i.Basenote)
	c.detune = C.char(i.Detune)
	c.velocity_lo = C.char(i.Velocity[0])
	c.velocity_hi = C.char(i.Velocity[1])
	c.key_lo = C.char(i.Key[0])
	c.key_hi = C.char(i.Key[1])
	c.loop_count = C.int(i.LoopCount)
	var index int
	for ; index < i.LoopCount; index++ {
		c.loops[index].mode = C.int(i.Loops[index].Mode)
		c.loops[index].start = C.uint32_t(i.Loops[index].Start)
		c.loops[index].end = C.uint32_t(i.Loops[index].End)
		c.loops[index].count = C.uint32_t(i.Loops[index].Count)
	}
	for ; index < 16; index++ {
		c.loops[index].mode = C.int(None)
		// why is this necessary? libsndfile doesn't check loopcount for AIFF
	}

	r := C.sf_command(f.s, C.SFC_SET_INSTRUMENT, unsafe.Pointer(c), C.int(unsafe.Sizeof(*c)))
	return (r == C.SF_TRUE)
}

// This allows libsndfile experts to use the command interface for commands not currently supported. See http://www.mega-nerd.com/libsndfile/command.html
// The f argument may be nil in cases where the command does not require a SNDFILE argument.
// The method's cmd, data, and datasize arguments are used the same way as the correspondingly named arguments for sf_command
func GenericCmd(f *File, cmd C.int, data unsafe.Pointer, datasize int) int {
	var s *C.SNDFILE = nil
	if f != nil {
		s = f.s
	}
	return int(C.sf_command(s, cmd, data, C.int(datasize)))
}

//Set the the Variable Bit Rate encoding quality. The encoding quality value should be between 0.0 (lowest quality) and 1.0 (highest quality). Untested.
func (f *File) SetVbrQuality(q float64) (err error) {
	r := C.sf_command(f.s, C.SFC_SET_VBR_ENCODING_QUALITY, unsafe.Pointer(&q), 8)
	if r != 0 {
		err = errors.New(C.GoString(C.sf_strerror(f.s)))
	}
	return
}

// Set the Broadcast Extension Chunk from WAV (and related) files.
func (f *File) SetBroadcastInfo(bi *BroadcastInfo) (err error) {
	c := cFromBroadcast(bi)
	r := C.sf_command(f.s, C.SFC_SET_BROADCAST_INFO, unsafe.Pointer(c), C.int(unsafe.Sizeof(*c)))
	if r == C.SF_FALSE {
		err = errors.New(C.GoString(C.sf_strerror(f.s)))
	}
	return
}

//Change the data start offset for files opened up as SF_FORMAT_RAW. libsndfile implements this but it appears to not do anything useful that you can't accomplish with seek, so consider this deprecated.
func (f *File) SetRawStartOffset(count int64) (err error) {
	r := C.sf_command(f.s, C.SFC_SET_RAW_START_OFFSET, unsafe.Pointer(&count), 8)

	if r != 0 {
		err = errors.New(C.GoString(C.sf_strerror(f.s)))
	}
	return
}

// Truncates a file to /count/ frames.  After this command, both the read and the write pointer will be at the new end of the file. This command will fail (returning non-zero) if the requested truncate position is beyond the end of the file.
func (f *File) Truncate(count int64) (err error) {
	r := C.sf_command(f.s, C.SFC_FILE_TRUNCATE, unsafe.Pointer(&count), 8)

	if r != 0 {
		err = errors.New(C.GoString(C.sf_strerror(f.s)))
	}
	return
}

//Enumerate the subtypes (this function does not translate a subtype into a string describing that subtype). A typical use case might be retrieving a string description of all subtypes so that a dialog box can be filled in.
func GetSubFormatInfo(format int) (oformat int, name string, ok bool) {
	var o C.SF_FORMAT_INFO
	o.format = C.int(format)
	ok = (0 == C.sf_command(nil, C.SFC_GET_FORMAT_SUBTYPE, unsafe.Pointer(&o), C.int(unsafe.Sizeof(o))))
	oformat = int(o.format)
	name = C.GoString(o.name)
	return
}

func (f *File) genericBoolBoolCmd(cmd C.int, i bool) bool {
	ib := C.SF_FALSE
	if i {
		ib = C.SF_TRUE
	}

	n := C.sf_command(f.s, cmd, nil, C.int(ib))
	return (n == C.SF_TRUE)
}

//Retrieve information about a major format type
//For a more comprehensive example, see the program list_formats.c in the examples/ directory of the libsndfile source code distribution.
func GetMajorFormatInfo(format int) (oformat int, name string, extension string, ok bool) {
	var o C.SF_FORMAT_INFO
	o.format = C.int(format)
	ok = (0 == C.sf_command(nil, C.SFC_GET_FORMAT_MAJOR, unsafe.Pointer(&o), C.int(unsafe.Sizeof(o))))
	oformat = int(o.format)
	name = C.GoString(o.name)
	extension = C.GoString(o.extension)
	return
}

//Calculate the normalised peak for each channel. This involves reading through the whole file which can be slow on large files.
func (f *File) CalcNormMaxAllChannels() (ret []float64, err error) {
	c := f.Format.Channels
	ret = make([]float64, c)
	e := C.sf_command(f.s, C.SFC_CALC_NORM_MAX_ALL_CHANNELS, unsafe.Pointer(&ret[0]), C.int(c*8))
	if e != 0 {
		err = sErrorType(e)
	}
	return
}

//Retrieve the peak value for the file as stored in the file header.
func (f *File) GetMaxAllChannels() (ret []float64, ok bool) {
	c := f.Format.Channels
	ret = make([]float64, c)
	e := C.sf_command(f.s, C.SFC_GET_MAX_ALL_CHANNELS, unsafe.Pointer(&ret[0]), C.int(c*8))
	if e == C.SF_TRUE {
		ok = true
	}
	return
}

//Get the file offset and file length of a file enbedded within another larger file.
//The value of the offset return value will be the offsets in bytes from the start of the outer file to the start of the embedded audio file.
//The value of the length return value will be the length in bytes of the embedded file.
// Untested.
func (f *File) GetEmbeddedFileInfo() (offset, length int64, err error) {
	var s C.SF_EMBED_FILE_INFO
	r := C.sf_command(f.s, C.SFC_GET_EMBED_FILE_INFO, unsafe.Pointer(&s), C.int(unsafe.Sizeof(s)))
	if r != 0 {
		err = errors.New(C.GoString(C.sf_strerror(f.s)))
	}
	offset = int64(s.offset)
	length = int64(s.length)
	return
}

// Retrieve the Broadcast Extension Chunk from WAV (and related) files.
func (f *File) GetBroadcastInfo() (bi *BroadcastInfo, ok bool) {
	bic := new(C.SF_BROADCAST_INFO)

	r := C.sf_command(f.s, C.SFC_GET_BROADCAST_INFO, unsafe.Pointer(bic), C.int(unsafe.Sizeof(*bic)))
	if r == C.SF_TRUE {
		bi = broadcastFromC(bic)
		ok = true
	}
	return
}

// Returns populated structure if file contains loop info, otherwise nil. Untested.
func (f *File) GetLoopInfo() (i *LoopInfo) {
	c := new(C.SF_LOOP_INFO)
	r := C.sf_command(f.s, C.SFC_GET_LOOP_INFO, unsafe.Pointer(c), C.int(unsafe.Sizeof(*c)))
	if r == C.SF_TRUE {
		i = new(LoopInfo)
		i.TimeSig.Numerator = int16(c.time_sig_num)
		i.TimeSig.Denominator = int16(c.time_sig_den)
		i.Mode = LoopMode(c.loop_mode)
		i.Beats = int(c.num_beats)
		i.Bpm = float32(c.bpm)
		i.RootKey = int(c.root_key)
		for index, value := range c.future {
			i.Future[index] = int(value)
		}
	}
	return
}

// Return pointer to populated structure if the file header contains instrument information for the file. nil otherwise.
func (f *File) GetInstrument() (i *Instrument) {
	c := new(C.SF_INSTRUMENT)
	i = new(Instrument)
	r := C.sf_command(f.s, C.SFC_GET_INSTRUMENT, unsafe.Pointer(c), C.int(unsafe.Sizeof(*c)))
	if r == C.SF_TRUE {
		i.Gain = int(c.gain)
		i.Basenote = int8(c.basenote)
		i.Detune = int8(c.detune)
		i.Velocity[0] = int8(c.velocity_lo)
		i.Velocity[1] = int8(c.velocity_hi)
		i.Key[0] = int8(c.key_lo)
		i.Key[1] = int8(c.key_hi)
		i.LoopCount = int(c.loop_count)
		for index, loop := range c.loops {
			i.Loops[index].Mode = LoopMode(loop.mode)
			i.Loops[index].Start = uint(loop.start)
			i.Loops[index].End = uint(loop.end)
			i.Loops[index].Count = uint(loop.count)
		}
	}
	return
}

//Retrieve the number of major formats supported by libsndfile.
func GetMajorFormatCount() int {
	var o C.int
	C.sf_command(nil, C.SFC_GET_FORMAT_MAJOR_COUNT, unsafe.Pointer(&o), C.int(unsafe.Sizeof(o)))
	return int(o)
}