86 lines
1.8 KiB
Go
86 lines
1.8 KiB
Go
package iconv
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import (
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"io"
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"os"
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)
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type Writer struct {
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destination io.Writer
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converter *Converter
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buffer []byte
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readPos, writePos int
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err os.Error
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}
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func NewWriter(destination io.Writer, fromEncoding string, toEncoding string) (*Writer, os.Error) {
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// create a converter
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converter, err := NewConverter(fromEncoding, toEncoding)
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if err == nil {
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return NewWriterFromConverter(destination, converter), err
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}
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// return the error
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return nil, err
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}
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func NewWriterFromConverter(destination io.Writer, converter *Converter) (writer *Writer) {
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writer = new(Writer)
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// copy elements
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writer.destination = destination
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writer.converter = converter
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// create 8K buffers
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writer.buffer = make([]byte, 8 * 1024)
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return writer
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}
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func (this *Writer) emptyBuffer() {
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// write new data out of buffer
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bytesWritten, err := this.destination.Write(this.buffer[this.readPos:this.writePos])
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// update read position
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this.readPos += bytesWritten
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// slide existing data to beginning
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if this.readPos > 0 {
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// copy current bytes - is this guaranteed safe?
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copy(this.buffer, this.buffer[this.readPos:this.writePos])
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// adjust positions
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this.writePos -= this.readPos
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this.readPos = 0
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}
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// track any reader error / EOF
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if err != nil {
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this.err = err
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}
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}
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// implement the io.Writer interface
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func (this *Writer) Write(p []byte) (n int, err os.Error) {
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// write data into our internal buffer
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bytesRead, bytesWritten, err := this.converter.Convert(p, this.buffer[this.writePos:])
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// update bytes written for return
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n += bytesRead
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this.writePos += bytesWritten
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// checks for when we have a full buffer
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for this.writePos > 0 {
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// if we have an error, just return it
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if this.err != nil {
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return
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}
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// else empty the buffer
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this.emptyBuffer()
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}
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return n, err
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}
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