116 lines
2.7 KiB
Go
116 lines
2.7 KiB
Go
package iconv
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import (
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"io"
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"syscall"
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)
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const bufferSize = 8 * 1024
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type Reader struct {
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source io.Reader
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converter *Converter
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buffer []byte
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readPos, writePos int
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err error
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}
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func NewReader(source io.Reader, fromEncoding string, toEncoding string) (*Reader, 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 NewReaderFromConverter(source, 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 NewReaderFromConverter(source io.Reader, converter *Converter) (reader *Reader) {
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reader = new(Reader)
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// copy elements
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reader.source = source
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reader.converter = converter
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// create 8K buffers
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reader.buffer = make([]byte, bufferSize)
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return reader
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}
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func (this *Reader) fillBuffer() int {
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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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// read new data into buffer at write position
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bytesRead, err := this.source.Read(this.buffer[this.writePos:])
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// adjust write position
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this.writePos += bytesRead
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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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return bytesRead
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}
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// implement the io.Reader interface
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func (this *Reader) Read(p []byte) (n int, err error) {
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// checks for when we have no data
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for this.writePos == 0 || this.readPos == this.writePos {
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// if we have an error / EOF, just return it
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if this.err != nil {
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return n, this.err
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}
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// else, fill our buffer
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this.fillBuffer()
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}
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// TODO: checks for when we have less data than len(p)
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// we should have an appropriate amount of data, convert it into the given buffer
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bytesRead, bytesWritten, err := this.converter.Convert(this.buffer[this.readPos:this.writePos], p)
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// adjust byte counters
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this.readPos += bytesRead
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n += bytesWritten
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// if we experienced an iconv error, check it
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if err != nil {
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// EINVAL:
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// An incomplete multibyte sequence is encountered in the input,
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// and the input byte sequence terminates after it.
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if err == syscall.EINVAL {
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// If we can read new data, then this should NOT be
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// considered as an error.
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newData := this.fillBuffer()
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if newData > 0 {
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return n, nil
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}
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}
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// E2BIG errors can be ignored (we'll get them often) as long
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// as at least 1 byte was written. If we experienced an E2BIG
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// and no bytes were written then the buffer is too small for
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// even the next character
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if err != syscall.E2BIG || bytesWritten == 0 {
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// track anything else
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this.err = err
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}
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}
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// return our results
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return n, this.err
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}
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