96 lines
1.9 KiB
V
96 lines
1.9 KiB
V
module io
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// BufferedReader provides a buffered interface for a reader
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struct BufferedReader {
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mut:
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reader Reader
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buf []byte
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// current offset in the buffer
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offset int
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len int
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}
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// BufferedReaderConfig are options that can be given to a reader
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pub struct BufferedReaderConfig {
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reader Reader
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buf_cap int = 128 * 1024 // large for fast reading of big(ish) files
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}
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// new_buffered_reader creates new BufferedReader
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pub fn new_buffered_reader(o BufferedReaderConfig) &BufferedReader {
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assert o.buf_cap >= 2
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// create
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r := &BufferedReader{
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reader: o.reader
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buf: []byte{len: o.buf_cap, cap: o.buf_cap}
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offset: 0
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}
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return r
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}
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// read fufills the Reader interface
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pub fn (mut r BufferedReader) read(mut buf []byte) ?int {
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// read data out of the buffer if we dont have any
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if r.offset >= r.len-1 {
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r.fill_buffer()?
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}
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read := copy(buf, r.buf[r.offset..r.len])
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r.offset += read
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return read
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}
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// fill buffer attempts to refill the internal buffer
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fn (mut r BufferedReader) fill_buffer() ? {
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// TODO we should keep track of when we get an end of stream
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// from the upstream reader so that we dont have to keep
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// trying to call this
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r.offset = 0
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r.len = r.reader.read(mut r.buf) or {
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0
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}
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}
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// read_line reads a line from the buffered reader
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pub fn (mut r BufferedReader) read_line() ?string {
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mut line := []byte{}
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for {
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if r.offset >= (r.len-1) {
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// go fetch some new data
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r.fill_buffer()?
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}
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if r.len == 0 {
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// if we have no data then return nothing
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return none
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}
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// try and find a newline character
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mut i := r.offset
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for ; i < r.len; i++ {
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c := r.buf[i]
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if c == `\n` {
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// great, we hit something
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// do some checking for whether we hit \r\n or just \n
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if i != 0 && r.buf[i-1] == `\r` {
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x := i-1
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line << r.buf[r.offset..x]
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} else {
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line << r.buf[r.offset..i]
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}
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r.offset = i + 1
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return line.bytestr()
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}
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}
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line << r.buf[r.offset..i]
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r.offset = i
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}
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}
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