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package bytes
import "core:io"
import "core:unicode/utf8"
Reader :: struct {
s: []byte, // read-only buffer
i: i64, // current reading index
prev_rune: int, // previous reading index of rune or < 0
}
reader_init :: proc(r: ^Reader, s: []byte) -> io.Stream {
r.s = s
r.i = 0
r.prev_rune = -1
return reader_to_stream(r)
}
reader_to_stream :: proc(r: ^Reader) -> (s: io.Stream) {
s.data = r
s.procedure = _reader_proc
return
}
reader_length :: proc(r: ^Reader) -> int {
if r.i >= i64(len(r.s)) {
return 0
}
return int(i64(len(r.s)) - r.i)
}
reader_size :: proc(r: ^Reader) -> i64 {
return i64(len(r.s))
}
reader_read :: proc(r: ^Reader, p: []byte) -> (n: int, err: io.Error) {
if len(p) == 0 {
return 0, nil
}
if r.i >= i64(len(r.s)) {
return 0, .EOF
}
r.prev_rune = -1
n = copy(p, r.s[r.i:])
r.i += i64(n)
return
}
reader_read_at :: proc(r: ^Reader, p: []byte, off: i64) -> (n: int, err: io.Error) {
if len(p) == 0 {
return 0, nil
}
if off < 0 {
return 0, .Invalid_Offset
}
if off >= i64(len(r.s)) {
return 0, .EOF
}
n = copy(p, r.s[off:])
if n < len(p) {
err = .EOF
}
return
}
reader_read_byte :: proc(r: ^Reader) -> (byte, io.Error) {
r.prev_rune = -1
if r.i >= i64(len(r.s)) {
return 0, .EOF
}
b := r.s[r.i]
r.i += 1
return b, nil
}
reader_unread_byte :: proc(r: ^Reader) -> io.Error {
if r.i <= 0 {
return .Invalid_Unread
}
r.prev_rune = -1
r.i -= 1
return nil
}
reader_read_rune :: proc(r: ^Reader) -> (ch: rune, size: int, err: io.Error) {
if r.i >= i64(len(r.s)) {
r.prev_rune = -1
return 0, 0, .EOF
}
r.prev_rune = int(r.i)
if c := r.s[r.i]; c < utf8.RUNE_SELF {
r.i += 1
return rune(c), 1, nil
}
ch, size = utf8.decode_rune(r.s[r.i:])
r.i += i64(size)
return
}
reader_unread_rune :: proc(r: ^Reader) -> io.Error {
if r.i <= 0 {
return .Invalid_Unread
}
if r.prev_rune < 0 {
return .Invalid_Unread
}
r.i = i64(r.prev_rune)
r.prev_rune = -1
return nil
}
reader_seek :: proc(r: ^Reader, offset: i64, whence: io.Seek_From) -> (i64, io.Error) {
abs: i64
switch whence {
case .Start:
abs = offset
case .Current:
abs = r.i + offset
case .End:
abs = i64(len(r.s)) + offset
case:
return 0, .Invalid_Whence
}
if abs < 0 {
return 0, .Invalid_Offset
}
r.i = abs
r.prev_rune = -1
return abs, nil
}
reader_write_to :: proc(r: ^Reader, w: io.Writer) -> (n: i64, err: io.Error) {
r.prev_rune = -1
if r.i >= i64(len(r.s)) {
return 0, nil
}
s := r.s[r.i:]
m: int
m, err = io.write(w, s)
if m > len(s) {
panic("bytes.Reader.write_to: invalid io.write_string count")
}
r.i += i64(m)
n = i64(m)
if m != len(s) && err == nil {
err = .Short_Write
}
return
}
@(private)
_reader_proc :: proc(stream_data: rawptr, mode: io.Stream_Mode, p: []byte, offset: i64, whence: io.Seek_From) -> (n: i64, err: io.Error) {
r := (^Reader)(stream_data)
#partial switch mode {
case .Read:
return io._i64_err(reader_read(r, p))
case .Read_At:
return io._i64_err(reader_read_at(r, p, offset))
case .Seek:
n, err = reader_seek(r, offset, whence)
return
case .Size:
n = reader_size(r)
return
case .Query:
return io.query_utility({.Read, .Read_At, .Seek, .Size, .Query})
}
return 0, .Empty
}
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