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v/vlib/strings/builder.v
2020-07-01 00:53:53 +02:00

133 lines
2.5 KiB
V

// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
module strings
pub struct Builder {
// TODO
pub mut:
buf []byte
str_calls int
len int
initial_size int = 1
}
pub fn new_builder(initial_size int) Builder {
return Builder{
//buf: make(0, initial_size)
buf: []byte{cap: initial_size}
str_calls: 0
len: 0
initial_size: initial_size
}
}
pub fn (mut b Builder) write_bytes(bytes byteptr, howmany int) {
b.buf.push_many(bytes, howmany)
b.len += howmany
}
pub fn (mut b Builder) write_b(data byte) {
b.buf << data
b.len++
}
pub fn (mut b Builder) write(s string) {
if s == '' {
return
}
b.buf.push_many(s.str, s.len)
// for c in s {
// b.buf << c
// }
// b.buf << []byte(s) // TODO
b.len += s.len
}
pub fn (mut b Builder) go_back(n int) {
b.buf.trim(b.buf.len-n)
b.len -= n
}
fn bytes2string(b []byte) string {
mut copy := b.clone()
copy << `\0`
res := tos(copy.data, copy.len-1)
return res
}
pub fn (mut b Builder) cut_last(n int) string {
res := bytes2string( b.buf[b.len-n..] )
b.buf.trim(b.buf.len-n)
b.len -= n
return res
}
/*
pub fn (mut b Builder) cut_to(pos int) string {
res := bytes2string( b.buf[pos..] )
b.buf.trim(pos)
b.len = pos
return res
}
*/
pub fn (mut b Builder) go_back_to(pos int) {
b.buf.trim(pos)
b.len = pos
}
pub fn (mut b Builder) writeln(s string) {
// for c in s {
// b.buf << c
// }
b.buf.push_many(s.str, s.len)
// b.buf << []byte(s) // TODO
b.buf << `\n`
b.len += s.len + 1
}
// buf == 'hello world'
// last_n(5) returns 'world'
pub fn (b &Builder) last_n(n int) string {
if n > b.len {
return ''
}
return bytes2string( b.buf[b.len-n..] )
}
// buf == 'hello world'
// after(6) returns 'world'
pub fn (b &Builder) after(n int) string {
if n >= b.len {
return ''
}
return bytes2string( b.buf[n..] )
}
// NB: in order to avoid memleaks and additional memory copies, after a call to b.str(),
// the builder b will be empty. The returned string *owns* the accumulated data so far.
pub fn (mut b Builder) str() string {
b.str_calls++
if b.str_calls > 1 {
panic('builder.str() should be called just once.\n' +
'If you want to reuse a builder, call b.free() first.')
}
b.buf << `\0`
s := string(b.buf,b.len)
bis := b.initial_size
//free(b.buf.data)
b.buf = []byte{cap: bis}
b.len = 0
return s
}
pub fn (mut b Builder) free() {
unsafe{
free(b.buf.data)
}
//b.buf = []byte{cap: b.initial_size}
b.len = 0
b.str_calls = 0
}