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v/vlib/strings/builder.v

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// Copyright (c) 2019-2020 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
// that can be found in the LICENSE file.
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module strings
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pub struct Builder {
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// TODO
pub mut:
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buf []byte
str_calls int
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len int
initial_size int = 1
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}
pub fn new_builder(initial_size int) Builder {
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return Builder{
//buf: make(0, initial_size)
buf: []byte{cap: initial_size}
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str_calls: 0
len: 0
initial_size: initial_size
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}
}
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pub fn (mut b Builder) write_bytes(bytes byteptr, howmany int) {
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b.buf.push_many(bytes, howmany)
b.len += howmany
}
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pub fn (mut b Builder) write_b(data byte) {
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b.buf << data
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b.len++
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}
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pub fn (mut b Builder) write(s string) {
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if s == '' {
return
}
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b.buf.push_many(s.str, s.len)
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// for c in s {
// b.buf << c
// }
// b.buf << []byte(s) // TODO
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b.len += s.len
}
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pub fn (mut b Builder) go_back(n int) {
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b.buf.trim(b.buf.len-n)
b.len -= n
}
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fn bytes2string(b []byte) string {
mut copy := b.clone()
copy << `\0`
res := tos(copy.data, copy.len-1)
return res
}
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pub fn (mut b Builder) cut_last(n int) string {
res := bytes2string( b.buf[b.len-n..] )
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b.buf.trim(b.buf.len-n)
b.len -= n
return res
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}
/*
pub fn (mut b Builder) cut_to(pos int) string {
res := bytes2string( b.buf[pos..] )
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b.buf.trim(pos)
b.len = pos
return res
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}
*/
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pub fn (mut b Builder) go_back_to(pos int) {
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b.buf.trim(pos)
b.len = pos
}
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pub fn (mut b Builder) writeln(s string) {
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// for c in s {
// b.buf << c
// }
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b.buf.push_many(s.str, s.len)
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// b.buf << []byte(s) // TODO
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b.buf << `\n`
b.len += s.len + 1
}
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// buf == 'hello world'
// last_n(5) returns 'world'
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pub fn (b &Builder) last_n(n int) string {
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if n > b.len {
return ''
}
return bytes2string( b.buf[b.len-n..] )
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}
// buf == 'hello world'
// after(6) returns 'world'
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pub fn (b &Builder) after(n int) string {
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if n >= b.len {
return ''
}
return bytes2string( b.buf[n..] )
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}
// 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.
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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.')
}
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b.buf << `\0`
s := string(b.buf,b.len)
bis := b.initial_size
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//free(b.buf.data)
b.buf = []byte{cap: bis}
b.len = 0
return s
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}
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pub fn (mut b Builder) free() {
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unsafe{
free(b.buf.data)
}
//b.buf = []byte{cap: b.initial_size}
b.len = 0
b.str_calls = 0
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}