141 lines
3.5 KiB
V
141 lines
3.5 KiB
V
// Copyright (c) 2019-2021 Alexander Medvednikov. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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module strings
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// strings.Builder is used to efficiently append many strings to a large
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// dynamically growing buffer, then use the resulting large string. Using
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// a string builder is much better for performance/memory usage than doing
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// constantly string concatenation.
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pub type Builder = []byte
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// new_builder returns a new string builder, with an initial capacity of `initial_size`
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pub fn new_builder(initial_size int) Builder {
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return Builder([]byte{cap: initial_size})
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}
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// write_ptr writes `len` bytes provided byteptr to the accumulated buffer
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[unsafe]
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pub fn (mut b Builder) write_ptr(ptr &byte, len int) {
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if len == 0 {
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return
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}
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unsafe { b.push_many(ptr, len) }
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}
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// write_b appends a single `data` byte to the accumulated buffer
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pub fn (mut b Builder) write_b(data byte) {
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b << data
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}
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// write implements the Writer interface
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pub fn (mut b Builder) write(data []byte) ?int {
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if data.len == 0 {
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return 0
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}
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b << data
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return data.len
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}
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[inline]
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pub fn (b &Builder) byte_at(n int) byte {
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return unsafe { (&[]byte(b))[n] }
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}
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// write appends the string `s` to the buffer
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[inline]
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pub fn (mut b Builder) write_string(s string) {
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if s.len == 0 {
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return
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}
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unsafe { b.push_many(s.str, s.len) }
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// for c in s {
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// b.buf << c
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// }
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// b.buf << []byte(s) // TODO
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}
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// go_back discards the last `n` bytes from the buffer
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pub fn (mut b Builder) go_back(n int) {
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b.trim(b.len - n)
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}
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// cut_last cuts the last `n` bytes from the buffer and returns them
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pub fn (mut b Builder) cut_last(n int) string {
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cut_pos := b.len - n
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x := unsafe { (&[]byte(b))[cut_pos..] }
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res := x.bytestr()
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b.trim(cut_pos)
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return res
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}
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// cut_to cuts the string after `pos` and returns it.
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// if `pos` is superior to builder length, returns an empty string
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// and cancel further operations
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pub fn (mut b Builder) cut_to(pos int) string {
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if pos > b.len {
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return ''
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}
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return b.cut_last(b.len - pos)
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}
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// go_back_to resets the buffer to the given position `pos`
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// NB: pos should be < than the existing buffer length.
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pub fn (mut b Builder) go_back_to(pos int) {
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b.trim(pos)
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}
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// writeln appends the string `s`, and then a newline character.
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[inline]
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pub fn (mut b Builder) writeln(s string) {
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// for c in s {
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// b.buf << c
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// }
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if s.len > 0 {
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unsafe { b.push_many(s.str, s.len) }
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}
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// b.buf << []byte(s) // TODO
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b << byte(`\n`)
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}
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// last_n(5) returns 'world'
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// buf == 'hello world'
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pub fn (b &Builder) last_n(n int) string {
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if n > b.len {
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return ''
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}
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x := unsafe { (&[]byte(b))[b.len - n..] }
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return x.bytestr()
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}
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// after(6) returns 'world'
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// buf == 'hello world'
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pub fn (b &Builder) after(n int) string {
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if n >= b.len {
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return ''
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}
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x := unsafe { (&[]byte(b))[n..] }
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return x.bytestr()
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}
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// str returns a copy of all of the accumulated buffer content.
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// NB: after a call to b.str(), the builder b should not be
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// used again, you need to call b.free() first, or just leave
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// it to be freed by -autofree when it goes out of scope.
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// The returned string *owns* its own separate copy of the
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// accumulated data that was in the string builder, before the
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// .str() call.
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pub fn (mut b Builder) str() string {
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b << byte(0)
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bcopy := unsafe { &byte(memdup(b.data, b.len)) }
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s := unsafe { bcopy.vstring_with_len(b.len - 1) }
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b.trim(0)
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return s
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}
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// free is for manually freeing the contents of the buffer
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[unsafe]
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pub fn (mut b Builder) free() {
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unsafe { free(b.data) }
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}
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