io: add a string_reader submodule (#20893)

vlib/io/buffered_reader.v

@@ -24,6 +24,7 @@ pub struct BufferedReaderConfig {
 // BufferedReadLineConfig are options that can be given to the read_line() function.
 @[params]
 pub struct BufferedReadLineConfig {
+pub:
 	delim u8 = `\n` // line delimiter
 }
 

vlib/io/reader_test.v

@@ -38,13 +38,13 @@ fn test_read_all_huge() {
 	assert res == '123'.repeat(100000).bytes()
 }
 
-struct StringReader {
+struct StringReaderTest {
 	text string
 mut:
 	place int
 }
 
-fn (mut s StringReader) read(mut buf []u8) !int {
+fn (mut s StringReaderTest) read(mut buf []u8) !int {
 	if s.place >= s.text.len {
 		return Eof{}
 	}
@@ -55,9 +55,9 @@ fn (mut s StringReader) read(mut buf []u8) !int {
 
 const newline_count = 100000
 
-fn test_stringreader() {
+fn test_stringreadertest() {
 	text := '12345\n'.repeat(io.newline_count)
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)
@@ -80,9 +80,9 @@ fn test_stringreader() {
 	}
 }
 
-fn test_stringreader2() {
+fn test_stringreadertest2() {
 	text := '12345\r\n'.repeat(io.newline_count)
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)
@@ -107,7 +107,7 @@ fn test_stringreader2() {
 
 fn test_leftover() {
 	text := 'This is a test\r\nNice try!'
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)
@@ -129,7 +129,7 @@ fn test_leftover() {
 
 fn test_totalread_read() {
 	text := 'Some testing text'
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)
@@ -145,7 +145,7 @@ fn test_totalread_read() {
 
 fn test_totalread_readline() {
 	text := 'Some testing text\nmore_enters'
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)
@@ -164,7 +164,7 @@ fn test_totalread_readline() {
 
 fn test_read_line_until_zero_terminated() {
 	text := 'This is a test\0Nice try!\0'
-	mut s := StringReader{
+	mut s := StringReaderTest{
 		text: text
 	}
 	mut r := new_buffered_reader(reader: s)

vlib/io/string_reader/string_reader.v

@@ -0,0 +1,292 @@
+module string_reader
+
+import io
+import strings
+
+@[params]
+pub struct StringReaderParams {
+	// the reader interface
+	reader ?io.Reader
+	// initialize the builder with this source string
+	source ?string
+	// if no source is given the string builder is initialized with this size
+	initial_size int
+}
+
+// StringReader is able to read data from a Reader interface and/or source string to a dynamically
+// growing buffer using a string builder. Unlike the BufferedReader, StringReader will
+// keep the entire contents of the buffer in memory, allowing the incoming data to be reused
+// and read in an efficient matter. The StringReader will not set a maximum capacity to the string
+// builders buffer and could grow very large.
+pub struct StringReader {
+mut:
+	reader ?io.Reader
+	offset int // current offset in the buffer
+pub mut:
+	end_of_stream bool // whether we reached the end of the upstream reader
+	builder       strings.Builder
+}
+
+// new creates a new StringReader and sets the string builder size to `initial_size`.
+// If a source
+pub fn StringReader.new(params StringReaderParams) StringReader {
+	mut r := StringReader{
+		reader: params.reader
+	}
+
+	if source := params.source {
+		r.builder = strings.new_builder(source.len)
+		r.builder.write_string(source)
+	} else {
+		r.builder = strings.new_builder(params.initial_size)
+	}
+
+	return r
+}
+
+// needs_fill returns whether the buffer needs refilling
+pub fn (r StringReader) needs_fill() bool {
+	return r.offset >= r.builder.len
+}
+
+// needs_fill_until returns whether the buffer needs refilling in order to read
+// `n` bytes
+pub fn (r StringReader) needs_fill_until(n int) bool {
+	return r.offset + n >= r.builder.len
+}
+
+// fill_bufer tries to read data into the buffer until either a 0 length read or if read_to_end_of_stream
+// is true then the end of the stream. It returns the number of bytes read
+pub fn (mut r StringReader) fill_buffer(read_till_end_of_stream bool) !int {
+	if r.end_of_stream {
+		return io.Eof{}
+	}
+
+	mut reader := r.reader or { return error('reader is not set') }
+
+	start := r.builder.len
+	mut end := start
+
+	// make sure there is enough room in the string builder
+	unsafe { r.builder.grow_len(io.read_all_len) }
+	defer {
+		// shrink the length of the buffer to the total of bytes read
+		r.builder.go_back(r.builder.len - end)
+	}
+
+	for {
+		read := reader.read(mut r.builder[start..]) or {
+			r.end_of_stream = true
+			break
+		}
+		end += read
+
+		if !read_till_end_of_stream && read == 0 {
+			break
+		} else if r.builder.len == end {
+			unsafe { r.builder.grow_len(io.read_all_grow_len) }
+		}
+	}
+
+	if end == start {
+		return io.Eof{}
+	}
+
+	return end - start
+}
+
+// fill_buffer_until tries read `n` amount of bytes from the reader into the buffer
+// and returns the actual number of bytes read
+pub fn (mut r StringReader) fill_buffer_until(n int) !int {
+	if r.end_of_stream {
+		return io.Eof{}
+	}
+
+	mut reader := r.reader or { return error('reader is not set') }
+
+	start := r.builder.len
+	// make sure there is enough room in the string builder
+	if n > io.read_all_len {
+		unsafe { r.builder.grow_len(io.read_all_len) }
+	} else {
+		unsafe { r.builder.grow_len(n) }
+	}
+
+	mut end := start
+	for {
+		read := reader.read(mut r.builder[start..]) or {
+			r.end_of_stream = true
+			break
+		}
+		end += read
+
+		if read == 0 || end - start == n {
+			break
+		} else if r.builder.len == end {
+			if n - end > io.read_all_grow_len {
+				unsafe { r.builder.grow_len(io.read_all_grow_len) }
+			} else {
+				unsafe { r.builder.grow_len(n - end) }
+			}
+		}
+	}
+
+	if end == start {
+		return io.Eof{}
+	}
+	return end - start
+}
+
+// read_all_bytes reads all bytes from a reader until either a 0 length read or if read_to_end_of_stream
+// is true then the end of the stream. It returns a copy of the read data
+pub fn (mut r StringReader) read_all_bytes(read_till_end_of_stream bool) ![]u8 {
+	start := r.offset
+	// ignore Eof error from fill buffer
+	r.fill_buffer(read_till_end_of_stream) or {}
+	r.offset = r.builder.len
+	// check if there was still data in the buffer, but the reader has reached its end of stream
+	if start == r.offset {
+		return io.Eof{}
+	}
+
+	return r.get_part(start, r.offset - start)!
+}
+
+// read_all reads all bytes from a reader until either a 0 length read or if read_to_end_of_stream
+// is true then the end of the stream. It produces a string from the read data
+pub fn (mut r StringReader) read_all(read_till_end_of_stream bool) !string {
+	buf := r.read_all_bytes(read_till_end_of_stream)!
+	return unsafe { tos(buf.data, buf.len) }
+}
+
+// read_bytes tries to read n amount of bytes from the reader
+pub fn (mut r StringReader) read_bytes(n int) ![]u8 {
+	start := r.offset
+
+	if r.needs_fill_until(n) {
+		actual_read := r.fill_buffer_until(n - (r.builder.len - r.offset))!
+		r.offset += actual_read
+	} else {
+		r.offset += n
+	}
+
+	return r.get_part(start, r.offset - start)!
+}
+
+// read_bytes tries to read `n` amount of bytes from the reader and produces a string
+// from the read data
+pub fn (mut r StringReader) read_string(n int) !string {
+	buf := r.read_bytes(n)!
+	return unsafe { tos(buf.data, buf.len) }
+}
+
+// read implements the Reader interface
+pub fn (mut r StringReader) read(mut buf []u8) !int {
+	start := r.offset
+
+	read := r.fill_buffer_until(buf.len - start)!
+	r.offset += read
+
+	copy(mut buf, r.builder[start..read])
+	return r.builder.len - start
+}
+
+// read_line attempts to read a line from the reader.
+// It will read until it finds the specified line delimiter
+// such as (\n, the default or \0) or the end of stream.
+@[direct_array_access]
+pub fn (mut r StringReader) read_line(config io.BufferedReadLineConfig) !string {
+	if r.end_of_stream && r.needs_fill() {
+		return io.Eof{}
+	}
+
+	start := r.offset
+	for {
+		if r.needs_fill() {
+			r.fill_buffer(false) or {
+				// we are at the end of the stream
+				if r.offset == start {
+					return io.Eof{}
+				}
+				return r.get_string_part(start, r.offset - start)!
+			}
+		}
+		// try to find a newline character
+		mut i := r.offset
+		for ; i < r.builder.len; i++ {
+			c := r.builder[i]
+			if c == config.delim {
+				// great, we hit something
+				// do some checking for whether we hit \r\n or just \n
+				mut x := i
+				if i != 0 && config.delim == `\n` && r.builder[i - 1] == `\r` {
+					x--
+				}
+				r.offset = i + 1
+				return r.get_string_part(start, x - start)!
+			}
+		}
+		r.offset = i
+	}
+
+	return io.Eof{}
+}
+
+// write implements the Writer interface
+pub fn (mut r StringReader) write(buf []u8) !int {
+	return r.builder.write(buf)!
+}
+
+// get_data returns a copy of the buffer
+@[inline]
+pub fn (r StringReader) get_data() []u8 {
+	unsafe {
+		mut x := malloc_noscan(r.builder.len)
+		vmemcpy(x, &u8(r.builder.data), r.builder.len)
+		return x.vbytes(r.builder.len)
+	}
+}
+
+// get get_part returns a copy of a part of the buffer from `start` till `start` + `n`
+pub fn (r StringReader) get_part(start int, n int) ![]u8 {
+	if start + n > r.builder.len {
+		return io.Eof{}
+	}
+
+	unsafe {
+		mut x := malloc_noscan(n)
+		vmemcpy(x, &u8(r.builder.data) + start, n)
+		return x.vbytes(n)
+	}
+}
+
+// get_string produces a string from all the bytes in the buffer
+@[inline]
+pub fn (r StringReader) get_string() string {
+	return r.builder.spart(0, r.builder.len)
+}
+
+// get_string_part produces a string from `start` till `start` + `n` of the buffer
+pub fn (r StringReader) get_string_part(start int, n int) !string {
+	if start + n > r.builder.len {
+		return io.Eof{}
+	}
+
+	return r.builder.spart(start, n)
+}
+
+// flush clears the stringbuilder and returns the resulting string and the stringreaders
+// offset is reset to 0
+pub fn (mut r StringReader) flush() string {
+	r.offset = 0
+	return r.builder.str()
+}
+
+// free frees the memory block used for the string builders buffer,
+// a new string builder with size 0 is initialized and the stringreaders offset is reset to 0
+@[unsafe]
+pub fn (mut r StringReader) free() {
+	unsafe { r.builder.free() }
+	r.builder = strings.new_builder(0)
+	r.offset = 0
+}