Optional byte limit for readline

---------

Co-authored-by: Christoffer Lerno <christoffer@aegik.com>
Co-authored-by: Christoffer Lerno <christoffer.lerno@gmail.com>

lib/std/io/io.c3

@@ -50,31 +50,17 @@ faultdef
  or to the end of the stream, whatever comes first.
  "\r" will be filtered from the String.
 
+ @param [&inout] allocator : "The allocator used to allocate the read string."
  @param stream : `The stream to read from.`
+ @param limit : `Optionally limits the amount of bytes to read in a single line. Will NOT discard the remaining line data.`
  @require @is_not_instream_if_ptr(stream) : "The value for 'stream' should have been passed as a pointer and not as a value, please add '&'."
  @require @is_instream(stream) : `Make sure that the stream is actually an InStream.`
  @param [inout] allocator : `the allocator to use.`
  @return `The string containing the data read.`
 *>
-macro String? readline(Allocator allocator, stream = io::stdin())
+macro String? readline(Allocator allocator, stream = io::stdin(), usz limit = 0)
 {
-	return readline_impl{$typeof(stream)}(allocator, stream);
+	return readline_impl{$typeof(stream)}(allocator, stream, limit);
-}
-
-fn String? readline_impl(Allocator allocator, Stream stream) <Stream> @private
-{
-	if (allocator == tmem)
-	{
-		DString str = dstring::temp_with_capacity(256);
-		readline_to_stream(&str, stream)!;
-		return str.str_view();
-	}
-	@pool()
-	{
-		DString str = dstring::temp_with_capacity(256);
-		readline_to_stream(&str, stream)!;
-		return str.copy_str(allocator);
-	};
 }
 
 <*
@@ -82,13 +68,30 @@ fn String? readline_impl(Allocator allocator, Stream stream) <Stream> @private
  on the temporary allocator and does not need to be freed.
 
  @param stream : `The stream to read from.`
+ @param limit : `Optionally limits the amount of bytes to read in a single line. Will NOT discard the remaining line data.`
  @require @is_not_instream_if_ptr(stream) : "The value for 'stream' should have been passed as a pointer and not as a value, please add '&'."
  @require @is_instream(stream) : `The stream must implement InStream.`
  @return `The temporary string containing the data read.`
 *>
-macro String? treadline(stream = io::stdin())
+macro String? treadline(stream = io::stdin(), usz limit = 0)
 {
-	return readline(tmem, stream) @inline;
+	return readline(tmem, stream, limit) @inline;
+}
+
+fn String? readline_impl(Allocator allocator, Stream stream, usz limit) <Stream> @private
+{
+	if (allocator == tmem)
+	{
+		DString str = dstring::temp_with_capacity(256);
+		readline_to_stream(&str, stream, limit)!;
+		return str.str_view();
+	}
+	@pool()
+	{
+		DString str = dstring::temp_with_capacity(256);
+		readline_to_stream(&str, stream, limit)!;
+		return str.copy_str(allocator);
+	};
 }
 
 <*
@@ -96,18 +99,19 @@ macro String? treadline(stream = io::stdin())
 
  @param out_stream : `The stream to write to`
  @param in_stream : `The stream to read from.`
+ @param limit : `Optionally limits the byte-length of the allocated output string.`
  @require @is_not_instream_if_ptr(in_stream) : "The value for 'in_stream' should have been passed as a pointer and not as a value, please add '&'."
  @require @is_not_outstream_if_ptr(out_stream) : "The value for 'out_stream' should have been passed as a pointer and not as a value, please add '&'."
  @require @is_instream(in_stream) : `The in_stream must implement InStream.`
  @require @is_outstream(out_stream) : `The out_stream must implement OutStream.`
- @return `The number of bytes written`
+ @return `The number of bytes written. When a 'limit' is provided and the return value is equal to it, there may be more to read on the current line.`
 *>
-macro usz? readline_to_stream(out_stream, in_stream = io::stdin())
+macro usz? readline_to_stream(out_stream, in_stream = io::stdin(), usz limit = 0)
 {
-	return readline_to_stream_impl{$typeof(in_stream), $typeof(out_stream)}(out_stream, in_stream);
+	return readline_to_stream_impl{$typeof(in_stream), $typeof(out_stream)}(out_stream, in_stream, limit);
 }
 
-fn usz? readline_to_stream_impl(OStream out_stream, IStream in_stream) <IStream, OStream> @private
+fn usz? readline_to_stream_impl(OStream out_stream, IStream in_stream, usz limit) <IStream, OStream> @private
 {
 	bool $is_stream = IStream == InStream;
 	$if $is_stream:
@@ -132,7 +136,7 @@ fn usz? readline_to_stream_impl(OStream out_stream, IStream in_stream) <IStream,
 		$endif
 		len++;
 	}
-	while (1)
+	while (!limit || len < limit)
 	{
 		$if $is_stream:
 			char? c = func((void*)in_stream);

releasenotes.md

@@ -14,6 +14,7 @@
 - Remove dependency on temp allocator in File.open.
 - Added PEM encoding/decoding. #2858
 - Add Murmur3 hash.
+- Add optional line-length limitations to `io::readline` and `io::readline_to_stream`. #2879
 
 ### Fixes
 - Add error message if directory with output file name already exists