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bio.readto and EOF

Hi,

When using bio.readto I often want to be able to tell if the delimeter
was found, or if the file was truncated, but there doesn't appear to
be a way to tell if readto stopped searching because it found what it
was looking for or if it reached EOF, other than to do another read.

A simple solution to this would be a new function that reads to and
includes the delimeter in the returned slice if it was found, which can
be used intead when you care. I've tentatively included a patch for this.

Is this something that would be wanted? Is there a better solution? Or a
better name?

--
Carlin

NB. I've stolen the `Keep tag that was already there but apparently
never used. Not sure if it was intended for a higher purpose.

>From c230b380fbf0e7ba2c24aae332e4ce8016843d66 Mon Sep 17 00:00:00 2001
From: Carlin Bingham <cb@viennan.net>
Date: Sat, 16 Mar 2019 10:20:23 +1300
Subject: [PATCH] Add bio.readtoinc - read to including delimiter
X-Spam-Status: No, hits=0.000000 required=0.900000

Similar to bio.readto except it includes the delimeter in the returned
slice if it was found, making the absence of the delimiter indicate EOF

--- a/lib/bio/bio.myr

+++ b/lib/bio/bio.myr

@@ -28,6 +28,7 @@

 	/* delimited read; returns freshly allocated buffer. */

 	const readln	: (f : file#	-> std.result(byte[:], err))

 	const readto	: (f : file#, delim : byte[:]	-> std.result(byte[:], err))

+	const readtoinc	: (f: file#, delim : byte[:]	-> std.result(byte[:], err))

 	const skipto	: (f : file#, delim : byte[:]	-> bool)

 	const skipspace	: (f : file# -> bool)

@@ -327,6 +328,11 @@

 	-> readdelim(f, delim, `Read)

 }

+/* same as readto, but includes the delimiter if it was found */

+const readtoinc = {f, delim

+	-> readdelim(f, delim, `Keep)

+}

+

 /* same as readto, but drops the read data. */

 const skipto = {f, delim

 	match readdelim(f, delim, `Drop)

@@ -413,7 +419,7 @@

 			match mode

 			| `Drop:	f.rstart += f.rend - f.rstart

 			| `Read:	readinto(f, &ret, f.rend - f.rstart)

-			| `Keep:

+			| `Keep:	readinto(f, &ret, f.rend - f.rstart)

 			;;

 			match ret.len

 			| 0:	-> `std.Err `Eof

@@ -432,11 +438,14 @@

 			;;

 			/* If we found it, return that information */

 			match mode

-			| `Drop:	f.rstart = i

-			| `Read:	readinto(f, &ret, i - f.rstart)

-			| `Keep:	

+			| `Drop:

+				f.rstart = i + delim.len

+			| `Read:

+				readinto(f, &ret, i - f.rstart)

+				f.rstart += delim.len

+			| `Keep:

+				readinto(f, &ret, i + delim.len - f.rstart)

 			;;

-			f.rstart += delim.len

 			-> `std.Ok ret

 :nextiter

 		;;

@@ -443,7 +452,7 @@

 		match mode

 		| `Drop:	f.rstart = i

 		| `Read:	readinto(f, &ret, i - f.rstart)

-		| `Keep:

+		| `Keep:	readinto(f, &ret, i - f.rstart)

 		;;

 	;;

 	std.die("unreachable")

--- /dev/null

+++ b/lib/bio/test/bio-readtoinc.myr

@@ -1,0 +1,30 @@

+use std

+use bio

+

+const main = {

+	var f

+

+	f = std.try(bio.open("data/bio-readtoinc", bio.Rd))

+

+	readtoinc(f, ";")

+	readtoinc(f, "]]]")

+	readtoinc(f, "\n")

+	readtoinc(f, ",")

+	readtoinc(f, ",")

+	readtoinc(f, ",")

+	readtoinc(f, "the end")

+

+	bio.close(f)

+}

+

+const readtoinc = {f, d

+	match bio.readtoinc(f, d)

+	| `std.Ok s:

+		std.put("{}\n", s)

+		std.slfree(s)

+	| `std.Err `bio.Eof:

+		std.put("eof\n")

+	| `std.Err _:

+		std.put("err\n")

+	;;

+}

--- /dev/null

+++ b/lib/bio/test/data/bio-readtoinc

@@ -1,0 +1,2 @@

+data with semicolon;multiple delims]]]a new line

+data separated,with commas until,no more

--- /dev/null

+++ b/lib/bio/test/data/bio-readtoinc-expected

@@ -1,0 +1,9 @@

+data with semicolon;

+multiple delims]]]

+a new line

+

+data separated,

+with commas until,

+no more

+

+eof

--- a/lib/bio/test/tests

+++ b/lib/bio/test/tests

@@ -24,6 +24,7 @@

 B bio-read	C

 B bio-write	F	tmpout/test-write

 B bio-delim	C

+B bio-readtoinc	C

 B bio-endianwr	F	tmpout/test-endianwr

 B bio-endianrd	C

 B bio-unitwr	F	tmpout/test-unitwr