From 2e1da4b4bc3e9655e19bf6128ff68a24380a13f9 Mon Sep 17 00:00:00 2001
From: Alvydas Vitkauskas <alvydas.vitkauskas@gmail.com>
Date: Wed, 31 Jul 2019 11:56:36 +0300
Subject: [PATCH] Merge pull request #1050 from avitkauskas/fix-read-lines

os: fix read_lines
---
 vlib/os/os.v | 31 +++++++++++++++++++++++--------
 1 file changed, 23 insertions(+), 8 deletions(-)

diff --git a/vlib/os/os.v b/vlib/os/os.v
index c1d27347c3..06a9e0993f 100644
--- a/vlib/os/os.v
+++ b/vlib/os/os.v
@@ -162,29 +162,44 @@ pub fn mv(old, new string) {
 // TODO return `?[]string` TODO implement `?[]` support
 pub fn read_lines(path string) []string {
 	mut res := []string
-	mut buf := [1000]byte
+	mut buf_len := 1024
+	mut buf := malloc(buf_len)
+
 	mode := 'rb'
 	mut fp := &C.FILE{}
 	$if windows {
 		fp = C._wfopen(path.to_wide(), mode.to_wide())
 	} $else {
-		cpath := path.str
-		fp = C.fopen(cpath, mode.str) 
+		fp = C.fopen(path.str, mode.str) 
 	}
 	if isnil(fp) {
 		// TODO
 		// return error('failed to open file "$path"')
 		return res
 	}
-	for C.fgets(buf, 1000, fp) != 0 {
-		mut val := ''
-		buf[C.strlen(buf) - 1] = `\0` // eat the newline fgets() stores
+
+	mut buf_index := 0
+	for C.fgets(buf + buf_index, buf_len - buf_index, fp) != 0 {
+		len := C.strlen(buf)
+		if len == buf_len - 1 && buf[len - 1] != 10 {
+			buf_len *= 2
+			buf = C.realloc(buf, buf_len)
+			if isnil(buf) {
+				panic('Could not reallocate the read buffer')
+			}
+			buf_index = len
+			continue
+		}
+		if buf[len - 1] == 10 {
+			buf[len - 1] = `\0`
+		}
 		$if windows {
-			if buf[strlen(buf)-2] == 13 {
-				buf[strlen(buf) - 2] = `\0`
+			if buf[len - 2] == 13 {
+				buf[len - 2] = `\0`
 			}
 		}
 		res << tos_clone(buf)
+		buf_index = 0
 	}
 	C.fclose(fp)
 	return res