encoding.csv: fix bug in RandomAccessReader, spotted on windows with mingw32 (#20571)

vlib/encoding/csv/csv_reader_random_access.v

@@ -252,7 +252,7 @@ pub fn (mut cr RandomAccessReader) map_csv() ! {
 			// println("${i:-12d} of ${cr.f_len:-12d} readed: ${read_bytes_count}")
 			mut p1 := p
 			mut i1 := i64(0)
-			for i1 <= read_bytes_count {
+			for i1 < read_bytes_count {
 				// println("loop char: ${*&u8(p1):c}")
 				// manage quote char
 				if *p1 == cr.quote {
@@ -529,7 +529,7 @@ pub fn (mut cr RandomAccessReader) rows_count() !i64 {
 			// println("${i:-12d} of ${cr.f_len:-12d} readed: ${read_bytes_count}")
 			mut p1 := p
 			mut i1 := 0
-			for i1 <= read_bytes_count {
+			for i1 < read_bytes_count {
 				if *p1 == cr.end_line {
 					count++
 				}

vlib/encoding/csv/csv_reader_test.v

@@ -10,6 +10,7 @@ This file contains tests
 Known limitations:
 */
 import encoding.csv
+import strings
 import os
 
 /******************************************************************************
@@ -267,7 +268,7 @@ fn test_csv_string() {
 	// parse the temp file
 	csvr = csv.csv_reader(
 		file_path: file_path_str
-		mem_buf_size: 64
+		mem_buf_size: 32
 		end_line_len: csv.endline_crlf_len
 	)!
 	perform_test(mut csvr)!
@@ -295,6 +296,53 @@ fn test_csv_string() {
 	csvr.dispose_csv_reader()
 }
 
+fn test_coherence() {
+	file_path_str := os.join_path(os.temp_dir(), 'test_csv.csv')
+	mut f := os.open_file(file_path_str, 'w')!
+	mut b := strings.new_builder(64536)
+	mut i := u64(0)
+	mut sum := u64(0)
+	for rows in 0 .. 1000 {
+		for col in 0 .. 1000 {
+			if col > 0 {
+				b.write_u8(`,`)
+			}
+			b.write_string(i.str())
+			i++
+			sum += i
+		}
+		b.write_string('\n')
+	}
+	f.write_string(b.str())!
+	f.close()
+
+	sum -= i
+	// println('sum: ${sum}')
+
+	// parse the temp file
+	mut csvr := csv.csv_reader(
+		file_path: file_path_str
+		mem_buf_size: 32
+		end_line_len: csv.endline_cr_len
+	)!
+
+	mut sum1 := u64(0)
+	for row_index in 0 .. csvr.csv_map.len {
+		row := csvr.get_row(row_index)!
+		for x in row {
+			sum1 += u64(x.int())
+		}
+	}
+	// println('sum: ${sum1}')
+
+	csvr.dispose_csv_reader()
+
+	// remove the temp file
+	os.rm(file_path_str)!
+
+	assert sum == sum1, 'csv coherence test failed'
+}
+
 // Debug code
 fn main() {
 	test_csv_string()