make multiple substitutions work and other cleanup

sed-lite/src/main.zig

@@ -45,8 +45,6 @@ pub fn main() !u8 {
         };
         defer file.close();
 
-        var buffer: [4096]u8 = undefined;
-
         const temp_path = try std.fmt.allocPrint(allocator, "{s}.tmp", .{file_path});
         defer allocator.free(temp_path);
 
@@ -56,12 +54,16 @@ pub fn main() !u8 {
         };
         defer temp_file.close();
 
-        var output_buffer: [4096]u8 = undefined;
-        var reader = file.reader(&buffer).interface;
-        var writer = temp_file.writer(&output_buffer).interface;
+        // don't screw with vars and consts in this block...
+        var reader_buffer: [4096]u8 = undefined;
+        var freader = file.reader(&reader_buffer);
+        const reader = &freader.interface;
+        var writer_buffer: [4096]u8 = undefined;
+        var fwriter = temp_file.writer(&writer_buffer);
+        const writer = &fwriter.interface;
         try substituteLines(
-            &reader,
-            &writer,
+            reader,
+            writer,
             substitutions,
         );
         try writer.flush();
@@ -82,27 +84,23 @@ const Substitution = struct {
 };
 
 fn substituteLines(reader: *std.Io.Reader, writer: *std.Io.Writer, substitutions: []const Substitution) !void {
-    var line_buf: [1024]u8 = undefined;
-    var line = std.Io.Writer.fixed(&line_buf);
-
-    while ((try reader.streamDelimiterEnding(&line, '\n')) > 0) : (_ = line.consumeAll()) {
-        const line_content = line.buffered();
+    while (reader.takeDelimiterExclusive('\n')) |line| {
         var substituted = false;
         for (substitutions) |sub| {
-            if (std.mem.eql(u8, line_content, sub.original)) {
+            if (std.mem.eql(u8, line, sub.original)) {
                 try writer.writeAll(sub.replacement);
                 substituted = true;
                 break;
             }
         }
         if (!substituted)
-            try writer.writeAll(line_content);
+            try writer.writeAll(line);
 
-        // Write our \n
-        if (reader.takeByte()) |b|
-            try writer.writeByte(b)
-        else |_| {} // end of stream
-    }
+        if (reader.peekByte() != error.EndOfStream)
+            try writer.writeByte('\n');
+    } else |err| if (err != error.EndOfStream) return err;
+    // write the final newline
+    // try writer.writeByte('\n');
 }
 
 test "substitute lines exact match" {

sed-lite/test.txt

@@ -1,5 +0,0 @@
-line1
-old_text
-line3
-another_old
-line5