std: merge io.PeekStream and io.BufferedInStreamCustom

Author: daurnimator

lib/std/io.zig

@@ -98,9 +98,6 @@ pub const bufferedOutStream = @import("io/buffered_out_stream.zig").bufferedOutS
 pub const BufferedInStream = @import("io/buffered_in_stream.zig").BufferedInStream;
 pub const bufferedInStream = @import("io/buffered_in_stream.zig").bufferedInStream;
 
-pub const PeekStream = @import("io/peek_stream.zig").PeekStream;
-pub const peekStream = @import("io/peek_stream.zig").peekStream;
-
 pub const FixedBufferStream = @import("io/fixed_buffer_stream.zig").FixedBufferStream;
 pub const fixedBufferStream = @import("io/fixed_buffer_stream.zig").fixedBufferStream;
 

lib/std/io/buffered_in_stream.zig

@@ -3,6 +3,9 @@ const io = std.io;
 const assert = std.debug.assert;
 const testing = std.testing;
 
+/// Creates a readable stream which buffers data
+/// It also supports 'un-reading' data, so that it can be read again.
+/// This makes look-ahead style parsing much easier.
 pub fn BufferedInStream(comptime buffer_type: std.fifo.LinearFifoBufferType, comptime InStreamType: type) type {
     return struct {
         unbuffered_in_stream: InStreamType,
@@ -62,6 +65,14 @@ pub fn BufferedInStream(comptime buffer_type: std.fifo.LinearFifoBufferType, com
             return dest.len;
         }
 
+        pub fn putBackByte(self: *Self, byte: u8) !void {
+            try self.putBack(&[_]u8{byte});
+        }
+
+        pub fn putBack(self: *Self, bytes: []const u8) !void {
+            try self.fifo.unget(bytes);
+        }
+
         pub fn inStream(self: *Self) InStream {
             return .{ .context = self };
         }
@@ -111,3 +122,36 @@ test "io.BufferedInStream" {
     defer testing.allocator.free(res);
     testing.expectEqualSlices(u8, str, res);
 }
+
+test "io.BufferedInStream.putBack*" {
+    const bytes = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };
+    var fbs = io.fixedBufferStream(&bytes);
+    var ps = BufferedInStream(.{ .Static = 2 }, @TypeOf(fbs.inStream())).init(fbs.inStream());
+
+    var dest: [4]u8 = undefined;
+
+    try ps.putBackByte(9);
+    try ps.putBackByte(10);
+
+    var read = try ps.inStream().read(dest[0..4]);
+    testing.expectEqual(@as(usize, 4), read);
+    testing.expectEqual(@as(u8, 10), dest[0]);
+    testing.expectEqual(@as(u8, 9), dest[1]);
+    testing.expectEqualSlices(u8, bytes[0..2], dest[2..4]);
+
+    read = try ps.inStream().read(dest[0..4]);
+    testing.expectEqual(@as(usize, 4), read);
+    testing.expectEqualSlices(u8, bytes[2..6], dest[0..4]);
+
+    read = try ps.inStream().read(dest[0..4]);
+    testing.expectEqual(@as(usize, 2), read);
+    testing.expectEqualSlices(u8, bytes[6..8], dest[0..2]);
+
+    try ps.putBackByte(11);
+    try ps.putBackByte(12);
+
+    read = try ps.inStream().read(dest[0..4]);
+    testing.expectEqual(@as(usize, 2), read);
+    testing.expectEqual(@as(u8, 12), dest[0]);
+    testing.expectEqual(@as(u8, 11), dest[1]);
+}