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std: merge io.PeekStream and io.BufferedInStreamCustom #4505

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std: merge io.PeekStream and io.BufferedInStreamCustom #4505

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127 changes: 47 additions & 80 deletions lib/std/io.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -109,30 +109,63 @@ pub fn readFileAlloc(allocator: *mem.Allocator, path: []const u8) ![]u8 {
}

pub fn BufferedInStream(comptime Error: type) type {
return BufferedInStreamCustom(mem.page_size, Error);
return BufferedInStreamCustom(.{ .Static = mem.page_size }, Error);
}

pub fn BufferedInStreamCustom(comptime buffer_size: usize, comptime Error: type) type {
/// 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 BufferedInStreamCustom(comptime buffer_type: std.fifo.LinearFifoBufferType, comptime InStreamError: type) type {
return struct {
const Self = @This();
const Stream = InStream(Error);
pub const Error = InStreamError;
pub const Stream = InStream(Error);

stream: Stream,
base: *Stream,

unbuffered_in_stream: *Stream,

const FifoType = std.fifo.LinearFifo(u8, std.fifo.LinearFifoBufferType{ .Static = buffer_size });
const FifoType = std.fifo.LinearFifo(u8, buffer_type);
fifo: FifoType,

pub fn init(unbuffered_in_stream: *Stream) Self {
return Self{
.unbuffered_in_stream = unbuffered_in_stream,
.fifo = FifoType.init(),
.stream = Stream{ .readFn = readFn },
};
pub usingnamespace switch (buffer_type) {
.Static => struct {
pub fn init(base: *Stream) Self {
return .{
.base = base,
.fifo = FifoType.init(),
.stream = Stream{ .readFn = readFn },
};
}
},
.Slice => struct {
pub fn init(base: *Stream, buf: []u8) Self {
return .{
.base = base,
.fifo = FifoType.init(buf),
.stream = Stream{ .readFn = readFn },
};
}
},
.Dynamic => struct {
pub fn init(base: *Stream, allocator: *mem.Allocator) Self {
return .{
.base = base,
.fifo = FifoType.init(allocator),
.stream = Stream{ .readFn = readFn },
};
}
},
};

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);
}

fn readFn(in_stream: *Stream, dest: []u8) !usize {
fn readFn(in_stream: *Stream, dest: []u8) Error!usize {
const self = @fieldParentPtr(Self, "stream", in_stream);
var dest_index: usize = 0;
while (dest_index < dest.len) {
Expand All @@ -141,7 +174,7 @@ pub fn BufferedInStreamCustom(comptime buffer_size: usize, comptime Error: type)
// fifo empty, fill it
const writable = self.fifo.writableSlice(0);
assert(writable.len > 0);
const n = try self.unbuffered_in_stream.read(writable);
const n = try self.base.read(writable);
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can you add a test case to catch the bug here, where it does not leave any reserved buffer space, and putBack would fail here?

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I don't understand the issue. Which bug are you referring to?

if (n == 0) {
// reading from the unbuffered stream returned nothing
// so we have nothing left to read.
Expand Down Expand Up @@ -194,72 +227,6 @@ test "io.BufferedInStream" {
testing.expectEqualSlices(u8, str, res);
}

/// Creates a stream which supports 'un-reading' data, so that it can be read again.
/// This makes look-ahead style parsing much easier.
pub fn PeekStream(comptime buffer_type: std.fifo.LinearFifoBufferType, comptime InStreamError: type) type {
return struct {
const Self = @This();
pub const Error = InStreamError;
pub const Stream = InStream(Error);

stream: Stream,
base: *Stream,

const FifoType = std.fifo.LinearFifo(u8, buffer_type);
fifo: FifoType,

pub usingnamespace switch (buffer_type) {
.Static => struct {
pub fn init(base: *Stream) Self {
return .{
.base = base,
.fifo = FifoType.init(),
.stream = Stream{ .readFn = readFn },
};
}
},
.Slice => struct {
pub fn init(base: *Stream, buf: []u8) Self {
return .{
.base = base,
.fifo = FifoType.init(buf),
.stream = Stream{ .readFn = readFn },
};
}
},
.Dynamic => struct {
pub fn init(base: *Stream, allocator: *mem.Allocator) Self {
return .{
.base = base,
.fifo = FifoType.init(allocator),
.stream = Stream{ .readFn = readFn },
};
}
},
};

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);
}

fn readFn(in_stream: *Stream, dest: []u8) Error!usize {
const self = @fieldParentPtr(Self, "stream", in_stream);

// copy over anything putBack()'d
var dest_index = self.fifo.read(dest);
if (dest_index == dest.len) return dest_index;

// ask the backing stream for more
dest_index += try self.base.read(dest[dest_index..]);
return dest_index;
}
};
}

pub const SliceInStream = struct {
const Self = @This();
pub const Error = error{};
Expand Down
4 changes: 2 additions & 2 deletions lib/std/io/test.zig
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Original file line number Diff line number Diff line change
Expand Up @@ -91,10 +91,10 @@ test "SliceInStream" {
expect(read == 0);
}

test "PeekStream" {
test "BufferedInStream putBack" {
const bytes = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };
var ss = io.SliceInStream.init(&bytes);
var ps = io.PeekStream(.{ .Static = 2 }, io.SliceInStream.Error).init(&ss.stream);
var ps = io.BufferedInStreamCustom(.{ .Static = 2 }, io.SliceInStream.Error).init(&ss.stream);

var dest: [4]u8 = undefined;

Expand Down