mirror of
https://github.com/ziglang/zig.git
synced 2025-12-06 14:23:09 +00:00
d29871977f
We already have a LICENSE file that covers the Zig Standard Library. We no longer need to remind everyone that the license is MIT in every single file. Previously this was introduced to clarify the situation for a fork of Zig that made Zig's LICENSE file harder to find, and replaced it with their own license that required annual payments to their company. However that fork now appears to be dead. So there is no need to reinforce the copyright notice in every single file.
113 lines
3.5 KiB
Zig
113 lines
3.5 KiB
Zig
const std = @import("../std.zig");
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const io = std.io;
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const mem = std.mem;
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const testing = std.testing;
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/// Creates a stream which supports 'un-reading' data, so that it can be read again.
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/// This makes look-ahead style parsing much easier.
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/// TODO merge this with `std.io.BufferedReader`: https://github.com/ziglang/zig/issues/4501
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pub fn PeekStream(
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comptime buffer_type: std.fifo.LinearFifoBufferType,
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comptime ReaderType: type,
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) type {
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return struct {
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unbuffered_reader: ReaderType,
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fifo: FifoType,
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pub const Error = ReaderType.Error;
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pub const Reader = io.Reader(*Self, Error, read);
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const Self = @This();
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const FifoType = std.fifo.LinearFifo(u8, buffer_type);
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pub usingnamespace switch (buffer_type) {
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.Static => struct {
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pub fn init(base: ReaderType) Self {
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return .{
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.unbuffered_reader = base,
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.fifo = FifoType.init(),
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};
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}
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},
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.Slice => struct {
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pub fn init(base: ReaderType, buf: []u8) Self {
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return .{
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.unbuffered_reader = base,
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.fifo = FifoType.init(buf),
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};
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}
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},
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.Dynamic => struct {
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pub fn init(base: ReaderType, allocator: *mem.Allocator) Self {
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return .{
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.unbuffered_reader = base,
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.fifo = FifoType.init(allocator),
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};
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}
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},
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};
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pub fn putBackByte(self: *Self, byte: u8) !void {
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try self.putBack(&[_]u8{byte});
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}
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pub fn putBack(self: *Self, bytes: []const u8) !void {
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try self.fifo.unget(bytes);
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}
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pub fn read(self: *Self, dest: []u8) Error!usize {
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// copy over anything putBack()'d
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var dest_index = self.fifo.read(dest);
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if (dest_index == dest.len) return dest_index;
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// ask the backing stream for more
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dest_index += try self.unbuffered_reader.read(dest[dest_index..]);
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return dest_index;
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}
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pub fn reader(self: *Self) Reader {
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return .{ .context = self };
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}
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};
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}
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pub fn peekStream(
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comptime lookahead: comptime_int,
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underlying_stream: anytype,
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) PeekStream(.{ .Static = lookahead }, @TypeOf(underlying_stream)) {
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return PeekStream(.{ .Static = lookahead }, @TypeOf(underlying_stream)).init(underlying_stream);
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}
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test "PeekStream" {
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const bytes = [_]u8{ 1, 2, 3, 4, 5, 6, 7, 8 };
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var fbs = io.fixedBufferStream(&bytes);
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var ps = peekStream(2, fbs.reader());
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var dest: [4]u8 = undefined;
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try ps.putBackByte(9);
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try ps.putBackByte(10);
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var read = try ps.reader().read(dest[0..4]);
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try testing.expect(read == 4);
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try testing.expect(dest[0] == 10);
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try testing.expect(dest[1] == 9);
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try testing.expect(mem.eql(u8, dest[2..4], bytes[0..2]));
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read = try ps.reader().read(dest[0..4]);
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try testing.expect(read == 4);
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try testing.expect(mem.eql(u8, dest[0..4], bytes[2..6]));
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read = try ps.reader().read(dest[0..4]);
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try testing.expect(read == 2);
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try testing.expect(mem.eql(u8, dest[0..2], bytes[6..8]));
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try ps.putBackByte(11);
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try ps.putBackByte(12);
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read = try ps.reader().read(dest[0..4]);
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try testing.expect(read == 2);
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try testing.expect(dest[0] == 12);
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try testing.expect(dest[1] == 11);
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}
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