diff --git a/CMakeLists.txt b/CMakeLists.txt index 49dde70f5e..3d02749d26 100644 --- a/CMakeLists.txt +++ b/CMakeLists.txt @@ -375,8 +375,9 @@ set(ZIG_STAGE2_SOURCES "${CMAKE_SOURCE_DIR}/lib/std/io/buffered_atomic_file.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/buffered_writer.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/change_detection_stream.zig" - "${CMAKE_SOURCE_DIR}/lib/std/io/counting_writer.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/counting_reader.zig" + "${CMAKE_SOURCE_DIR}/lib/std/io/counting_writer.zig" + "${CMAKE_SOURCE_DIR}/lib/std/io/early_eof_reader.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/find_byte_writer.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/fixed_buffer_stream.zig" "${CMAKE_SOURCE_DIR}/lib/std/io/reader.zig" diff --git a/lib/std/io.zig b/lib/std/io.zig index fb5f00805c..fa0d5d8698 100644 --- a/lib/std/io.zig +++ b/lib/std/io.zig @@ -125,6 +125,9 @@ pub const fixedBufferStream = @import("io/fixed_buffer_stream.zig").fixedBufferS pub const CWriter = @import("io/c_writer.zig").CWriter; pub const cWriter = @import("io/c_writer.zig").cWriter; +pub const EarlyEOFReader = @import("io/early_eof_reader.zig").EarlyEOFReader; +pub const earlyEOFReader = @import("io/early_eof_reader.zig").earlyEOFReader; + pub const CountingWriter = @import("io/counting_writer.zig").CountingWriter; pub const countingWriter = @import("io/counting_writer.zig").countingWriter; pub const CountingReader = @import("io/counting_reader.zig").CountingReader; diff --git a/lib/std/io/early_eof_reader.zig b/lib/std/io/early_eof_reader.zig new file mode 100644 index 0000000000..5ddb340455 --- /dev/null +++ b/lib/std/io/early_eof_reader.zig @@ -0,0 +1,50 @@ +// SPDX-License-Identifier: MIT +// Copyright (c) 2015-2020 Zig Contributors +// This file is part of [zig](https://ziglang.org/), which is MIT licensed. +// The MIT license requires this copyright notice to be included in all copies +// and substantial portions of the software. +const std = @import("../std.zig"); +const io = std.io; +const assert = std.debug.assert; +const testing = std.testing; + +pub fn EarlyEOFReader(comptime ReaderType: type) type { + return struct { + inner_reader: ReaderType, + bytes_left: u64, + + pub const Error = ReaderType.Error; + pub const Reader = io.Reader(*Self, Error, read); + + const Self = @This(); + + pub fn read(self: *Self, dest: []u8) Error!usize { + const max_read = std.math.min(self.bytes_left, dest.len); + const n = try self.inner_reader.read(dest[0..max_read]); + self.bytes_left -= n; + return n; + } + + pub fn reader(self: *Self) Reader { + return .{ .context = self }; + } + }; +} + +/// Returns an initialised `EarlyEOFReader` +/// `bytes_left` is a `u64` to be able to take 64 bit file offsets +pub fn earlyEOFReader(inner_reader: anytype, bytes_left: u64) EarlyEOFReader(@TypeOf(inner_reader)) { + return .{ .inner_reader = inner_reader, .bytes_left = bytes_left }; +} + +test "io.EarlyEOFReader" { + const data = "hello world"; + var fbs = std.io.fixedBufferStream(data); + var early_stream = earlyEOFReader(fbs.reader(), 3); + + var buf: [5]u8 = undefined; + testing.expectEqual(@as(usize, 3), try early_stream.reader().read(&buf)); + testing.expectEqualSlices(u8, data[0..3], buf[0..3]); + testing.expectEqual(@as(usize, 0), try early_stream.reader().read(&buf)); + testing.expectError(error.EndOfStream, early_stream.reader().skipBytes(10, .{})); +}