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const std = @import("../std.zig");
const io = std.io;
const mem = std.mem;
const assert = std.debug.assert;
const testing = std.testing;
pub fn BufferedReader(comptime buffer_size: usize, comptime ReaderType: type) type {
return struct {
unbuffered_reader: ReaderType,
buf: [buffer_size]u8 = undefined,
start: usize = 0,
end: usize = 0,
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 {
// First try reading from the already buffered data onto the destination.
const current = self.buf[self.start..self.end];
if (current.len != 0) {
const to_transfer = @min(current.len, dest.len);
@memcpy(dest[0..to_transfer], current[0..to_transfer]);
self.start += to_transfer;
return to_transfer;
}
// If dest is large, read from the unbuffered reader directly into the destination.
if (dest.len >= buffer_size) {
return self.unbuffered_reader.read(dest);
}
// If dest is small, read from the unbuffered reader into our own internal buffer,
// and then transfer to destination.
self.end = try self.unbuffered_reader.read(&self.buf);
const to_transfer = @min(self.end, dest.len);
@memcpy(dest[0..to_transfer], self.buf[0..to_transfer]);
self.start = to_transfer;
return to_transfer;
}
pub fn reader(self: *Self) Reader {
return .{ .context = self };
}
};
}
pub fn bufferedReader(reader: anytype) BufferedReader(4096, @TypeOf(reader)) {
return .{ .unbuffered_reader = reader };
}
pub fn bufferedReaderSize(comptime size: usize, reader: anytype) BufferedReader(size, @TypeOf(reader)) {
return .{ .unbuffered_reader = reader };
}
test "OneByte" {
const OneByteReadReader = struct {
str: []const u8,
curr: usize,
const Error = error{NoError};
const Self = @This();
const Reader = io.Reader(*Self, Error, read);
fn init(str: []const u8) Self {
return Self{
.str = str,
.curr = 0,
};
}
fn read(self: *Self, dest: []u8) Error!usize {
if (self.str.len <= self.curr or dest.len == 0)
return 0;
dest[0] = self.str[self.curr];
self.curr += 1;
return 1;
}
fn reader(self: *Self) Reader {
return .{ .context = self };
}
};
const str = "This is a test";
var one_byte_stream = OneByteReadReader.init(str);
var buf_reader = bufferedReader(one_byte_stream.reader());
const stream = buf_reader.reader();
const res = try stream.readAllAlloc(testing.allocator, str.len + 1);
defer testing.allocator.free(res);
try testing.expectEqualSlices(u8, str, res);
}
fn smallBufferedReader(underlying_stream: anytype) BufferedReader(8, @TypeOf(underlying_stream)) {
return .{ .unbuffered_reader = underlying_stream };
}
test "Block" {
const BlockReader = struct {
block: []const u8,
reads_allowed: usize,
curr_read: usize,
const Error = error{NoError};
const Self = @This();
const Reader = io.Reader(*Self, Error, read);
fn init(block: []const u8, reads_allowed: usize) Self {
return Self{
.block = block,
.reads_allowed = reads_allowed,
.curr_read = 0,
};
}
fn read(self: *Self, dest: []u8) Error!usize {
if (self.curr_read >= self.reads_allowed) return 0;
@memcpy(dest[0..self.block.len], self.block);
self.curr_read += 1;
return self.block.len;
}
fn reader(self: *Self) Reader {
return .{ .context = self };
}
};
const block = "0123";
// len out == block
{
var test_buf_reader: BufferedReader(4, BlockReader) = .{
.unbuffered_reader = BlockReader.init(block, 2),
};
const reader = test_buf_reader.reader();
var out_buf: [4]u8 = undefined;
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, block);
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, block);
try testing.expectEqual(try reader.readAll(&out_buf), 0);
}
// len out < block
{
var test_buf_reader: BufferedReader(4, BlockReader) = .{
.unbuffered_reader = BlockReader.init(block, 2),
};
const reader = test_buf_reader.reader();
var out_buf: [3]u8 = undefined;
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, "012");
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, "301");
const n = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, out_buf[0..n], "23");
try testing.expectEqual(try reader.readAll(&out_buf), 0);
}
// len out > block
{
var test_buf_reader: BufferedReader(4, BlockReader) = .{
.unbuffered_reader = BlockReader.init(block, 2),
};
const reader = test_buf_reader.reader();
var out_buf: [5]u8 = undefined;
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, "01230");
const n = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, out_buf[0..n], "123");
try testing.expectEqual(try reader.readAll(&out_buf), 0);
}
// len out == 0
{
var test_buf_reader: BufferedReader(4, BlockReader) = .{
.unbuffered_reader = BlockReader.init(block, 2),
};
const reader = test_buf_reader.reader();
var out_buf: [0]u8 = undefined;
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, "");
}
// len bufreader buf > block
{
var test_buf_reader: BufferedReader(5, BlockReader) = .{
.unbuffered_reader = BlockReader.init(block, 2),
};
const reader = test_buf_reader.reader();
var out_buf: [4]u8 = undefined;
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, block);
_ = try reader.readAll(&out_buf);
try testing.expectEqualSlices(u8, &out_buf, block);
try testing.expectEqual(try reader.readAll(&out_buf), 0);
}
}
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