Added explicit interface example with fd_t

Author: permutationlock

README.md

@@ -76,20 +76,18 @@ pub const io = struct {
     }
 };
 
-// A type satisfying the Reader interface (uses default ReadError)
-const FixedBufferReader = struct {
-    buffer: []const u8,
-    pos: usize = 0,
-
-    pub fn read(self: *@This(), out_buffer: []u8) error{}!usize {
-        const len = @min(self.buffer[self.pos..].len, out_buffer.len);
-        @memcpy(out_buffer[0..len], self.buffer[self.pos..][0..len]);
-        self.pos += len;
-        return len;
-    }
-};
-
 test "use FixedBufferReader as a reader" {
+    const FixedBufferReader = struct {
+        buffer: []const u8,
+        pos: usize = 0,
+
+        pub fn read(self: *@This(), out_buffer: []u8) error{}!usize {
+            const len = @min(self.buffer[self.pos..].len, out_buffer.len);
+            @memcpy(out_buffer[0..len], self.buffer[self.pos..][0..len]);
+            self.pos += len;
+            return len;
+        }
+    };
     const in_buf: []const u8 = "I really hope that this works!";
     var reader = FixedBufferReader{ .buffer = in_buf };
 
@@ -106,6 +104,18 @@ test "use std.File as a reader" {
 
     try std.testing.expectEqualStrings("Hello, I am a file!", &buffer);
 }
+
+test "use std.os.fd_t as a reader with an explicit interface" {
+    var buffer: [19]u8 = undefined;
+    var file = try std.os.open("my_file.txt", std.os.O.RDONLY, 0);
+    try io.readAll(
+        file,
+        .{ .read = std.os.read, .ReadError = std.os.ReadError, },
+        &buffer,
+    );
+
+    try std.testing.expectEqualStrings("Hello, I am a file!", &buffer);
+}
 ```
 
 More in-depth [examples][4] are provided.

examples/read_file.zig

@@ -1,8 +1,9 @@
 const std = @import("std");
 const io = @import("io.zig");
 const FixedBufferStream = io.FixedBufferStream;
+const Impl = @import("zimpl").Impl;
 
-test {
+test "read file with std.fs.File" {
     const file = try std.fs.cwd().openFile("examples/read_file/test.txt", .{});
     var buffer: [32]u8 = undefined;
     var fbs: FixedBufferStream = .{ .buffer = &buffer };
@@ -12,3 +13,22 @@ test {
         fbs.getWritten(),
     );
 }
+
+test "read file with std.os.fd_t" {
+    const fd = try std.os.open(
+        "examples/read_file/test.txt",
+        std.os.O.RDONLY,
+        0,
+    );
+    const fd_reader: Impl(std.os.fd_t, io.Reader) = .{
+        .read = std.os.read,
+        .ReadError = std.os.ReadError,
+    };
+    var buffer: [32]u8 = undefined;
+    var fbs: FixedBufferStream = .{ .buffer = &buffer };
+    try io.streamUntilDelimiter(fd, fd_reader, &fbs, .{}, '\n', 32);
+    try std.testing.expectEqualStrings(
+        "Hello, I am a file!",
+        fbs.getWritten(),
+    );
+}