From 4b99f5978f35e54d4b4f1bfae022f48f193e40fd Mon Sep 17 00:00:00 2001
From: Andrew Kelley <superjoe30@gmail.com>
Date: Thu, 23 Feb 2017 18:56:10 -0500
Subject: [PATCH] add character format specifier to std.io.OutStream.printf

---
 std/io.zig         | 21 +++++++++++++++++++++
 test/run_tests.cpp |  4 ++--
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/std/io.zig b/std/io.zig
index 47e8ba287b..8fc2092fcf 100644
--- a/std/io.zig
+++ b/std/io.zig
@@ -101,6 +101,7 @@ pub const OutStream = struct {
         CloseBrace,
         Integer,
         IntegerWidth,
+        Character,
     };
 
     /// Calls print and then flushes the buffer.
@@ -155,6 +156,9 @@ pub const OutStream = struct {
                         width = 0;
                         state = State.Integer;
                     },
+                    'c' => {
+                        state = State.Character;
+                    },
                     else => @compileError("Unknown format character: " ++ []u8{c}),
                 },
                 State.CloseBrace => switch (c) {
@@ -188,6 +192,15 @@ pub const OutStream = struct {
                     '0' ... '9' => {},
                     else => @compileError("Unexpected character in format string: " ++ []u8{c}),
                 },
+                State.Character => switch (c) {
+                    '}' => {
+                        self.printAsciiChar(args[next_arg]);
+                        next_arg += 1;
+                        state = State.Start;
+                        start_index = i + 1;
+                    },
+                    else => @compileError("Unexpected character in format string: " ++ []u8{c}),
+                },
             }
         }
         comptime {
@@ -228,6 +241,14 @@ pub const OutStream = struct {
         self.index += amt_printed;
     }
 
+    pub fn printAsciiChar(self: &OutStream, c: u8) -> %void {
+        if (self.index + 1 >= self.buffer.len) {
+            %return self.flush();
+        }
+        self.buffer[self.index] = c;
+        self.index += 1;
+    }
+
     pub fn flush(self: &OutStream) -> %void {
         while (true) {
             const write_ret = system.write(self.fd, &self.buffer[0], self.index);
diff --git a/test/run_tests.cpp b/test/run_tests.cpp
index a49cfdbdda..58affc1cce 100644
--- a/test/run_tests.cpp
+++ b/test/run_tests.cpp
@@ -335,9 +335,9 @@ pub const b_text = a_text;
 const io = @import("std").io;
 
 pub fn main(args: [][]u8) -> %void {
-    %%io.stdout.printf("Hello, world!\n{d4} {x3}\n", u32(12), u16(0x12));
+    %%io.stdout.printf("Hello, world!\n{d4} {x3} {c}\n", u32(12), u16(0x12), u8('a'));
 }
-    )SOURCE", "Hello, world!\n0012 012\n");
+    )SOURCE", "Hello, world!\n0012 012 a\n");
 
 
     add_simple_case_libc("number literals", R"SOURCE(