From 87f9f02d1fa62121173c33175a2107fbfb06ce30 Mon Sep 17 00:00:00 2001
From: Ben Sima <ben@bsima.me>
Date: Fri, 29 Jun 2018 20:09:42 -0700
Subject: Prototype-quality printf

Needed help on the convert function
---
 xyo-networks/.gitignore  |  2 ++
 xyo-networks/Makefile    |  6 ++++
 xyo-networks/build.sh    |  5 +++
 xyo-networks/default.nix |  7 ++++
 xyo-networks/printf.c    | 91 ++++++++++++++++++++++++++++++++++++++++++++++++
 xyo-networks/printf.h    |  3 ++
 6 files changed, 114 insertions(+)
 create mode 100644 xyo-networks/.gitignore
 create mode 100644 xyo-networks/Makefile
 create mode 100644 xyo-networks/build.sh
 create mode 100644 xyo-networks/default.nix
 create mode 100644 xyo-networks/printf.c
 create mode 100644 xyo-networks/printf.h

diff --git a/xyo-networks/.gitignore b/xyo-networks/.gitignore
new file mode 100644
index 0000000..29af1e7
--- /dev/null
+++ b/xyo-networks/.gitignore
@@ -0,0 +1,2 @@
+printf
+*.o
diff --git a/xyo-networks/Makefile b/xyo-networks/Makefile
new file mode 100644
index 0000000..a7502e4
--- /dev/null
+++ b/xyo-networks/Makefile
@@ -0,0 +1,6 @@
+
+printf: printf.c
+	gcc -Wall -Wextra -Werror -O2 -std=c99 -pedantic -o printf printf.c
+
+clean:
+	rm -f printf printf.o
diff --git a/xyo-networks/build.sh b/xyo-networks/build.sh
new file mode 100644
index 0000000..af769a9
--- /dev/null
+++ b/xyo-networks/build.sh
@@ -0,0 +1,5 @@
+source $stdenv/setup
+
+PATH="$coreutils/bin:$gcc/bin:$PATH"
+mkdir $out
+make
diff --git a/xyo-networks/default.nix b/xyo-networks/default.nix
new file mode 100644
index 0000000..ee63f97
--- /dev/null
+++ b/xyo-networks/default.nix
@@ -0,0 +1,7 @@
+with (import <nixpkgs> {});
+
+stdenv.mkDerivation {
+  name = "my_printf";
+  builder = "${bash}/bin/bash";
+  src = ./.;
+}
diff --git a/xyo-networks/printf.c b/xyo-networks/printf.c
new file mode 100644
index 0000000..4fa165c
--- /dev/null
+++ b/xyo-networks/printf.c
@@ -0,0 +1,91 @@
+#include <stdio.h>
+#include <stdarg.h>
+#include "printf.h"
+
+/*
+ * my_printf("str: %s\nchr: %c\nhex: %x\nint: %d\noct: %o",
+              1, 1, 1, 1, 1);
+*/
+
+int
+main()
+{
+    my_printf("str: %s\nchr: %c\nhex: %x\nint: %d\noct: %o", 
+              "hi", 'a', 0x32, 10, 8);
+    return 0;
+}
+
+void
+my_printf(char *format, ...)
+{
+    char *c; // a char in the `format` string
+    va_list args;
+
+    va_start(args, format);
+
+    for (c = format; *c != '\0'; c++)
+    {
+        while (*c != '%')
+        {
+            putchar(*c);
+            c++;
+        }
+
+        c++;
+        
+        switch(*c)
+        {
+            case 'c': 
+            {
+                putchar(va_arg(args, int));
+                putchar('\n');
+                break;
+            }
+
+            case 'd': 
+            {
+                puts(convert(va_arg(args, int), 10));
+                break;
+            }
+
+            case 'o': 
+            {
+                puts(convert(va_arg(args, unsigned int), 8));
+                break;
+            }
+
+            case 'x': 
+            {
+                puts(convert(va_arg(args, unsigned int), 16));
+                break;
+            }
+
+            case 's': 
+            {
+                puts(va_arg(args, char*));
+                break;
+            }
+        }
+    }
+
+    va_end(args);
+}
+
+
+char*
+convert(unsigned int num, int base)
+{
+	static char rep[]= "0123456789ABCDEF";
+	static char buffer[50]; 
+	char *ptr; 
+	
+	ptr = &buffer[49]; 
+	*ptr = '\0'; 
+	
+	do { 
+		*--ptr = rep[num%base]; 
+		num /= base; 
+	} while (num != 0); 
+	
+	return(ptr); 
+}
diff --git a/xyo-networks/printf.h b/xyo-networks/printf.h
new file mode 100644
index 0000000..27ced90
--- /dev/null
+++ b/xyo-networks/printf.h
@@ -0,0 +1,3 @@
+
+void my_printf(char*, ...);
+char* convert(unsigned int, int);
-- 
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