initial public commit

diff --git a/README.md b/README.md
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+A (WIP) collection of portable, strict C99, single-header implementations of common libc extensions.
+
+### How to
+
+Include the header in every file needed as usual:
+
+```
+#include "<ext-func-name.h>"
+```
+
+In the file chosen for the function implementation:
+
+```
+#define <EXT-FUNC-NAME>_IMPLEMENTATION_
+#include "<ext-func-name.h>"
+```
+
+By default, the header won't have any includes, change that with:
+
+```
+#define <EXT-FUNC-NAME>_INCLUDE_LIBC_
+```
+
+Or disable function override with:
+
+```
+#define HAVE_<EXT-FUNC-NAME>
+```

diff --git a/asprintf.h b/asprintf.h
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+++ b/asprintf.h
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+/* https://git.datadissipation.net */
+#ifndef ASPRINTF_H_
+ #define ASPRINTF_H_
+
+ #ifdef ASPRINTF_INCLUDE_LIBC_
+  #include <stdarg.h>
+  #include <stdio.h>
+  #include <stdlib.h>
+ #endif
+
+ #ifndef HAVE_ASPRINTF
+  int vasprintf_(char **strp, const char *fmt, va_list ap);
+  int asprintf_(char **strp, const char *fmt, ...);
+  /* 
+   * Credit for a big part of the macro madness:
+   * Jens Gudstedt
+   * https://gustedt.wordpress.com/2010/06/08/detect-empty-macro-arguments/
+   */
+  #define vasprintf(s, f, a)   vasprintf_(s, f, a)
+  #define I_COND_COMMA_(...) ,
+  #define I_PICK_ARG_(_1, _2, ARG, ...) ARG
+  #define I_HAS_COMMA_(...) I_PICK_ARG_(__VA_ARGS__, 1, 0)
+ 
+  #define I_ISEMPTY_(...)                                                      \
+  II_ISEMPTY_(                                                                 \
+         /* test if there is just one argument, eventually an empty           \
+         one */                                                               \
+         I_HAS_COMMA_(__VA_ARGS__),                                           \
+         /* test if I_COND_COMMA_ together with the argument                  \
+         adds a comma */                                                      \
+         I_HAS_COMMA_(I_COND_COMMA_ __VA_ARGS__),                             \
+         /* test if the argument together with a parenthesis                  \
+         adds a comma */                                                      \
+         I_HAS_COMMA_(__VA_ARGS__ (/*empty*/)),                               \
+         /* test if placing it between I_COND_COMMA_ and the                  \
+         parenthesis adds a comma */                                          \
+         I_HAS_COMMA_(I_COND_COMMA_ __VA_ARGS__ (/*empty*/))                  \
+         )
+ 
+  #define I_PASTE5_(_0, _1, _2, _3, _4) _0 ## _1 ## _2 ## _3 ## _4
+  #define II_ISEMPTY_(_0, _1, _2, _3)\
+  I_HAS_COMMA_(I_PASTE5_(I_IS_EMPTY_CASE_, _0, _1, _2, _3))
+  #define I_IS_EMPTY_CASE_0001 ,
+
+  #define II_PASTE_(a) I_EMPTY_##a
+  #define I_PASTE_(a) II_PASTE_(a)
+
+  #define I_GET_ARG_(...) I_PICK_ARG_(__VA_ARGS__)
+  #define asprintf(s, f, ...)\
+  asprintf_(s, f I_PASTE_(I_ISEMPTY_(I_GET_ARG_(, , __VA_ARGS__))) __VA_ARGS__)
+  #define I_EMPTY_1
+  #define I_EMPTY_0 I_COND_COMMA_()
+ #endif
+
+ #ifdef ASPRINTF_IMPLEMENTATION_
+ int vasprintf_(char **strp, const char *fmt, va_list ap) {
+        int size, ret;
+        va_list tp;
+
+        va_copy(tp, ap);
+        size = vsnprintf(NULL, 0, fmt, tp);
+        va_end(tp);
+
+        if (size < 0) {
+                return -1;
+        }
+        *strp = malloc(size + 1);
+        if (*strp == NULL) {
+                return -1;
+        }
+
+        ret = vsnprintf(*strp, size + 1, fmt, ap);
+        if (ret < 0) {
+                free(*strp);
+                return -1;
+        }
+
+        return ret;
+ }
+
+ int asprintf_(char **strp, const char *fmt, ...) {
+        int ret;
+        va_list ap;
+
+        va_start(ap, fmt);
+        ret = vasprintf(strp, fmt, ap);
+        va_end(ap);
+
+        return ret;
+ }
+ #endif
+#endif